GHG emissions are now far higher than even
the worst-case scenario envisaged by the IPCC's fourth assessment report published
in 2007, according to statement by Christopher Field, a lead author on that
report. This statement was delivered at the annual meeting of the American Association for the Advancement
of Science (AAAS) in Chicago,
USA, last week
(14 February 2009). He added that while emissions increased at a rate of 0.9%
per year between 1990 and 1999, they have increased at a "startling"
3.5% per year since 2000. What is causing this increase? Read on to find out.
This increase could be attributed mainly to developing countries such as China and India using mostly coal during the rapid expansion of their electricity generation. If developing countries continue to use coal and other carbon-intensive fuels to meet their energy needs this trend is likely to continue, said Field. "We are looking at a future climate that is beyond anything we have considered in past models," he said.
The IPCC used models developed in 2000 in assessments for its fourth report. In addition to underestimating future carbon emissions these models did not reflect the complexities of the effects of tropical forests, ocean cycles and the thawing of the Arctic permafrost, said Field. More recent models show that atmospheric carbon dioxide concentrations could increase as tropical forests are cut down or destroyed by fire, which is increasingly likely as they dry out because of climate change. He also mentioned that “It is increasingly clear that as you produce a warmer world, lots of forested areas that had been acting as carbon sinks could be converted to carbon sources.”
Meanwhile recent studies show that warming has altered wind patterns in the Southern Ocean, which in turn has reduced the ocean's capacity to soak up excess atmospheric carbon dioxide. However, the most critical short-term concern arises from new estimates of the amount of carbon that lies frozen in permafrost soils in the Arctic. As the Arctic warms it could release billions of tonnes of carbon into the atmosphere. There's a vicious-cycle component to both the tundra-thawing and the tropical forest feedbacks, but the IPCC fourth assessment didn't consider either of them in detail, purely because they weren't well understood at the time.
Visit the reports section of Cabi's Environmental Impact database to find the latest on GHG emissions and climate change.
Source: News Section of SciDev Net