Human-induced global warming is proceeding more rapidly than expected, and there are many reasons to suggest that future climate change will exceed today's mainstream projections. Failing to reduce emissions is increasingly likely to lead to sudden and disruptive changes that would have devastating, even catastrophic, consequences for the environment and future generations. The awarding of the 2007 Nobel Peace Prize jointly to the Intergovernmental Panel on Climate Change (IPCC) and former Vice-President Al Gore, which I attended at his invitation, greatly enhanced international recognition of the need and desire for acting. We can still avoid the worst outcomes, but the window of opportunity is rapidly closing.
Each of the last four major climate change assessments by the Intergovernmental Panel on Climate Change (IPCC) has concluded that global warming was occurring more rapidly than the preceding one. Whereas the warming that had occurred up to 1990 was “broadly consistent” with scientific understanding, the greater warming up through 2006 is now “unequivocal” and “very likely [greater than 90% probability] due to the observed increase in anthropogenic greenhouse gas concentrations.” Indeed, there are no longer any viable alternative explanations.
In addition to the intensified warming, the sequence of assessments has found that the pace of the impacts of climate change is accelerating. Snow cover and mountain glaciers are melting, Arctic sea ice is retreating, the Greenland and Antarctic ice sheets are deteriorating, and the ranges of plant and animal species are shifting poleward—all more rapidly than previously anticipated. Shifts in weather are occurring (e.g., tornadoes in January in Wisconsin), precipitation is becoming more intense, and amplified drying is causing more extensive fires across the western U.S.
That human-induced climate change is occurring has been recognized unanimously by the IPCC, whose members are the 150-plus nations of the world that sponsor periodic preparation of very extensively reviewed scientific assessments. While the unanimous agreement over two decades is impressive, the process of seeking such a strong consensus necessarily means that the IPCC findings are not at the cutting edge of scientific research.
At the 20th anniversary symposium of the Climate Institute in September 2006, the papers from which have just been published by Earthscan, Australian scientist A. Barrie Pittock identified 10 reasons that the mainstream results cited by the IPCC could be leading to underestimating the amount and seriousness of climate change that lies ahead. Recent findings indeed suggest the pace of warming is increasing: greenhouse gas emissions are following IPCC's highest emissions scenario as China and India build more coal-fired electric power plants; the uptake of carbon dioxide by the oceans is slowing; permafrost is thawing, increasing the release of methane, which exerts its own very potent warming influence; global and especially Arctic temperatures are rising; and hurricanes are intensifying.
Participating experts also described how the cryosphere is changing. The Greenland and Antarctic ice sheets are already deteriorating at unexpected rates. Arctic summertime sea ice is retreating much more rapidly than current projections, leading to changes in fall weather patterns and concern that especially disruptive seasonal changes lie ahead. Cryospheric changes and ocean warming are contributing to sea level rise, the recent pace of which is twice that for the 20th century. Sea level rise and more intense storms increasingly endanger coastlines around the world, from the disappearing marshlands protecting New Orleans to estuaries such as Chesapeake Bay and urban areas like New York City, for which plans for protective barriers are now being investigated. Ecosystems are also changing, especially in high latitudes, where the warming weather has led to pest outbreaks, massive tree deaths, and forest fires, and where the retreating sea ice is stressing polar bear populations.
Despite the slow pace of international negotiations agreed to in December in Bali and the limited steps nations are taking toward sharply cutting back emissions, experts at the Climate Institute's symposium offered some reasons for hope. There are many opportunities for improving energy efficiency, and cogeneration (i.e., using existing waste heat) can greatly increase the effective efficiency of coal-fired power plants. To promote significant action, an increasing number of business leaders are calling for strong government policies that will incentivize change, religious leaders are urging their members to respond because of issues of equity and stewardship, and student groups are mobilizing to demand action that recognizes intergenerational responsibilities. In addition to speaking out, each group is also taking action to limit their emissions.
As John Ashton, UK's ambassador at large for climate change indicated at the symposium, “[c]limate change is not primarily an environmental issue; it is a security issue.” He then added, “fixing this problem will not cost us the Earth, whereas not fixing it will certainly cost us the Earth.” Iceland and many island nations with a special concern about sea level rise are starting to show what is possible—the rest of us need to move to join them ion order to reduce the rapidly increasing risk of sudden and very disruptive change.
Michael MacCracken is Chief Scientist for Climate Change Programs with the Climate Institute in Washington DC and co-editor of Sudden and Disruptive Climate Change: Exploring the Real Risks and How We Can Avoid Them, published by Earthscan.