CLIMATE CHANGE RESEARCH AND POLICY: UPDATES

INSTITUTE FOR PROSPECTIVE TECHNOLOGICAL STUDIES SEVILLE W.T.C., Isla de la Cartuja, s/n, E-41092 Sevilla CLIMATE CHANGE RESEARCH AND POLICY: UPDATES...
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INSTITUTE FOR PROSPECTIVE TECHNOLOGICAL STUDIES

SEVILLE W.T.C., Isla de la Cartuja, s/n, E-41092 Sevilla

CLIMATE CHANGE RESEARCH AND POLICY: UPDATES Recent Results of Global Climate Change Research and Assessment of Carbon Sequestration under the Joint Implementation Scheme

A periodic survey for the Commission of the European Communities

No. 11- June 1998

EUR 18088 EN

Astrid Zwick

EUROPEAN COMMISSION JOINT RESEARCH CENTRE

 ECSC-EEC-EAEC, Brussels • Luxembourg, 1998 The views expressed in this study do not necessarily reflect those of the European Commission (EC). The European Commission retains copyright, but reproduction is authorised, except for commercial purposes, provided the source is acknowledged: neither the European Commission nor any person acting on behalf of the Commission is responsible for the use which might be made of the following information. Printed in Spain

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Foreword Climate change policy constitutes an important element for the concept of sustainable development, which has also been acknowledged in Article 2 of the United Nations Framework Convention on Climate Change (UNFCCC). Climate change policy and emission reduction negotiations could provide incentives to reinforce efforts towards more sustainable development schemes. Within a few years’ time a subject such as sustainability science might even be taught at universities, creating skills to comply with the new challenge. Many initiatives are underway that focus on environmentally sound activities stipulating a new policy direction for the 21st century. Activities that could arise from climate and environment policy would have positive spin-off effects. For example, energy efficiency saves money in the long run and the reduction of material can decrease production prices and reduce the waste. The reduction of CO2 emissions can be synergistic to the reduction of other air pollutants. Improvements of air quality can reduce the negative health impacts related to air pollution. Any implementation of climate change policy strategies could be facilitated taking synergies to other sectors into account. The implementation concepts, however, need to be carefully designed considering ecological as well as economic aspects.

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Table of Contents - LIST OF ABBREVIATIONS........................................................................................... 5 - LIST OF FIGURES AND TABLES................................................................................ 6 - EXECUTIVE SUMMARY............................................................................................... 7 1.

INTRODUCTION.................................................................................................................................12

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PART I - CLIMATE CHANGE RESEARCH RESULTS.....................................................................13 EVIDENCE OF CLIMATE CHANGE ...................................................................................................13

2.1 2.1.1

Present and Historic Climatological Variability.......................................................................13

2.1.2

Palaeoclimatological Variability ..............................................................................................16

2.1.3

Climate Modelling ....................................................................................................................20 MAJOR DRIVING FORCES OF CLIMATE ..........................................................................................21

2.2 2.2.1

External Forcing.......................................................................................................................21

2.2.2

Internal Forcing and Feedback Mechanisms............................................................................31

PART II - CLIMATE POLICY: JOINT IMPLEMENTATION AND CARBON SEQUESTRATION

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THROUGH LAND-USE MEASURES ...........................................................................................................37 JOINT IMPLEMENTATION ................................................................................................................37

3.1 3.1.1

The Concept ..............................................................................................................................37

3.1.2

Beneficial Aspects.....................................................................................................................38

3.1.3

Concerns...................................................................................................................................39

3.1.4

Types of Joint Implementation ..................................................................................................43

3.1.5

International Experience with Joint Implementation ................................................................44 CARBON SEQUESTRATION THROUGH LAND-USE ........................................................................47

3.2 3.2.1

Carbon Sequestration through Forestry Activities....................................................................48

3.2.2

Carbon Sequestration through Agricultural Activities..............................................................51

3.2.3

The Determination of the Baseline............................................................................................54

3.2.4

Costs of Carbon Sequestration..................................................................................................56

3.2.5

Global Land Availability...........................................................................................................60

3.2.6

Timing.......................................................................................................................................62

3.2.7

Barriers of Carbon Sequestration .............................................................................................62 SET OF CRITERIA FOR CARBON SEQUESTRATION UNDER A JOINT IMPLEMENTATION

3.3

CONCEPT .........................................................................................................................................................75

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3.3.1

Definition of Baseline and Monitoring......................................................................................76

3.3.2

Forest Management and Agricultural Practices .......................................................................78

3.3.3

Verification and Crediting ........................................................................................................79

3.3.4

Reduction of Risk of Leakages ............................................................................................. .....80

CONCLUDING REMARKS........................................................................................................... .....81

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List of Abbreviations AGBM: AIJ BP: CDM: COP: ENSO: FACE: FCCC: GCM: GCTE: GDP: GEF: GHG: Gt: GWP: IGBP: IPCC: JI: NBP: NEP: NOAA: NPC: NPP: ppmv: ppbv: SAR: SBI SBSTA SGS: SST: THC: yr:

Ad Hoc Group on the Berlin Mandate Activities Implemented Jointly Before Present Clean Development Mechanism Conference of the Parties El Niño/Southern Oscillation Forests Absorbing Carbon dioxide Emissions Framework Convention on Climate Change Global Circulation Model Global Change and Terrestrial Ecosystems Gross Domestic Product Global Environmental Facility Greenhouse Gas Giga tons Global Warming Potential International Geosphere-Biosphere Programme Intergovernmental Panel on Climate Change Joint Implementation Net Biome Production Net Ecosystem Production National Oceanic and Atmospheric Association Net Present Cost Net Primary Production Parts per million per volume Parts per billion per volume Second Assessment Report Subsidiary Body for Implementation (UNFCCC) Subsidiary Body for Scientific and Technological Advice (UNFCCC) Societô Generale de Surveillance Sea Surface Temperature Thermohaline Circulation year

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List of Figures and Tables

Figure 1: Possible structure of an institutional JI verification system based on theoretical considerations, available experience and international concerns (modified after (Wuppertal Institut für Klima, 1996). 76 Table 1: Overview of (assumed) advantages and disadvantages for the investing and host countries (Hendriks et al., 1998). 40 Table 2: Inventories for Greenhouse gas emissions within the EU-15 in 1990 (Gg) (EC, 1996). 42 Table 3: Forest management scheme to enhance the carbon sequestration potential for forestry as set up for the case of Mexico (IEA, 1998) . 48 Table 4: Aggregate net sequestration (t C/ha) under low, medium and high baseline scenarios in the sector of forestry for the case of Mexico (IEA, 1998). 50 Table 5: Technical options for carbon sequestration by agriculture (IEA, 1998). 52 Table 6: Aggregate net sequestration (tC/ha) as possible under certain agricultural practices under low, medium and high baseline scenarios for agricultural activities (IEA, 1998). 54 Table 7: Estimates of costs from afforestation (IEA, 1995). 56 Table 8: Costs per tonne of CO2 (in US$) sequestered in the year 1996 (Verweij, 1998). 59 Table 9: Forest areas of the world, previous catastrophes due to forest fires and the area affected as well as usual deforestation through burning. Sources: (FAO, 1997); (Re, 1997); (EEA, 1995); (IEA, 1997). 61 Table 10: Average annual balance of CO2 perturbations for 1980-1989 (GCTE, 1997). 65

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Executive Summary The current update has been divided into two parts. The first focus is set on the monitoring of climate change research results while the second focus, the climate change policy, centers around the debate of Joint Implementation (JI) and carbon sequestration through land-use measures. Part I, climate change research results, of the current update is summarising recent research results collected over the last year. Information is provided on climate observation and modelling as well as on the forcing factors of climate such as the solar radiation changes, the atmospheric greenhouse gas (GHG) concentration and internal mechanisms like the impact of changes in the ocean circulation patterns on the atmosphere. Most importantly, the monitoring showed that the temperature record of the 20th century has been the warmest period of time over the past 600 years. 1990, 1995 and 1997 even have been years with the highest temperature on record. This current trend underlines the importance of the climate models that predicted the increase in temperature under an elevated atmospheric CO2 concentration. Nevertheless there are inconsistencies among the models due to different parameterisation approaches. A recent simulation, for example, circumvented a climate model specific problem, the so-called flux correction, and simulated a less stronger global warming than commonly suggested. It resulted in a maximum temperature increase of about 2°C under a doubling concentration of atmospheric CO2 and not as the IPCC suggested with a maximum temperature of 3.5 °C. This change of temperature is assumed to have a significant impact on the hydrological cycle. It is expected that precipitation intensity will increase in some areas while it will significantly decrease in others. In fact, an increase in global precipitation of about 2 % could be observed since the beginning of this century. The simulation of hurricane patterns, however, could not yet clarify whether climate change would cause an increase in the intensity or in the number of hurricanes. The latter option has been set aside through the latest investigations. The debate on the influence of solar radiation changes through sunspot activity or solar flares is continuing. It has been suggested that radiative forcing of solar activity might have a stronger influence on the earth’s climate than the radiative forcing of anthropogenically emitted GHG. Some evidence was found by investigations of the 11-year sunspot cycle whereas another recent simulation detected the contrary.

