•Congress. After winning a majority in the House and Senate in November's election, Democrats have climate-change bills in the works. House Speaker Nancy Pelosi, D-Calif., is creating a special committee on climate change. Next week, the House Science and Technology Committee will discuss the IPCC report.
•States. More than 12 states are taking steps to reduce greenhouse gases. California Gov. Arnold Schwarzenegger this month ordered the world's first low-carbon limits on passenger-car fuels in the most populous state. The new standard would reduce the carbon content of transportation fuels at least 10% by the year 2020.
•Cities. More than 375 mayors who have signed pledges since 2005 to cut greenhouse-gas emissions in their communities launched a drive last week for major climate legislation in Congress this year. They represent 56 million people in all 50 states. The day after the State of the Union address, the U.S. Conference of Mayors announced global warming is No. 1 on its top-10 list of priorities.
•Industry. Ten major companies, including industrial giants General Electric, Alcoa and DuPont, joined four environmental and climate groups last week to demand swift passage of federal legislation to cut emissions that worsen warming. Their U.S. Climate Action Partnership says further delay only "increases the risk of unavoidable consequences … at potentially greater economic cost and social disruption."
In their own studies, Tebaldi and her colleagues at NCAR found broad agreement in climate projections for North America by 2100, including a rise in average temperatures from 3 to 9 degrees.
That could lead to more frequent heat waves and more warm nights when daytime temperatures linger longer after sundown, especially in the South and West, Tebaldi's group concluded. NCAR also says increasing rain would soak northern states but bypass the already dry Southwest, where drought would be more common except when torrential rains bring flash floods.
The IPCC report is likely to reflect climate uncertainties and disagreements, too. Scientists have strongly debated the last two years, without resolution, whether global warming intensifies hurricanes.
Rising sea levels are a huge concern for the USA because more than half the population lives within 50 miles of the coastlines, according to the National Oceanic and Atmospheric Administration. The 2001 report contained a wide estimate of the rise this century — from 3.5 inches to 34. MacCracken says that projection has fallen to about 20 inches or less.
Such a drop in the top estimate alarms glacier experts such as John Turner of the British Antarctic Survey, who was quoted in the United Kingdom's Guardian newspaper as saying the low projection is "misleading." He says the low number accounts only for the heat-related rise of sea level and slow trickles from ebbing glaciers, and it ignores potential ice-sheet collapses in Antarctica or Greenland.
"Greenland is just a relic of the last Ice Age, after all, just jutting out into the Atlantic, frozen at latitudes further south than anything else," MacCracken says. "What might happen when it gets warmer?"
Are reports too cautious?
MacCracken contends past IPCC reports have been too conservative, partly by design, in warning about the dangers of climate change, especially sea level rise.
"Scientists don't like to be wrong, so they tend to discount the most uncertain things," MacCracken says. "And that's good, but policymakers and risk managers usually want to know the worst case, as well as the middle one, when they plan for things."
Every IPCC report has been controversial. When the 1995 report's economic analysis estimated that the worth of a human life in a developing nation is less than in developed ones, it triggered protests and sit-ins.
In 2005, federal hurricane researcher Chris Landsea resigned from the IPCC, suggesting its hurricane warnings were too overblown and "politicized."
Climate scientist Roger Pielke Sr. of the University of Colorado at Boulder has suggested that development and deforestation, rather than the burning of fossil fuels, are the main drivers behind global warming. He says on his climate-science website that the IPCC should recognize the importance of these other factors.
In contrast, Australian scientist Tim Flannery has complained in his 2005 book The Weather Makers: How Man is Changing the Climate and What it Means for Life on Earth that IPCC estimates downplay the impact of warming.
In Paris this week, the process of negotiating and revising the short summary is painstaking and "line by line," says Kevin Trenberth, one of the lead authors and climate analysis chief at the National Center for Atmospheric Research. More than 100 of the panel's 193 member nations are taking part in the negotiations on the summary, he says.
"They'll do a lot of rewriting. It's all going to change to cover the concerns of each nation," whether it's monsoons in India or polar bears in Canada, says MacCracken, who helped lead the USA's involvement in the IPCC in 1995 and 2001. The summary also must be translated in six official U.N. languages.
