Last month, Papua New Guinea announced that it would begin evacuating the 980 residents of the Carteret atolls to Bougainville Island because of rising sea levels linked to global warming. The atolls, barely above sea level, are expected to be completely submerged by 2015.
A number of climate scientists said the steady march of warm temperatures, along with retreating sea ice, melting glaciers and rising sea levels, were clear evidence that global warming caused by the human production of greenhouse gases was already dramatically affecting the planet.
"Could these changes arise from natural climate variability alone? The answer is no," said Ben Santer, a physicist and climate modeler at the Lawrence Livermore National Laboratory. "Even today, one can hear statements -- sometimes from senior members of our government -- saying we know nothing about the causes and effects of climate change. That's really not true."
Angela Ledford Anderson, director of the environmental coalition Clear the Air, called for the U.S. Senate to create "mandatory pollution limits with clear deadlines" to curb the chemicals that are causing warming.
Bush administration officials said Thursday that they were taking climate change seriously by launching an array of voluntary programs to reduce greenhouse gases and investing nearly $2 billion to monitor and study climate change. At the same time, administration officials downplayed the 2005 temperature data, saying it remained unclear how much human activities had contributed to the warming trend.
"The observed conditions of any one particular year are a combination of natural and human-related factors," said Michele St. Martin, a spokeswoman for the White House Council on Environmental Quality.
Pielke, who directs the Colorado Climate Center at Colorado State University, doubts the accuracy of global temperature estimates because some temperature monitors record extra warmth when placed too close to buildings and because they do not measure humidity, which is an important factor in gauging heat.
"This raises issues about the validity of this data," he said, adding that he does believe the planet is warming, but not as quickly as global temperatures suggest.
Scientists expect global temperatures to continue rising. Hansen had predicted in a report issued in February that 2005 temperatures could rival or exceed those of 1998 because the Earth is "out of energy balance" and is absorbing more heat from solar radiation than it is radiating out to space.
He now predicts that the 2005 and 1998 records will soon be broken.
