Arctic sea ice cover
When a national newspaper asked Professor Edward Hanna whether Britain would be enjoying a white Christmas last year, the internationally renowned climatologist declined to play Santa Claus.
‘Individual weather forecasts are not my field of expertise,’ says Professor Hanna, whose collaborative work with leading American and European oceanographers and climatologists is advancing our understanding of the interaction between the rapidly receding Arctic ice cover and the warming climate.
What he has discovered makes uncomfortable reading. Recently published research by Professor Hanna and his international colleagues shows that the Greenland ice sheet – which covers an area of almost 2 million square kilometres – is melting at a much faster rate than previously, and this melt rate is accelerating. Also, at the same time, Arctic sea-ice cover has reached a record low.
This has profound implications for policymakers around the globe, both in terms of rising sea levels and the frequency of severe weather episodes such as the huge forest fires in America and Russia and the recent flooding in Pakistan.
However, here in Britain one aspect of the study was picked up more than any other ¬– the impact on our summer weather – prompting headlines about ‘wash out weather.’
‘It really puts global warming in the public eye. It's virtually impossible to predict the weather for any particular summer but we could have cooler, wetter summers on average in the UK because of this effect,’ Professor Hanna said.
‘That's not to say we won't get hot, dry summers but just that these might not be as frequent as you might expect from a straightforward global warming effect. There seems to have been a new regime in the summer of 2007 that has more or less stayed in place since.
‘We would still expect the occasional hot summer because of natural variability, and when it is hot, it is going to be really hot because you have the underlying global warming trend behind all this,’ Professor Hanna adds.
His research shows that it is the interconnectedness of climate change and the Arctic ice cover that is the key to understanding the change in weather patterns.
‘The loss of snow cover and ice in the northern hemisphere is changing the heat gradient across northern latitudes. This, in turn, is changing the energy that is driving the global heat engine. The result is a weakening of the jet stream leading to cold air outbreaks from the Arctic into the mid-latitudes and more warm air outbreaks from the South that go North into Arctic latitudes. While it is hard to predict the weather patterns from year to year, the tendency over the last six summers is for us here in Britain to get more of these cold, north-westerly outbreaks of air, from the Arctic and more unsettled weather.’
But the other side of this coin is that the changing weather system is warming the Arctic faster than almost anywhere else on the planet. ‘Our research gets fed in to all the other studies that inform the work of the Intergovernmental Panel on Climate Change. It supports the scientific consensus that climate change is a real and tangible threat and one that we cannot ignore. The world is too interconnected for us to think that rising sea levels and increased climate-related hazards in the developing world won’t have an impact on the global economy, and thus our own livelihoods.’
The challenge for researchers such as Professor Hanna is not only to carry out the rigorous study of the Arctic ice cover and how it interacts with the climate, but also to articulate these findings in a way that can be understood by policymakers and the public.
‘It is important that we engage with the public and that we do so in a way that is clear and understandable. All too often science gets overlooked in the mainstream media, and when it is discussed it is done so in a way that often distorts what it is happening within the scientific community. I understand that the media has to appear impartial and balanced, but on climate change when the media seek an alternative view, it is one that is often not based on good science. Our role is to provide the good science and to explain it to the public and policy makers in a way that is accessible and easily understood.’