Temperature 2007

This last January showed a strong el Nino, leading to the largest monthly global temperature anomaly ever recorded (according to NASA GISS), 0.87 deg.C. This caused researchers at the Hadley Centre for Climate Change Research to announce that 2007 would probably break the record for hottest year ever.

I said at the time that I thought the pronouncement was premature, because sometimes el Nino lasts a good long time (like 1998) but sometimes it’s very brief. The 2007 el Nino turned out to be brief, and it’s very unlikely that 2007 will break the record after all. The good people at the Hadley Centre will end up with egg on their faces. Even so, 2007 will turn out to be one of the hottest on record. Although it’s not yet complete, let’s use NASA GISS analysis to estimate where it will fall on the all-time-hottest-years list. The ten hottest complete years ever recorded, with their average temperature anomalies, are:

• 2005 @ 0.6225
• 1998 @ 0.5667
• 2002 @ 0.5592
• 2003 @ 0.55
• 2006 @ 0.5383
• 2004 @ 0.4867
• 2001 @ 0.4792
• 1997 @ 0.3992
• 1995 @ 0.3792
• 1990 @ 0.3775

So far this year, the average temperature anomaly is 0.597, which would put 2007 in 2nd place. If the average anomaly for November and December combined is greater than 0.415, then 2007 will indeed edge out 1998 for 2nd place. This is very likely to occur. The last time any month showed an anomaly less than 0.415 was July of 2004; since then we’ve had 40 months in a row hotter than that.

These results are for the calendar year, which runs from January to December. The climatological year runs from December through the following November. That way it includes uninterrupted seasons, winter (Dec, Jan, Feb), spring (Mar, Apr, May), summer (Jun, Jul, Aug), and autumn (Sep, Oct, Nov). The ten hottest complete climatological years ever recorded, with their average temperature anomalies, are:

• 2005 @ 0.6158
• 2002 @ 0.5717
• 1998 @ 0.5683
• 2006 @ 0.53
• 2003 @ 0.5233
• 2004 @ 0.5008
• 2001 @ 0.4533
• 1997 @ 0.3817
• 1995 @ 0.3792
• 1990 @ 0.3692

So far this climatological year the average temperature anomaly is 0.6055, which would also put 2007 in 2nd place. If the anomaly for November is greater than 0.2, then 2007 will indeed edge out 2002 for 2nd place. This too is very likely to occur. The last time any month showed an anomaly less than or equal to 0.2 was December of 2000; since then we’ve had 82 months in a row hotter than that.

Is it possible 2007 could still surpass 2005 for 1st place? In order for the calendar year 2007 average to exceed 2005’s, November and December would have to show an average anomaly of 0.75, which has only happened for three months in history (Jan 2007 @ 0.87, Mar 2002 @ 0.84, and Feb. 1998 @ 0.79). So it’s not impossible, but not very likely. In order for the climatological year 2007 average to exceed 2005’s, November would have to show an average anomaly of 0.73, which again has only been observed on three occasions.

So it seems very unlikely that 2007 will break the 2005 record, and similarly unlikely that it will fail to move into 2nd place on both all-time lists.

UPDATE UPDATE UPDATE

By request, here’s part of figure 7 from Thompson et al. 2003, Climatic Change 59, 137–155.