Mathematician Luboš Motls takes on the new UAH data (source here) and some current thinking about slopes in global climate by adding his own perspective and analysis. Be sure to visit his blog and leave some comments for him - Anthony

UAH: June 2009: anomaly near zero

© unknownGlobal mean temperature according to UAH MSU for the first 8.5 years i.e. 102 months of this century. Linear regression gives a cooling trend by a hefty -1.45 °C per century in this interval. So if someone tells you that the trend is "of course" positive as long as we omit the year 1998, you may be very certain that he or she is not telling you the truth.

UAH MSU has officially released their June 2009 data. This time, they're faster than RSS MSU. The anomaly was +0.001 °C, meaning that the global temperature was essentially equal to the average June temperature since 1979. June 2009 actually belonged to the cooler half of the Junes since 1979.

Global warming is supposed to exist and to be bad. Sometimes, we hear that global warming causes cooling. In this case, global warming causes global averageness. In all three cases, it is bad news. The three main enemies of environmentalism are warm weather, cool weather, and average weather.

It is not a coincidence that these enemies are very similar to the four main enemies of communism. The four main enemies that were spoiling the success of communism were Spring, Summer, Fall, and Winter. :-) See Anthony Watts' blog for additional discussion.

Bonus: trends over different intervals

You may have been intrigued by my comment that the cooling trend during the last 8.5 years is -1.45 °C. What is the result if you choose the last "N" months and perform the linear regression?

You may see that the cooling trends are dominating for most intervals shorter than 110 months; the trend in the last 50 months is around -6 °C per century. Only when the period gets longer than 150 months i.e. 12.5 years (but less than 31 years), the trend becomes uniformly positive, around 1.2 °C per century for the intervals whose length is close to 30 years.

Note that those 12.5 years - where you still get a vanishing trend - is from January 1997 to June 2009. If you consider the UAH mid troposphere data instead (relevant for the part of the atmosphere where the greenhouse warming should be most pronounced, according to both proper atmospheric science and the IPCC report, page 675), all the trends are shifted downwards: