If global warming real why is it cold?
Guest post by Colin Summerhayes
A recent BBC poll suggested that the public's belief in global warming has declined steeply since November. The apparent erosion of in climate science was put down to the University of East Anglia email row and various gaffes by the Intergovernmental Panel on Climate Change. I strongly suspect, from talking to people in the street, that the poll result may have much more to do with the weather than with what people may or may not have been doing at the UEA.
In the public mind, climate and weather remain inextricably linked. In the first week of my job in Cambridge, I was asked by BBC radio to come in and talk about climate; it was April 2004 and it was cold. The reporter asked me how I could justify global warming when it was so cold outside. Given such ignorance on the part of the media, it is not surprising that the man in the street thinks as he does.
Data from satellites and surface measurements show that January 2010 was globally the warmest in the 32-year satellite record, but the overwhelming focus on "white-out Britain" meant that this record went virtually unremarked.
There is a very good reason why our local temperatures have been cold in contrast with the global picture. This winter has seen a 'blocking high' over Greenland and Baffin Island that has brought temperatures 7C above normal in these areas, and cold weather to the surrounding regions - Northern Europe, the UK and the north east coast of America.
To make matters worse, El Niño is near its peak of its seven year cycle. Upward fluctuations over the short term on the global temperature curve occur during years when warm El Nino events develop in the Pacific, and downward departures occur when there are cool La Nina events there. We have now moved in to an El Nino year, suggesting that global temperatures will be warmer than average. During El Nino years, like this one, northern cities can be hit with record amounts of snow due to the extra moisture in the air.
Regardless of such local variations, there is overwhelming evidence that the Earth is getting hotter.
Taking unlikely inspiration from a sceptic blog, I would like to see a link from the homepage of the Met Office: "Press here to find out why global warming is real even though it is cold in the UK."
Here are a few observations that might be included:
Here are a few observations that might be included:
1. that ocean temperatures are increasing and ocean heat content has increased considerably over the upper 700 metres since 1965, as shown by a wide variety of ocean thermometers including those from the Argo float programme.
2. that as a result of that warming, the ocean has expanded, and sea-level has risen, as shown by tide gauge data on the one hand and satellite altimeters on the other hand.
3. that the warmer ocean waters are penetrating beneath the outlet glaciers in Greenland and in the Amundsen Sea Embayment of West Antarctica, where they are contributing to the melting and thinning of those glaciers, which, as a consequence have speeded up and are now discharging significantly more ice from the land into the sea, thus adding to the rate at which sea level is rising.
4. that warm air is contributing to the melting of Arctic sea ice and the latest records show that this downward trend continued through 2009 and into 2010. We do not see this around Antarctica, where the sea ice is growing in area by 1% per year, but we now know that this is because of the shielding effect on the continent and its surrounding surface waters by the vortex of circumpolar winds, which have been strengthened by 15% since the mid 1970s because of the effects of the ozone hole. The effect of the ozone hole on the winds is protecting Antarctica from global warming. The wall of winds keeps warm air out, except locally, over the Antarctic peninsula.
5. that glaciers are in retreat in most mountain areas, including Patagonia and the Antarctic Peninsula. The rate at which these glaciers are retreating has increased significantly since about 1970.
6. that plants, animals, birds, and insects, especially in north temperate regions, are advancing their ranges northwards at significant rates, and that seasonal migrations are starting earlier, in response to warming.
7. UEA data aside, there are other records of air temperature from around the world that confirm that the air temperatures on balance are warming. All of these analyses attempt to remove from the data set measuring sites that are suspect in some way. Not surprisingly this means that to some extent they will be using the same data sets. But some, like the NASA GISS set cover additional areas (the Arctic) to that covered by the UEA set.
8. that there is an observed trend for the stratosphere to cool and the troposphere to warm. This is strongly evident over Antarctica, for example.
9. that the sun's energy has not increased significantly since around 1970, during which time global temperatures in both atmosphere and ocean have continued to increase.
10. that permafrost is melting in many parts of the Arctic, causing damage to housing and infrastructure.
Faced with these observable facts, and knowing that carbon dioxide and methane have increased significantly in abundance since the industrial revolution, my conclusion is that the Earth is warming due to absorption of reflected radiation by greenhouses gases in the atmosphere. A single cold January in the UK does nothing to alter this view. If scientists and media did a better job at making the distinction between climate and weather, the BBC poll may have come up with a quite different result.
Dr Colin Summerhayes is an oceanographer and geologist at the Scott Polar Research Institute in Cambridge
