Greenhouse Warming or Greenhouse Gases??
The fingerprint of
anthropogenic greenhouse warming predicted by computer models is absent from
real-world, observed trends in atmospheric temperature change
THE
FACT of warming tells us nothing of the cause. Yet the scientific consensus is
that, though the rapid climatic warming from 1906 to 1940 was a natural
recovery from the historically low temperatures of the Little Ice Age, it is we
who are chiefly to blame for the equally rapid warming from 1975 to the present.
Since some climatologists challenge this consensus, can we settle the debate by
predicting with models and then detecting by observation a characteristic
“signature” in the climate data that allows us definitively to distinguish
between anthropogenic and natural warming of the Earth’s atmosphere? This paper
answers that key question.
To identify the distinctive signature of anthropogenic warming caused by
greenhouse-gas emissions, we begin with a little elementary atmospheric
physics.
The surface of the Earth does not cool primarily by thermal radiation. The main
greenhouse gas, water vapor, generally maximizes at the surface in the tropics
and sharply decreases with both altitude and latitude. There is so much
greenhouse opacity immediately above the ground that the surface cannot
effectively cool by the emission of thermal radiation.
Instead, heat is carried away from the surface by fluid motions ranging from
the cumulonimbus towers of the tropics to the weather and planetary scale waves
of the extratropics. These motions carry the heat upward and poleward to the
“characteristic emission level” one optical depth into the atmosphere, known as
τ=1. From here emitted thermal radiation can escape to space. Crudely speaking,
the emitted thermal radiation is proportional to the fourth power of the
temperature at the characteristic emission level.
In the diagram, lighter shading represents reduced opacity as water-vapor
density diminishes with altitude. Largely because of the motions of the
atmosphere, the temperature decreases with altitude to a level known as the
tropopause. The height of the tropopause varies with latitude. In the tropics
it is about 16 km, dropping to about 12 km near 30 degrees latitude, and 8 km
near the poles. Beneath the tropopause, we have the troposphere.
How the greenhouse effect changes global
temperature
τ is infrared absorption measured from
the top of the atmosphere looking down. Diagram (a): When the earth is in
radiative balance with space, net incoming solar radiation (NISR) is balanced
by outgoing longwave radiation (OLR) from the characteristic emission level,
τ=1. Diagram (b): When greenhouse gases are added to the atmosphere, the
characteristic emission level is raised in altitude. Since atmospheric
temperature decreases with altitude at about 10 ºC per mile, the new
characteristic emission level is colder than the previous level. Therefore
outgoing longwave radiation no longer balances net incoming solar radiation.
The Earth is no longer in thermal balance with space. This imbalance is called
“radiative forcing”. To re-establish balance, the temperature at the new τ=1
level must increase to about the temperature that had existed at the initial
τ=1 level, which is typically 7-8 km in the tropics and lower elsewhere. The
warming at τ=1 is the fundamental warming associated with the greenhouse
effect. How warming at the characteristic emission level τ=1 relates to warming
at the surface is not altogether clear, but computer models can be helpful
here. Source: Lindzen (2007).
Computer models are able to assist us in distinguishing between the warming
caused by adding greenhouse gases to the atmosphere and warming that is
attributable to other causes.
The UN, in its 2007 climate assessment report, displays a series of plots of
predicted rates of temperature change over the decades at altitudes from the
Earth’s surface to 30 km, at latitudes from the South Pole via the Equator to
the North Pole. Colors are used to illustrate the rates of change in
temperature which the UN’s climate models predict, measured in degrees Celsius
per decade. Each distinct cause of warming produces a visibly-distinct plot.
Six causes of atmospheric warming are considered. First, plots of natural
warming caused by changes in total incoming solar radiation and changes in
volcanic activity are shown, followed by plots of anthropogenic warming caused
by emissions of greenhouse gases, changes in tropospheric and stratospheric
ozone concentration, and the radiative forcing caused by sulphate aerosol
particles (which actually cause cooling). Finally, the five plots of predicted
warming are combined to create a single, sixth plot.
