Climate change is set to trigger more extreme weather events around the world, an international team of scientists claims.
In a new report, Explaining Extreme Events of 2011 from a Climate Perspective, researchers carried out for the first time so-called 'climate attribution studies', looking at six key weather events shortly after they happened.
"While we didn't find evidence that climate change has affected the odds of all the extreme weather events we looked at, we did see that some events were significantly more likely," says Dr Peter Stott, head of climate monitoring and attribution at the UK's Met Office.
"Overall we're seeing that human influence is having a marked impact on some types of extreme weather."
In general say the scientists, extreme heat is becoming more likely, while the odds on unusually cold periods lengthen.
In 2011, Texas had its hottest and driest summer since 1895. And while the heat wave was associated with La Nina conditions in the Pacific Ocean, it was 20 times more likely in such conditions than it would have been only 50 years ago, they say.
Meanwhile, December 2010 was the second coldest and November 2011 the second warmest in Central England since 1659. And, says the team, November's warmth is 60 times more likely to have occurred than in the 1960s.
The change in odds of the extremely cold December was considerably less, though, being only about half as likely. Even without climate change, unusual circulation patterns can still bring very cold winter months.
"We are in the golden age of satellite technology - we can see our planet changing in more detail than ever before," says Dr Kate Willett, a Met Office climate monitoring and attribution scientist.
"As a result, we see evidence far beyond changing temperatures and have observed intricate links in our climate system - these changes can differ radically from region to region, and impact our daily lives in many different ways."