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Impacts of a Warming Arctic: Arctic Climate Impact Assessment
Arctic Council
(November 2004)

The Arctic is warming almost twice as fast as the rest of the world, with significant impacts apparent now, according to a major new four-year study conducted by an international team of 300 scientists. The Arctic Climate Impact Assessment found that in Alaska, western Canada and eastern Russia average winter temperatures have increased as much as 4 degrees to 7 degrees Fahrenheit in the past 50 years. Inuit elders are reporting that hunting has become more difficult and dangerous due to less reliable sea-ice conditions. Even the most conservative estimates project that Arctic sea ice during the summer will decline by 50 percent by the end of this century, with some models showing near-complete disappearance of summer sea ice. This is very likely to have devastating consequences for polar bears and some species of seals, as well as for local people for whom these animals are a primary food source. Changes being observed in the Arctic now are a bellwether for the rest of the world and have global implications: More sunlight is absorbed by open water and bare ground than by shiny sea ice and snow, and melting glaciers will accelerate sea-level rise.

Melting Ice Caps
Thomas et al., Science 2004 306: 255-258
(October 8, 2004)
Rignot et al., Geophysical Research Letters, Vol. 31, No. 18, L18401
(September 22, 2004)
Scambos et al., Geophysical Research Letters, Vol. 31, No. 18, L18402
(September 22, 2004)

Reports from Earth's poles paint a disturbing picture of global warming and indicate that vast ice sheets in Greenland and Antarctic are vulnerable to collapse. The latest satellite images produced by NASA's Josefino Comiso show that perennial Arctic sea ice has declined by more than 20 percent since 1979. The minimum ice extent seen on September 11, 2004 was similar to the minimum seen in 2003 and only slightly larger than the record low ice extent seen in 2002. At the other pole, NASA and University of Colorado researches found that the break up of the Larsen B ice shelf in 2002 led to a significant acceleration of West Antarctic glaciers flowing into the Weddell Sea. On the other side of West Antarctica researchers also found that glaciers flowing into the Amundsen Sea have sped up considerably during the last decade. Together these findings show that the melting of West Antarctic glaciers is accelerating sea level rise and increase concern that the West Antarctic ice sheet could collapse, raising sea levels by as much as 20 feet over a few centuries.

Impact of Global Warming on Hurricane Intensity
Knutson and Tuleya, Journal of Climate Vol. 17, No. 18
(September 15, 2004)

As Floridians continue to dig out after being struck by a record four hurricanes in one year, many people are wondering whether global warming is playing a role. Scientists know that warm sea surface temperatures provide the energy source for tropical storms, but many other factors influence whether hurricanes form and which way they go. While scientists disagree about what role, if any, global warming played in 2004's extraordinary hurricane season, a new study by researchers at NOAA's Princeton laboratory shows clearly that global warming will increase the intensity of hurricanes over time. Using a version of NOAA's hurricane prediction model, the scientists created 648 virtual hurricanes under current climate conditions and an equal number under climate conditions projected for 2080 by nine different global climate models. Comparing the results, they found that global warming would increase hurricane intensity (measured as central pressure drop) by 8 to 16 percent, with rainfall increasing by 12 to 26 percent within 60 miles of the storm center. These increases correspond to about one-half of a category on the five-step Saphir-Simpson scale. This means that if the frequency of tropical cyclones remains the same, global warming would result in a significant increase in the most destructive Category 5 storms. Meanwhile, sea level rise due to global warming will push shorelines inland by 400 feet or more in low-lying areas, making storm surges even more damaging.

  • For more information: full study (Adobe Acrobat file)

Emissions Pathways, Climate Change, and Impacts on California
Hayhoe et al., Proceedings of the National Academy of Sciences
(August 2004)

Unmitigated global warming would have severe consequences for the Golden State according to a comprehensive study published in the Proceedings of the National Academy of Sciences. If emissions of heat-trapping pollution follow a fossil-fuel intensive pathway, by the end of this century Los Angeles would see 600 to 1,000 additional heat-related deaths per year, the Sierra Nevada snowpack would decline by 70 percent to 90 percent, and excessive temperatures and summer water shortages would harm California's $30 billion agricultural industry. This is bad news not just for Californians, but also for everyone who enjoys the fruit of their vines; the quality of California wine grapes would be degraded by excessive temperatures during ripening. The good news, according to the study, is that the most severe consequences of global warming can be avoided by acting now to limit emissions of heat-trapping gases.

