Gordon James explains how climate change is causing the jet stream to bring us this summer’s bad weather
A recent BBC radio early-morning news bulletin informed us that “much of the UK is bracing itself for more heavy rain and flooding today”. This sort of statement has become familiar, pretty well summing up the spring and summer we have experienced so far this year.
Following record breaking rainfall in April and June, with Wales experiencing some of the worst flooding, there seems to be no let-up. While my daughter is struggling to work through 40C plus days in Spain, I’m longing for just a few days of Welsh sunshine.
The BBC newscaster later stated, “Parts of west Yorkshire had a month’s rain fall in just three hours yesterday”. This happened just days after a foot of water tumbled from the skies in 24 hours killing over 170 people in southern Russia.
Across the Atlantic, a heatwave is shattering records, triggering wildfires, droughts and freak storms. In Rome, ancient monuments are reported to be eroding as a result of the big freeze that hit Europe in February. This also brought snow to the streets of Tripoli in North Africa.
Such weather extremes are occurring with increasing frequency. A recent paper by ‘the grandfather of climate change science’, James Hansen, and colleagues at NASA shows that heat extremes, which covered much less than 1% of the Earth’s surface around 40 years ago, now typically cover about 10% of the land area.
What on earth is going on!?
Although climate scientists have been careful not to link specific events to man-made climate change, the finger is being pointed increasingly in this direction. The NASA scientists concluded that, “extreme heat waves, such as that in Texas and Oklahoma in 2011 and Moscow in 2010, were ‘caused’ by global warming, because their likelihood was negligible prior to the recent rapid global warming”.
Last week, the Met Office announced ground breaking research detailing how climate change has significantly increased the odds of some recent extreme weather events. It gives as an example the record warm temperature in the UK last November which was 60 times more likely to happen because of climate change.
These studies support the conclusions of an UN-backed report last November which confirmed the link between climate change and current trends in extreme weather. This report noted a significant increase in heavy rainfall in some areas and predicted that this is likely to increase during this century. Margareta Wahlström, the UN Secretary-General’s Special Representative for Disaster Risk Reduction warned:
“The world has entered a deadly new age where today’s extreme weather events are likely to become the norm”.
Our news broadcasts and weather forecasts have always been reluctant to acknowledge any human influence, often putting the blame on a misbehaving jet stream. This would seem to be a perfectly plausible explanation of a natural phenomenon that absolves humans of blame. But evidence is now emerging that the jet stream is behaving abnormally because of warming in the Arctic.
The jet stream is driven by the difference in temperature between the warm tropics and cold poles. As the Arctic is warming faster than the rest of the planet, partly because it’s reflecting less heat as the snow and ice melts, the temperature difference is reducing which, in turn, is weakening the jet stream.
Last December, the New Scientist reported on studies in the USA which indicated that a slowdown of the jet stream means it is more likely to develop enormous kinks. This allows cold Arctic air to spill south causing abnormal events such as the severely cold winter of 2010-11 in Western Europe. In its latest issue, the magazine reports on further research which shows that in summers with less sea ice in the Arctic, as is happening this year, a weaker jet stream takes a more meandering path. This can stay in one place for weeks shepherding one low-pressure system after another towards the UK.
While other factors, such as the North Atlantic Oscillation and El Nino/La Nina, also have an influence in a complex climate system, it is becoming ever-more clear that human activity is already triggering dangerous abnormalities. As James Hansen and his NASA colleagues point out,
“The small 0.5oC global warming of the past three decades already has practical effects, which will become major impacts if projected global warming of 2oC or more this century is allowed to occur”.
How can we respond to the challenges of such a harsh reality? Firstly, we have to accept the scientific evidence that our high carbon lifestyles are skewing the climate and posing a major threat to our children and grandchildren. We have to appreciate that shifting to a low carbon future could, as the UN recently announced, create tens of millions of new jobs that would help to lift millions of people out of poverty.
And we have to stop kidding ourselves that we only have to take small measures while we defer the tough decisions to a later date. This point was made by Jonathon Porritt, in his Click on Wales article last week (11th July), assessing the Welsh Government’s Sustainable Development Bill. I won’t hold my breath that they will deliver “a strong Bill which makes Wales a green economic leader”. Now, as another rain-laden Atlantic low heads towards west Wales, I’ll seek some solace by listening to my all-time hero Paul Robeson sing about ‘Summertime’.