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Heatwaves and Blizzards — Which is the Best Evidence for Global Warming?

By Mark Lynas

Congratulations are due to North Texas this summer, for smashing the heat record set in 1980 of 69 days of triple-digit temperatures. With the mercury touching 106 degrees in Dallas on Tuesday, September 13, a new heat record was set for that day too.

But no-one will be celebrating the 46 additional deaths the ongoing heatwave reportedly caused in and around Dallas. Nor was there be much joy over the  devastating wildfires which burned through more than 100,000 acres, destroying over a thousand homes in the state.

Mark Lynas is the author of the new book “The God Species: Saving the Planet in the Age of Humans,” on sale Oct. 4, 2011.

Some have contrasted presidential aspirant Governor Rick Perry’s scepticism of global warming with the apparent impacts of climate change which already seem to be causing chaos in his own home state. “It is hard to know how bad the Texas climate would have to get before he [Perry] would concede that climate scientists were right,” complained Climate Progress blogger Joe Romm.

And indeed the Texas climate,  along with that of the U.S. and indeed the rest of the world, is undeniably warming up. Last month the U.S. National Weather Service confirmed that the Texas months of June, July and August were the hottest ever recorded in the history of the United States – trumping the previous record set by Oklahoma during the 1934 Dust Bowl.

This meshes with figures from NASA that 2010 tied with 2005 as the warmest year on record globally. Global warming is best described scientifically as a changing average, the shifting of a climatic baseline. So every year in the 1990s was warmer than the average of the 1980s, whilst every year in the 2000s was similarly warmer than the average of the 1990s.

Climate scientists are always careful to point out that no single event can be entirely ascribed to climate change. But a changing baseline means that extreme heat – and its impacts like fire and drought in places like Texas – is arriving more and more frequently, an notching up ever-higher records. In contrast, cold events are becoming rarer and less extreme.

But wait a minute, climate sceptics will argue. What about the cold winters of recent years? Well, here’s where the story gets interesting, and where we discover the value of the scientific method as opposed to our very human ‘gut feelings’, everyday experiences and short memories. This may seem difficult to believe, but according to a recent paper published in the journal Geophysical Research Letters (GRL), the last two winters’ warm extremes were more “severe” than their cold snaps.

In winter everyone notices a blizzard – if your car is buried in snow, the highways are in chaos, and no-one can get to work, this creates a sense of crisis and lasting memories. Hence the so-called ‘snowmaggedon’ events in 2010, which were used by some conservatives as evidence against the reality of global warming.

This stands to reason, of course – if the world is getting warmer, why is it snowing so much in winter? The answer lies in what we don’t notice – those mild days in winter when no snow lies, and the weather feels strangely springlike, even in January and February. According to the GRL paper, when taken in the context of the last 63 northern hemisphere winters, those of 2009-10 and 2010-11 were more unusual for their warmth than for their cold. For cold extremes, they ranked 21st and 34th respectively, whilst for warm ‘snaps’ they came in at 12th and 4th.

Unfortunately, when ‘common sense’ comes up against science, many of us stick with our common sense – even when statistically our own perceptions can be shown to be almost certainly wrong. Perhaps that is part of the reason why those arguing for stronger U.S. domestic action on global warming have such a high mountain to climb.

Mark Lynas is an environmental writer and commentator. He is the author of “Six Degrees: Our Future on a Hotter Planet,” which won the Royal Society Prize for Science Books in 2008. His other book,” High Tide: News from a Warming World,” was short-listed for a Guardian First Book Award. In September 2010, he was appointed the Advisor on Climate Change to Mohamed Nasheed, president of the Republic of Maldives. Lynas is also a Visiting Research Associate at Oxford University’s School of Geography and Environment.

Comments

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