世界経済・社会統計 = World development indicators

Impatti, adattamento e vulnerabilita Le cause e le responsabilita dei cambiamenti climatici sono state trattate sul numero di ottobre della rivista Cda. Approfondiamo l’argomento presentando il documento: “Cambiamenti climatici 2007: impatti, adattamento e vulnerabilita” votato ad aprile 2007 dal secondo gruppo di lavoro del Comitato Intergovernativo sui Cambiamenti Climatici (Intergovernmental Panel on Climate Change). Si tratta del secondo di tre documenti che compongono il quarto rapporto sui cambiamenti climatici.

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Climate Change 2007: Impacts, Adaptation and Vulnerability.

Greenhouse gas emissions are fundamental both to the world’s energy system and to its food production. The production of CO2, the predominant gas implicated in climate change, is intrinsic to fossil fuel combustion; specifically, thermal energy is generated by breaking the chemical bonds in the carbohydrates oil, coal, and natural gas and oxidizing the components to CO2 and H2O. One cannot have cheap energy without carbon dioxide emissions. Similarly, methane (CH4) emissions, an important greenhouse gas in its own right, are necessary to prevent the build-up of hydrogen in anaerobic digestion and decomposition. One cannot have beef, mutton, dairy, or rice without methane emissions. Climate change is the mother of all externalities: larger, more complex, and more uncertain than any other environmental problem. The sources of greenhouse gas emissions are more diffuse than any other environmental problem. Every company, every farm, every household emits some greenhouse gases. The effects are similarly pervasive. Weather affects agriculture, energy use, health, and many aspects of nature—which in turn affects everything and everyone. The causes and consequences of climate change are very diverse, and those in low-income countries who contribute least to climate change are most vulnerable to its effects. Climate change is also a long-term problem. Some greenhouse gases have an atmospheric life-time measured in tens of thousands of years. The quantities of emissions involved are enormous. In 2000, carbon dioxide emissions alone (and excluding land use change) were 24 billion metric tons of carbon dioxide (tCO2).

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The Economic Effects of Climate Change

Sea level rise (SLR) due to climate change is a serious global threat. The scientific evidence is now overwhelming. Continued growth of greenhouse gas emissions and associated global warming could well promote SLR of 1m-3m in this century, and unexpectedly rapid breakup of the Greenland and West Antarctic ice sheets might produce a 5m SLR. In this paper, the authors have assessed the consequences of continued SLR for 84 developing countries. Geographic Information System (GIS) software has been used to overlay the best available, spatially-disaggregated global data on critical impact elements (land, population, agriculture, urban extent, wetlands, and GDP) with the inundation zones projected for 1-5m SLR. The results reveal that hundreds of millions of people in the developing world are likely to be displaced by SLR within this century, and accompanying economic and ecological damage will be severe for many. At the country level, results are extremely skewed, with severe impacts limited to a relatively small number of countries. For these countries (such as Vietnam, A. R. of Egypt, and The Bahamas), however, the consequences of SLR are potentially catastrophic. For many others, including some of the largest (such as China), the absolute magnitudes of potential impacts are very large. At the other extreme, many developing countries experience limited impacts. Among regions, East Asia and the Middle East and North Africa exhibit the greatest relative impacts. To date, there is little evidence that the international community has seriously considered the implications of SLR for population location and infrastructure planning in developing countries. The authors hope that the information provided in this paper will encourage immediate planning for adaptation.

The Impact of Sea Level Rise on Developing Countries: A Comparative Analysis

In 2005 the UK Government hosted the Avoiding Dangerous Climate Change conference to take an in-depth look at the scientific issues associated with climate change. This volume presents the most recent findings from the leading international scientists that attended the conference. The topics addressed include critical thresholds and key vulnerabilities of the climate system, impacts on human and natural systems, socioeconomic costs and benefits of emissions pathways, and technological options for meeting different stabilisation levels of greenhouse gases in the atmosphere. Contents are: Foreword from Prime Minister Tony Blair; Introduction from Rajendra Pachauri, Chairman of the IPCC; followed by 41 papers arranged in seven sections entitled: Key Vulnerabilities of the Climate System and Critical Thresholds; General Perspectives on Dangerous Impacts; Key Vulnerabilities for Ecosystems and Biodiversity; Socio-Economic Effects; Regional Perspectives; Emission Pathways; and Technological Options. Four papers have been abstracted separately for the Coal Abstracts database.