It is at once visible that the predicted warming caused by greenhouse-gas
concentrations produces a pattern strongly distinct from other causes of
warming. A “hot spot” appears between 8km and 12km of altitude in or near the
tropics. At this computer-predicted “hot spot” high above the Earth, the UN’s
models project that greenhouse warming will cause temperature to rise over the
decades at a rate up to three times faster than at the surface.
Greenhouse warming is distinguishable from other forcings
hPa - Left hand side
km - Right hand side
Zonal mean simulated atmospheric
temperature change (ºC per century, 1890-1999), from two natural causes, three
anthropogenic causes and one combined cause, simulated by the UN’s PCM model.
The “hot-spot” signature of greenhouse warming is visible in (c) and (f).
(IPCC, 2007, p. 675, based on Santer et al, 2003. See also IPCC, 2007, Appendix
9C).
The UN’s diagram shows the pattern of zonal mean simulated atmospheric
temperature change from 1890 to 1999, in °C per century from six causes –
(a) natural radiative
forcing from changes in solar activity;
(b) natural radiative forcing from changes in volcanic activity;
(c) anthropogenic radiative forcing
from emissions of CO2 and other well-mixed greenhouse gases;
(d) anthropogenic radiative forcing from changes in tropospheric and
stratospheric ozone;
(e) anthropogenic radiative forcing from pollutant sulphate aerosol particles
emitted to the atmosphere; and
(f) all natural and anthropogenic
forcings combined.
These six plots, from 1,000 hPa to 10 hPa barometric pressure (left scale),
equivalent to 0-30 km (right scale), demonstrate that anthropogenic emission of
well-mixed greenhouse gases, whether
on its own (c) or combined with all other natural and anthropogenic forcings
(f), is predicted to produce a signature distinct from that of
other forcings alone. The reason why the combined-forcings plot (f) appears so
similar to the greenhouse-gas forcing plot (c) is that the UN’s computer models
predict that the impact of greenhouse-gas emissions on temperature is greater
than that of all other forcings.
This instantly-recognizable “hot-spot” on the altitude-versus-latitude plot of
predicted rates of temperature change is the unmistakable signature or
characteristic fingerprint of greenhouse warming which we have been looking
for. The warming which the computer models predict will arise from growing
emissions of greenhouse gases is visibly distinct in its magnitude and in its
altitudinal and latitudinal distribution from any other cause of natural or
anthropogenic warming.
Following common meteorological practice, height is represented in these plots
by atmospheric pressure level. Atmospheric pressure decreases approximately
exponentially with height: 100 millibars corresponds roughly to 16 km; 200 mb
to 12 km; 500 mb to 6 km; and 1000 mb to the surface. Predicted greenhouse-gas
warming visibly peaks strongly in the tropical troposphere near the τ=1
characteristic emission level, which differs from one computer model another
because the amount of water vapor differs among the models.
Within the tropical “hot-spot” at about 8 to 12 km altitude, the rate of
increase in warming is more than twice and up to three times the rate of
increase in warming at the Earth’s surface. This does not mean that absolute
temperature in the mid-troposphere is greater than at the surface. Far from it:
the temperature at altitude is very much colder than at the surface. But the
rate at which temperature is predicted to increase in the “hot-spot” over the
decades is two or three times the rate at which temperature is predicted to
increase at the surface.
To put it another way, if we observe warming in the tropical upper troposphere,
then the models predict that the contribution to warming at the surface that is
caused by our greenhouse-gas emissions should be between less than half and one
third of the warming seen in the upper troposphere. There is, of course, some
greenhouse warming, indicated by the observed cooling of the stratosphere as
less outgoing long-wave radiation reaches it. But the absence of the predicted
“hot-spot” in the tropical mid-troposphere severely constrains the magnitude of
the greenhouse warming.
