Latest information researched by Ant.
Plot from the Berkeley full data set. I've found a problem with spatial sampling and station location changes. I'm working through identification of changing spatial sampling and its effect on the result, but it will take me weeks more. But leaving that aside for now, this is the data presented.
A longer time scale (of previous data) looks like this:
So yes, there has been some warming recently. But we have also been coming out of Maunder and Dalton minima where the temperature was lower.
Next I looked at the CO2 record (from an article by Dr Tim Bell in the Canada Free Press citing data from Ernst Beck):
I found that CO2 was around 400 ppm in 1800 and around 300 in 1960. Below is a CO2 record from NOAA at their observatory at Mauna Loa (active volcano, emitting CO2).
I see that the CO2 is currently about 400 ppm, much the same as it was in 1940, 1860, 1820, and other dates.
I plotted the Berkeley data for 2002-2011 (with the same color coding as above). The black line is a linear least squares regression fit. The slope is negative, and not statistically different from zero with this data set.
There has not been any global warming since about 2002. CO2 has been rising, but due mainly to natural phenomena (including eruptions). CO2 levels were "high" in 1820, yet the temperature was cool.
See this also: