The Global Surface Air Temperature
Record Must Be Wrong
Volume 3, Number 12: 15 June 2000
(Read more about this subject in www.co2science.org)
Although we rarely deal with things not published in the conventional peer-reviewed
scientific literature, we take exception this issue to discuss a matter that
has recently been addressed in several such publications. This deviation from
our standard policy is taken for the important reason that these publications
have convinced us that the global surface air temperature record, which is used
to support the idea that the earth has warmed dramatically over the past century
or so, is incorrect. Although we could easily have lived with the statement
of Mann et al. (1999) that "the past decade and past year are likely the
warmest for the Northern Hemisphere this millennium" - since that claim
says nothing about why that might be so - we now feel that such is definitely
not the case; and, hence, we feel obligated to address the veracity of this
claim, which is generating all manner of hysteria over the use of CO2-emitting
If you want to contribute with our work, sending no money,
Our conversion on this matter began with our reading of John Daly's treatise
on the global surface air temperature record (Daly,
2000), which is posted on the website of the Greening
Earth Society. In reference to the divergent trends of the surface air
temperature record, which exhibits a dramatic warming over the past 21 years,
and the lower tropospheric temperature record produced by satellite microwave
sounding units, which exhibits no such warming, he cites the only three explanations
that can possibly account for this discrepancy: (1) the surface record is incorrect,
(2) the satellite record is incorrect, (3) both records are correct, and their
different temperature trends are due to some unknown atmospheric process or
Considering the same issue, Balling (2000) notes that the recent National Research
Council (2000) report on the subject acknowledges that the two records should
produce similar trends: "if global warming is caused by the buildup of
greenhouse gases in the atmosphere, it should be evident not only at the earth's
surface, but also in the lower to mid-troposphere." Indeed, the report
says that the best climate models available "predict that the lower to
mid troposphere should warm at least as rapidly as the earth's surface."
Hence, since the two temperature trends should be close to identical, Daly's
third explanation for their divergence can be ruled out, leaving us either his
first or second explanation as the correct one.
Daly opts for explanation number one - the surface air temperature record is
incorrect. He supports his contention with illustrations of a number of potential
sources of error that are known to plague this record:
(1) temporal changes in microclimate surrounding the
temperature measurement site, such as urbanization, which go unrecognized or
for which insufficient adjustments are made,
(2) long-term degradation of the shelter housing the temperature-measuring equipment,
such as its white paint becoming less reflective and its louvers partially obstructed,
(3) changes in what is actually being measured, such as true daily maximum and
minimum temperatures or temperatures at specified times of day,
(4) changes in measurement devices and ways of accessing the data, such as changing
from having to open the shelter door to read the temperature, as was done in
earlier days, to not having to do so due to the automatic recording of the data,
as has become typical in more recent times,
(5) general station degradation and many station closures over time,
(6) changing and uneven geographical representation in the surface temperature
(7) poor attention to careful acquisition of data in many parts of the world,
(8) a number of problems associated with obtaining a correct and geographically
complete record of surface air temperature over the 70% of the globe that is
covered by oceans.
Michaels and Balling (2000) additionally point out the great difficulty of appropriately
correcting for the onset and development of urbanization effects in stations
that once were considered rural but have, in the past decade or two, experienced
the encroachment of nearby cities. As they describe the situation, urban effects
have largely been removed from specific temperature records when they dominate
them for many decades; but when encroaching urbanization has begun to exert
its influence over only the past 10 to 15 years, "we have no objective
mechanism for isolating the effect." Hence, as they correctly state,
"the urban effect is here [in the latter part of the record], and it
will grow exponentially."
But how do we absolutely know that all, or even any, of these potential problems
are indeed occurring? One way suggested by Balling is to compare the satellite
record with the surface air temperature record over the portion of the earth
that is known to possess the highest quality surface air temperature data. This
data set comes from the U.S. Historical Climatology Network, and contains, among
other things, monthly averages of mean near-surface air temperature for 1,221
high-quality largely non-urban stations within the 48 contiguous states of the
United States of America.
In making this comparison, Balling found that the surface and satellite records
for this portion of the globe were nearly identical, and that each showed no
statistically significant trend, nor did the time series of differences between
them show any such trend. He acknowledges, however, that the conterminous United
States only covers 1.54% of the earth's total surface area; but he makes the
point that the best near-surface air temperature records to be found on the
planet match up beautifully with the measurements made from satellites. We thus
conclude with him that if equally good surface air temperature records were
available for the rest of the earth, they too would match up equally beautifully
with the corresponding satellite record
and show no warming.
But are there any other reasons to believe that this should be the case? In
a word, yes. And we start with a contribution from Daly on this point.
Daly notes that although various climate models differ substantially in their
predictions of greenhouse warming around the globe, they all agree on one thing:
the warming, if it occurs at all, should be accentuated in earth's higher latitudes.
Hence, the planet's polar regions should be prime candidates for displaying
the postulated warming. But when high-quality scientifically-supervised temperature
records from these regions of the earth - both north and south - are checked,
they too show no warming.
Finally, we have the radiosonde or weather balloon record of temperature in
the same part of the atmosphere that is monitored by satellite. Both Balling
and Daly point out that its temperature history of the past two decades closely
mirrors that of the satellite record, and that it once again shows no warming.
In view of the near-perfect agreement among the satellite and surface records
over the conterminous United States, which all show no warming over the past
two decades, as well as the similar finding of no warming in high-quality stations
from both of the earth's polar regions, where greenhouse warming is predicted
to be greatest, plus the fact that the satellite and balloon records shows no
warming over the entire earth over this period, we thus conclude that there
truly has been no warming due to any cause over this period of time over the
entire planet, and that the only reason the surface record for the globe shows
warming is that outside of the United States and a few other places of high-quality
temperature measurement, the surface record is just plain wrong, for the host
of reasons listed, described and illustrated by Daly, Balling, and Michaels.
Furthermore, since the significant increase in greenhouse gas radiative forcing
experienced to date should surely have produced some warming by now, if it were
not thwarted by compensating mechanisms in the real atmosphere, we also believe
there is no compelling reason to believe that it will necessarily produce any
warming in the foreseeable future.
Dr. Craig D. Idso
Dr. Keith E. Idso
Balling Jr., R.C. 2000. Reconsidering reconciliation: Understanding the NRC
report. In: Michaels, P.J. (Ed.). State of the Climate Report: Essays on Global
Climate Change. New Hope Environmental Services, pp. 8-13.
Daly, J.L. 2000. The surface record: "Global mean temperature" and
how it is determined at surface level. Report to the Greening Earth Society.
Available at www.greeningearthsociety.org.
Mann, M.E., Bradley, R.S. and Hughes, M.K. 1999. Northern Hemisphere temperatures
during the past millennium: Inferences, uncertainties, and limitations. Geophysical
Research Letters 26: 759-762.
Michaels, P.J. and Balling Jr., R.C. 2000. The Satanic Gases: Clearing the Air
About Global Warming. Cato Institute, Washington, DC.
National Research Council, Panel on Reconciling Temperature Observations. 2000.
Reconciling Observations of Global Temperature Change. National Academy Press,
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