The past few months saw the first snowfall ever in Baghdad, record dumps in North America and China's coldest winter in a century. Does this mean global warming is out of steam?
Skeptics of human-caused global warming say the past winter supports theories that the sun has more to do with Earth's temperature than carbon emissions, but others say cold air from the south is a more likely explanation.
"Most of what we have seen can be related to this phenomenon called La Niña," said David Phillips a spokesperson on weather and climate for Environment Canada.
La Niña is El Niño's counterpart and occurs when strong winds blow the upper layers of warm ocean water off the coast of South America and cooler waters surface from the ocean's depths. These colder waters cool the atmosphere above and cause a variety of weather conditions around the world, including a colder winter in the northwest of North America and wetter weather in parts of Australia and Indonesia.
"A lot of people are saying this means global warming is finished," said Phillips. "It doesn't mean anything about global warming. This is just weather, this is not climate." However, Phillips adds that the cooling was remarkable.
"Although we certainly have seen some brutal weather in China, we've seen some record snowfalls in Canada and the eastern part of the United States, and we've had some extreme cold in the North.
"In fact, the ice has grown back in the eastern Arctic to where it's more extensive and thicker than it has been in 15 years."
Phillips said that while many people are shocked by the record cold, climatologists are not. "You just knew the odd time you're going to get the cooler than average [winter]." His comments are echoed by Ian Bruce, a climate change specialist with the David Suzuki Foundation.
"Global warming is the long term trend in our weather system that we're observing so it's not unexpected to have one year colder than others," said Bruce.
Bruce added that regardless of this winter's record lows, the coming year is predicted to be one of the hottest in a decade.
Tim Ball, a climatologist and global warming skeptic disagrees this year's weather is caused by La Niña and instead points to a decrease in solar activity as the cause of cooler temperatures.
Solar physicists have long known that the sun goes through regular cycles of inactive and active phases. During active phases the sun emits sun spots which increase the amount of warming radiation that reaches Earth. The last active cycle is nearly a year behind schedule and skeptics say this is the cause of this year's lower temperatures. Ball contends that a cooling of the sun is more worrisome than warming and something governments should be prepared to address.
"Planning for warming means that if it cools you're in a lot of trouble, the adaptation to that would be huge. But if you plan for cooling and it warms that's a lot easier adaptation. So you're preparing for the cooling but if it warms then that's a bonus," says Ball.
Solar physicist Ken Tapping with the National Research Council has confirmed the sun is late entering its active phase but said it is too early to conclude the Earth could be heading toward a serious cooling period.
However, Tapping did say that if solar activity doesn't pick up by 2010 it could be a cause for concern. Some theories suggest a bitter cold spell lasting from 1650 to 1715 was caused, at least in part, by an extended period of inactivity by the sun.
Additional reporting by Joan Delaney
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