SEARCH BLOG: GLOBAL WARMING and GIGO
I have written that if global warming was happening, and there was no real indication that new high temperature records were increasingly being set, then the calculated warming had to come from higher minimum temperatures being recorded. [here]
Since then, there has been a significant effort by Steve McIntyre at Climate Audit and Anthony Watts at surfacestations.org that reveal both improper manipulation of weather data that falsely creates upward trends in temperature... and improper maintenance and siting of many weather recording stations that cause artificially high temperatures to be recorded.
Now, from Climate Science, we learn that there is more than just improper siting leading to recording of artificially high minimum temperatures:
So, maybe some warming has occurred, but not so much, and it has been in higher lower temperatures, in winter, at high latitudes.
“…Therefore, the use of minimum temperatures at 1.5 or 2 m for interpreting climate system heat change is not appropriate. This means that the 1.5 to 2m observations of minimum temperatures that are used as part of the analysis to assess climate system heat changes (e.g., such as used to construct Figure SPM-3 in IPCC  and in Parker [2004, 2006] study) lead to a greater long term temperature trend than would be found if higher heights within the surface boundary layer were used….”
This means that a significant warm bias exists in the 2007 IPCC Report on the trends of the global average radiative forcing, since they base their estimate on a surface air temperature trend that includes minimum temperatures over land. This bias, which occurs whenever the nighttime surface boundary layer is stably stratified over land and the winds are light is, therefore, very significant at high latitudes in the winter, where much of the warming is reported to have occurred. This error in the IPCC construction does not mean that no warming has occurred, but it does mean that they have significantly overstated global warming in their report.
So tell me again why we should be so panicked? I really haven't seen much in the way of higher minimum temperatures in Michigan, but maybe 45° N isn't a high enough latitude... or maybe it's just that the change has been too negligible to have any real impact on anything.