Reducing Risks from Climate Change: No More Time for Delay

Confronting Climate Change: Avoiding the Unmanageable and Managing the Unavoidable outlines a roadmap for preventing climate changes by using technology to seize opportunities around the globe to reduce emissions and provide other economic, environmental and social benefits, including meeting the United Nations' Millennium Development Goals.

Among the many suggestions, it calls for policy makers to improve efficiency in the transportation sector through vehicle efficiency standards, fuel taxes and registration fees/rebates; expand the use of biofuels through energy portfolio standards and incentives to growers and consumers; and ultimately improving preparedness/response strategies and management of natural resources to cope with future climatic conditions using new energy technologies and sustainable development. The opening of the Executive Summary follows:

Scientific Expert Group Report on Climate Change and Sustainable Development.

Global climate change, driven largely by the combustion of fossil fuels and by deforestation, is a growing threat to human well-being in developing and industrialized nations alike. Significant harm from climate change is already occurring, and further damages are a certainty. The challenge now is to keep climate change from becoming a catastrophe. There is still a good chance of succeeding in this, and of doing so by means that create economic opportunities that are greater than the costs and that advance rather than impede other societal goals. But seizing this chance requires an immediate and major acceleration of efforts on two fronts: mitigation measures (such as reductions in emissions of greenhouse gases and black soot) to prevent the degree of climate change from becoming unmanageable; and adaptation measures (such as building dikes and adjusting agricultural practices) to reduce the harm from climate change that proves unavoidable.

Avoiding the Unmanageable

Human activities have changed the climate of the Earth, with significant impacts on ecosystems and human society, and the pace of change is increasing. The global-average surface temperature is now about 0.8 degrees C above its level in 1750, with most of the increase having occurred in the 20th century and the most rapid rise occurring since 1970. Temperature changes over the continents have been greater than the global average and the changes over the continents at high latitudes have been greater still.

The pattern of the observed changes matches closely what climate science predicts from the buildup in the atmospheric concentrations of carbon dioxide (CO2), methane (CH4), and other greenhouse gases (GHGs), taking into account other known influences on the temperature. The largest of all of the human and natural influences on climate over the past 250 years has been the increase in the atmospheric CO2 concentration resulting from deforestation and fossil-fuel burning. The CO2 emissions in recent decades, which have been responsible for the largest part of this buildup, have come 75% to 85% from fossil fuels (largely in the industrialized countries) and 15% to 25% from deforestation and other land-cover change (largely from developing countries in the tropics).

The seemingly modest changes in average temperature experienced over the 20th century have been accompanied by significant increases in the incidence of floods, droughts, heat waves, and wildfires, particularly since 1970. It now appears that the intensity of tropical storms has been increasing as well. There have also been large reductions in the extent of summer sea ice in the Arctic, large increases in summer melting on the Greenland Ice Sheet, signs of instability in the West Antarctic Ice Sheet, and movement in the geographic and altitudinal ranges of large numbers of plant and animal species.

Even if human emissions could be instantaneously stopped, the world would not escape further climatic change. The slow equilibration of the oceans with changes in atmospheric composition means that a further 0.4degreesC to 0.5degreesC rise in global-average surface temperature will take place as a result of the current atmospheric concentrations of greenhouse gases and particles.

If CO2 emissions and concentrations grow according to mid-range projections, moreover, the global average surface temperature is expected to rise by 0.2degreesC to 0.4degreesC per decade throughout the 21st century and would continue to rise thereafter. The cumulative warming by 2100 would be approximately 3degreesC to 5degreesC over preindustrial conditions. Accumulating scientific evidence suggests that changes in the average temperature of this magnitude are likely to be associated with large and perhaps abrupt changes in climatic patterns that, far more than average temperature alone, will adversely impact agriculture, forestry, fisheries, the availability of fresh water, the geography of disease, the livability of human settlements, and more. Even over the next decade, the growing impacts of climate change will make it difficult to meet the UN's Millennium Development Goals (MDGs).