February 15, 2014 — andyextance

In a sane world, the worldwide weather chaos that has engulfed the start of 2014 would be memorable. As the eastern US and Canada freeze in winter storms of ‘historical proportions’ as far south as Texas, California remains parched and record temperatures have baked Alaska. As increasingly regular heatwaves scorch Australia, the UK is drowning under record rainfall and being battered by hurricane-force winds, with storms also felt elsewhere in Europe. Yet we may soon forget these dramas and have our attentions sucked in by a new set of meteorological monsters, if they’re linked to changing climate. But are they? Though it’s a murky question, if you look at it like sport, it’s easier to get a feel for than you might think.

Even if you detest football (or soccer, if you prefer), you’ll likely know that in sport the metaphorical playing field is often uneven. Take, for example, last Saturday’s English Premier League match between Manchester City and Norwich City. The Manchester side is owned by Sheikh Mansour bin Zayed Al Nahyan, whose personal wealth is estimated at £20 billion, lavished happily on players for his club. The joint majority owner of the Norwich side is celebrity chef Delia Smith who, despite her success, doesn’t quite have Sheikh Mansour’s financial muscle.

The status difference can be seen in Manchester City’s current lofty league position, and Norwich’s place near the foot of the table. It was obvious last November, when Manchester City thumped Norwich 7-0. So even though last weekend’s match was in Norwich, bookmakers knew Manchester City’s chances of winning were good. Their odds rated a Manchester City win as nearly eight times as likely as a Norwich win, and nearly four times as likely as a draw. But with the unpredictability that gives sport its excitement, Norwich battled hard and kept their opponents from scoring, earning themselves a 0-0 draw.

Tilting the playing field in a new direction

This unlikely result is a bit like an ‘extreme weather event’ (or as I like to call it after being out in a downpour, an EW! event). These things can happen and always have done, due to chance or ‘natural variability’. And like football odds, we can also work out the likeliness of extreme weather events happening. That’s what Stefan Rahmstorf from the Potsdam Institute for Climate Impact Research did in 2011, doing some simple calculations from scratch.

In Stefan’s work and in real life, when scientists started measuring weather, the first year by definition set new records in all areas. For a few years afterwards the likelihood of record-breaking conditions would have been quite high, as chance made some weather weirder than the original record. But then, reconstructing a stable climate where natural variability stays within the same limits, the chance of setting records gets progressively less.

Worldwide air temperature records today go back to 1880. On that basis the chance of setting new temperature records should be as slim as, if not slimmer than, the chances of Manchester City not beating Norwich City. But something’s happening to change those odds. It’s as if the Manchester City team decided to go out and get drunk the night before the game. They’re still world-class players, it’s quite possible that they could win when they’re hung-over – and of course chance would still play a role. But what was previously unlikely is now more likely.

“The expected number of extremes is now several times larger than that in a stationary climate,” Stefan wrote in his 2011 paper. And though Stefan only looked at temperature records, warmer air can also hold more water and lead to records related to rainfall, both wet and dry. There is “an increasing body of evidence that shows that extreme daily rainfall rates are becoming more intense, and that the rate of increase is consistent with what is expected from the fundamental physics of a warming world,” the UK’s Met Office wrote on Wednesday.

Go home weather, you’re drunk

UK folk buffeted by rare hurricane force winds this week may also want to think about research done by a team from the Royal Netherlands Meteorological Institute (KNMI). Last year they projected that once-in-a-century hurricane-force winds may become as much as 25 times as likely in parts of Western Europe at the end of the 21st century.

As even unlikely weather extremes are still technically possible without climate change, scientists struggle to say if there’s definitely a link – though they’re getting better at it. But if they’re becoming more likely, do we need to ask this question? And does it matter whether they’re linked to the melting Arctic, or changes in the jet stream? Isn’t that a bit like trying to work out which player to blame for an unlikely Manchester City loss, when they’d all been down the pub?

This may be a light-hearted way to try and understand the mess we’re in, but I’ve written it because the situation is so serious. People’s homes and even lives are at stake, yet the world is in disarray over how to react. Much of the media still doesn’t get the climate link. In the UK at least, politicians have been blaming each other and their civil servants rather than looking at the bigger picture.

Beyond personal harm, think too about what more damage like this will do to our economies. If we’re paying to fix flood damage, where does that money come from? Do our schools, our other government-funded services suffer? We need so desperately to get a grip, there’s no way to put this too simply. We know the atmosphere is drunk, because we’ve spiked it with CO2 from the fossil fuels we burn. Because of that the chances of previously unlikely events happening are higher. Now we need to recognise this, get past it, and figure out what to do about all the carnage it’s causing.

Journal references:

Stefan Rahmstorf and, & Dim Coumou (2011). Increase of extreme events in a warming world Proceedings of the National Academy of Sciences of the USA DOI: 10.1073/pnas.1101766108

Haarsma, R., Hazeleger, W., Severijns, C., de Vries, H., Sterl, A., Bintanja, R., van Oldenborgh, G., & van den Brink, H. (2013). More hurricanes to hit Western Europe due to global warming Geophysical Research Letters DOI: 10.1002/grl.50360