From Nature: Climate change: The case of the missing heat
Of course, this is actual science, so don't expect it to appear in any denier memes...
Climate change: The case of the missing heat
For several years, scientists wrote off the stall as noise in the climate system: the natural variations in the atmosphere, oceans and biosphere that drive warm or cool spells around the globe. But the pause has persisted, sparking a minor crisis of confidence in the field. Although there have been jumps and dips, average atmospheric temperatures have risen little since 1998, in seeming defiance of projections of climate models and the ever-increasing emissions of greenhouse gases. Climate sceptics have seized on the temperature trends as evidence that global warming has ground to a halt. Climate scientists, meanwhile, know that heat must still be building up somewhere in the climate system, but they have struggled to explain where it is going, if not into the atmosphere. Some have begun to wonder whether there is something amiss in their models.
Now, as the global-warming hiatus enters its sixteenth year, scientists are at last making headway in the case of the missing heat. Some have pointed to the Sun, volcanoes and even pollution from China as potential culprits, but recent studies suggest that the oceans are key to explaining the anomaly. The latest suspect is the El Niño of 1997–98, which pumped prodigious quantities of heat out of the oceans and into the atmosphere — perhaps enough to tip the equatorial Pacific into a prolonged cold state that has suppressed global temperatures ever since.
“The 1997 to ’98 El Niño event was a trigger for the changes in the Pacific, and I think that’s very probably the beginning of the hiatus,” says Kevin Trenberth, a climate scientist at the National Center for Atmospheric Research (NCAR) in Boulder, Colorado. According to this theory, the tropical Pacific should snap out of its prolonged cold spell in the coming years.“Eventually,” Trenberth says, “it will switch back in the other direction.”
The simplest explanation for both the hiatus and the discrepancy in the models is natural variability. Much like the swings between warm and cold in day-to-day weather, chaotic climate fluctuations can knock global temperatures up or down from year to year and decade to decade. Records of past climate show some long-lasting global heatwaves and cold snaps, and climate models suggest that either of these can occur as the world warms under the influence of greenhouse gases.
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