February 15, 2009

Global Warming Has Been Underestimated

According to a top climate scientist, warnings about global warming have not been severe enough.

Just over a year ago, the Nobel-winning Intergovernmental Panel on Climate Change (IPCC) issued a report warning of expanding deserts, intense storms, rising sea levels, and an extinction of up to 30 percent of animals and plants due to global warming.

A recent study suggests that the report underestimated the severity of climate change over the next century, says a senior member of the IPCC.

"We now have data showing that from 2000 to 2007, greenhouse gas emissions increased far more rapidly than we expected," Chris Field, who was lead author of the IPCC report, told the AFP.

According to Field, this is because "developing countries like China and India saw a huge upsurge in electric power generation, almost all of it based on coal."

If global warming is not slowed, higher temperatures could thaw the Arctic tundra and ignite tropical forests, thus releasing billions of tons of carbon dioxide into the atmosphere.

If that happens, temperature could rise more rapidly and create a cycle that could quickly spin out of control.

"We don't want to cross a critical threshold where this massive release of carbon starts to run on autopilot," said Field, who is also a professor of biology at Stanford University.

An estimated 350 billion tons of carbon dioxide have been released into the atmosphere since the Industrial Revolution.  Researchers estimate that nearly 1,000 tons of carbon dioxide could be released from permafrost soils in the Arctic, an area warming faster than any other on the planet.

In addition, deforestation could increase the concentration of carbon dioxide in the air by 10 to 100 parts per million over the next 100 years.

Currently, carbon dioxide levels are near the 380 parts per million level.

"Tropical forests are essentially inflammable," Field said. "You couldn't get a fire to burn there if you tried. But if they dry out just a little bit, the result can be very large and destructive wildfires."

According to other studies, global warming could also be reducing the ocean's ability to store carbon by altering wind patterns in the Southern Ocean.

"As the Earth warms, it generates faster winds over the oceans surrounding Antarctica," said Field.

"These winds essentially blow the surface water out of the way, allowing water with higher concentrations of CO2 to rise to the surface. This higher-CO2 water is closer to CO2-saturated, so it takes up less carbon dioxide from the atmosphere."

Field helps lead the group that will assess the impact of climate change on natural, economic, and social systems for the IPCC's fifth assessment of global warming in 2014.

According to Field, the fourth assessment, released in 2007, was "very conservative." 

The next report will "include futures with a lot more warming," Field said.

"We now know that, without effective action, climate change is going to be larger and more difficult to deal with than we thought."


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