Anomalies in global average surface temperatures for La Niña and other years. Credit: WMO.
Global temperatures in 2011 will likely rank as the 10th-warmest on record, according to the World Meteorological Organization (WMO). If this ranking holds up once data from November and December come in, it would mean that 13 of the warmest years since record-keeing began have all occurred during just the past 15 years.
Still, the 2011 figures would mark a dip from last year, which was tied as the warmest year on record. Some people might think this means that planet is no longer warming, but that wouldn’t be a valid conclusion in any case. Global warming doesn’t mean the globe will literally be warmer each year than it was the year before. It’s an overall upward trend over a period of decades: no individual year means much by itself.
What’s remarkable, in fact, is that temperatures in 2011 did not cool off more than they did. The the fact that they didn’t may be just another indication that manmade global warming is really happening.
For much of this year, an unusually intense La Niña event — the strongest in at least 60 years — took place in the tropical Pacific Ocean. La Niña, which is part of a natural climate cycle, is characterized by a large area of cooler than average sea surface temperatures near the equator. Through a series of interactions between the ocean and air above it, these cooler waters can help reconfigure global weather patterns. In 2011 alone, La Niña has been implicated in everything from the (still ongoing) Texas drought to historic flooding in eastern Australia and southern Asia this year.
La Niña cools and this has been the strongest one in a long, long time. And, by checking the chart, we can see that the year following a La Niña usually has global temperatures at least 0.15°C higher, with some being almost 0.25 °C. This could make 2012 the warmest year in recorded history.
Of course, we do have 2 months to go and maybe things could change. But the fact that a cooling, very strong La Niña had such a small effect on cooling is worrisome.