It is worth noticing that if we considered only global temperatures, as many
climatologists do, this signature of anthropogenic as distinct from natural
warming would not become visible. Accordingly, the objections of Essex and
McKitrick (2002) and Essex et al. (2007) to the use of globally averaged
temperature are justifiable. Had we used globally averaged temperatures, it
would have been almost impossible correctly to relate the underlying physics to
the observations.
We shall now demonstrate that several of the atmosphere-ocean
general-circulation models relied upon by the UN do indeed predict the
“hot-spot” in the mid-troposphere at low latitudes that is the signature of anthropogenic
“global warming”.
The computer-predicted signature of
greenhouse warming
hPa - Left hand side
km - Right hand side
Zonally-averaged distribution of
predicted temperature change (CCSP, 2006)
Zonally-averaged distributions of
predicted temperature change in ºK at CO2 doubling (2xCO2 – control), as a
function of latitude and pressure level, for four general-circulation models
(Lee et al., 2007).
Predicted acceleration in the rate of temperature increase in tropical
mid-troposphere in response to continuing emission of well-mixed greenhouse
gases, compared with surface temperature change, generates a distinctive
“hot-spot” graph that is the signature of anthropogenic as opposed to natural
“global warming”. All general-circulation models show this characteristic
amplification of the decadal rate of change in temperature with altitude at low
latitudes, up to a factor of ~ 3 at 10 km over the equator.
All five of the computer models whose plots are shown above unmistakably
predict the characteristic “hot-spot” signature that UN’s graphs show to be
unique to warming of the atmosphere caused by emissions of greenhouse gases.
But does observation demonstrate what the models predict?
Real-world temperatures in the upper atmosphere have been measured with
balloons since at least the 1960's and with microwave satellite sensors since
1979. However, the Hadley Centre’s plot of real-world radiosonde observations
does not demonstrate the “global warming hot-spot” at all. The predicted
phenomenon is startlingly and entirely absent from the observational record –
No “greenhouse warming” signature is
observed in reality
hPa - Left hand side
km - Right hand side
–0.6 –0.5 –0.4 –0.3 –0.2 –0.1 0 +0.1 +0.2 +0.3 +0.4
+0.5 +0.6 ºC
No “hot-spot” signature of anthropogenic
“greenhouse warming” appears in the record of real-world temperature observations.
Source: HadAT2 radiosonde observations, from CCSP (2006), p. 116, fig. 5.7E.
The contrast between the five computer models’ predicted signature of
greenhouse warming and the Hadley Centre’s plot of observed decadal rates of
change in temperature could not be starker. This astonishing result is
explicitly confirmed by the UN’s 2007 assessment report, which describes the
near-total absence of its own predicted “hot-spot” signature of anthropogenic
greenhouse warming in the observed temperature record, but apparently without
appreciating its significance –
“9.4.4.1 Observed Changes
“... All data sets show
that the global mean and tropical troposphere has warmed from 1958 to the
present, with the warming trend in the troposphere slightly greater than at the
surface. Since 1979, it is likely that there is slightly greater warming in the
troposphere than at the surface, although uncertainties remain in observed
tropospheric warming trends and whether these are greater or less than the
surface trend. The range (due to different data sets) of the global mean
tropospheric temperature trend since 1979 is 0.12°C to 0.19°C per decade based
on satellite-based estimates (Chapter 3) compared to a range of 0.16°C to
0.18°C per decade for the global surface warming.”
Global observation of tropospheric temperatures by balloon-borne radiosondes
has been available since 1958, and by satellite telemetry since 1979. Therefore
there are several multi-decadal observational rate-of-temperature-change
datasets that demonstrate the absence in reality of the “hot-spot” signature
that the general-circulation computer models predict in theory –
No overlap between theoretical modeling and
real-world observation
Model-predicted differentials between
decadal rates of increase in temperature at the surface (TS) and in the lower
troposphere (T2LT) from latitude 20º N – 20º S in response to anthropogenic
enhancement of the natural greenhouse effect by emission of carbon dioxide and
other well-mixed greenhouse gases (pink hatched rectangle) do not overlap at
any point with real-world observations from RATPAC radiosondes (purple
circles); HadAT2 radiosondes (green circles); University of Alabama at
Huntsville satellites (blue squares); and RSS satellites (red squares). Source:
CCSP (2006), Executive Summary.
