I read this in the Herald and thought I'd share it with you...

The increasingly chaotic weather seen across the world is no longer natural but man-made by pollution, a leading Scottish climate scientist has warned.

The rain that has drenched parts of the UK and the heat wave that has baked the US can be blamed on carbon emissions that are causing global warming and disrupting the climate.

New evidence suggests one reason why the jet stream responsible for the bad weather may be stuck to the south of the UK is melting Arctic ice, triggered by higher global temperatures.

"There is now no such thing as 'natural' weather," says Peter Singleton, the environmental futures manager at the Scottish Environment Protection Agency (Sepa). "The growing impact of mankind and its resulting pollution has changed both the weather and climate of the planet...starting with deforestation and followed by excessive use of fossil fuels and pollution."

The world is now reaching a "crunch point" at which pollution could cause natural systems to break down and trigger greater change, Singleton argues. This makes unusual or extreme weather events more likely.

"The present unusual weather is entirely consistent with our understanding of how the climate has changed and will change as a result of mankind's impacts," he says.

According to the Met Office, research suggests reducing amounts of Arctic sea ice could be affecting weather patterns. The current levels of ice are at a record low for this time of year.

Warmer air from the Arctic lessens the temperature difference with air from the tropics and slows down the jet stream. That means it is more likely to meander south in the summer and get stuck, causing prolonged poor weather in northern Europe.

Wary of accusations of exaggeration in the past, the Met Office remains cautious. But, says a spokesman: "We do know that the warmer air is, the more moisture it can hold."

As a result of rising global temperatures, there had been an increase of 4-5% in atmospheric moisture. "This means when we do get unusual weather patterns, it's likely there will be more rainfall," Singleton adds. "It seems when it does rain, it is heavier."

Four of the wettest months since records began in 1910 have occurred in the last four years, including the wettest April and June this year.

"If wet months occurred randomly, we would expect only one record to have been broken since 2006," says the Met Office.

Dr Richard Dixon, the director of WWF Scotland, says: "It seems the shifting jet stream may be the first really major impact of climate change on our local weather patterns.

"We'll still have some great summers and washouts but it may be the average summer will now be dull and wet, even as global temperatures rise."

David Crichton, a leading expert on flooding and climate change, says: "People who don't yet believe the climate is changing may be thinking again, as each month seems to bring record-breaking weather."

More can be read at http://www.heraldscotland.com/news/h...-made.18153470