The effect of the CO2 fertilisation of the terrestrial biosphere is also undergoing a critical review. Researchers detected a threshold of carbon assimilation by plants. The carbon assimilation is dependent on other limiting nutrients such as nitrogen and phosphor. The complexity of the interactions occurring in the plants and in the soil have not yet been fully understood. Methane is another important GHG contributing to a change of the radiative forcing, however, its sources are manifold and diffcult to detect. More sources of methane emissions could recently be added to the methane balance. Russian peatlands, for example, are significant sources of methane. Even lake ecosystems contribute to the global methane emissions to a larger extent than previously estimated. Wetland rice fields are a well known source for methane emissions. As suggested recently, a control of the cultivation practices in the rice fields could have a significant mitigating effect. In the context of the reduction of GHG the control of other air pollutants would bear tremendous beneficial effects. The widespread biomass burning, e.g., is made responsible for the buildup of tropospheric ozone in the air currents. These currents even transport the ozone to previously unpolluted areas. Ozone is also generated by NOx-emissions from aircraft traffic which is steadily growing. Researchers recognised that more than 10 % of the GHG are due to emissions from air traffic, an additional threat for the climate change regime. The increasing concentration of GHG may as well be partially responsible for the very large Arctic stratospheric ozone loss, in particular in 1997, since with an increase in GHG a cooling of the lower stratosphere has been forecast. This effect has implications on the stratospheric ozone, since ozone destruction is accelerated through cooler temperatures.

The ocean is a carrier of enormous heat masses that, released to the atmosphere, are steering climate patterns. The heat masses are transported by the oceanic circulation. The oceanic circulation is not only sensitive to changes in CO2 but also sensitive to the rate of change as recent models suggested. Ocean circulation patterns, as recorded by palaeoclimatological records, reveal more periodic variability than previously assumed which complicates further assessment of future ocean circulation patterns under a more variable climate. For example, the periodic El Niño phenomenon seems to undergo decadal fluctuations of strength. Advocates of climate change, however, attribute the latest strong El Niño events to the increase of global temperatures.

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Warmer temperatures of the air and of the ocean can have a serious effect on the glacial cover of the earth, according to climate models. A disintegration of a significant part of the Antarctic ice sheet has recently been observed by satellites. It is not clear whether this is due to internal ice dynamics or to the recently increased global air temperatures as mentioned above. However, the recognition of an unprecedented warming trend in the last 150 years in the Arctic by a compilation of proxy data over a period of the last 400 years has contributed to the knowledge that both, natural and human induced changes influence the climate over the Arctic. The highest temperatures occurred between the mid-19th and the mid-20th centuries with some dramatic environmental change pre-dating the period of the industrial revolution.

Climate change research results provided both, contradicting opinions on the contribution of climate forcing factors as well as compelling evidence of a recent significant variability in climate patterns. Climate change research also provided information on processes in the carbon balance of the terrestrial ecosystems, which will play a pivotal role in future climate policy. The Kyoto Protocol underlines the role to be played by Joint Implementation (JI) as a useful climate policy option to mitigate the anthropogenic GHG emissions. Experience on JI already exists through various projects that have been launched under a JI pilot phase. Joint Implementation can basically be realised in two ways, namely technologically-based JI and environmentally-based JI. The latter encompasses the capture of carbon by sequestration in terrestrial biomass. The problems involved in this option are manifold and discussed below. The most fundamental problem involves the determination of the baseline emissions. Discrepancies in deforestation estimates and difficulty in the prediction of future land-use changes, in particular, in tropical countries still impede a realisation of the JI scheme under the carbon sequestration option. The discrepancies call for a stringent emission inventory system. In this inventory system, projections of the future sink capacity have to be taken into account as well. The assumed CO2 fertilisation under an elevated concentration of atmospheric CO2 complicates such an assessment. CO2 fertilisation stimulates the photosynthesis providing an enhanced sink capacity, however, an interaction with other parameters such as the availability of other nutrients or the climatic conditions are limiting factors. It has even been argued that the sink capacity could reach a threshold and lead to a 9

reverse reaction. Thus, terrestrial ecosystems such as forests might become a source of carbon in the future. A delay of this effect was suggested due to the different timescales of carbon assimilation and carbon release by respiration. It is also argued that this delay may have something to do with the missing sink which might only mask the inertia of the ecosystem. Projects to measure the carbon fluxes in terrestrial ecosystems have been started some years ago, however, to establish an inventory in order to reliably determine the baselines for JI projects is an action which has only been taken up by some projects over the past few years. Results still have to be evaluated and compared. The confirmation of the data obtained requires additional time, probably in the range of a few years’ intensive research efforts. This effort is necessary to be able to design the projects appropriately. The carbon sequestration through land-use activities as proposed in the Kyoto Protocol can follow different pathways such as forest management, af/reforestation, and agricultural practices. Timber extraction would still be possible under a sound forest management. Sustainable harvesting of wood from sequestration forests could increase GHG abatement, provided the wood is used to replace high energy-content products such as cement or displace fossil fuels. Afforestation can improve the microclimate and avoid the degradation of soils. It can slow down the run-off of surface water, thus, filtering the water through the root system which improves the water quality and enhances the soil moisture. On the other hand, it also can have adverse effects on the environment, e.g. lowering the groundwater level, acidifying the soil or reducing biodiversity. Additionally, an analysis of prevailing local socio-economic conditions is a prerequisite for a successful adoption of the carbon sequestration scheme. Sequestration forestry, e.g., could lead to the removal of necessary agricultural land and it might perturb traditional cultivation methods. Various assessments of the costs of carbon sequestration by land-use have been made under very different assumptions. The costs basically differ depending on geographical location and project type. The costs of land and of the establishment of a plantation were estimated. The costs also depend on the life of the forest and the quantities of carbon absorbed. The alternative demands for the land and the availability of adequate water supply were crucial factors. More experience is required on this issue. A homogenous assessment of the costs was not possible. Given the analysis above, a set of recommendations could be given for the carbon sequestration under a JI scheme. However, carbon sequestration by land-use cannot be 10

considered as the ultimate solution for anthropogenic GHG emission reduction. It can be effective on a short-term time scale to mitigate climate change immediately. However, if reasonably applied, it could contribute to a necessary conservation of the terrestrial ecosystems and the reduction of further emissions from land-use activities.

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1.

Introduction

Over the last year scientific research has provided many points of discussion on the question of the distinction between natural variability of climate and anthropogenically induced climate forcing. While the debate on the influence of the solar radiation only recently shifted into the centre of the discussion on external climate driving forces, some of the most impressive findings concern studies on an internal forcing factor of climate, namely the ocean circulation. The ocean circulation plays a pivotal role for the variability of the climate, and periodic and even non-periodic changes in its mode are subject to various fundamental discussions. The following chapters of Part I, climate change research results, provide an outline of the major elements of the current debates. Since the discussion of the Kyoto Protocol and the policy options raise very controverse opinions, Part II of this report, climate change policy, is focusing on the policy instrument of Joint Implementation in the context of carbon sequestration through land-use. Critical voices emerged after the finalisation of the Kyoto Protocol arguing that the Protocol still contains some major loopholes while others consider the Protocol as a major step forward in climate change policy since it provides a clear signal for the governments of the parties. In particular, the inclusion of carbon sequestration through land-use activities raised major concern due to the uncertainties of the accounting of carbon sequestration in natural sinks and, especially, in anthropogenically enhanced natural sinks. The analysis of carbon sequestration under a JI scheme also encompasses the discussion of recent scientific findings on the carbon balance of the terrestrial biosphere. The data obtained by research reveal some unexpected results on the carbon fluxes in terrestrial ecosystems. Both, measurements and models as well as a stringent verification mechanism will play a pivotal role for future activities aiming at the enhancement of the natural carbon sinks. Thus, carbon sequestration under Joint Implementation requires a delicate framing of project conditions balancing the various environmental and socio-economic aspects involved. Some recommendations could be provided on the basis of the discussions.

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2.