Observed temperature change is less than predicted
Temperature trend-line (10–3K / decade) versus log
pressure (altitude) for different zonal averages. Observations (filled symbols,
solid lines): MSU, ST (Hadley), NNR, HadRT2.0 radiosondes. Models (open
symbols, dotted lines): Hadley model CM3, DOE PCM, and GISS SI2000. Tropopause
range is shaded. Tropopause data can be found at http://cdc.noaa.gov/. (a)
Global average. All of the data sets have an average taken from 90S to 90N with
exception of ST (Hadley), whose average was taken from 67.5S to 67.5N. (b)
Tropics. (30S to 30N). (c) Southern Hemisphere (60S to 30S). (d) Northern
Hemisphere. (30N to 60N). The tropical “hot-spot” at 300 hPa (about six miles
up in the troposphere) is not significant enough to indicate a high climate
sensitivity to anthropogenic enhancement of the natural greenhouse effect. .
From Douglass et al. (2004).
The discrepancy between the predicted “signature” of anthropogenic greenhouse
warming and its absence in half a century of observed temperature records is
currently under active discussion among climatologists. A report by the US
Climate Change Science Program (CCSP, 2006), says –
“For longer-timescale temperature changes over 1979 to 1999, only one of four
observed upper-air data sets has larger tropical warming aloft than in the
surface records.” [Even this single dataset does not show enough troposphere
warming to match the models’ predictions that justify the UN’s high central
estimate of climate sensitivity to anthropogenic greenhouse warming]. “All
model runs with surface warming over this period show amplified warming aloft.
These results could arise due to errors common to all models; to significant
non-climatic influences remaining within some or all of the observational data
sets, leading to biased long-term trend estimates; or a combination of these
factors. The new evidence in this Report (model-to-model consistency of
amplification results, the large uncertainties in observed tropospheric
temperature trends, and independent physical evidence supporting substantial
tropospheric warming) favors the second explanation. A full resolution of this
issue will require reducing the large observational uncertainties that currently
exist. These uncertainties make it difficult to determine whether models still
have common, fundamental errors in their representation of the vertical
structure of atmospheric temperature change.”
Applying Occam’s Razor, the simplest explanation for the discrepancy between
theoretical modeling and real-world observation is that the models on which the
case for alarm about climate change are based are very substantially
overestimating the effect of anthropogenic greenhouse warming on global
temperatures. The Climate Change Science Program, however, prefers to assume
that it is observation, rather than theory, that is deficient. Yet the plot of
its latest synthesis of all corrections to satellite and balloon radiosonde
data to date (CCSP, 2006), shown below, shows no significant difference between
surface and mid-tropospheric decadal temperature trends, and indicates a trend
of no more than 0.05 +/- 0.07 ºC per decade (Spencer et al, 2007):
No difference between surface and mid-troposphere
trends
Vertical profiles of temperature trend in °C per
decade for 1958-2004 (left) and 1979-2004 (right) as a function of altitude
expressed as pressure from 1000 (surface) to 25 hPa, computed from the RATPAC
(violet) and HadAT2 (green) radiosonde datasets, and based on temperature that
has been averaged over the tropics, 20º N - 20º S. Filled symbols denote trends
estimated to be statistically significantly different from zero (at the 5%
level) (CCSP, 2006).
Further to investigate whether the tropical mid-troposphere “hot-spot”
signature of anthropogenic greenhouse warming exists, a three-way test was
developed using the Microwave Sounding Unit satellite temperature record for
the atmosphere between the surface and an altitude of 5 miles, and the
radiosonde record for the region between 1 mile and 5 miles above the surface.
