Natural Hazards Observer
March 2007
- Looting after a Disaster: A Myth or Reality
- IPCC: The Earth's Getting Warmer — and It's Our Fault
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IPCC: The Earth’s Getting Warmer
– and It’s Our Fault
Stronger Hurricanes, More Intense Precipitation, Severe Drought Cited as Potential Consequences
Editors’ note: We encourage those interested to read the online summary of this report, available at www.ipcc.ch. The original report is, of course, much more detailed and sophisticated than the articles that appear in the mainstream media. The media summaries not only focus on selected details, but also often give a false impression of the contents; in some cases they are simply incorrect. The IPCC summary report is only 11 pages long, with another nine pages of tables, graphs, and other illustrations. It is well worth reading.
Global warming is “unequivocal [and] evident from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice, and rising global mean sea level.” Moreover, “most of the observed increase in globally averaged temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations.” These and other compelling conclusions are offered by the Intergovernmental Panel on Climate Change (IPCC) in a much-heralded report released February 2—Climate Change 2007: The Physical Science Basis—Summary for Policymakers. “Very likely,” in IPCC speak, means that the panel considers its conclusion to be 90% certain.
The Summary for Policymakers is only a brief synopsis of the first of four parts of a much larger report from the IPPC on global climate change, the fourth such report by the panel since 1988. In the third, published in 2001, the IPCC said that it was only “likely” that humans were responsible, “likely” meaning 66% certain. The latest report states, “The atmospheric concentration of carbon dioxide in 2005 exceeds by far the natural range over the last 650,000 years. The primary source of [this increase] since the pre-industrial period results from fossil fuel use.” Moreover, the report concludes that the increase in temperature so far is “unprecedented in more than 10,000 years,” and global temperatures are likely to rise about 0.2°C in each of the next two decades. Additionally, “Continued greenhouse gas emissions at or above current rates would cause further warming and induce many changes in the global climate system during the 21st century that would very likely be larger than those observed during the 20th century.” At the same time the report suggests that ocean levels could rise as much as two feet in the next century, but the authors are quick to acknowledge the uncertainty of that estimate, because the interactions of the many processes leading to higher sea levels are not well understood.
As a result of the report’s nearly unequivocal conclusion that human activity is heating the planet, IPCC leaders and others around the world have called for governments, businesses, and individuals to take immediate action to combat climate change.
The report states, “At continental, regional, and ocean basin scales, numerous long-term changes in climate have been observed. These include changes in Arctic temperatures and ice, widespread changes in precipitation amounts, ocean salinity, wind patterns and aspects of extreme weather including droughts, heavy precipitation, heat waves, and the intensity of tropical
cyclones.”
Thus, compounding the problems of warming and consequent sea-level rise, the panel notes that global warming could induce future water shortages, intensify heat waves, and increase the magnitude of hurricanes and related storm surge in some parts of the world, as well as increase and alter the distribution of heavy precipitation and other climate-related hazards. Consequently, both floods and droughts could increase.
In one of its more controversial statements, the panel notes, “There is observational evidence for an increase of intense tropical cyclone activity in the North Atlantic since about 1970, correlated with increases in tropical sea surface temperatures. [However,] there is no clear trend in the annual numbers of tropical cyclones.” The report also suggests that the locations of hurricanes will probably move “poleward, with consequent changes in wind [and] precipitation.”
The report drew from thousands of pieces of research and an array of climate models that employ scenarios that vary greatly in their assumptions about human population growth, adaptation, and change.
The Summary for Policymakers presents the work of only one of three IPCC working groups. This first working group was charged with assessing physical science analyses of the climate system and climate change. The findings of the second group, which is assessing the vulnerability of socioeconomic and natural systems to climate change, consequences, and adaptation options, are due in April. The report of the third group, assessing options for limiting greenhouse gas emissions and otherwise mitigating climate change, will be published in May.
A “Synthesis Report” integrating the findings of all three working groups will be published later this year. The complete study draws on research by more than 2,500 climate scientists, involves more than 800 contributing authors from over 130 countries, and will have taken six years to complete.
The Summary for Policymakers, as well as the complete report of the IPCC working group on the scientific aspects of climate change, is now available online at http://www.ipcc.ch/SPM2feb07.pdf. Additional information is available from the IPCC Web site: www.ipcc.ch.