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July 17, 2008, 12:50 pm — Updated: 12:05 pm --> Ice Update and Unfiltered U.S. Climate Report

By Andrew C. Revkin
Sea ice around the North Pole is still seeing a shrinking trend. (Credit: Andrew C. Revkin/The New York Times)

Arctic Ocean Ice
The latest summary of experts’ projections for this summer’s retreat of sea ice on the Arctic Ocean is out, and — partly because of different weather patterns than last year — the consensus for the moment is that the remarkable ice loss in 2007 will not be matched this year. But all of the 15 teams offering projections say ice extent will remain well below the average for the last quarter century and a downward trend in summer ice around the North Pole has not abated. As I’ve discussed before, the sea ice around Antarctica in winter has been expanding of late (there’s virtually none in the austral summer). The Antarctic sea-ice changes are consistent with expectations in a warming world, some experts say.) When both polar ocean ice sheaths are tracked together, this year is back below the quarter-century sea-ice average again.

United States Climate Impacts

The Bush administration’s Climate Change Science Program has issued the detailed draft of its report on impacts of human-caused climate change and is now seeking public comments before the final version is produced later in the year. The straightforward descriptions stand in stark contrast to those in government reports on climate science earlier in President Bush’s tenure, when Phil Cooney, the former head of the oil industry’s “climate team,” was the White House editor of such documents. At the time, the passage, “Warming will also cause reductions in mountain glaciers,” was excised along with other passages described as “speculative findings/musings.” Mr. Cooney moved on to Exxon Mobil.

Compare that editing to the language below. The full draft document is available as a set of pdf files at climatescience.gov.

Global Climate Change Impacts in the United States

Once considered a problem mainly for the future, climate change is now upon us. People are at the heart of this problem: we are causing it, and we are being affected by it. The rapid onset of many aspects of climate change highlights the urgency of confronting this challenge without further delay. The choices that we make now will influence current and future emissions of heat-trapping gases, and can help to reduce future warming. Likewise, our decisions on whether and how to adapt to the degree of warming that is already inevitable can help us reduce the impacts of future warming.

1. Human-induced climate change and its impacts are apparent now throughout the United States. Global warming is unequivocal and is due primarily to human-induced emissions of heat-trapping gases and other pollutants. [This actually is technically an error, if their baseline is the Intergovernmental Panel on Climate Change reports from last year. They assert that humans are the dominant warming influence since 1950 with greater than 90 percent confidence, which is different than the certainty here. (UPDATE 7/18: Susan Hassol helpfully pointed out that the IPCC's "very likely" confidence level is "greater than 90 percent.")] Observed changes in the United States include temperature increases, sea-level rise, increased heavy downpours, rapidly retreating glaciers, regional droughts, substantial changes in sensitive wildlife, earlier snowmelt, and altered timing and amount of river flows. Impacts of these changes are apparent in many facets of society including health, water, food, energy, and quality of life.

2. Many climatic changes are occurring faster than projected even a few years ago. Global emissions of heat-trapping gases are now increasing even more rapidly than the highest emissions scenario scientists have been analyzing. Arctic sea ice and the large ice sheets on Greenland and parts of Antarctica are melting faster than expected.

3. The degree to which future climate will change, and the scope and magnitude of the impacts, depend on choices made now. Another 1°F of warming in the next few decades (on top of the observed 1.5°F rise) is already locked in due to past emissions. The amount of warming we will experience beyond the next few decades depends upon choices about emissions made now and in the near future. Lower emissions of heat-trapping gases will result in less climate change and related impacts.

4. Extreme weather and climate are having increasing impacts on society. The United States has experienced increases in heat waves, wildfires, heavy downpours, and in some regions, droughts, all of which are disrupting our lives. Extreme events affect every aspect of society and nature including human health, energy, transportation, agriculture, ecosystems, and water resources. Atlantic hurricane intensity has increased in recent decades and additional future increases are projected. [There is still significant uncertainty and scientific debate about hurricanes in a warming world.]

5. Sea-level rise and storm surges place many U.S. coastal regions at increasing risk. The low-lying East Coast and Gulf Coast of the United States are vulnerable to combined effects of sea-level rise, storm surges, and hurricanes. Alaska’s coast is vulnerable to the effects of sea-ice retreat, thawing of coastal permafrost, and rising sea level, all of which are caused by warming, and combine to increase coastal erosion. Sea-level rise threatens the long-term viability of island communities by exacerbating the impacts of coastal storms, flooding infrastructure and ecosystems, and contaminating freshwater supplies with seawater.

6. Assuring an adequate and clean water supply will be an increasing challenge in many parts of the United States. Most of the West’s surface water comes from snowpack, which is declining as more precipitation falls as rain and snowpack melts earlier, leaving less water available for summer when it is needed most. Growing populations and changing precipitation patterns will increase competition among urban, industrial, agricultural, and natural ecosystem water needs in regions where overall water supply declines.

7. Interactions among climate-related and other stresses will present complex challenges to society.
Simultaneous and back-to-back extreme weather events can amplify impacts, challenging our response capabilities. Climate change can combine with other stresses including pollution, invasive species, and the overuse of resources to create impacts larger than any of these alone. Trade-offs will be necessary. For example, increasing water scarcity in some regions will force hard choices about the allocation of water for growing food, producing electricity, providing for urban uses, and protecting ecosystems.

8. Our vulnerability to climate change has been increased by some of our decisions. Population and development patterns have put more people in places that are vulnerable to climate change impacts. U.S. population has grown rapidly in cities on the Atlantic and Gulf coasts, which are vulnerable to extreme heat, sea-level rise, hurricanes, and storm surge. There has been very rapid population growth in arid western states where water is projected to become increasingly scarce in a warming world.

9. Historical climate and weather patterns are no longer an adequate guide to the future. Planning for providing water, energy, transportation, and other services has assumed the future would be like the past; this is no longer justifiable. Long-lived infrastructure, from power plants to roads and buildings, must be designed and built taking climate change into account. Long term planning will have to continually incorporate the latest information, as climate will be ever changing, requiring adaptation strategies to constantly evolve.

10. Responses to climate change entail reducing emissions to limit future warming and adapting to the changes that are unavoidable. Large cuts in emissions would be required to limit warming to the low end of the range of scenarios, making successful adaptation more likely. There are limits to adaptation. For example, the financial and technical challenges of defending coasts against sea-level rise under high emissions scenarios would probably result in the inundation and abandonment of many areas. Applying the best scientific information can help avoid unintended consequences of our responses to climate change.
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