•States. More than 12 states are taking steps to reduce greenhouse gases. California Gov. Arnold Schwarzenegger this month ordered the world's first low-carbon limits on passenger-car fuels in the most populous state. The new standard would reduce the carbon content of transportation fuels at least 10% by the year 2020.
•Cities. More than 375 mayors who have signed pledges since 2005 to cut greenhouse-gas emissions in their communities launched a drive last week for major climate legislation in Congress this year. They represent 56 million people in all 50 states. The day after the State of the Union address, the U.S. Conference of Mayors announced global warming is No. 1 on its top-10 list of priorities.
•Industry. Ten major companies, including industrial giants General Electric, Alcoa and DuPont, joined four environmental and climate groups last week to demand swift passage of federal legislation to cut emissions that worsen warming. Their U.S. Climate Action Partnership says further delay only "increases the risk of unavoidable consequences … at potentially greater economic cost and social disruption."
In their own studies, Tebaldi and her colleagues at NCAR found broad agreement in climate projections for North America by 2100, including a rise in average temperatures from 3 to 9 degrees.
That could lead to more frequent heat waves and more warm nights when daytime temperatures linger longer after sundown, especially in the South and West, Tebaldi's group concluded. NCAR also says increasing rain would soak northern states but bypass the already dry Southwest, where drought would be more common except when torrential rains bring flash floods.
The IPCC report is likely to reflect climate uncertainties and disagreements, too. Scientists have strongly debated the last two years, without resolution, whether global warming intensifies hurricanes.
Rising sea levels are a huge concern for the USA because more than half the population lives within 50 miles of the coastlines, according to the National Oceanic and Atmospheric Administration. The 2001 report contained a wide estimate of the rise this century — from 3.5 inches to 34. MacCracken says that projection has fallen to about 20 inches or less.
Such a drop in the top estimate alarms glacier experts such as John Turner of the British Antarctic Survey, who was quoted in the United Kingdom's Guardian newspaper as saying the low projection is "misleading." He says the low number accounts only for the heat-related rise of sea level and slow trickles from ebbing glaciers, and it ignores potential ice-sheet collapses in Antarctica or Greenland.
"Greenland is just a relic of the last Ice Age, after all, just jutting out into the Atlantic, frozen at latitudes further south than anything else," MacCracken says. "What might happen when it gets warmer?"
Are reports too cautious?
MacCracken contends past IPCC reports have been too conservative, partly by design, in warning about the dangers of climate change, especially sea level rise.
"Scientists don't like to be wrong, so they tend to discount the most uncertain things," MacCracken says. "And that's good, but policymakers and risk managers usually want to know the worst case, as well as the middle one, when they plan for things."
Every IPCC report has been controversial. When the 1995 report's economic analysis estimated that the worth of a human life in a developing nation is less than in developed ones, it triggered protests and sit-ins.
In 2005, federal hurricane researcher Chris Landsea resigned from the IPCC, suggesting its hurricane warnings were too overblown and "politicized."
Climate scientist Roger Pielke Sr. of the University of Colorado at Boulder has suggested that development and deforestation, rather than the burning of fossil fuels, are the main drivers behind global warming. He says on his climate-science website that the IPCC should recognize the importance of these other factors.
In contrast, Australian scientist Tim Flannery has complained in his 2005 book The Weather Makers: How Man is Changing the Climate and What it Means for Life on Earth that IPCC estimates downplay the impact of warming.
In Paris this week, the process of negotiating and revising the short summary is painstaking and "line by line," says Kevin Trenberth, one of the lead authors and climate analysis chief at the National Center for Atmospheric Research. More than 100 of the panel's 193 member nations are taking part in the negotiations on the summary, he says.
"They'll do a lot of rewriting. It's all going to change to cover the concerns of each nation," whether it's monsoons in India or polar bears in Canada, says MacCracken, who helped lead the USA's involvement in the IPCC in 1995 and 2001. The summary also must be translated in six official U.N. languages.
Original source : http://www.usatoday.com/tech/science/2007-01-30-ipcc-report_x.htm
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