The most quantitative evidence for global warming consists of 1.6 billion earth land surface temperature measurements dating back to Thomas Jefferson and Benjamin Franklin.
There is useable Earth coverage from 1800 to the present, and excellent coverage from 1900 onward. There have been several criticisms of the prior analyses of these data by NOAA, NASA, and the UK.
These include data selection bias (the groups use on 20% or less of the available stations), poor station quality (80% of the US stations are ranked poor by US govt standards), unseparated influence of urban heat islands, and possible bias from the adjustment procedures applied to the data to compensate for station moves and instrument changes.
We have now completed a new study of all these issues. Using a statistical approach developed by team member Robert Rohde, we are able to use virtually all the data. We’ve studied each of the systematics in depth, and have looked at possible driving forces other than the greenhouse effect. Our ongoing work consists of analysis of ocean data and exploratory analysis of other climate effects. In particular, North Atlantic Oscillations appear to play a larger role in global climate than had been previously recognized.