Regression lines were plotted using the online routine at www.co2science.org
Upper panel: Radiosonde temperature data for 850 to
300 hPa (1 mile to 6 miles above surface), 1979 to 2004, for latitudes 90S to
30S, 10S to 10N, and 30N to 90N. From Angell et al. (1999), updated. Lower
panel: Satellite microwave sounding unit data for 0 to 400 hPa (surface to 5
miles), 1979 to 2006, for latitudes 90S to 22.5S, 20S to 20N, and 22.5N to 90N.
From Christy et al. (2000), updated.
The purpose of the test was to study whether the rate of temperature change
between the commencement of the satellite record in 1979 and the beginning of
the 21st century was a little higher in the tropics than in the northern or
southern hemispheres, as it should be if the tropical mid-troposphere
“hot-spot” were strong enough to justify the IPCC’s chosen 3-degrees-Celsius
central estimate of climate sensitivity to CO2 doubling.
First, the satellite
record showed that the rate of temperature change in the tropics was lower than
in either the northern or the southern hemisphere.
Secondly, the
radiosonde record also showed that the observed tropical rate of change in
temperature was less than the northern or southern hemisphere rates of change:
in fact, it showed a steep decline over the period.
Thirdly, the
radiosonde record should have showed a slightly greater rate of temperature
change over the period than the satellite record, since the former was closer
to the altitude at which the models predict the “hot-spot” to be present than
the latter. However, the satellite record shows a decline in temperatures over
the period, while the radiosonde record shows an increase.
The conclusion of this three-part experiment is clear – all three of the tests
fail to show any evidence of the expected differential between tropical and
non-tropical rates of change in temperature, or between the tropical radiosonde
and satellite readings. The tropical mid-troposphere “hot-spot” indeed seems to
be absent.
Since theoretical modeling and real-world observation differ so markedly, and
since all or nearly all observations from many sources over half a century,
confirmed by our own experiment, fail to establish the model-predicted
existence of the tropical mid-troposphere “hot-spot” signature of greenhouse
warming caused by human activities, either the models or the observations or
both are wrong.
Some fundamental considerations in elementary atmospheric physics, as well as
some additional atmospheric measurements, suggest that it is the theoretical
models that are more likely to be in error than the data from actual
observations.
We established at the outset that the atmosphere and the oceans act together as
a conveyor of radiant energy from the tropics toward the poles. Satellite
measurements confirm that this is indeed the case –
Measurements show no increase in global greenhouse
effect
Wm-2, Ranging from 90N to
Equator to 90S
The Earth’s radiation
balance (watts per square meter: y axis) against latitude (degrees: x axis).
Latitudinal spacing is proportional to the area of the Earth’s surface between
latitudes (i.e. the sine of the latitude). Upper solid curve: mean flux of
solar energy reaching the outer atmosphere. Lower solid curve: mean 1974-1978
satellite-observed solar energy. Dashed curve: mean 1974-1978 satellite-observed
outgoing long-wave radiation. Red: accumulated energy. Blue: the necessary
energy transfer via ocean and atmosphere currents to Polar
Regions to maintain mean radiation balance. Distance between solid
curves: mean Earth albedo (here 25%): tropical albedo fluctuations are caused
by variations in cloud cover between 10% and 40%. Source: Winston et al.
(1979), vol. 2.
The observations in the above diagram, though they only cover a short period,
strongly suggest that it is variations in outgoing longwave radiation in the
tropics that are the principal influence on increases in global temperature,
and that any increase in tropical outgoing longwave radiation will have a
disproportionately large impact on temperatures in the polar regions, through
transport of surplus radiative energy from the tropics to the poles by
advection and other atmospheric and oceanic processes.
Therefore the disproportionately rapid observed increase in temperature at high
latitudes, particularly in the northern hemisphere, is not – as has often been
suggested – an indication of anthropogenic “global warming”. It is what is
likely to occur regardless of the source of the warming. In particular, it will
occur if there is an increase in outgoing longwave radiation in the tropics.
Such an increase can occur either in response to an increase in solar activity
or in response to a decrease in tropical cloud cover. Volcanic eruptions and El
Nino or La Nina events can also have an effect.
