CHICAGO – The international organization that exhaustively analyzed climate-change data and brought the world a grim report in 2007 has released new data that is painting a clearer picture of some of the mechanisms underlying global warming. The Intergovernmental Panel on Climate Change (IPCC), an organization composed of hundreds of scientists from around the world, is now compiling and examining the most recent climate research findings—based on more recent observations and better climate models—for its next report (to be finished in 2014). The new data suggest that humans need to cut greenhouse gas emissions sooner than the last report suggested, or face the need for even bigger cuts down the road, says Chris Field, director of the Department of Global Ecology at the Carnegie Institution of Washington. –Karen Rowan
Greenhouse Gas Emissions
The most recent round of data indicates that emissions of carbon dioxide from 2000 to 2007 were higher than the worst-case scenario considered for the last report, Field said, speaking at the American Association for the Advancement of Science's annual conference in Chicago. From 1990 to 1999, worldwide emissions increased at a rate of about 0.9 percent each year, but since 2000, they have increased at a rate of 3.5 percent each year, he said. This means humans are now on a course to unleash 800 billion to 2 trillion tons during this century. Since the beginning of the industrial revolution, human activities have released about 300 billion tons of carbon dioxide.
The unpredicted rise was caused by increased economic growth and a rapid expansion in the burning of coal to generate electricity, Field said, with China and India producing the sharpest increases (although their emissions are still only about one-sixth that of U.S emissions per capita). Some had hoped that economic growth and awareness would lead to the development of technologies that lower greenhouse gas emissions, but this hasn't happened, according to Field.
Another significant source of greenhouse gas is the melting Arctic permafrost–the frozen soils that cover 24 percent of the northern hemisphere. With better climate models, scientists now say that permafrost will release more carbon dioxide than previously expected. The frozen areas are full of plant matter–little bits of stems and leaves that have amassed over time and remained frozen for thousands of years. As the Earth warms, the plant matter will begin to decay, unleashing 500 to 1000 billion tons of additional carbon dioxide into the atmosphere.
The Arctic has warmed at a faster rate than the rest of the planet, says Peter Lemke, head of Climate Sciences Research Division at the Alfred Wegener Institute in Germany. Before now, scientists didn't have good estimates of how much carbon would be released from plant matter–predictions were previously around 400 billion tons total. Recent research on soils in Siberia contributed to scientists' new estimates. The melting permafrost also releases methane–a greenhouse gas that is 22 times as potent a greenhouse gas as carbon dioxide. One recent study found that methane releases from permafrost increased by up to 60 percent between 1970 and 2000.
New research using satellite measurements shows that sea levels are climbing faster than they have been for the last 50 years, says Anny Cazenave, a scientist at the Centre National d'Etudes Spatiales in France. Over that period, scientists estimate the oceans rose about 1.6 to 1.8 millimeters each year, on average. Cazenave's new data shows that from 1993 to 2008, the sea level rose about 3.5 millimeters each year. Cazenave analyzed data from sensitive satellite altimeters that measure sea level with greater precision than the tide gauges used in the past. The satellites have the added bonus of reading sea levels all over the globe (tide gauges can only measure water levels where they are placed). The new findings show that the change is not happening at a uniform rate. For example, areas of the western Pacific are showing increases of 1 centimeter each year.