Stabilization Wedges: Solving the Climate Problem for the Next 50 Years with Current Technologies
S. Pacala and R. Socolow, Science 2004 305: 968-972
(August 13, 2004)

The good news about global warming is that we know how to stop it. A recent analysis by Princeton University scientists shows that by deploying already available technologies it is possible to prevent a doubling of carbon dioxide in the atmosphere during the next 50 years and avoid the most dangerous threats from global warming. The Princeton team breaks the problem down by noting that global carbon dioxide emissions need to capped at roughly current levels through the middle of the century and then steadily reduced to stabilize CO2 concentrations at 500 parts per million (the current concentration is 370 parts per million). New technologies may be needed to achieve the reductions have 2050, according to the authors, but for the next 50 years available technologies can be deployed more widely to offset the growth in emissions that would otherwise be expected. No one approach can solve the problem by itself, but a portfolio of emission reduction "wedges" from measures such as hybrid cars, wind power, geological carbon dioxide storage, and reforestation add up to a feasible pathway to carbon dioxide stabilization.

Dissolving Corals
Feely et al., Science 2004 305: 362-366
(July 16, 2004)

Coral reefs are in serious jeopardy due to carbon dioxide emissions and global warming. Severe bleaching has been observed in reefs throughout the tropics due to excessively warm ocean temperatures and other environmental stresses. In addition, new research shows that carbon dioxide is a direct threat to corals because ocean water becomes more acidic (lower pH) as it absorbs some of the CO2 emitted by power plants, automobiles and other sources. At high enough concentrations carbonic acid (CO2 dissolved in water) dissolves calcium carbonate, the basic building block of coral reefs, but CO2 concentrations are not expected to get that high during this century. Nonetheless, researchers have found that the rate at which ocean organisms, including corals, can build calcium carbonate structures decreases with rising CO2 concentrations well before this point is reached. With corals already suffering from rising temperatures, the additional stress of falling pH could push them over the edge.

Heat Advisory: How Global Warming Causes More Bad Air Days
Patz, et al.
(July 2004)

A new analysis by some of the nation's top medical experts projects that hotter temperatures caused by global warming will speed formation of the lung-damaging pollution commonly known as smog, significantly reducing the number healthy air days enjoyed by residents in more than a dozen U.S. cities in coming summers. That means more people will have to restrict outdoor activities, while those with asthma and other respiratory troubles face increased risk to their health. The deteriorations in air quality examined in the report are due strictly to rising summer temperatures, and do not take into account changing emissions of ozone-forming pollutants from cars and other sources. These emissions are expected to decline significantly over the next several years as air pollution standards set during the 1990s take full effect, but could rebound after that if further controls are not put into place. By mid-century, if global warming is not curtailed and ozone precursor emissions are the same as they were in the mid-1990s, people living in 15 cities in the eastern United States would see, on average, a 60 percent increase in the number of days when ozone levels exceed the health-based air quality standard set by the EPA (using an eight-hour measurement) and a doubling of "red alert" air quality days from two per summer today to four per summer. Correspondingly, residents would see a 20 percent drop in the number of summer days with "good" air from an average of 50 days per summer to 40 days per summer.

Satellite Data Confirms Climate Change
Nature 2004 429:7
(May 2004)

Scientists at the University of Washington and the Air Resources Laboratory of the National Oceanic and Atmospheric Administration found that satellite measurements of lower atmospheric temperatures show as much global warming as surface temperature measurements when the data are analyzed correctly. The team made the discovery using a new technique for separating the signals originating from the lower and upper atmosphere. Previous efforts to measure temperature trends using satellites suggested that the lower atmosphere is warming more slowly than the earth's surface and have been repeatedly cited by global warming skeptics. The new study found that the upper atmosphere is cooling apparently due to increased heat trapping in the lower atmosphere and stratospheric ozone depletion.

Inside the Greenhouse: The Impacts of CO2 and Climate Change on Public Health in the Inner City
Harvard Medical School
(April 2004)

A new report from the Center for Health and the Global Environment at Harvard Medical School shows that residents of the inner city are particularly vulnerable to the effects of climate change and global warming. The most direct threat is from heat waves. Exposure to excessive heat caused over 8,000 deaths in the United States between 1979 and 1999, and the incidence of heat waves is expected to double by the middle of this century if heat-trapping pollution is not curtailed. Higher temperatures also elevate the level of ozone smog in urban areas, which contributes to excess mortality and triggers more asthma attacks. In addition, higher concentrations of carbon dioxide, the primary heat-trapping pollutant that causes global warming, has been shown to increase the formation of allergenic pollen, which may increase the incidence of asthma and respiratory allergies.

Climatology: Threatened Loss of the Greenland Ice-Sheet
Nature 2004 428: 616
(April 2004)

Unless heat-trapping emissions are reduced substantially, Greenland is likely to warm by at least 3 degrees Celsius by the year 2100, enough to trigger the complete and irreversible meltdown of the Greenland ice sheet, reported scientists in the April 8 issue of Nature. The Greenland ice sheet is second in size only to Antarctica, and its complete meltdown could raise the global average sea level by 7 meters (23 feet). While the complete collapse of the Greenland ice sheet could take as long as 1,000 years, that process could become inevitable by the end of this century.

Defusing the Global Warming Time Bomb
Scientific American
(March 2004)

In the face of clear evidence that the earth's energy balance has already been altered by pollution, Dr. James Hansen remains optimistic about our ability to prevent dangerous global warming if we act now. The Director of the NASA Goddard Institute for Space Studies wrote in the March issue of Scientific American that global warming can be controlled if we begin earnestly to improve our energy efficiency and increase our use of renewable energy sources. Any delay would be dangerous, Hansen argues, because an additional warming of merely one degree Celsius could be enough to trigger the eventual disintegration of ice sheets in Greenland and parts of Antarctica.

Global Warming: The Imperatives for Action from the Science of Climate Change
Sir David King, Chief Scientific Adviser to the U.K. Government; Address to the AAAS
(February 2004)

Sir David King, the chief scientific adviser to the British Government, sounded a similar note of urgency when he delivered a plenary address at the American Association for the Advancement of Science (AAAS) Annual Meeting in Seattle on Feb 13. The British government has committed to reducing its emissions of heat-trapping gases by 60 percent from 1990 levels by mid-century and is urging other industrialized countries to adopt the same goal. Sir David emphasized that the international community needs to work together immediately, not only to stabilize the level of heat-trapping greenhouse gases, but also to develop alternative technologies in order to move away from our dependence on fossil fuels.

In his article published in the January 9, 2004, issue of Science Sir David brings optimism by pointing out that reducing carbon emissions "does not necessarily make us poorer. Between 1990 and 2000, Great Britain's economy grew by 30 percent, employment increased by 4.8 percent, and our greenhouse gas emissions intensity fell by 30 percent." However, he stressed that delaying action will only make it "more disruptive and more expensive" to deal with global warming.

The Effects of Climate Change on Water Resources in the West
Climatic Change 62 (1-3): 1-11
(January 2004)
As the West Goes Dry
Science 2004 303: 1124-1127
(February 2004)

The American West will have more wintertime floods and summertime droughts if the climate continues to warm, according to scientists reporting in the January issue of the journal Climatic Change. Over the past 50 years, total snow accumulation in some locations in the Cascade Mountains in Oregon and Washington has dropped by 60 percent while spring melt is occurring earlier, with spring runoff in streams throughout California's Sierra Nevada running as much as three weeks earlier than it did in 1948.

Researchers predict that over the next 50 years, precipitation over the Cascades and the Sierra Nevada will fall more as rain than snow in winter, leading to a further decrease in snow accumulation by 30 percent to 40 percent and an increased risk of wintertime floods.

Throughout the West, higher temperatures will decrease snowpack and cause spring runoff to start 30 to 40 days earlier than it does today. A smaller snow reservoir and earlier spring runoff mean that there will be less water to last through the summer. According to an article published in the February 20, 2004, issue of Science, drier summers are predicted to cause farmland values to drop by more than 15 percent in California. Fire danger is also expected to soar, doubling the mean area burned over the next 80 years.

NOAA 2003 Climate Report
National Oceanic and Atmospheric Administration
(January 2004)

The most recent data show that 2003 tied 2002 as the second hottest year on record, following 1998. The five hottest years have all occurred since 1997 and the 10 hottest since 1990. Extreme heat waves caused more than 20,000 deaths in Europe and more than 1500 deaths in India during 2003.

Extinction Risk from Climate Change
Nature 2004 427:145-148
(January 2004)

This study, the first comprehensive assessment of the extinction risk from global warming, found that more than 1 million species could be committed to extinction by 2050 if global warming pollution is not curtailed. This ranks global warming alongside direct habitat destruction as the greatest threats to global biodiversity. The 19-member research team featured expertise on ecosystems in five diverse regions: Mexico's Chihuahuan Desert; Amazonia; Europe; South Africa's Cape Floristic Region; and Queensland, Australia. The scientists used information on the climate tolerances of species and the well-known relationship between species diversity and habitat area to project the effects of global warming under various assumptions. Their mid-range estimates indicated that 24 percent of existing species would eventually become extinct due to climate change projected to occur by 2050. Fortunately this risk could be significantly reduced by acting soon to reduce emissions of carbon dioxide and other heat-trapping gases, according to the study.

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