Tuesday, November 29, 2011

2011 is on track to be tied for the 10th warmest year on record

It's raining (a lot) today, so when I saw the news that 2011 is cooler than 2010 and is only the 10th warmest year on record, I thought of the news hitting the denialist camps and them bouncing it around, saying, "Yeah! See? The world's cooling! It's cooler this year than it was at any year from 2002 through 2010 (save for 2008, which was a La Nina year, so that's anomalous)."

But wait... 2011 is a La Nina year, too, and according to a recent press release from the World Meteorological Organization, 2011 is on track to be tied (roughly) with 2001 (which wasn't a La Nina year) as having the 10th warmest world temperatures on record. This shouldn't be too much of a surprise for people (save if your political or religious or philosophical viewpoints don't allow for the possibility of physics happening).

However, there's one thing that people are missing: 2011 is the warmest La Nina year on record.

La Nina years are usually characterized by being cooler 0.1 to 0.15 degree C cooler than the years that precede and succeed them. In the graph, these years are shown in blue, and it's pretty clear that they are all cooler than the red year bars that surround them. However, the worrying trend is that past La Nina years have also been increasing in magnitude (values from here):
  • 1989: +0.12 degree C
  • 2000: +0.27 degree C
  • 2008: +0.36 degree C
  • 2011: +0.41 degree C
This creates a worrying trend: when a La Nina year places in the top-ten hottest years on record, then we've got to worry, because it's not an indication of cooling: its an indication of warming. Since La Nina patterns are usually 0.1 to 0.15 degree C cooler, then there is a good chance that 2012 will be in the +0.5 (tied for 3rd warmest year on record) to +0.55 (1st warmest year on record) degree C.

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