2007 warmest year on record? Coldest in this century

As Lubos explains,

One month ago, we noticed that November 2007 was the coldest month since January 2000. Well, the RSS MSU satellite data prepared by remss.com show that December was even cooler. The December anomaly was -0.046 °C, compared to -0.014 °C in November. That means that December 2007 was also cooler than the average December from 1979. Moreover, we can finally complete the ranking of the years!

Let me start with forecasts in the mainstream media.

In January 2007, we were informed that 2007 was either likely or certain to surpass 1998 and become the world's warmest year on record by most media, including:

Reuters
AP & Foxnews
IHT
BBC
MSNBC
CBS
USA Today
The New York Times
The New York Sun
The Washington Post
National Geographic
CBC
The Guardian
The Independent
China People Daily
ABC Australia
Discovery Channel
Science Daily
Met Office

as well as virtually all other media you know. They justified this statement by referring to scientists who have combined greenhouse gases with the observed El Nino. Many sources, such as the New York Sun, even gave you the probability that 2007 would be the hottest year as 60 percent. They immediately added that this should "add momentum for the next phase of the Kyoto protocol", a comment that clarifies what is the actual goal of many of the people who study these questions professionally.

In the middle of the year when it started to be clear that the prediction was bogus, Phil Jones (Reuters) changed his mind only infinitesimally. It would be the second hottest year, he said. These big-shot agenda-driven scientists never have the courage to say that they were simply wrong.

Reality: thermometers

However, the greenhouse gases are not too important and El Nino was replaced by La Nina. As a consequence, RSS MSU data for the lower troposphere (graph, more graphs) show that 2007 was the coldest year in this century so far. In alarmist jargon, it was the ninth hottest year on record: the most recent year was cooler than all other years in this century as well as 1998 (by a whopping 0.41 °C) and even 1995. According to different datasets (HadCRUT3, UAH MSU, NOAA), the year is going to be approximately the 8th (HadCRUT3) or 7th (NOAA) or 6th warmest year. UAH might report 2007 as the 4th warmest year and GISS will be a real exception because 2007 will be almost certainly its 2nd warmest year (as James Hansen said a few weeks ago, after 2005 but slightly above 1998) - but it is still very far from the hype about the hottest year. Your humble correspondent is not the only one who believes that the satellite measurements such as RSS, UAH are more accurate than GISS, HadCRUT3. It just happens that HadCRUT3 is closer to RSS than UAH to RSS, as far as the recent rankings go.

The RSS MSU linear trend extracted from the 1998-2007 interval is -0.48 °C per century of cooling! Numerically, it's almost the same trend that we assign to the 20th century but with the opposite sign. The RSS MSU data imply that 2007 was 0.12 °C cooler than the already cool year 2006. Other teams will generate qualitatively compatible results but substantially different numbers, raising doubts about the reliability of the temperature measurement even in the modern era.



Figure 1: Global cooling. Nine hottest years on record as shown by the RSS MSU calculations, from the hottest year 1998 to the coolest year 2007.

The choice of 1998 as the beginning of this graph is, of course, a P.R. trick to make the trend look as cooling as possible. If someone chooses e.g. a year in 1970s - the coldest year in the last 70 years - as his beginning, it is a P.R. trick, too, even though the goal has the opposite one. Certain qualitative conclusions simply depend on these choices and one must be careful about this fact. Similar issues are also discussed in the fast comments. Moreover, I only included the last 10 years for efficiency because typing three times as many numbers to the Excel file would be rather tiresome. Incidentally, if I wanted to demonstrate recent global cooling, I could have been even tougher and show you 36 months since January 2005, including the linear regression:



Figure 2: Global cooling 2005-2007. The trend is over 15 °C of cooling per century. ;-) Also, the trend is accelerating: for the 12 months of 2007, a similar linear regression gives about 35 °C of cooling per century. :-)