Humans are causing extreme weather, say scientists

For the first time ever, climatologists have attributed extreme weather to human activity. Therefore the age old question of “is this weather because of global warming?” might finally have an answer.

Climate scientists have now been able to attribute certain extreme weather events to human induced climate change. This is a major coup for climate scientists, as it has always been difficult to isolate certain weather events from the background ‘noise’ of climate variability.

"We are much more confident about attributing [weather effects] to climate change,” said Peter Stott, of the UK's Met Office.

“This is all adding up to a stronger and stronger picture of human influence on the climate.”

Over the past decade or so, confidence has gradually increased in attribution studies. We have gone from being able to show that long-term increases in temperature in a certain region of the world were due to human influence, to being able to attribute shorter and more localised events, to now being able to attribute specific climatic events to our greenhouse gas emissions.

Specifically, the scientists said that recent warm weather in November was 60 times more likely to happen because of climate change than for natural reasons; in other words, there was a less than two per cent chance that climate change was not responsible for the event. The heatwave in Texas last year had around a five per cent chance of being due to natural variation compared to a 95 per cent chance of being caused by climate change.

Of course, not all extreme events are due to climate change. For example, the cold British winter of 2010/11 is half as likely to happen than it was 50 years ago. Other human factors can also be responsible; for example flooding in Thailand last year was deemed to be due to river management, rather than climate change.

Whether current events, such as the heatwave in the US or the wet summer in the UK, is down to climate change is yet to be seen. There are strong arguments, however, that the last few years of unusual jet stream locations during the summer are being cause by changes in the Arctic circulation, as a result of reduced sea ice. If so, northern Europe could continue to see poorer summers and milder winters as a result. The weather is by nature unpredictable, however, so there will always be bucks in the trend.