PART I - Climate Change Research Results

2.1 Evidence of Climate Change

2.1.1 Present and Historic Climatological Variability

2.1.1.1 Temperature Climate observations constitute a prerequisite for the assessment of climate variability and the prediction of the future climate. Climate observations detected that an increase in the global average temperature of about 0.5 °C has occurred over the past 150 years. The cause of this warming still remains unknown. The increase in temperature might stem from anthropogenically released greenhouse gas (GHG) emissions or it can be the reflection of the natural variability of climate or both. Long-term observation and climate modelling are the only tools that could help singling out the driving force of this increase in temperature. A strong evidence for the anthropogenic influence was recently provided by data of a new 300-site survey of borehole temperatures from Europe, North America, Australia and South Africa over the last five centuries. The measurements confirmed that the Earth is getting warmer and the rate of warming has been accelerating rapidly since 1900 (Pollack, 1997). Subsurface rock temperatures revealed that the average global surface temperature has increased about 1°C over the last five centuries with one-half of that warming taking place in the last 100 years. According to this study, the 20th century is the warmest and has experienced the fastest rate of warming of any of the five centuries. Mann et al., (1998) obtained similar results through the analysis of proxy data. The proxy data include chemical evidence of climatic change contained in tiny marine fossils, corals and ancient ice, along with fossilized pollen in lake sediments and annual growth rings in trees. They could reconstruct temperature variations in the Northern Hemisphere since about the 15th century. Combining this evidence with thermometer readings and historical records, they concluded that the 20th century has been the warmest century in the last 600 years. The warmest years in all of that period have been the most recent ones, 1990, 1995 and 1997. 13

In 1997, temperature has been half a degree above the normal value (=16.5 °C from 1961-1990). Karl (1998) assigns this trend to the anthropogenic influence on climate, whereas Parker (1997) argued that probably El Niño can be made responsible for the increase in surface temperatures of continents and oceans. Taking the analysis one step further, Mann et al. (1998) examined the multiple forces that determine the earth's temperature. Until the 20th century, they found, a variety of mostly natural factors combined that might influence the climate. These factors included changes in solar radiation, volcanic haze that reflects sunlight and heat-trapping greenhouse gases (GHG), mainly carbon dioxide, in the atmosphere. But in the 20th century, they found, the GHG have been the dominant influence. Atmospheric concentrations of carbon dioxide have been rising because of the burning of fossil fuels like coal, oil and natural gas. Yet, the uncertainty involved with this human fingerprint could not be eradicated. And yet, the current warming trend might only be a small flickering in the thermometer in comparison what might expect us by the second half of the next century. According to (Singh, 1997), the real significant forecast global warming effect will be only perceived in the second half of the next century. Interestingly, the influence of microclimate in cities might also have a significant influence on longer-scale weather patterns as scientists from the Pennsylvania State University detected (Loefken, 1998b). Satellite images shed light on this issue presenting urban areas as hot spots similar to deserts which could have an impact on the local climate. Adapting urban architecture more to its natural environment through the greening of areas might not only improve urban microclimate but also foster better living conditions.

2.1.1.2 Precipitation Scientists have long held that precipitation is one of the most important aspects in Earth's climate system because of its impact on the global biosphere. In addition, precipitation determines the amount of water vapor in the atmosphere. Water vapor is the most important greenhouse gas and, thus, strongly influences Earth's surface temperature. The amount of water vapor in the atmosphere determines when and where clouds form. It is suggested that a change in temperature will also change the hydrological cycle leading to an intensification of the precipitation patterns.

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In fact, global land precipitation has increased during the 20th century, especially at the mid and high latitudes (NASA, 1997a). A recalibrated compilation and analysis of data from 1900-1988 confirms this result. A global land trend of a 2.4 mm per decade increase in annual precipitation could be detected. Multiplied by almost nine decades, this means that there is about 22 mm more rain falling now each year than there was at the turn of the century. Rainfall as a global mean has risen by slightly more than two percent. Further long-term study is needed to help ascertain the reasons for this change. Investigations showed that both the spatial pattern and the rate of precipitation increase are reminiscent of global climate model predictions of the atmosphere’s response to an increase in greenhouse gas concentrations. Tracking precipitation and its relationship to global climate, however, has been difficult because the data were not recorded into coordinated databases until recently. In addition, precipitation measurements vary widely across small geographic areas making it difficult to measure accurately. Further research should shed light on the global rainfall patterns.

2.1.1.3 Extreme Weather Events Intensified hurricane activity due to climate change is still subject to discussions. Contrasting model results show both an increase in the number of hurricanes and an increase in the intensity of hurricanes. The impact of climate warming on hurricane intensities was investigated with a regional, high-resolution, hurricane prediction model (Knutson et al., 1998). In a case study, 51 western Pacific storm cases under present-day climate conditions were compared with 51 storm cases under high CO2 conditions. More idealized experiments were additionally performed. The large-scale initial conditions were obtained from a global climate model. For a sea surface temperature warming of about 2.2°C, the simulations yielded hurricanes that were more intense by 3 to 7 m/s (5 to 12 %) for wind speed and 7 to 20 millibars for central surface pressure. According to the simulations, a reversion of the thermal differences inducing these storms would also be possible leading to their weakening. El Niño caused the 19971 Atlantic hurricane season to be less active than normal. The season produced only seven severe storms and three hurricanes. Tropical storms form when maximum winds reach 62 km/h. They become hurricanes when top winds reach 118

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km/h. El Niño intensifies winds in the upper levels of the atmosphere and these impede the formation of the giant storms. Hurricanes can be compared to giant columns of clouds wrapped around a clear center, or eye, and stretching from the sea surface high into the atmosphere. The intensity of the storm is determined by how tightly the clouds are wound around the center. The El Niño-powered winds batter the top of the cloud formation and prevent the cloud spirals from growing tighter. As a consequence, it is expected that the now fading El Niño phenomenon (see chapter 2.2.2.2) in the Pacific Ocean will lead to a modestly more active hurricane season than normal in the Atlantic this year, with around 10 tropical storms expected to form in the Atlantic Ocean between June 1 and Nov. 30. Six out of them are supposed to become hurricanes - with winds exceeding 118 km/h - and two of those would be intense, with winds of 178 km/h or greater. The average Atlantic hurricane season produces 9.3 tropical storms and 5.8 hurricanes, 2.1 of them intense hurricanes. The above-average sea surface temperatures in the north, east and tropical regions of the Atlantic and a weaker ridge of high pressure near the Azores Islands typically help promote hurricane formation. However one lingering uncertainty over the 1998 season was rainfall in the western Sahel region of Africa. A wetter-than-average season there usually promotes hurricane activity. Although last season was below average, the span from 1995-97 was the busiest three-year period on record, with 39 severe storms and 23 hurricanes, 13 of them intense.

2.1.2 Palaeoclimatological Variability Palaeoclimatological investigations identified a high-frequency instability in the late Pleistocene on timescales of a few millennia, centuries or even decades. Two of major oscillations are the so-called Dansgaard–Oeschger and Heinrich events2. Simple box model experiments indicate that Laurentide ice sheet internal instabilities could control such strong cold Heinrich events and the warm oscillations which followed them (Corijo, 1997). The models suggest a high sensitivity of deep water properties to 1

The 1997 El Niño phenomenon was the strongest in recorded history and was blamed for climate changes

ranging from severe drought in Brazil and southeast Asia to vicious storms in California and swarms of killer tornadoes in Georgia and Florida. 2

These are abrupt changes of climate cooling during the last interglacial period, the Eemian (135.000-

115.000 yr BP), observed in one of the Greenland ice cores. They must correspond either to variations in sea

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surface salinity changes over the last glacial period. A decrease in the thermohaline circulation activity would, in turn, induce a high latitude atmospheric cooling. The cool phase of the smaller Dansgaard-Oeschger events are also associated with ice rafted detritus and surface water oxygen isotope ratio anomalies. However, the analytical noise is still too large to know if there is a corresponding deep water carbon isotope ratio decrease for these low amplitude cooling events. There seems to be evidence enough for a supraregional character of the DansgaardOeschger cycles, as presented in the previous update of this series. Their effects could even be traced in the Gulf of California and along the northeast Pacific margin. Schulz et al. (1998) also assume a general relationship between low-latitude monsoonal climate variability and the rapid temperature fluctuations of high northern latitudes that are recorded in the Greenland ice records. The authors records suggest that Dansgaard– Oeschger and Heinrich events are strongly expressed in low-latitude (monsoonal) climate variability, suggesting the importance of common forcing agents such as atmospheric moisture and other greenhouse gases. They investigated sediment cores from the northeastern Arabian Sea. The sediment cores show laminated, organic-carbon-rich bands, reflecting strong monsoon-induced biological productivity, that correlate with the mild interstadial climate events in the northern North Atlantic region. In contrast, periods of lowered southwest monsoonal intensity, indicated by bioturbated, organic-carbon-poor bands, are associated with intervals of high-latitude atmospheric cooling and the injection of melt water into the North Atlantic basin.

Recent work on climate changes on sub-Milankovitch frequencies suggests now that the southern hemisphere surface ocean has not varied synchronously with respect to northern hemisphere fluctuations (Schneider & Little, 1997). Palaeontological records revealed that between 70,000 yr and 10,000 yr BP strong wind-driven upwelling events occurred in the South Atlantic simultaneously with warm periods in the northern hemisphere recorded from ice cores from Greenland. The record suggests large scale climatic teleconnections between the North Atlantic and the South Atlantic surface circulation related to the trade wind systems during the Dansgaard-Oeschger events. Periods of increased southeast trade wind intensity might have enhanced the northward transfer of subtropical surface waters and thus the cross-equatorial heat transport. The Gulf Stream may have favoured the rapid surface temperature and salinity or to massive discharge of icebergs, the so-called Heinrich events, into the North Atlantic ocean.

