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Blowing hot & cold

Posted 09/08/2012 by cgodfrey

Perhaps James Lovelock’s Gaia theory has just been granted further support by recent research? Can the Earth really change to accommodate our activities, or are they just too fast and too big for natural adjustment?

Research findings from a team at the University of Colorado at Boulder, US, published in Nature (doi: 10.1038/nature11299), suggest that the oceans and vegetation have more than doubled the amount of greenhouse gases they absorb since 1960, despite a quadrupling in CO2 emissions. But the team does not believe this effect will continue indefinitely and the progress hasn’t been linear. There was decreased CO2 uptake by the oceans and land in the 1990s, while increased sequestration has been observed over the period 2000-2010.

‘What we are seeing is that the Earth continues to do the heavy lifting by taking up huge amounts of carbon dioxide, even while humans have done very little to reduce carbon emissions,’ said team leader Ashley Ballantyne. ‘How long this will continue, we don’t know.’

The Greenland ice sheet is often cited as a key indicator for global warming. There have been various reports that it is about to disappear and that Greenland’s glacier are in retreat, while others have suggested that in fact the glaciers are growing and the ice sheet is only demonstrating seasonal effects.

In July 2012, the US National Aeronautical & Space Administration (NASA) reported that almost the entire surface of the Greenland ice sheet has been thawing during a rare warm spell. NASA added, however, that such an event might happen only once every 150 years. 

But only last week, Kurt Kjaer from the University of Copenhagen, commenting on his team’s research published last week in Science (doi: 10.1126/science.337.6094.502-k), said: ‘It is too early to proclaim the ice sheet’s future doom due to climate change.’

Kjaer’s team has been examining aerial photographs dating back to the 1940s, which have shown that between 1985 and 1993 there was a sharp thinning of glaciers in the north west of Greenland, with another sharp reduction between 2005 and 2010. Earlier in May this year, the team identified another period of warming and resultant ice decline in the 1930s.

‘It starts and then it stops’, Kjaer told the Reuters news agency. ‘This is a break from thinking that it is something that starts, accelerates and will consume Greenland all at once.’

But Kjaer has pointed out that the ice sheet did not get bigger in the periods between the reductions, so the disappearance is cumulative. Elsewhere in the world it has been reported that while some glaciers have retreated, others have grown, but no-one really knows what the cumulative effect has been.

So whether you are a believer in global warming or a nay-sayer, and whether you believe it is man-made or just part of the natural cycle of the Earth, the Sun or the Universe, there are researchers looking for evidence. And that has got to be a more scientific approach than just emotion.

Neil Eisberg - Editor

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