And on Tuesday, the National Oceanic and Atmospheric Administration (NOAA) released a report calling 2011 a year of extreme weather.
Remember Hurricane Irene? Or the floods in Thailand and southern China and the deadly drought in the Horn of Africa or the 2011 and 2012 flood in Lagos, Nigeria? Heavy rains in Brazil that resulted in massive landslides.
Nine of the top 10 warmest years globally have occurred since 2000, according to NOAA.
The real challenge is figuring out whether a particular storm or flood was due to climate change or natural variables, said Chris Field, founding director of the Carnegie Institution's Department of Global Ecology.
"As we change the climate, we're shifting the odds for extreme weather," he said.
It's sort of like upping your chances of a car accident if you're speeding.
The four classes of extremes -- high heat, heavy precipitation and floods, duration and intensity of droughts and extremes related to higher sea levels -- have changed in the last 50 years, Field said.
"Increasingly, we are loading the dice towards these very damaging kinds of extremes," he said.
But that's not to say every weather event is related to warming temperatures.
Southern Greenland, northern Russia, and the eastern two-thirds of North America have felt the greatest warmth in 2012, but many places -- Alaska, Mongolia and most of Australia -- have been cool anomalies.
The men's final at the Wimbledon tennis tournament Sunday was stopped briefly for rain. Rain, in Britain? Although it has a reputation for sogginess, it's been cooler and wetter than normal for the last few months in the British isles.
America's northwest has also escaped the heat. The state of Washington just marked its seventh coolest June ever.
"When you've got a planet that's nearest warmest levels on record, that doesn't mean every part of the world is going to be the warmest ever," said Jeff Masters, director of meteorology for Weather Underground.
Jake Crouch, a climate scientist at the National Climatic Data Center, said weather patterns -- including the jet stream or the ocean-atmosphere systems in the Pacific known as El Niño and La Niña -- have a great effect on weather.
In 2011, two back-to-back La Niñas, each characterized by cooler-than-average water temperatures in the eastern Pacific, affected significant weather events -- including droughts in the southern United States and northern Mexico and in east Africa.
Scientists also analyzed the United Kingdom's very warm November 2011 and a very cold December 2010. They said that cold Decembers are now half as likely to occur versus 50 years ago, whereas warm Novembers are now 62 times more likely.
The report pointed out that some weather events, like the Thailand flooding, are influenced by humans in other ways.
"Although the flooding was unprecedented, the amount of rain that fell in the river 'catchment' area was not very unusual," the report said. "Other factors, such as changes in reservoir policies and increased construction on the flood plain, were found most relevant in setting the scale of the disaster."
The 2012 hurricane season has gotten off to a robust start, though meteorologist Thomas Downs of Expert Weather Investigations attributed that to a cyclical warming of Atlantic waters.
"We've had a tremendous start to the system. We are in the middle of a warm phase," he said.
"The biggest thing of this year is the cumulative effect of the last two seasons. Some parts of the United States have been under drought conditions for the past two years," he said, and did not have much rain in April and May. Less solar energy is absorbed by hot, parched land.
In releasing the state of the climate report Tuesday, Deputy NOAA Administrator Kathryn Sullivan said 2011 will be remembered for extreme weather. This year seems to be on the same track.
From now on, she said, every weather event takes place in the context of a changing global environment.
Extract from CNN
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