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Avoiding dangerous climate change

This paper examines the impact of climate change on rich and poor countries across the world. We measure two indices of the relative impact of climate across countries, impact per capita, and impact per GDP. These measures sum market impacts across the climate-sensitive economic sectors of each country. Both indices reveal that climate change will have serious distributional impact across countries, grouped by income per capita. We predict that poor countries will suffer the bulk of the damages from climate change. Although adaptation, wealth, and technology may influence distributional consequences across countries, we argue that the primary reason that poor countries are so vulnerable is their location. Countries in the low latitudes start with very high temperatures. Further warming pushes these countries ever further away from optimal temperatures for climate- sensitive economic sectors.

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The distributional impact of climate change on rich and poor countries

In this paper we combine a climate-forecasting model, COSMIC, with a global impact model, GIM, to compare the market impacts of climate change projected by 14 general circulation models Given a specific date (2100), carbon dioxide concentration (612 ppmv), and global temperature sensitivity (25 ◦C), predicted impacts to economies are calculated using climate-response functions from Experimental and Cross-sectional evidence The Cross-sectional impact model predicts small global benefits across all climate models, whereas the Experimental impact model predicts a range from small benefits to small damages High-latitude countries are less sensitive to temperature increases than low-latitude countries because they are currently cool Uniform global temperature changes overestimate global damages because they underestimate the benefits in polar regions and overestimate the damages in tropical regions compared to the GCM predictions

Comparing impacts across climate models

This paper utilizes the predictions ofseveral Atmosphere-Ocean GeneralCirculation Models and the Global ImpactModel to create forecasts of the globalmarket impacts from climate change. Theforecasts of market impacts in 2100 varyconsiderably depending on climate scenariosand climate impact sensitivity. The modelsdo concur that tropical nations will behurt, temperate nations will be barelyaffected, and high latitude nations willbenefit. Although the size of theseeffects varies a great deal across models,the beneficial and harmful effects areoffsetting, so that the net impact on theglobe is relatively small in almost alloutcomes. Looking only at market impacts,the forecasts suggest that while the globalnet benefits of abatement are small, thedistribution of damages suggests a largeequity problem that could be addressedthrough a compensation program. The largeuncertainty surrounding these forecastsfurther suggests that continued monitoringof both the climate and impacts isworthwhile.

Comparing Forecasts of the Global Impacts of Climate Change

This study uses empirical agricultural impact models to compare the U.S. climate change predictions of 16 General Circulation Models (GCMs). The impact analysis provides a policy-relevant index by which to judge complex climate predictions. National aggregate impacts vary widely across the 16 GCMs because of varying regional and seasonal patterns of predicted climate change. Examining the predicted impacts from the full set of GCMs reveals that the seasonal detail in the GCM predictions is so noisy that it is not significantly different from a constant annual change. However, a consistent regional pattern does emerge across the set of models. Nonetheless, aggregating climate change across seasons and regions within the United States, using a national-annual climate change provides a reasonable and efficient approximation to the expected impact predicted by the 16 GCM models.

Evaluating GCM output with impact models

Sulfate aerosols (SO4) from anthropogenic emissions of sulfur dioxide (SO2) generally have a cooling effect. However, if SO2 emissions fall over time, accounting for sulfate aerosols will increase the predicted warming from greenhouse gases. This paper integrates the four marker emission scenarios for CO2 and SO4 from the Special Report on Emissions Scenarios (SRES), the UIUC general circulation model (GCM), and a country-specific impact model (GIM) to calculate the impacts of sulfate aerosols. By 2100, lower SO2 emissions slightly increase warming in the temperate and polar regions causing small damages in the former and small benefits in the latter. If SO2 emissions are also lower in tropical regions, temperatures will rise causing small damages there as well. However, if SO2 emissions rise in tropical regions, temperatures will fall leading to small benefits.

Larry Williams

Papers

The distributional impact of climate change on rich and poor countries

Comparing impacts across climate models

Comparing Forecasts of the Global Impacts of Climate Change

Evaluating GCM output with impact models

The climate impacts of sulfate aerosols