A simple question arises. Does observation demonstrate that increases in
outgoing longwave radiation in the tropics lead to increases in observed global
temperature? The answer to that question is Yes –
Tropical outgoing longwave radiation determines
global temperature
Grid spanning from 1979 through 2001
Upper figure: Tropical outgoing long-wave radiation
(W m–2), 20 ºS to 20 ºN, 1979-2001, chiefly oceanic, from six satellites.
Variations in tropical cloud cover, periodic El Nino and La Nina events, and
short-term increases in albedo following volcanic eruptions are principal
causes of changes. Lower figure: Global lower-troposphere temperature anoma
lies
(intervals 0.2 ºC), 1979-2000. Correction analysis yields a significant linear
correlation of 0.92, indicating that anomalies in outgoing long-wave radiation
from the tropical oceans cause about 85% of global lower-troposphere
temperature anomalies. Source: Moene (2006).
Given the startlingly close correlation between outgoing long-wave radiation in
the tropics and global temperatures throughout the 30-year period of satellite
observation, a correlation which atmospheric physics would lead us to expect
and which is indeed observed, one question remains. Is there a similarly close
correlation between atmospheric concentrations of carbon dioxide and global
temperatures? The answer is No –
No correlation between CO2 concentration and global
temperature
There is no correlation between the exceptionally
smooth year-on-year increases in global atmospheric CO2 concentration (above)
and the noticeably sharp annual changes in global temperature (previous graph).
The “sawtooth” variations in atmospheric CO2 concentration (green) are chiefly
caused by the seasonal exchanges of CO2 between the atmosphere and the
biosphere, chiefly in the Northern Hemisphere. The multi-decadal December trend
of carbon dioxide concentrations (black) shows a monotonic increase: in each
succeeding year, mean CO2 concentration is higher than the previous year. The
graph is exponential: the rate of increase in CO2 concentration is
accelerating, albeit very slowly, as the smoothed curve (red) shows. However,
the increase in global temperature arising from the additional greenhouse-gas
concentrations is logarithmic and hence very small: indeed, the scientific
consensus (Oreskes, 2004, IPCC, 2007) holds no more than that at least 0.25ºC
of the 0.5ºC global temperature increase since 1958 is anthropogenic. Data
source: Mauna Loa Observatory,
Hawaii. Missing data are omitted,
not extrapolated.
Conclusion
Though correlation does not always imply causation, and absence of correlation
does not always imply absence of causation, atmospheric physics would lead us
to expect what is in fact deduced from observation: that approximately
five-sixths of global temperature anomalies are attributable to variations in
outgoing long-wave radiation in the tropics; that these variations owe nothing
to anthropogenic “global warming”; and that increases in the concentration of
carbon dioxide are comparatively insignificant. This last conclusion is
supported, to some extent, by the limitations on the definition and extent of
the scientific “consensus” on climate sensitivity to additional greenhouse-gas
concentrations (Oreskes, 2004; IPCC 2007).
The UN’s fourth assessment report on climate change (IPCC, 2007) confirms that
computer modeling predicts the existence of a unique and distinct signature or fingerprint
of anthropogenic warming caused by our emissions of greenhouse gases. That
signature is the instantly-recognizable tropical, mid-troposphere “hot spot”
about 10km above the Earth’s surface. In the “hot spot”, the models predict
that the rate of increase in atmospheric temperature, measured in degrees
Celsius per decade, will be two or three times greater than at the Earth’s
surface.
In IPCC (2007), this predicted “hot-spot” signature of anthropogenic greenhouse
warming is clearly visible on plots of modeled greenhouse forcing and of all
forcings including the dominant greenhouse forcing, but is not visible on plots
of solar, volcanic, tropospheric and stratospheric ozone, or sulphate aerosol
forcings. The UN’s models accordingly distinguish clearly between greenhouse
warming and other climate forcings: at least five separate general-circulation
computer models of the climate all predict the existence of the “hot-spot”
signature of anthropogenic greenhouse warming in the tropical mid-troposphere.
