One of the questions that I'm often asked is how can global temperatures have reached near-record levels, when here in the UK we have had record breaking cold? It's an issue that many people have great difficulty in accepting.
Of course the answer is that the UK represents a tiny fraction of the planet, and where we have been experiencing extreme cold, other parts of the world have been experiencing unusual warmth.
The Arctic is one such region where temperatures have been way above average again this winter. In fact temperatures over the Arctic region have in places been as much as 6C above normal.
The main source of this warmth has come from unfrozen areas of the ocean which releases heat to the atmosphere, and wind patterns which have brought warm air into the Arctic.
In fact Arctic sea ice in January was at an all time low according to satellite data, which first started in 1978, continuing the long term downward trend, shown below.
The most frustrating aspect of measuring sea ice comes from the fact that we have reliable data which only goes back to 1978. But the trend, even from this comparatively short data set, is clear for all to see.
This is one of the feedback mechanisms which would lead to more heat being added to the planet.
The more the ice melts, the more heat the unfrozen sea releases to the atmosphere. In addition, ice acts to reflect sunlight back out into space; without the ice, solar radiation is absorbed by the sea, causing it to warm more than it would if it was covered by sea ice.
It may come as a surprise to learn that many climate sceptics and mainstream climate scientists have more in common than people believe.
Most, but not all, agree that increasing levels of Carbon Dioxide into the atmosphere will cause an increase in global temperatures.
A very rough approximation would be that a doubling of Carbon Dioxide leads to a 1C rise in global temperatures. But from this point onwards, their views become increasingly polarised.
Most climate scientists believe that this initial warming will cause further warming by way of positive feedback mechanisms, such as the one described above whereby melting sea ice can lead to more warming, which leads to more melting ice and so one.
Climate sceptics question whether such feedback mechanisms will all be positive - and if some are negative, then the earth could naturally cool itself down.
One such climate sceptic, Dr Roy Spencer at the University of Alabama, is convinced that clouds will act as a negative feedback; as the planet warms, it will become cloudier, blocking the suns heat, and leading to a natural cooling of the earth.
The continued low levels of Arctic sea ice continues to confound forecasts made by some climate sceptics over the last few years of a strong rebound in sea ice.
As a result of falling global temperatures recorded in the last few months, they may yet be proved correct in the coming months and years.
But if the continued drop in Arctic sea ice is at least in part down to a positive feedback, then it's a cause for concern.
Source: http://www.bbc.co.uk/blogs/paulhudson/2011/02/lowest-january-arctic-ice-on-s.shtml
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