A climate change warning
Panel says humans are probably causing shifts around world
Manmade global warming is probably already causing noticeable environmental changes throughout the world, the leading authority on climate change announced yesterday, such as the earlier arrival of spring in some regions, thawing permafrost, and the northward shift of some animal and plant habitats.
In a report released by the United Nations' Intergovernmental Panel on Climate Change (IPCC) , scientists for the first time linked changes being observed in nature on every continent and in most oceans to rising temperatures from greenhouse gases, chiefly carbon dioxide, emitted by power plants, factories, and cars.
If emissions are not reduced, the panel warned, 20 percent to 30 percent of plant and animal species could face increased risk of extinction, and rising temperatures could cause widespread human suffering from more frequent droughts, floods, and outbreaks of disease.
The report also underscores deep disparities between wealthy and poor nations in their ability to adapt to a warming world. Poor countries, especially in the tropics, will be affected most dramatically because they have the fewest resources to protect or prepare their populations.
"If a government doesn't react to this [report], it could be considered negligence," said Susanne Moser, a research scientist at the National Center for Atmospheric Research in Colorado and a contributing author to the document. "It's a fairly bleak picture."
The report's depiction of the effects of global warming are the most detailed, definitive, and grim since international scientists began assessing the state of the warming world in a formal way. The report says tens of millions of people could suffer from water scarcity, and coastal regions all over the world could face severe flooding.
The report's release in Brussels was delayed for several hours in part because officials of several governments, including the United States, Saudi Arabia, and China, debated wording with scientists, including how the report characterized scientists' certainty that global warming is already influencing physical and biological systems. According to IPCC rules, all governments had to sign off on the document; its release was preceded by four days of intense negotiations with officials from more than 100 countries. The wording was ultimately changed to reflect less certainty, over the objections of the panel's scientists. The final report says it is "likely" that manmade warming has had a discernible influence on many physical and biological systems.
"That was a really hard discussion," said Patricia Romero Lankao, a lead author of the report who was part of the Brussels negotiations and who works at the National Center for Atmospheric Research.
In a press briefing yesterday morning, a White House official said that any alterations the US pushed for were made to reflect what is really known about the impact of climate change.
"We took our role very seriously in getting a summary document that accurately reflects the underlying science," said Sharon Hays, the leader of the US delegation at the Brussels meeting and the associate director for science for the White House Office of Science and Technology Policy.
Still, the report's message to government officials around the world was that if emissions of greenhouse gases continue to increase at the current rate, the world will experience a changing environment that plants and animals may not be able to adapt to.
If emissions are not curbed, North Americans can expect more heat waves in cities, which tend to be hotter than less populated areas, putting at risk many vulnerable people, including the elderly. Forests will have more wildfires and tree pests, the report predicts, and there could be increased flooding and fiercer storms. The Southwest will get drier. Regions such as the Western United States that get drinking water from melting mountain snow will suffer shortages. The warming temperatures are projected to increase smog in the Eastern United States, with as much as a 68 percent increase in the number of days with poor air quality by 2050.
Not all of the news was bad: Crop yields could increase by as much as 20 percent in North America, largely because of longer growing seasons. Cold-related deaths could decrease.
While yesterday's report did not address changes specific to New England, scientists have said the region is experiencing pronounced warming that is consistent with global warming. Winter temperatures have risen on average 4.4 degrees in the last 30 years, reducing ice and snow and extending the growing season. More specific regional assessments by the IPCC will be released during the next two weeks.
The new 23-page report is a summary of a much longer scientific treatise and is the second of four being produced by the IPCC this year to educate policy makers about the science and predictions of global climate change. The IPCC assessments, issued about every five years since 1990, have shown that scientists are becoming progressively more certain that humans are causing much of the warming. The report two months ago said scientists are more than 90 percent certain that warming temperatures in the last 50 years are mostly due to human activities. The growing weight of scientific evidence was a factor in Monday's US Supreme Court ruling that greenhouse gases are pollutants, a decision that some climate change analysts say may push the Bush administration to regulate carbon dioxide emissions from cars and power plants.
IPCC scientists said yesterday they are highly confident they are seeing impacts today of climate change. As part of the report they reviewed 75 studies that showed significant changes in everything from ice on lakes to species' migration. Of those changes, more than 89 percent are consistent with a warming world. Natural variability in temperatures, alone, is unlikely to account for so many changes, the scientists said.
"People are beginning to experience global warming in a way they have not before. We are all sensing the changes in the Northeast, the warmer winters, the hotter summers," said Peter Frumhoff, director of science and policy for the Union of Concerned Scientists, a national advocacy group based in Cambridge.
Scientists acknowledged in the report that they had too little data to link some recent dramatic climate events to global warming, such as European heat waves.
Yet they were very clear about what would happen if IPCC projections hold true and the earth warms 3.2 to 7.2 degrees Fahrenheit and seas rise as much as 23 inches in the next century. As soon as 2020, water scarcity could become a major issue for more than 75 million Africans. Drier places will get drier.
In Asia, glacier melt in the Himalayas is projected to increase flooding and cause more rock avalanches from destabilized slopes within 30 years.
Small islands the world over are particularly threatened because of sea-level rise and more extreme storms, the report says.
Beth Daley can be reached by e-mail at bdaley@globe.com 