Saturday, November 08, 2008

Warming of polar regions attributed to human activity

The current issue of Nature Geoscience has a letter which contains some pretty interesting stuff, and luckily, they are nice enough to make it freely available on the internet.

Attribution of polar warming to human influence

The polar regions have long been expected to warm strongly as a result of anthropogenic climate change, because of the positive feedbacks associated with melting ice and snow. Several studies have noted a rise in Arctic temperatures over recent decades, but have not formally attributed the changes to human influence, owing to sparse observations and large natural variability. Both warming and cooling trends have been observed in Antarctica, which the Intergovernmental Panel on Climate Change Fourth Assessment Report concludes is the only continent where anthropogenic temperature changes have not been detected so far, possibly as a result of insufficient observational coverage. Here we use an up-to-date gridded data set of land surface temperatures and simulations from four coupled climate models to assess the causes of the observed polar temperature changes. We find that the observed changes in Arctic and Antarctic temperatures are not consistent with internal climate variability or natural climate drivers alone, and are directly attributable to human influence. Our results demonstrate that human activities have already caused significant warming in both polar regions, with likely impacts on polar biology, indigenous communities, ice-sheet mass balance and global sea level.

Basically, what the letter says, is that the scientists looked at the observed temperatures, and found that the only way they could be explained, was through anthropogenic temperature changes (i.e. through humans).

The fact that it's a letter, might make people think that it carries little weight, but letters in Nature Geoscience are actually papers which has passed peer-review, and not just the opinion of the writers (as they are in e.g. newspapers). So, in other words, this is a scientific study, like any other study published in Nature Geoscience.

The melting of the polar areas have long been a major example of how anthropogenic temperature changes affect the world, but until now, it has been hard to attribute the changes there directly to anthropogenic temperature changes. This paper goes a long way towards that.

Not that this conclusion was really in doubt among climate scientists, however, there has always been some uncertainty about whether part of the changes, in those parts of the world, might have had other causes. According to this study, it appears that they didn't.

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