Sea Level Rise—The level of the world's oceans will rise, likely inundating low-lying land, turning freshwater brackish and potentially triggering widespread migration of human populations from affected areas.
"As temperatures rise, thermal expansion will lead to sea-level rise, independent of melting ice," says chemical engineer Lenny Bernstein, another lead author of the recent IPCC report. "The indications are that this factor alone could cause serious problems [and] ice-sheet melting would greatly accelerate [it]."
Such ice-sheet melting, which the IPCC explicitly did not include in its predictions of sea-level rise, has already been observed and may be speeding up, according to recent research that determined that the melting of Greenland's ice cap has accelerated to six times the average flow of the Colorado River. Research has also shown that the world has consistently emitted greenhouse gases at the highest projected levels examined and sea-level rise has also outpaced projections from the IPCC's last assessment in 2001.
"We are above the high scenario now," says climatologist Stephen Schneider of Stanford University, an IPCC lead author. "This is not a safe world."
Other recent findings include:
Carbon Intensity Increasing—The amount of carbon dioxide per car built, burger served or widget sold had been consistently declining until the turn of the century. But since 2000, CO2 emissions have grown by more than 3 percent annually. This is largely due to the economic booms in China and India, which rely on polluting coal to power production. But emissions in the developed world have started to rise as well, increasing by 2.6 percent since 2000, according to reports made by those countries to the United Nations Framework Convention on Climate Change. Researchers at the Massachusetts Institute of Technology also recently argued that U.S. emissions may continue to increase as a result of growing energy demand.
Carbon Sinks Slowing—The world's oceans and forests are absorbing less of the CO2 released by human activity, resulting in a faster rise in atmospheric levels of greenhouse gases. All told, humanity released 9.9 billion metric tons (2.18 X 1013 pounds) of carbon in 2006 at the same time that the ability of the North Atlantic to take in such emissions, for example, dropped by 50 percent.
Impacts Accelerating—Warming temperatures have prompted earlier springs in the far north and have caused plant species to spread farther into formerly icy terrain. Meanwhile, sea ice in the Arctic reached a record low this year, covering just 1.59 million square miles and thus shattering the previous 2005 minimum of 2.05 million square miles.
"The observed rate of loss is faster than anything predicted," says senior research scientist Mark Serreze of the U.S. National Snow and Ice Data Center in Boulder, Colo. "We're already set up for another big loss next year. We've got so much open water in the Arctic now that has absorbed so much energy over the summer that the ocean has warmed. The ice that grows back this autumn will be thin."
The negative consequences of such reinforcing, positive feedbacks (white ice is replaced by dark water, which absorbs more energy and prevents the formation of more white ice) remain even when they seemingly work in our favor.