An extremely detailed write up on this with graphs. Wow.
I pasted a couple of tid bits from it.. For those wondering how they measure read paragraph 3 here.
But paragraph 2 is absolute key in possible errors!
A Big Picture Look At
"It appears that a significant decline in temperatures occurred during the last 17 months"
"The surface temperature record is burdened with issues of questionable siting, changes in siting, changes in equipment, changes in the number of measurement locations, modeling to fill in gaps in measurement locations, corrections to account for missing, erroneous or biased measurements, and the urban heat island effect"
"Since 1979 Earth’s “temperature” has also been measured via satellite. “The temperature measurements from space are verified by two direct and independent methods. The first involves actual in-situ measurements of the lower atmosphere made by balloon-borne observations around the world. The second uses intercalibration and comparison among identical experiments on different orbiting platforms. The result is that the satellite temperature measurements are accurate to within three one-hundredths of a degree Centigrade (0.03 C) when compared to ground-launched balloons taking measurements of the same region of the atmosphere at the same time"
"Conclusion:
“Earth’s “Temperature” appears to have increased during the last several decades, but there does not appear to be any evidence of rapid or accelerating warming."