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warming of northern hemisphere climate on millennial time scales and increased the delivery of moisture to the higher latitudes, accelerating the growth of continental ice sheets. This implies that the asynchronous behaviour of both the hemispheres at suborbital timescales relies on fluctuations in northward cross-equatorial heat transport into the North Atlantic forced by the subtropical trade wind system.

Adkins et al. (1998) could detect decadal to centennial changes in ventilation of the deep North Atlantic around 15,400 years ago. Coupled radiocarbon and thorium-230 dates from benthic coral species reveal that the ventilation rate of the North Atlantic upper deep water varied greatly during the last deglaciation. Radiocarbon ages in several corals of the same age, 15,410 ± 0.17 years, and nearly the same depth, 1,800 m, in the western North Atlantic Ocean increased by as much as 670 years during the 30- to 160-year life spans of the samples. Cadmium/calcium ratios in one coral imply that the nutrient content of these deep waters also increased. The data show that the deep ocean changed on decadalcentennial time scales during rapid changes in the surface ocean and the atmosphere.

These investigations of climate-proxy records of the past 100,000 years show that the earth’s climate has varied significantly and continuously on timescales within intervals of a few thousand years. A similar variability has also recently been observed for the interval 340,000–500,000 years ago (Raymo et al., 1998). The record shows that global climate varies on regular cycles lasting from 1,200 to 6,000 years, in glacial and interglacial periods alike. These dramatic climate shifts, expressed most strongly in the North Atlantic region, may as well be linked to – and possibly amplified by – alterations in the mode of the ocean thermohaline circulation. The authors used sediment records of past iceberg discharge and deep-water chemistry to show that such millennial-scale oscillations in climate occurred over one million years ago. This was a time of significantly different climate boundary conditions; not only was the early Pleistocene epoch generally warmer, but global climate variations were governed largely by changes in earth’s orbital obliquity. These cycles have an approximately constant pacing that is similar to that documented for the last glacial cycle. The findings suggest that such climate variations are inherent to the late Pleistocene, regardless of glacial state. Sea surface temperature during a particular warm peak, varied by 0.5° to 1°C, less than the 4° to 4.5°C estimated during times of ice growth and the 3°C estimated for glacial maxima. Coherent deep ocean circulation changes were associated with glacial oscillations in sea surface temperature. The authors' results 18

suggest that such millennial-scale climate instability may be a pervasive and long-term characteristic of earth’s climate, rather than just a feature of the strong glacial–interglacial cycles of the past 800,000 years. This theory of the alterations of the thermohaline circulation does not yet rule out a primary forcing by external processes. It is a finding that offers a mixed message of reassurance and warning about the future of our own climate as GHG warm the world.

An investigation on the African climate over the past 9,000 years has been conducted with similar outcome as before (Wawrzinek, 1997). Periodic changes in the climate from humid and wet to cold and dry with a temperature difference of up to 8 °C could be detected. These results are in accordance with previous investigations of oscillations in the ocean as they can be identified for every 1,500 years when the Northern Atlantic was cooling down. It is suggested that as a consequence the borderline between the cold and the warm tropical water in the Atlantic was shifting, causing subsequent abrupt climate changes in Africa as well.

Evidence for a cooling event synchronous with the Younger Dryas (12,000 yr BP), a sudden cold event after the last deglaciation, has been found in the North Pacific Ocean north of 30°N in records of surface and subsurface water properties. These changes may be related to a temporary shut-down of North Atlantic Deep Water formation and associated surface cooling over the North Atlantic. It has remained unclear, however, whether this North Atlantic cooling was communicated to the North Pacific Ocean through the atmosphere or through the ocean. Results of a sensitivity experiment with a coupled oceanatmosphere general circulation model support a primarily atmospheric forcing of North Atlantic climate variations (Mikolajewitz et al., 1997). Changes in wind strongly affect coastal upwelling at the North American west coast, and surface cooling by the atmosphere causes better ventilation of the thermocline waters of the northeast Pacific. This effect is amplified by oceanic propagation to the Pacific of the signal arising from the collapse of the North Atlantic Deep Water formation. These teleconnections may also explain earlier North Pacific and western North American millennial-scale cooling events of a similar nature.

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2.1.3 Climate Modelling As seen above in the previous chapter, climate modelling can help in the reconstruction of climate processes. However, they are not free of problems. One of the major concerns about computer models of the earth’s climate has been the need for so-called "flux corrections" that prevent models from drifting into unrealistic climate states when run over a period of centuries. A new model developed by scientists at the National Center for Atmospheric Research (NCAR—Boulder, Colorado) appears to be the first to simulate present-day climate without the need for these corrections, since the flux correction introduces an artificial viscosity into the model (Kerr, 1997). One of the key changes made by NCAR researchers in the new model is an improved method for incorporating the effects of ocean eddies. These eddies affect climate by moving heat around the ocean, but are typically much smaller than the grid scales used by the current generation of models. The NCAR model does not use a smaller grid, but rather employs "parameterisation" to pass the effects of the eddies into the larger grid scale of the model. As a result, the new model doesn't drift away from a reasonably realistic climate even when run for 300 years. The first results from the model suggest that greenhouse warming may be milder than other models have predicted and could take many decades to become apparent, an assumption that has been made by Singh (1997) as well (see chapter 2.1.1.1). Doubling atmospheric CO2 conditions in the model resulted in a global temperature increase of only 2° C, putting the model results at the low end of current estimates. In addition, a 300 year run with no increase in greenhouse gases produced long-term natural variations in temperature of about 0.5° C. If the model is indeed realistically simulating global climate, the researchers point out that over half of the temperature variations seen in the past century could be explained by natural variability.

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2.2 Major Driving Forces of Climate

2.2.1 External Forcing The climate system is highly complex. It is driven by external forces (earth orbital parameters - effective only at a long-term timescale -, cyclic solar radiation changes - on a decadal to centennial scale - or GHG forcing). The exogenous variables partially trigger mechanisms that indirectly lead to a reinforcement of climate changes. In such a way stimulated, internal forcing mechanisms of the climate system such as the oceanic circulation, cloudiness and aerosols can therefore lead to enormous, and also non-periodic changes in global climate.

2.2.1.1 Solar Activity and Sunspot Cycles The energy flux stemming from solar activity - changes in sunspots, solar flares and other activity - has been subject to numerous discussions. Sunspots were the first extraterrestrial phenomenon found to harbour magnetic fields. But the physical nature of sunspots and their relationship to the sun’s global magnetic field are still poorly understood. Perhaps the largest uncertainty is related to the outermost region of sunspots (the penumbra) and, in particular, the nature of the so-called evershed flow - a stream of material emanating radially from sunspots at velocities of up to ~6km/s, before vanishing abruptly at the outer penumbral edges. Lassen and Friis-Christensen, scientists at the Danish Meteorological Institute, have suggested that the current rise in the earth’s temperature owes everything to the long-term changes in the sun’s output and nothing to greenhouse gases released by burning fossil fuels (Carpenter, 1998c). Their studies showed that the earth’s climate is influenced by cosmic and solar rays impacting on the earth’s magnetic field. Cosmic rays vary with the solar cycle and interact with the solar wind- an electromagnetic stream from the sun - , which has a direct impact on the world’s cloud formation and therefore on the climate. They found that the world’s cloud cover varies between 65 percent to 68 percent over the solar cycle. The amount of cloud cover will have a direct influence on the amount of the sun’s heat which is absorbed or reflected back into space. The solar theory explained why more than 1,000 years ago Greenland was warm enough to attract Viking settlement. 21

During Roman times southern England supported a red wine industry. A direct link between the drop in temperature of 1945 to 1970 and a decrease in the sun’s activity has also been assumed. However, this direct link between cosmic rays and cloud formation has not yet been unambiguously established. Further investigations need to be made in order to confirm this theory. Nevertheless, a strong support to the sun-climate relationship has been given by Vos et al. (1997) who investigated lake sediments and discovered periodicities in varve thicknesses of about 11, 88 and 208 year, exactly the intervals in which sunspot cycles occur. Westendorp Plaza et al. (1997) made use of a recently developed optical tomographic technique to obtain a three- dimensional model of the magnetic field and mass flow in the vicinity of a sunspot. They found that some of the magnetic field lines, together with a significant part of the evershed mass flux, flow back towards the Sun in the deepest atmospheric layers at the outer edge of the sunspot and its surroundings. This observation should provide an important clue to the understanding of the appearance, stability and decay of sunspots, the most conspicuous tracers of the solar activity cycle.

Changes in the radiation of the sun could have boosting effects on global climate as suggested by Haigh (1998) at a recent conference of the American Association for the Advancement of Science. Changes in ultraviolet radiation and electric charges in solar wind are affecting the atmosphere on Earth. A computer model showed that shifts in ultraviolet radiation were having corresponding effects on the Earth’s protective ozone layer. About 2 to 3 % in the amount of ultraviolet radiation was coming from the sun, resulting in a corresponding shift of 2 to 3 % in ozone levels. Ozone is created by ultraviolet radiation hitting oxygen molecules in the atmosphere and the changes observed were at the wavelengths that affect ozone production. This damaging radiation is at slightly different wavelengths from the radiation that produces the ozone. However, it is argued that these observations were a very different phenomenon from the huge holes in the ozone layer recorded over the South Pole and over northern latitudes. One change which had been correlated was a slight shift (around 70 km) in the tracks taken by storms such as hurricanes and typhoons in mid latitudes. The effect was observed to be stronger in summer. Tinsley of the University of Texas at Dallas, at the same meeting, could observe that the solar wind could freeze particles on the top of high clouds. The phenomenon was due to changes in electrostatic charge. The effects could be considerable. If there are thin high 22

clouds and they are turned to ice they will dissipate. If the rate, at which clouds dissipate, is increasing, more solar radiation reaches the earth. Advocates of the theory on solar activity related to climate change suggest that half or more of all global warming measured this century was due to the activity of the sun. However, a model by Cubasch et al. (1997b) attributes only a part of the radiative forcing to solar activity. The researchers simulated the impact of solar variability on climate by a global coupled ocean-atmosphere circulation model. Results showed that the near-surface temperature simulated by the model is dominated by the long periodic solar fluctuations, the 88-year Gleissberg cycle, with global temperatures varying by about 0.5 K. Both solar variability and an increase in greenhouse gases resulted in a comparable pattern of surface temperature change, i.e. an increase in the land-sea contrast. While the solar-induced warming in annual means and summer is more centered over the subtropics, the GHGinduced warming was more uniform. In addition, the observed temperature rise is larger than it could have been via a solar forcing. Thus, Cubasch et al. (1997) suggest that it is more likely that the observed warming is due to the increase of atmospheric greenhouse gas concentration.

2.2.1.2 CO2 In 1997, climate change carbon emissions reached a record high worldwide totaling 6.3 billion tons, according to a recently released report by the Worldwatch Institute (Vital Signs 1998, The Environmental Trends Shaping Our Future). This is an increase of around 1.5% in comparison to 6.2 billion tons emissions of carbon in 1996. Atmospheric concentrations of CO2 climbed to 364 ppmv, the highest in 160,000 years. Atmospheric CO2 is contributing to the radiative forcing in the climate system. Thus, its unprecedented increase leads to a disequilibrium in the system, which is assumed to induce a non-natural warming of the climate and disrupt prevailing weather patterns. Apart from its Global Warming Potential CO2 has a direct effect on ecosystems as well. In particular terrestrial ecosystems, which constitute a natural sink for CO2, respond to an increase in its concentration within a short time. The response depends on the species affected, on the concentrations of other nutrients, and last but not least, on the climatic conditions. Considering an implementation of carbon sequestration under the Kyoto Protocol, future projections of carbon storage potential require an investigation of the effect of elevated CO2. 23

2.2.1.2.1 Terrestrial Biosphere and Elevated CO2 The response of terrestrial ecosystems to an increase in atmospheric CO2 is manifested in a higher uptake of CO2 inducing a fertilisation. A recently detected increase in plant growth in the northern high latitudes indicating the response of vegetation to the increase of atmospheric CO2, has given support to the fertilisation theory for boreal forests (Chapin III, 1996). De Lucia et al. (1998) investigated the increase of growth of a forest ecosystem under enhanced CO2 conditions. After the exposure of a forest ecosystem to a step increase of ambient plus 200 mLL-1CO2 (~550mLL-1) the average growth rate of the dominant pine trees in their experiment increased by approximately 27 % relative to trees growing under ambient conditions. The net primary production increased by approximately 21%, despite a concomitant 6 % increase in carbon loss from the soil. Additional CO2 enrichment experiments on birch trees only showed a faster growth rate, up to 50 %, within the first months due to the increase of their photosynthesis rate. After that period plants stabilised their growth rate. After four years the birch trees achieved the size normally to be expected after six years (Jarvis, 1998). It was suggested that comparisons on the effects of treatments should be made rather at the same size than at the same time. Similar results were produced by another CO2 enrichment experiment (Jifon & Wolfe, 1998). The researchers investigated bean plants under ambient and elevated CO2 concentration, adding nitrogen and inoculating with Rhizobium to the CO2 enriched plants. Photosynthesis capacity experienced a decline as determined from the initial slope of response of light-saturated assimilation rate to internal CO2 concentration. The decline was higher under low nitrogen than under high nitrogen enrichment. The result could imply a limitation of the sink capacity of terrestrial ecosystems. Also Hartwig et al. (1998) suggest, that increased carbon sequestration under elevated atmospheric pCO2 is counterbalanced by an appropriately increased symbiotic N fixation, thus maintaining the C:N ratio at the whole ecosystem level. Since inadequate N supply would restrict an increase in extra carbon sequestration into the ecosystem under elevated pCO2, symbiotic N fixation is considered to be a crucial driving force for increased carbon sequestration in a CO2-rich world.

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Under certain conditions the efflux of CO2 of ecosystems can also be increased under CO2 fertilisation as examined by [Dukes, 1998 #1071]. The decomposition of organic material in the soil might accelerate under elevated CO2 conditions due to changes in species and chemical composition of the material.

Rovira & Valejo (1998) emphasise the relevance of the grain size in soils for the control of the carbon budget. They deduced, according to measurements in Mediterranean soils, an upper limit of soils in the capacity to accumulate and stabilise organic carbon. The limit is related to the content of fine silt plus clay in the soil profile, i.e. to the finest size fractions.

The GCTE (Global Change and Terrestrial Ecosystems) Synthesis Project (GCTE, 1998) has summarised some of the major results of the effect of elevated CO2 on particular terrestrial ecosystems. Within an experimental time frame (< 10 years), all ecosystems respond to elevated CO2 (increased net CO2 uptake) to some extent, the cold system, e.g. tundra, being less responsive. It was also observed that an increased concentration of carbon relative to nitrogen (protein) can be detected in live leaves grown under elevated CO2. Whole-ecosystem elevated CO2 experiments on crops, grasslands and tree seedlings showed consistent stomatal closure under elevated CO2, and consequent reduction in loss of water through transpiration. Data from studies on mature trees suggest that the stomatal closure and reduced loss of water found in herbaceous systems and tree seedlings may not occur in mature forests. The effects of increasing atmospheric CO2 (2 x CO2) on crop yields will be much smaller than the 30% increase often assumed a few years ago. In the mid-latitudes CO2 induced yield increases in wheat are unlikely to exceed 10% under laboratory conditions, and only 5-7% under field conditions. Even rangeland livestock production will be affected by an increase in the atmospheric CO2 concentration. In rangelands and pastures a 2 x CO2 increase is predicted to increase above-ground production by up to 20 %. In cultivated pastures, limited sensitivity analysis suggests that a 5% increase in pasture growth will lead to about a 3 % increase in liveweight gain.

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2.2.1.2.2 Carbon Fluxes in the Ocean Carbon uptake by the ocean takes place via two basic processes. The so-called biological pump involves carbon fixation through photosynthetic activity of algae. Circulation patterns and other physico-chemical conditions govern CO2 solubility, gas transfer rates across the sea surface, and the bulk transport of carbon within the oceans. Recent measurements of the stable organic carbon isotope ratio from surface sediments provided more evidence for the fact that CO2 released by human activities has been stored in southern ocean surface waters (Fischer et al., 1997). Another theory emerged on how the oceans can take up excessive CO2 (Verdugo et al., 1998). Dissolved organic material could form lumps of gel. These polymer molecules stem from photosynthesis of algae or terrestrial plants. Calcium can accumulate in these lumps. Under minimal changes of the pH value, calcite crystallises from calcium. These carbon compounds sink down to the sea floor where they remain deposited.

An unknown source reported on a different pattern of biological carbon fixation in various climate zones. Over the arctic summer a higher percentage of algae reach the ocean floor, while in the tropical and temperate oceanic zones, only 1 % of the algae are deposited on the ocean floor in the same season. A stronger grazing activity in the Arctic was suggested to be responsible for this observation.

2.2.1.3 Methane Highly divers sources of methane complicate a quantification of methane emissions to the atmosphere. Investigations continue, and new data of methane emission emerged. Hahn (1997) found that the biggest share of the methane emissions in Russia is produced by microorganisms in peatlands which stands against the theory of a high rate of leakages from Russian gas pipelines. A further important source of methane has been detected by limnologists (Caspar, 1997). Investigations showed a reasonably high outgassing of CO2 and particularly CH4 from lakes. On the outgassing of CO2 by lakes has been reported in the Climate Change Research and Policy Report No. 7 (1995).

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The amount of CO2 and CH4 flux to the atmosphere from “Priest Pot”, a eutrophic lake with a surface area of 1 hectare and a depth of 3.5 meters, was about 12000 liters per day. An estimation on the surface of the lakes worldwide (about 2.5 Mkm2) showed that under the assumption of the gas flux of Priest Pot, half of the lakes in the world would emit about 50 Mt CH4 annually, i.e. almost 8 % of the annual CH4 emissions. According to the scientists, the avoidance of lake fertilisation and lake eutrophication, respectively, would significantly lower the output of the greenhouse gases from this source. Further investigation is clearly needed to evaluate the balance of GHG in lakes on a global scale.

Wetland rice fields are another significant source for methane emissions. Measurements on methane fluxes from wetland rice fields in the Philippines through laboratory and field experiments have been conducted (Denier van der Gon, 1996). Various factors are influencing the methane flux in the field, namely the climate, the stage of ripening of the plant which determines the methane oxidation capacity, plant type (high root-oxidising varieties of rice might be a promising mitigation tool), soil types with regard to their dynamics to elucidate the complex biogeochemical interactions, salinity, sulfate availability and organic amendments such as fertilisers, in particular rice straw and green manure (whereas composting seemed to be a cheap climate change mitigation option). The results showed that wetland rice fields on saline, low-sulfate soils emit less methane than comparable non-saline rice fields. Soils high in sulfate or amended with large amounts of sulfate containing substances fostered even more methane emission reduction. The addition of sulfate to a rice field could reduce CH4 emission by 50-70 %. Soil drying also releases considerable amounts of soil-entrapped methane. During a full rice crop cycle soil drying releases about 10 % of the total methane emitted. A wet fallow period contributed to this phenomenon significantly. Previous monitoring studies did not take account of these phenomenon which may cause, according to Denier van den Gron (1996), an underestimation of total seasonal emissions by 10 -15 %. The current result and the result of the study by Kagotani et al. (1996), as reported in the Climate Change Research and Policy Report No. 9, confirm that an improved understanding of the methane balance in wetland rice fields can help identifying measures to reduce the emission from this source by appropriate agricultural practices.

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2.2.1.4 N2O Research on nitrous oxide provided only one new finding. Recent laboratory studies showed that the reaction of short-lived O2 molecules (lifetime ~10 picoseconds) with N2 and the photodissociation of the N2:O2 dimer produce NOX in the stratosphere at a rate comparable to the oxidation of N2O by O(1D) (Zipf, 1198). This finding implies the existence of unidentified NOX sinks in the stratosphere. The NO2 observed in this experiment is isotopically heavy with a large

15

N/14N enhancement. However,

photodissociation of this NO2 unexpectedly produced NO molecules with a low 15N/14N ratio. The diurnal odd-nitrogen cycle in the stratosphere will be marked by a complex isotope signature that will be imprinted on the halogen and HOX catalytic cycles.

2.2.1.5 Ozone

2.2.1.5.1 Tropospheric Ozone Tropospheric ozone is a key part of photochemical smog found in major cities throughout the world, often as the result of congested traffic. At elevated levels, it can cause breathing difficulties, increase the risk of asthma attacks, and adversely affect the growth of trees, shrubs, and cash crops ranging from vegetables to orchids. High concentrations of ozone are found in the Earth’s stratosphere, but strong stratification suppresses efficient exchange of this ozone-rich air with the underlying troposphere, according to Suhre et al. (1997). Upward transport of tropospheric trace constituents occurs mainly through equatorial deep convective systems. In contrast, significant downward transport of ozone-rich stratospheric air is thought to take place only outside the tropics by exchange processes in upper-level fronts associated with strong distortions of the tropopause. Ozone within the tropical troposphere is assumed to originate predominantly from ground-based emissions of ozone precursors, particularly from biomass burning, rather than from a stratospheric source. Recent measurements of ozone in the upper troposphere in convective regions over the Pacific Ocean indeed reveal near-zero concentrations. Here the authors present sharply contrasting observations: ozone-rich (100- 500 parts per billion by volume) transients were frequently encountered by specially equipped commercial aircraft at a cruising altitude of 10 - 12 km (in the upper troposphere) in the vicinity of strong convective activity over the equatorial Atlantic Ocean. This 28

strongly suggests that the input of stratospheric ozone into the troposphere can take place in the tropics. They suggest that this transport occurs either by direct downward movement of air masses or by quasi-isentropic transport from the extratropical stratosphere. Air quality monitoring experiments between Africa and South America in 1992 and across the South Pacific in 1996 detected that photochemical smog has begun to pollute the skies over the oceans in the southern hemisphere, resulting in higher than normal tropospheric ozone levels near remote islands in the tropics (Carpenter, 1998e). Long lasting plumes from biomass burnings due to the burning to clear woodland or bush travel across Africa and Australia to bring higher smog levels within range of remote locations in the southern oceans, such as Fiji. Even in rather isolated locations, such as Easter Island, the Galapagos Islands, and Ascension Island, researchers detected significant ozone concentrations. In 1996, about 500 miles north of Fiji ozone readings reached 131 ppbv. The pollution had traveled over Australia, with the major contributors of ozone likely coming from as far away as Africa. Similar observations have been made in the Mediterranean area by Kotzias (1998). Measurements showed, that volatile organic compounds, including oxygenated compounds, have lead to a production of ozone which was detected even in formerly unpolluted rural areas. It was encouraged due to the importance of the findings to take these gases into consideration while reducing emissions of GHG included in the Kyoto Protocol.

Recent findings recognise that more than 10 % of the greenhouse gases are due to air traffic (Loefken, 1998a). During the combustion, apart from CO2, also nitrous oxides are emitted which are converted into ozone in the troposphere. Given the estimated doubling of air traffic per decade, an alarming perspective has been created. A counteracting effect of the nitrous oxides, however, is their decomposition effect of methane.

2.2.1.5.2 Stratospheric Ozone Distribution and concentration of stratospheric ozone are influenced in two ways by human-driven activity in addition to natural, seasonal variations. The direct impact of industrially produced chlorofluorocarbons is of first sale importance. Although ozone 29

levels around the globe are expected to continue to decline over the next several years, NASA is now detecting decreasing growth rates of ozone-depleting compounds in the upper part of the atmosphere, indicating that international treaties to protect the ozone layer are working. Still, in late 1997, the levels of ozone depletion that were observed over the Arctic were larger than in any previous year on record by international research teams. It has been suggested that the increase in greenhouse gas emissions is one possible cause of the observed trends in Arctic ozone losses and that this may delay recovery of the ozone layer (NASA, 1998). Thus, the indirect impact of greenhouse gases on atmospheric temperatures were suggested as a second influence on stratospheric ozone levels. The buildup of greenhouse gases leads to global warming at the Earth’s surface, but cools the stratosphere. The ozone chemistry is very sensitive to temperature and a cooling results in more ozone depletion in the polar regions. Since upper atmospheric temperatures in the Northern Hemisphere during winter and spring generally are warmer than those in the Southern Hemisphere, ozone depletion over the Arctic has been much smaller than over the Antarctic during the 1980s and early 1990s. The Arctic stratosphere, however, gradually has cooled over the past few decades resulting in very large ozone depletion, especially during 1996-97. In the simulations performed, temperature and wind changes, induced by increasing greenhouse gases, clearly alter the dynamics of the atmosphere. According to simulations, as the abundance of greenhouse gases gradually increases, the frequency of Northern Hemisphere sudden stratospheric warming is reduced, leading to significantly colder lower stratospheric temperatures. If proven correct, this dynamic effect would add to the greenhouse cooling of the stratosphere. These results might suggest that the combination of these two cooling effects causes dramatically increased ozone depletion so that ozone loss in the Arctic by the year 2020 roughly is double what it would be without greenhouse gas increases. Increasing greenhouse gases therefore may be at least partially responsible for the very large Arctic ozone losses in recent winters. The researchers caution, however, that though the model predicts a general trend towards increasing ozone depletion, the year-to-year variability is quite large, especially in the Arctic. For example, several years in the late 1990s and early 2000s show very little Arctic ozone depletion, while others show record losses. In fact, the 1997-98 winter that just occurred was characterized by significantly less ozone loss than 30

the preceding six winters. A factor that should be considered, however, is the consistency in model predictions, i.e. whether the same results can be reproduced by other models. It is suggested that the severity and duration of the Antarctic ozone depletion may also increase due to greenhouse gas-induced stratospheric cooling over the coming decades. However, ozone in the Antarctic is already so depleted that any additional losses may be relatively small.

A ten years measuring campaign detected a further increase in halogens in the atmosphere (Elicki, 1998). This increase particularly concerned those which contain bromine, a highly effective compound. Stocks with this species still remained from the time before the Montreal Protocol. In 1994, China alone produced around 90 % of the total amount of halogens globally. The Montreal Protocol still permits the production for the developing countries until the year 2002. While the chlorine concentration is continuously decreasing it might be offset by this current trend.

