Computers, Society, and Nature

This will do it:

Greenland’s glaciers are melting into the sea twice as fast as previously believed, the result of a warming trend that renders obsolete predictions of how quickly Earth’s oceans will rise over the next century, scientists said yesterday.

The new data come from satellite imagery and give fresh urgency to worries about the role of human activity in global warming. The Greenland data are mirrored by findings from Bolivia to the Himalayas, scientists said, noting that rising sea levels threaten widespread flooding and severe storm damage in low-lying areas worldwide.

(A summary of the article in Science is here.)

If this wasn’t depressing enough, Jim Hansen, the NASA scientist who’s been prevented from speaking out about dramatic acceleration of climate change, had to publish his article in a newspaper in the UK:

a few weeks ago, when I – a NASA climate scientist – tried to talk to the media about these issues following a lecture I had given calling for prompt reductions in the emission of greenhouse gases, the Nasa public affairs team – staffed by political appointees from the Bush administration – tried to stop me doing so.

Creating mechanisms to capture carbon was one of the major topics of this past climate change conference. One way to do this is through forests: trees in forests capture, “sequester,” carbon dioxide by absorbing it as part of photosynthesis. In the Kyoto Protocol, countries can offset their greenhouse gas emissions by planting forests, so called ‘Kyoto forests’. There is strong incentive for countries that signed on to Kyoto to do afforestation, the planting of trees in areas where there previously were no trees, or reforestation, the planting of trees in areas where there used to be trees.

Instead of sequestering carbon, now it’s been shown that the expansion of forests in temperate climates might actually increase the emission of carbon dioxide. Why such a radical change in viewpoints? It may be a result of re-examining the assumptions of the computer simulations of climate change.

Johannes Feddema of the University of Kansas and six colleagues from the US National Centre for Atmospheric Research report in Science journal that they looked at changes in land use – the growth of cities, clearing of forests for agriculture, and draining of marshes – and their impact on climate change in the next 100 years. They confirmed something environmentalists have predicted for decades – the destruction of the Amazon forest would make the local climate 2C (4F) warmer because trees soak up carbon dioxide from the atmosphere, and burning them releases it. But then the scientists looked at temperate zones and found the opposite.

Simulations predicted the conversion of north American and European forests and grassland to agriculture would cool the region and counteract the effects of global warming by 25%-50%. This is because ripening corn and other staples would reflect more sunlight back into space, and release more moisture into the air, while dark forests would absorb sunlight and send thermometers soaring. Ken Caldeira and a Carnegie Institution team backed the finding in Geophysical Research Letters. “We were hoping to find that growing forests in the US would help slow global warming. But if we are not careful, growing forests could make global warming even worse.”

So is this model correct? Plenty of carbon models still show carbon sequestration occuring more uniformly across forest types. This latest model demonstrates that considerable uncertainty persists in understanding role of forests in lessening climate change and certainly calls into question the use of forestation to remediate climate changes.