U.S. and Global Temperatures: a correction

First, Dr Schmidt’s email: 

 I tried to post this on your blog, but got a "You are not authorized to perform this action" response. Regardless of whether this gets posted or not, you should know that Pilmer is not a trustworthy source of information. Gavin Schmidt ===================================== Many of the things that you "didn't previously know", are actually just not true, as a moment's research would have shown. For instance, the GISTEMP analysis is freely available online: http://data.nasa.giss.gov/gistemp and shows very clearly that, indeed, that the top ten warmest years have occurred since 1995, and that 1934 is nowhere near the warmest (anomaly -0.05, compared to the last ten years range of +0.32 to +0.62). http://data.giss.nasa.gov/gistemp/tabledata/GLB.Ts+dSST.txt What you are reading instead is a grotesque misquotation and distortion of an extremely minor correction involving only a set of US temperatures that had less than 0.002 degC impact on the global mean. http://data.giss.nasa.gov/gistemp/2007/ You are being lied to - and you can easily do some 'due diligence' of your own to prove it to yourself. http://www.realclimate.org/wiki/index.php?title=Ian_Plimer#Books ============ 

In fact, I had checked Ian Plimer’s asser­tion at the NASA GISS site before post­ing my review and had real­ized that the data was U.S. data only. So I am guilty of the same eli­sion that is in Plimer’s book (page 99). In his defense, Prof. Plimer was dis­cussing the dif­fer­ent promi­nence giv­en to find­ings that sup­port the case for alarm­ing warm­ing and those that con­tra­dict it. My eli­sion was the worse one. I can only plead that I men­tioned the fact in pass­ing and did not pay suf­fi­cient atten­tion to the implication.

I do not agree with Dr Schmidt that I am “being lied to” by Prof Plimer. I am aware, of course, that a num­ber of oth­er review­ers have also point­ed to state­ments in Heav­en + Earth that they say are wrong. Some have turned these (claimed) errors of fact into hys­ter­i­cal ad hominem claims. 

I would have been sur­prised if, in such a long book as Plimer’s, with such a vari­ety of argu­ment (and a bit of invec­tive as David Stock­well notes), there were not some errors. I can­not agree, how­ev­er, that this means Plimer is ‘lying’ to me or any­one else. I con­ced­ed in my review that his pur­pose was rhetor­i­cal (that is, to per­suade). But his approach is thor­ough­ly respectable in the sense that he punc­til­ious­ly cites sources, even to the point of exag­ger­a­tion. If he’s wrong in fact or inter­pre­ta­tion, he’ll be found out as Dr Schmidt has shown. That’s what schol­ar­ship is all about. It’s not at all what we expect of a liar.

But Dr Schmidt has a sec­ond good point, too, about doing the ‘due dil­gence’. The impact of the U.S. record on the glob­al tem­per­a­ture record was debat­ed at length in 2007. I was unaware of this at the time I wrote my review. I’ve caught up now: 

My conclusion

Comparison of GISS with satellite (UAH, RSS) temperature data

The U.S. sur­face sta­tion tem­per­a­ture record, from which this debate about 1934 springs, now seems to be, for the most part, ques­tion­able. No doubt it will be improved. But where does this leave the more inter­est­ing ques­tion of the impact on the glob­al tem­per­a­ture record? I agree again, here, with Dr Schmidt that the U.S. tem­per­a­ture record should make no more dif­fer­ence than the Unit­ed States’ 2% cov­er­age of the sur­face of the earth implies. But it’s very like­ly that the U.S. tem­per­a­ture record does have a dis­pro­por­tion­ate influ­ence on the glob­al record.

The pror­tion of GISS sta­tions out­side the Unit­ed States was esti­mat­ed to be only about 50% (for the oth­er 98% of the earth­’s sur­face) in 2005. Recent data indi­cates that the pro­por­tion has dropped dra­mat­i­cal­ly over the past thir­ty years as non-US sta­tions drop out of the net­work. This is said to be part of the expla­na­tion for the diver­gence between the GISS records and the glob­al satel­lite records that show still more clear­ly than GISS the fall in tem­per­a­tures since the start of this cen­tu­ry (GISS shows this trend, too).

At the least, the dis­pro­por­tion­ate rep­re­sen­ta­tion of the U.S. sta­tions in the GISS glob­al data­base is a rea­son for legit­i­mate con­cern that the errors in (and adjust­ments of) the U.S. data would per­me­ate to the rest of the GISS glob­al aver­ages temperatures. 

Foot­note: I do not nor­mal­ly repro­duce emails. But Dr Schmidt makes clear that this email trans­mits com­ments that he intend­ed, but was unable, to make on the sto­ry itself. So I have pre­sumed that he would not object to it being published.

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