2.2.2 Internal Forcing and Feedback Mechanisms

2.2.2.1 The Ocean Circulation Present estimates of the future oceanic uptake of anthropogenic CO2 and calculations of CO2 emission scenarios are based on the assumption that the natural carbon cycle is in steady state. But it is well known from palaeoclimate records and modelling studies that the climate system has more than one equilibrium state, and that perturbations can trigger transitions between them. Europe is warmed by the North Atlantic current, part of a system of warm and cool ocean currents that is driven by convective overturning at the northern end of the Atlantic. Human emissions of greenhouse gases could change temperature and rainfall patterns enough to stop this circulation, and so radically alter the regional climate. The rate of GHG increase may be as important as the final concentrations reached as Rahmstorf (1997) argues. Also Stocker & Schmittner (1997) emphasise that anticipated future changes in today’s climate system due to human activities have the potential to weaken the thermohaline circulation of the North Atlantic Ocean, which would greatly modify estimates of future 31

oceanic CO2 uptake. They used a simple coupled atmosphere--ocean climate model to show that the Atlantic thermohaline circulation is not only sensitive to the final atmospheric CO2 concentration attained, but also depends on the rate of change of the CO2 concentration in the atmosphere. A modelled increase to 750 ppmv CO2 within 100 years (corresponding approximately to a continuation of today’s growth rate) leads to a permanent shut-down of the thermohaline circulation. If the final atmospheric concentration of 750 ppmv CO2 is attained more slowly, the thermohaline circulation simply slows down. The reason for this rate-sensitive response of the climate system lies with the transfer of buoyancy in the form of heat and fresh water from the uppermost layers of the ocean into the deep waters below. This sensitivity of the simulated thermohaline circulation to the rate of change of atmospheric CO2 concentration has potentially important implications for the choice of future CO2 emission scenarios.

The Mediterranean Sea is subject to a large-scale research project called Mediterranean Targeted Project (MTP) financed under the European Community’s RTD programme in the field of Marine Science and Technology (MAST). Important results of this project include a increase in temperature of the deep layers of the Western and Eastern Mediterranean basin during the last 3-4 decades and an increase in salinity. These changes were attributed to changes in the climate. The residence rate of the deep water masses is relatively short with 100 years so that the water is sensitive to climate variability. Thus, the temperature and salinity changes could have a profound influence on the ecosystem functioning of the next few decades.

2.2.2.2 The El Niño/Southern Oscillation (ENSO) Preliminary research results suggest that global warming may be contributing to the increased frequency and severity of the El Niño3 weather disasters (Glantz, 1997). El

3

Normally, warm ocean water builds up in the western part of the equatorial Pacific Ocean near Australia,

the Philippines and Indonesia. This build-up results from strong westward flowing winds blowing across the ocean from the Peruvian coast. Every so often these winds weaken and sometimes reverse and blow towards the east, which allows a warm pool of water to form in the central and eastern part of the Pacific Ocean with a subsequent evaporation from the warm water increases. This leads to cloud formation and ultimately rainfall. Areas that are normally wet such as Indonesia, the Philippines and northwest Australia become plagued with drought, while areas that are normally dry such as the west coasts of Peru, California, and Chile become excessively wet. El Niño is counter-balanced in the Southern Oscillation (SO) which takes place in the atmosphere on the other side of the Pacific. When the pressure is low in the region around Darwin, Australia,

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Niño's strange recent behaviour between 1991 and 1995 might result from the influence of global warming on the Pacific. Both the recent trend for more El Niño events since 1976 and the prolonged 1990-1995 El Niño are unexpected given the previous record, with a probability of occurrence of about once in every 2000 years. On average, El Niño events occur every three to seven years but scientists have identified a warm water flow pattern in the Pacific Ocean that may explain why El Niño fluctuates in strength approximately every 10 years, and they speculate that global warming may have "swamped" this natural rhythm in recent years, increasing the frequency and intensity of the weather pattern. A novel explanation for the fact that El Niño strength historically appears to fluctuate every 10 years was given in Carpenter (1998d). A submerged layer of unusually hot water swirls clockwise down from midlatitudes over a period of years and eventually raises the sea temperature in the tropics. The process begins around Hawaii, when strong winds drive warm surface water down to depths of 500 to 700 feet. This layer, as much as 1 degree Fahrenheit warmer than average for its depth, travels slowly toward the equator, where it finally rises within 300 feet of the surface. That, in turn, makes the equatorial ocean warmer than it would be, presumably increasing the likelihood of strong El Niños. The scientists based their theory on a pattern they found when they examined ocean temperature readings at various depths taken since the mid-1960s. In the early 1970s, the northern Pacific was uncommonly warm and the tropics cooler than usual. But then in 1976 and 1977, the arrangement began to reverse itself. By the early 1980s, as the researchers believe, the northern warm water flow had found its way to the equator, and probably influenced the severity of the 1982-83 El Niño. The decadal variation of the strength of El Niño is subject to continuous controverse debates. A solution has not yet been found and a collection of further data is necessary.

Another climate periodicity has been detected in the Pacific which exists beside the El Niño phenomenon (Vaas, 1997). An analysis of periodic events shed light on this additional decadal oscillation that could clearly be distinguished from the El Niño oscillation. The Pacific decadal oscillation (PDO) probably explains why temperatures increase at the north American west coast while the winters in the southern parts of the it is usually high in the region of Tahiti. These two processes (EN+SO) together produce ENSO. Although El Niño refers to a local phenomenon off Peru and the ENSO to the basinwide event across the entire Pacific

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United States become more humid than usual. A further periodicity ranging from 10 to 30 years was also detected, probably influencing the climate in North America and in the Pacific area.

2.2.2.3 The Cryosphere and Fluctuations of the Sea Level Natural causes, not just human-induced forces, played a significant role in an unprecedented warming trend in the Arctic in the last 150 years, according to Overpeck et al. (1997). A compilation of palaeoenvironmental data included information from glaciers, tree rings and marine, lake and pond sediments. Until recently the record of Arctic climate change was geographically and historically limited, but this study contributes to an improved understanding of the area’s environmental variability. The study found that the Arctic experienced its highest temperatures in 400 years between the mid-19th and mid20th centuries. Contrary to previous assumptions, the evidence indicates that the Arctic is characterized by significant climatic change even without the influence of environmental effects caused by humans. Some of the warming observed after the time of the Industrial Revolution may be attributed to atmospheric greenhouse gases, but the analysis of dramatic environmental change pre-dates this period.

The findings suggest the Arctic is especially susceptible to global climate change caused by both natural and human sources. Climate change in the Arctic can in turn influence changes at lower latitudes through mechanisms such as river runoff into the Arctic Ocean and subsequent changes in the thermohaline circulation. The period of warming that began in the 1840s terminated the Little Ice Age, caused melting of permafrost and sea ice and alterations in land and lake ecosystems.

Direct global estimates of the Antarctic sea-ice cover from satellite observations, only possible since the 1970s, have not shown clear trends. Comparisons between satellite observations and ice-edge charts obtained from early ship records suggest that sea-ice extent in the 1970s was less than during the 1930s, an indication supported by limited regional observations (de la Mare, 1977). But these observations have been regarded as inconclusive, owing to the limited spatial and temporal scope of the early records. A

including El Niño, many people, including scientists, now use these terms interchangeably.

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significant data source has, however, been overlooked. The southern limit of whaling was constrained by sea ice, and since 1931 whaling records have been collected for every whale caught, giving a circumpolar coverage from spring to autumn until 1987. Here, an analysis of these catch records indicates that, averaged over October to April, the Antarctic summer sea-ice edge has moved southwards by 2.8º of latitude between the mid 1950s and early 1970s. This suggests a decline in the area covered by sea ice of some 25%. This abrupt change poses a challenge to model simulations of recent climate change, and could imply changes in Antarctic deep-water formation and in biological productivity, both important processes affecting atmospheric CO2 concentrations.

A very recent disintegration of a part of the Antarctic ice shelf caught the attention of researchers, since a decline in the extent of the Antarctic sea-ice is a commonly predicted effect of global warming (Carpenter, 1998b). Satellite images showed a 24-mile-long and 3-mile-wide section broken away from the continental ice mass, perhaps in response to decades of gradual warming in the South Polar region. The break occurred by the end of March 1998 in a segment of the Antarctic Peninsula ice cover known as Larsen B. The area, near the southern tip of South America, is the northernmost of the many floating ice shelves that are usually frozen tight to the continent. This is the biggest ice shelf yet to be threatened. A disintegration of the Larsen Ice Shelf could occur within a few years or even as little as one more warm season, according to scientists. Bits and pieces of various Antarctic ice shelves have been cracking off for decades as regional average temperatures have risen approximately 4.5 degrees Fahrenheit since the 1940s. The current rupture, which dislodged an area of about 75 square miles, is less than one-tenth the size of an iceberg that snapped off the Larsen shelf in January 1995. Records show that since 1974, approximately 100 ice shelf sections exceeding 15 miles in length have detached themselves from the continental ice mass, which is anchored to rock. The largest known was a piece from the Ross Ice Shelf south of New Zealand, which measured 96 by 22 miles. In all, the amount of Antarctic ice shelf lost to break-off is less than one-tenth of 1 % of the total ice cover in the area. The fragments do not contribute directly to sea-level rise,

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according to researchers involved4 in the investigations, because the shelves by definition already are floating on the surface. The more menacing question of course is what could happen to the glaciers behind the ice sheets. However, the Larson ice break is not as closely tied to the rest of the western Antarctic ice sheet as other adjacent formations and, thus, not threatening the west Antarctic ice. It is not clear whether internal ice dynamics (the flow of the ice caused over thousands of years) or global warming caused the new break or its predecessors.

New calculations of a future sea level rise under a global warming scenario were made by Gregory & Oerlemanns (1998). According to their results, sea level will be around 500 mm higher than today by 2100 under the doubling of the atmospheric concentration of CO2. The new assumption is that glaciers will contribute with around half of this rise. The results are in accordance with previous assumptions, except that they now provide a higher reliability. The model was refined by introducing regional and seasonal effects. This refinement had a significant effect on the contribution of the different sources of melting. It resulted in a 20 % higher contribution of glaciers to the sea level rise. Given the forecast warming of air temperature and the subsequent rise of the snowline in mountain regions, a higher contribution of melting glaciers enforces the threat of a future rise in the sea level.

4

Scientists at the National Snow and Ice Data Center (NSIDC), part of a joint project of the University of

Colorado and the National Oceanic and Atmospheric Administration (NOAA), routinely monitor the ice shelves using time-sequence images from polar-orbiting NOAA satellites.

36

3.

Part II - Climate Policy: Joint Implementation and Carbon

Sequestration through Land-use Measures

3.1 Joint Implementation

3.1.1 The Concept Joint Implementation (JI), which has been included in the Kyoto Protocol by the UN Framework Convention on Climate Change (UNFCCC) as one of the instruments for greenhouse gas emission reduction, involves a bilateral or multilateral deal. Countries facing high pollution abatement costs invest in abatement in countries with lower costs, and receive credit for the resulting reduction in greenhouse gas (GHG) emissions. The driving force behind Joint Implementation (JI) is obvious: it allows measures to reduce GHG emissions to be taken where they are least costly, on a world-wide level. This concept fits in with the nature of GHG, whose impact on global climate is the same regardless of where they are emitted. Some of the modalities for JI are given under Article 6 in the Kyoto Protocol. A JI project has to be approved by both parties involved, emission reduction should be additional to any that would occur otherwise and the reduction should be supplemental to domestic actions. The Fourth Conference of the Parties (COP-4) will take place in November 1998. It is foreseen to elaborate further modalities and guidelines for the implementation, verification and reporting.

A concept similar to that of JI with the exception that emission reduction is realised with a country that is without any reduction commitment is determined by Article 12 of the Kyoto Protocol. It defines a new funding mechanism for emission reduction projects, the Clean Development Mechanism. .... “The Clean Development Mechanism shall be to assist Parties not included in Annex 1 in achieving sustainable development and in contributing to the ultimate objective of the 37

Convention, and to assist Parties included in Annex I in achieving compliance with their quantified emission limitation and reduction commitments under article 3.1.” The CDM will enable the participation of countries not included in the binding target of the Kyoto Protocol. Some modalities have already been set up in the Protocol such as the certification of emission reductions and the set up of a supervising executive board, the approval by each Party. Emission reductions have to be real, measurable and include longterm benefits related to the mitigation of climate change as well as be additional to reduction that would occur anyhow. The CDM should assist in the arrangement of funding. Further modalities on transparency, efficiency, verification and accounting will have to be elaborated at the COP-4 in November 1998.

3.1.2 Beneficial Aspects JI may induce significant capital flows from private investors in the OECD countries to their counterparts in developing countries, in addition to already existing or forthcoming official capital flows between governments. Kuik et al., (1994) even consider to make it a condition for governments that the minimum expenditure for Official Development Aid (ODA) does not fall below 0.7 % of GDP due to their possible involvement into JI projects. Joint Implementation allows broad participation, and this may avoid 'leakage' of reduction potential that may occur under certain tax regimes (taxed activities may shift to other countries, outside of the agreement, where the GHG emissions will consequently rise). Emission targets could, thus, be even more ambitious than obligations under any agreement. An incentive for encouraging the private sector may be an exemption from taxes or the application of a quota system. For the host country, the acceptance of JI projects will primarily depend on the demonstrated economic value from both capital and technology transfer points of view. It can foster the transfer of know how and information services to developing countries. Additionally, a reduction in SOx, NOx and dust emissions by technology improvement, or reduced erosion, or the regeneration of deforested areas by reforestation will cause a secondary environmental benefit. This and spin-off effects of innovative technology in the country could provide important incentives for developing countries to participate. It should also be kept in mind that the transfer of technology is probably not the only solution to eradicate poverty and stimulate economic growth within a developing country. Raising 38

the level of education and skills is a precondition for improvements and for adopting the concept of sustainable development. It is also quite possible that century old national traditions, e.g. special agricultural practices, which were suppressed by modern structures might bear appropriate solutions for particular regions and in combination with an advanced scientific understanding of the underlying processes their applications might gain a new significance. This idealistic line of thoughts, however, might be difficult to be translated into a short-term concept such as Joint Implementation. JI may also make time to develop integrated environmentally sound technologies, which usually take longer to develop and would foster a dissemination of the so-called end-ofpipe technologies. This farsighted application of Joint Implementation might create a pathway for more ’sustainable’ solutions.

3.1.3 Concerns There are some major concerns involved in the realisation of JI. In Table 1 the advantages and disadvantages for the investing and for the host countries are summarised. First and most importantly, JI gives rise to an ethical question. Given that the aim of the UNFCCC is to mitigate climate change by reducing GHG emissions, it may seem counterintuitive that nations do not reduce emissions within their own territory, but try to offset them elsewhere. In this context, it can be questioned whether - contrary to the sustainable pathway mentioned above - JI would promote reliance on current fossil fuel technologies in the investing country and would reduce incentives for major breakthroughs in terms of future alternative technologies.

39

Table 1: Overview of (assumed) advantages and disadvantages for the investing and host countries (Hendriks et al., 1998). Advantages

Investing country

Host

Disadvantages



Cost efficient



Loss in local investments



Avoid or reduces non-voluntary policy instruments



Declined technological developments



Creates business opportunities



Improved transfer of know-how and technology



Reduce future low cost emission reduction potential



Additional resources and employment opportunities





Local environmental benefits (elimination of local pollutants such as NOx, SO2,...)

A possible mismatch between available infrastructure and rapid technological development



No incentive for local technological developments



Affects national integrity

Another main question concerns the involvement of non-Annex I countries. It has been projected that in 2015, annual global emissions will be 9.7 billion metric tons of carbon (GtC), with about 45% of these emissions coming from the developing world (EIA, 1997), particularly Asia and China. This scenario implies that it would be wise to respond in time to their future energy demand in an environmentally and economically sound way by a reinforced introduction of cleaner energy sources. A fundamental problem for the implementation of JI involves the definition of the baseline. Emissions reduction under JI should be ‘genuine’; i.e. countries should not be rewarded for emission reduction that would have taken place anyway. For this reason, Annex-I countries, with well-defined emissions, base years and emission targets, are the countries that can establish such a concept of JI easier (see Annex). The situation differs according to whether the agreement is with another Annex 1 country or with a non-Annex 1 country, since the latter is not bound to a commitment. In the second case the total reduced amount could be credited to the investing country. As soon as the country without commitment enters the group of countries with commitment its emissions will already be lower than it would have been without JI, which brings us back

40

to the baseline definition issue mentioned earlier. In any case, the host country will negotiate to get the most out of this deal.

A GHG emission inventory to monitor the emissions of the Annex I countries has been set up under the UN Framework Convention. Yet, not all Annex 1 countries reported their emissions by sector until today. Since the GHG inventory is not obligatory for developing countries, also the question of the baseline can only be tackled on a micro (project) level. When it comes to the issue of carbon sequestration by forestry or agricultural practices, the baseline definition is even more complicated. Scientific knowledge on the natural terrestrial carbon pools and their variability is still insufficient. In 1993, the Council Decision for a monitoring mechanism of Community CO2 and other greenhouse gas emissions was adopted in the framework of a Community strategy to limit CO2 emissions, to improve energy efficiency and to ensure that stabilisation of CO2 emissions can be fulfilled (EC, 1996). The Community inventories which have been set up using the same format as that required for reporting under the UN Framework Convention on Climate Change cover data only until 1990 (as far as it was stated in the Communication by 1996). The data are most complete for CO2, CH4, N2O, NOx, CO and NMVOC emission, while CO2 removals, stemming from land-use and forestry, are only reported by 9 Member States out of 15 (Table 2). It again confirms that emission measurements are easier to realise than measurements of sinks. A look into the data base of the UNFCCC reveals similar features. The estimates are often based on harmonised emission factors. Harmonised emission factors may vary between countries simple because the chemical composition of the fuels actually are different in different countries. Differences may arise because the underlying assumptions about the conversion of carbon to CO2 differ, i.e. assumptions regarding complete and incomplete combustion. Some international organisations use harmonised emission factors for all countries, a method which will inevitably mask differences in chemical fuel composition which often exist across the Member States.

41

Table 2: Inventories for Greenhouse gas emissions within the EU-15 in 1990 (Gg) (EC, 1996). Member State

CO2

CH4

N2O

NOx

CO

NMVOC

CO2 Removal

Austria

59200

603

4

222

1692

445

NE1

Belgium

114500

359

22

338

1219

361

NE

Denmark

52100

406

11

270

770

165

2600

Finland

53900

252

22

295

487

219

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