Watts Up With That?

My apologies if the quick response that I sent to
Andy Revkin and several other journalists, including the
suggestion that it was a tempest inside somebody’s
teapot dome, and that perhaps a light was not on
upstairs, was immoderate. It was not ad hominem, though.

I haven’t seen the original letter and don’t know who the
comment was about. However, it certainly sounds like an ad
hominem remark and one that is highly inappropriate for a
federal civil servant. I have a number of comments about
other aspects of the letter.
Hansen says:

Recently it was realized that the monthly
more-or-less-automatic updates of our global temperature
analysis (http://pubs.giss.nasa.gov/abstracts/2001/Hansen_etal.html)
had a flaw in the U.S. data. In that (2001) update of
the analysis method (originally published in our 1981
Science paper – http://pubs.giss.nasa.gov/abstracts/1981/Hansen_etal.html)
we included improvements that NOAA had made in station
records in the U.S., their corrections being based
mainly on station-by-station information about station
movement, change of time-of-day at which max-min are
recorded, etc.

Unfortunately, we didn’t realize that these
corrections would not continue to be readily available
in the near-real-time data streams. The same stations
are in the GHCN (Global Historical Climatology Network)
data stream, however, and thus what our analysis picked
up in subsequent years was station data without the NOAA
correction. Obviously, combining the uncorrected GHCN
with the NOAA-corrected records for earlier years caused
jumps in 2001 in the records at those stations, some up,
some down (over U.S. only).

The first sentence “it was realized” certainly makes it
sound like they identified the problem themselves (a
position not taken in the webpage itself.) Moving on, Hansen
says that the USHCN “corrections would not continue to be
readily available in the near-real-time data streams”. If
GISS is using USHCN adjusted data (as appears to be case
from the description in Hansen et al 2001 and the website),
this claim is incorrect. Readers in doubt of this may go to
the USHCN website ftp://ftp.ncdc.noaa.gov/pub/data/ushcn/ ;
the file hcn_doe_mean_data.Z contains three versions of
USHCN data, included the version that Hansen says is
unavailable. This file was most recently updated on March 1,
2007 and, for the majority of sites, contains adjusted USHCN
data up to Oct 2006. At present, GISS has only updated USHCN
records to March 2006. Thus, not only are the adjusted USHCN
versions available, they are available more recently than
presently incorporated into the GISS temperature
calculations.

Data from the other major station archive (GHCN) can be
downloaded from ftp://ftp.ncdc.noaa.gov/pub/data/ghcn/v2 .
The GHCN raw data set and v2.mean.Z and the adjusted data
set v2.mean_adj.Z are both updated all the time, most
recently Aug 11, 2007. In the version that I downloaded in
June, the USHCN record only went to March 2006, the period
of the GISS record. However, readers can confirm that both
the GHCN raw and GHCN adjusted versions have been archived
concurrently and that the switch from one version to another
was not required because of version unavailability.

In this context, the form of the present layer of GISS
corrections seems extremely rushed and inappropriate. If
GISS wishes to start with GHCN adjusted data, then it’s easy
to do so. Just use it. There’s no need to estimate the
required correction to undo the effect of switching data
sets. Just stick with the data set that they started with.
Far simpler and cleaner than throwing another “correction”
into the mix – a correction which has required overwriting
their entire input data for all 1221 USHCN stations prior to
2000.

1998
Hansen goes on to say:

Also our prior analysis had 1934 as the warmest
year in the U.S. (see the 2001 paper above), and it
continues to be the warmest year, both before and after
the correction to post 2000 temperatures. However, as we
note in that paper, the 1934 and 1998 temperature are
practically the same, the difference being much smaller
than the uncertainty.

Unfortunately, this statement is again untrue. The data
online at GISS http://data.giss.nasa.gov/gistemp/graphs/Fig.D.txt
immediately prior to the changes showed 1998 as the warmest
year (admittedly by a negligible margin of 0.01 deg C), but
still the warmest, contrary to the claim made here. GISS has
overwritten this data file and did not preserve an online
version of the uncorrected data that they had previously
shown. However, by chance, I happened to have had the data
in my R-session when GISS made the changes and I assure
readers that the GISS data
shown here
purported to show that 1998 was the “warmest”. Hansen may
have been for 1934 before he was against it. But now that
he’s for 1934 once again, he can’t say that he was for it
all along.

In the

NASA press release in 1999 , Hansen was very strongly
for 1934. He said then:

The U.S. has warmed during the past century, but
the warming hardly exceeds year-to-year
variability.Indeed, in the U.S. the warmest decade was
the 1930s and the warmest year was 1934.

This was illustrated with the following depiction of US
temperature history, showing that 1934 was almost 0.6 deg C
warmer than 1998.

From a Hansen 1999 News Release:
http://www.giss.nasa.gov/research/briefs/hansen_07/fig1x.gif

However within only two years, this relationship had
changed dramatically. In

Hansen et al 2001 (referred to in the Lights On letter),
1934 and 1998 were in a virtual dead heat with 1934 in a
slight lead. Hansen et al 2001 said

The U.S. annual (January-December) mean temperature
is slightly warmer in 1934 than in 1998 in the GISS
analysis (Plate 6)… the difference between 1934 and 1998
mean temperatures is a few hundredths of a degree.

From Hansen et al 2001 Plate 2. Note the change in
relationship between 1934 and 1998.

Between 2001 and 2007, for some reason, as noted above,
the ranks changed slightly with 1998 creeping into a slight
lead.

The main reason for the changes were the incorporation of
an additional layer of USHCN adjustments by Karl et al
overlaying the time-of-observation adjustments already
incorporated into Hansen et al 1999. Indeed, the validity
and statistical justification of these USHCN adjustments is
an important outstanding issue.

Arctic Changes

Changes in the relationship of the 1930s to recent values
have not merely been made in the United States. In the
Arctic, there has also been a progressive change in the
relationship of temperatures in the 1930s to recent
temperatures, a point previously discussed at
CA here .
Hansen and Lebedeff 1987 showed very warm 1930s in the
Arctic, as shown in the excerpted figure showing the 64-90N
temperature history.

Excerpt from Hansen and Lebedeff 1987, showing 64-90N
temperature. The horizontal plot is from 1880 to 1985 (as
seen in the full Figure 7 of the original article shown

here )

The graphic below compares the most recent version of the
same graph (plotted from online data at GISS), marking two
bold points for 1937 and 1938 obtained from the printed
information in Hansen and Lebedeff 1987 (which prints out
the data now shown online). For both 1937 and 1938, the GISS
estimates have been reduced by approximately 0.4 deg C.
Despite recent warming, 2005 was the first year in which
64-90N values exceeded the former 1938 value – see dotted
line – (indeed, 2003 was the first year that exceeded the
“adjusted” 1938 value). While there are undoubtedly “good”
reasons for these adjustments (and I am not here arguing the
point one way or the other), the net effect of the
adjustments has been to consistently lower temperatures in
the 1930s relative to more recent values. Whether these
adjustments prove justified or not, modifications to the
temperature record of this magnitude surely warrant the most
careful scrutiny before turning the “lights out upstairs.”

64-90N from Hansen 64-90N zone downloaded today. Thick – 5
year running mean (often used by Hansen). Points are
selected values from Hansen and Lebedeff 1987. Dotted line
compares 1938 value from Hansen and Lebedeff 1987 to other
values.