In the spirit of Earth Day, which happens today, I’ll blog about another important ecological topic: the alleged “global warming pause”.
About a year ago, I wrote a post about the climate-denier myth that “it’s been cooling since 1998″. As the post pointed out, this is based on cherry-picking the anomalously warm year of 1998 (atypical because it was an extraordinary El Niño year that brought a lot of heat from the tropical oceans into the atmosphere), then deliberately picking one or two years following and calling that “cooling”.
As the climate deniers have been called out about this lie, they’ve shifted the goalposts, and made the claim that the global warming has “paused” since 1998. As reported in Mother Jones, Fox News began playing this meme over and over again in 2012, so that soon the regular media were echoing their meme as well. But is it true? NO!
1) If you look at the record over the short-term (1998-2012), that’s a very short window to evaluate climate change, biasing your result by cherry-picking 1998 as the starting year. If you shift the frame just 5 years earlier (1993-2012), you’d get a warming trend instead, so such short-term averages are meaningless when they can be distorted by your choice of starting and ending points. In any case, climate scientists would point out that we can’t use the trend over 5 years or even 10 years to make any worthwhile conclusions. The main reason that we cannot look at records on the short term of 5-10 years or less is that there is too much “noise” in the data from short-term events, like the El Niño-La Niña cycles and other events that have nothing to do with the underlying causes of long-term climate change. The only valid approach to the data is to average over very long terms (20 to 30 years at the minimum). As you can see by clicking on the graphic, the long-term trend is unmistakable, and it’s scientifically invalid to cherry-pick a few short-term “cooling trends” of less than a decade in such a long-term record.
2) It turns out that this “pause” in the data set is not real—it’s due to missing data and incomplete data collection. For years, the global temperature average was calculated for about 84% of the earth’s surface, but did not have any of the Arctic temperature data because of the shortage of weather stations up there. But two different studies were just published which used the satellite temperature data from the Arctic to revise the global temperature average. Scientists have long known that the Arctic is warming and melting much faster than the rest of the world, since it is much more sensitive to climate change, and thus more likely to affect the average than other regions that are less sensitive. Sure enough, the “pause” disappears, and each year since 2003 shows much warmer global average temperatures than the old, incomplete data sets. When you fit a long-term regression to the more complete data, the upward trend is truly striking, with no “pause” whatsoever.
3. There may be another factor at work as well. The atmosphere is only a tiny part of the world’s complex system of water and gases that make up the hydrosphere and atmosphere. We’ve long known that most of the excess heat we’ve produced has gone into the largest sinks, the oceans, which have also warmed significantly over this time period as well (even though the high heat capacity of water makes the trend a lot slower). As a recent study by Trenberth and Fasullo (2012) just showed, since 1998 the Pacific Ocean has been warming much faster than in the past; another study has just confirmed it. This suggests that the capacity of the oceans to absorb all that carbon dioxide and heat energy has been exceeded, and now the oceans are taking up the heat faster than the atmosphere does. If this in indeed true, the new estimates that incorporate the missing Arctic data are not warming fast enough. If one includes the oceans and atmosphere together, the planet is warming much faster than anyone imagined!
Naturally, this complex scientific explanation goes right over the heads of most of the media, who can only understand and report on simplistic stories with a easy-to-remember punch line. Thus, we have plenty of people out there—not just the climate deniers and their backers in the right-wing think tanks and energy companies—who’ve been suckered in by this lie, and still haven’t learned what’s really going on.