why heat waves do matter in the end

An individual heat wave may not mean much. But we're not seeing the occasional heat wave, we're seeing a disturbing pattern of them.

Last time it was bitterly cold in winter, climate change denialists cheered that blizzards were the ultimate proof that the world is not warming up while hypocritically pooh-poohing heat waves as inconclusive and playing with charts to make record highs look as if they plateued or fell when a long term trendline showed no such things. Legions of them used to claim that the world simply couldn't be getting warmer when it was snowing outside their windows and rushed to say that a single hellishly hot day or even week was not sufficient to say anything about the climate. Aside from the glaring double standard, they have a valid point. Short term data cannot say anything about the trajectory of global climates without some sort of context. So should it matter that if we go by what's happening in the Southern Hemisphere now, the summer of 2013 will be blistering for those of us in the North? Should we take note that it's so insanely hot in Australia that a new color had to be added to the heat map as record highs are being set every day?

Well, actually, it should. If we were to list two decades worth of top global temperatures from the hottest to the coolest, as Wikipedia has helpfully done, we'd find every year since 1997 to 2011 on the list competing for the top spot. In fact, 11 of the top 15 hottest years on record were from this millenium, and with 2012 being the hottest year on record for the continental U.S., it's a fairly safe bet that once the global temperature data for last year is finally reviewed, it too will appear on this chart. When we're looking at potentially 13 years of climbing highs as close to being in a row as we can realistically expect from a natural system, suddenly, the next heat wave does start to matter and we can start pointing to greater and greater extremes in heat as a demonstration of what we're seeing in long term trends. Locally, weather and temperatures will vary wildly, true, but when we look at the global context, not only was the last decade the hottest on record, it was the hottest by the biggest margin: over half of a degree Celsius. The second warmest decade's anomaly from the mean? Less than a third of a degree. And that was the 1990s.

So if someone tells you that global warming has stopped or isn't happening and the heat waves and record setting overall highs don't matter, this person is either willfully ignorant or lying. Every scrap of evidence we have points to continued warming that's happening faster than at any time we know that Earth has warmed up naturally before. No, the global warming monster won't come to your house and rip your face off and taxing civilization into environmentalism won't help in the coming decades of higher temps, but we do have to face reality. The world is getting warmer, we are helping to make it that way, and we're having more record highs than record lows, and when we tally them all up, they show an ever hotter world. We should start thinking of the record highs seen in the Outback as symptoms of global warming if we aren't already and prepare for 2013 to crank up the heat when summertime comes around for those of us north of the equator. There's ample evidence that it's a pretty reasonable thing to do and no amount of denial of blaming the scientists and pointing to the stars will ever make this evidence go away.