Following this summer’s long heat wave, with weeks of hot sunny weather and hardly a drop of rain, there’s been a lot of talk about whether this is the new normal, thanks to man-made climate change.
Fortunately, the Guardian’s climate expert Fiona Harvey has an article that sets the record straight on this, helped by top climate scientists such as Peter Stott of the Met Office.
The article explains:
when it comes to global warming, we can forget the jolly predictions of Jeremy Clarkson and his ilk of a Mediterranean climate in which we lounge among the olive groves of Yorkshire sipping a fine Scottish champagne. The truth is likely to be much duller, and much nastier – and we have already had a taste of it. “We will see lots more floods, droughts, such as we’ve had this year in the UK,” says Peter Stott, leader of the climate change monitoring and attribution team at the Met Office.
And it’s not just a one-off, it’s part of a trend:
A series of unusually wet and cold summers has afflicted the UK for several years. Remember the devastating floods of 2007, when some areas received double their normal rainfall for June? Or the predictions of a “barbecue summer” in 2009 that backfired badly on the Met Office as the (correctly anticipated) high temperatures were accompanied by heavy clouds and rainstorms? The impression that many Britons have had that summer weather has been getting worse in recent years is borne out by the data – five out of the last six years (2007-2012), have shown below-average sunshine from June to August, and in some cases well below average. All have had above-average rainfall – in some cases more than 50% above the long-term average. “It is not just a perception – we have had a run of relatively poor summers,” says Stott.
Most importantly of course, this weather can now confidently be attributed to man-made climate change:
Stott says: “We are much more confident about attributing [weather effects] to climate change. This is all adding up to a stronger picture of human influence on the climate.”
The science linking man-made warming to our wet summers is explained by Edward Hanna from the University of Sheffield, so we can expect many more wet summers in the future:
The link, he believes, is that Arctic sea-ice losses and the release of heat over the Arctic Ocean have tended to weaken the jet stream and make it more meandering. This has brought more low pressures over Britain, less stable conditions, more cloud cover and rain-bearing weather systems from the Atlantic.
This year, the jet stream moved much more than usual, passing south of the UK. It also persisted in this position for an unusually long time. If this pushing of the jet stream southward is indeed linked to less sea ice over the Arctic circle, as Hanna suspects, then the signs are that we will see many more of these wet summers in future.