IPCC working group releases findings on climate change impacts, adaptation, vulnerability
In 2001, the Intergovernmental Panel on Climate Change (IPCC) issued its Third Assessment Report (TAR), attributing the buildup of greenhouse gases in the atmosphere primarily to human activities and concluding that these greenhouse gases are causing global climate change.
On April 6, in Brussels, Belgium, the IPCC's Working Group II formally released a Summary for Policymakers of its report on Impacts, Adaptation, and Vulnerability. The report is the second of four documents that together will make up the IPCC's Fourth Assessment Report (three Working Group reports plus a synthesis report). The Working Group I report on the physical science basis for climate change was issued early this year (EcoWeek February 5). It reinforced the TAR conclusions, saying with near certainty that human activities are the cause of most of the observed global warming over the past fifty years, and projecting further waarming over the next century.
Building on the TAR, Impacts, Adaptation, and Vulnerability conveys a broader and higher level of certainty regarding the impacts of climate change, based on new information derived from more studies and improved data contained in them. It provides the most comprehensive analysis to date concerning the earth's vulnerability to climate change, outlining the current and projected future impacts, and discusses the extent to which adaptation and mitigation can reduce these impacts. The report includes chapters on specific systems, sectors and regions, examining consequences for the environment and nature, for agriculture, forestry and fisheries, health and disaster prevention.
The Working Group II Assessment concludes, with high or very high confidence (defined as an eight or nine out of ten chance of being correct) that:
1. snow, ice and frozen ground (including permafrost), are undergoing changes, as evidenced by:
* enlargement and increased numbers of glacial lakes;
* increasing ground instability in permafrost regions, and rock avalanches in mountain regions; and
* changes in some Arctic and Antarctic ecosystems.
2. certain types of hydrological systems are being affected around the world, as indicated by:
* increased run-off and earlier spring peak discharge in many glacier- and snow-fed rivers; and
* warming of lakes and rivers in many regions, with effects on thermal structure and water quality.
3. recent warming is strongly affecting terrestrial biological systems, including such changes as:
* earlier timing of spring events, such as leaf-unfolding, bird migration and egg-laying; and
* poleward and upward shifts in ranges in plant and animal species.
In addition, says the report, the uptake by oceans of carbon from human activities since 1750 has made these water bodies slightly more acidic, although the effects of observed ocean acidification on the marine biosphere are as yet undocumented.
The Assessment provides new, more specific information on the nature of future impacts across a wide range of systems and sectors. While some conclusions build on the TAR findings, many others are new to this report. With regard to freshwater resources and their management, for example, it is forecast that by mid-century, annual average river runoff and water availability will increase by 10-40% at high latitudes and in some wet tropical areas, and decrease by 10-30% over some dry regions at mid-latitudes and in the dry tropics, some of which are already water-stressed areas.
In the course of the century, water supplies stored in glaciers and snow cover are projected to decline, reducing water availability in regions supplied by meltwater from major mountain ranges, where more than one-sixth of the world population currently lives. As well, drought-affected areas will likely increase in extent, while heavy precipitation events will very likely increase in frequency, augmenting flood risk.
Forecast ecosystem impacts include major changes in major changes in ecosystem structure and function associated with increases of more than 1.5-2.5*C in global average temperature and concomitant carbon dioxide concentrations. Temperature increases beyond this level will also likely put approximately 20-30% of plant and animal species assessed so far at increased risk of extinction. Over the course of this century net carbon uptake by terrestrial ecosystems is likely to peak before midcentury and then weaken or even reverse, thus amplifying climate change, the report adds.
Costs and benefits of climate change for industry, settlement, and society will vary widely by location and scale. Overall, however, the net effects will tend to be more negative the larger the change in climate. Where extreme weather events become more intense and/or more frequent, the economic and social costs of those events will increase, and these increases will be substantial in the areas most directly affected.
The report offers more specific region-based information concerning the nature of future impacts, addressing some locations not covered in previous assessments. These address Africa, Asia, Australia and New Zealand, Europe, Latin America, and small island systems in various areas of the world, as well as North America and the polar regions.
In North America, moderate climate change in the early decades of the century is projected to increase aggregate yields of rainfed agriculture by 5-20%, but with important variability among regions. Major challenges are projected for crops that are near the warm end of their suitable range or depend on highly utilized water resources. This confirms previous findings.
New projections indicate that disturbances from pests, diseases, and fire will have increasing impacts on forests, with an extended period of high fire risk and large increases in area burned. In addition, coastal communities and habitats will be increasingly stressed by climate change impacts interacting with development and pollution. Population growth and the rising value of infrastructure in coastal areas increase vulnerability to climate variability and future climate change, with losses projected to increase if the intensity of tropical storms increases. Current adaptation is uneven and readiness for increased exposure is low.
The report further reaffirms projected impacts on polar regions, such as reductions in thickness and extent of glaciers and ice sheets, and changes in natural ecosystems with detrimental effects on many organisms including migratory birds, mammals and higher predators.
Arctic human communities are already adapting to climate change, but both external and internal stressors challenge their adaptive capacities. Despite the resilience shown historically by Arctic indigenous communities, some traditional ways of life are being threatened and substantial investments are needed to adapt or relocate physical structures and communities.
In assessing overall current knowledge about responding to climate change, the report finds that some adaptation is occurring now, to observed and projected future climate change, but on a limited basis. Adaptation will be necessary to address impacts resulting from the warming which is already unavoidable due to past emissions.
A wide array of adaptation options is available, but more extensive adaptation than is currently occurring is required to reduce vulnerability to future climate change. There are barriers, limits and costs, but these are not fully understood.
Moreover, adaptation alone is not expected to cope with all the projected effects of climate change, and especially not over the long run as most impacts increase in magnitude.
Sustainable development can reduce vulnerability to climate change by enhancing adaptive capacity and
increasing resilience, says the report. At present, however, few plans for promoting sustainability have explicitly included either adapting to climate change impacts, or promoting adaptive capacity.
Conversely, climate change could slow the pace of nations' progress toward sustainable development either directly through increased exposure to adverse impact or indirectly through erosion of the capacity to adapt.
The Assessment adds that many impacts can be avoided, reduced or delayed by mitigation. A portfolio of adaptation and mitigation measures can diminish the risks associated with climate change. Such portfolios could combine policies with incentive-based approaches, and actions at all levels from the individual citizen through to national governments and international organizations.
But even the most stringent mitigation efforts cannot avoid further impacts of climate change in the next few decades, which makes adaptation essential, particularly in addressing near-term impacts. One way of increasing adaptive capacity is by introducing consideration of climate change impacts in development planning, for example, by:
* including adaptation measures in land-use planning and infrastructure design; and
* including measures to reduce vulnerability in existing disaster risk reduction strategies.
The Impacts, Adaptation, and Vulnerability report Summary for Policymakers may be viewed on the IPCC Web site, www,ipcc,ch.