A New Revelation

We have some new Climate e-mails to peruse. This one is from the fourth pdf. I transcribed it by hand so if you find any errors let me know.

Subject: Re: Fwd: US temperature correction graphic and file
From:Reto Ruedy
Date:Mon, 13 Aug 2007 11:30:24 -0400
To:James Hansen
CC:Makiko Sato , gavin@e-mail, klo@e-mail

Jim,

I did make those calculations (I assume you mean using only GHCN and hand-adjusting only St. Helens and Lihue, in both cases decreasing the trend, eliminating a 1C and .8C step, resp., as stated in our 1999 paper, also using our urban adjustment.

I only held them back because bringing in a new analysis at this time would confuse the situation beyond hope.

As far as global means are concerned, the effect of our cleaningis slightly negative for the pre-1950 period, slighly positive thereafter, the biggest deviations are -.01C in 1922, +.01C in 2006; the change in 1900-1999 (lin. trend) is .01C/century (i.e. without cleaning it would decrease by .01C).

The US trend however is a different story though not surprising: In addition to the change caused by the UHCN modifications (+.30C for the 1900-1999 change as noted in our 2001 paper: +.14 TOBS, +.16 station hist.adj), the other modifications added .08C/century to the trend. So the trend would decrease by .38C.

The deviations for the individual years caused by the cleaning range from -.13 in 1922 to +.37 in 2006. The optical impression this creates when you look at the table of data is totally misleading: the 1998 anomaly just happens to fall below 1C (.93C) whereas 1921, 1931, 1934 are above 1C (1.27, 1,20, 1.37C) !

Reto

It would be real nice to find out what this is about. At first glance it appears they adjust things in a way that adds almost .4°C to the US trend. Is this a valid adjustment? We would need to go back to the station data and then all the various adjustments and corrections to find out.

Think of it this way though. If the trend has been incorrectly adjusted by nearly .4°C a century then the temperature trend is almost non-existent.

H/T Author and Commenters at Watts Up With That

Cross Posted at Classical Values