Yet in the plot from the Hadley Centre’s radiosondes, showing actual, observed
temperatures in the troposphere, presented in the same altitude-vs-latitude
fashion as the predictions made by the five computer models, the computer
models’ repeatedly-predicted “hot-spot” signature of anthropogenic greenhouse
warming is entirely absent. Indeed, very nearly all observational data on
mid-tropospheric temperature trends over the past half-century show no tropical
“hot-spot” at all; and, in the one record that shows it at all, the magnitude
of the observed effect is insufficient to justify the UN’s choice of a very
high central estimate of climate sensitivity to anthropogenic enhancement of
the greenhouse effect. Our own small experiment also fails to demonstrate even
the existence of the “hot-spot” fingerprint of anthropogenic warming, still
less a magnitude sufficient to justify the IPCC’s high climate sensitivity.
These surprising results present a very real difficulty for the conventional
“global warming” theory – a difficulty that is not resolved either in CCSP
(2006) or in IPCC (2007).
Thorne et al. (2007) have attempted to resolve this difficulty by suggesting
that the error-bars in the observational datasets are so large that they could
in theory encompass the model-predicted “hot-spot”, that the datasets are not
designed to identify small temperature trends, and that the outputs are
exceptionally sensitive to the choice of limiting dates. However, it is on the
basis of the observed data that the models are contrived, and, if the observed
data are inadequate for drawing conclusions about whether the characteristic
fingerprint of anthropogenic greenhouse warming exists, then a fortiori the
outputs from theoretical models founded upon those data will be inadequate, and
no conclusion about the magnitude of the temperature response to anthropogenic
enhancement of the natural greenhouse effect can be legitimately drawn.
The observational and experimental graphs reproduced here contain between them
a dozen different observed-temperature datasets, not one of which exhibits the
“hot-spot” signature of anthropogenic “greenhouse warming” that is predicted by
the computer models upon which the UN so heavily relies. In every one of these
datasets, the trend in the troposphere is no greater, and generally smaller,
than the trend near the surface. According to Spencer et al. (2007), the
tropospheric temperature trend is now 0.05 ± 0.07 degrees Celsius per decade.
Therefore, the contribution of the anthropogenic enhancement of the greenhouse
effect to surface warming is somewhere between -0.02 and 0.12 degrees Celsius
per decade, with a central estimate of 0.5 degrees Celsius, or approximately
one-sixth of the UN’s central estimate of 3 degrees Celsius for a doubling of
atmospheric carbon dioxide concentration.
This result is broadly consistent with that of Schwartz (2007), who supports
the conclusions of Lindzen (2006), calculating by entirely different methods
that the temperature increase to be expected from a doubling of atmospheric
carbon dioxide concentration will be one-half to one-third of the UN’s central
estimate.
Can the discrepancy between prediction and observation be explained, as the
CCSP suggests, by uncertainties in the observed data? The very close correlation
between anomalies in tropical outgoing long-wave radiation and anomalies in
global lower-troposphere temperatures, taken with the near-total absence of
correlation between monotonic increases in CO2 concentration and chaotic
temperature anomalies, suggests that it is the computer models, not real-world
observations that are likely to be at fault. Ultimately this question can only
be resolved by collecting further data: but the CCSP’s predisposition in favor
of theoretical modeling and against the results of direct observation is
commonplace among official climate-science bodies. Or does the discrepancy
arise because the predictions are carried through to equilibrium climate
response, while the observations are perforce carried only to a transient response?
Professor Lindzen comments that this failure of observation to match prediction
cannot be so easily explained, since the transient response would be likely to
exceed the equilibrium response. He concludes that no more than about a third
of the observed trend at the surface is likely to be due to greenhouse warming,
and adds: “This is about as close as one ever gets to proof in climate
physics.”
On this analysis, “global warming” is unlikely to be dangerous and extremely
unlikely to be catastrophic.
References
CCSP. 2006. Climate Change Science Program Synthesis and Assessment Product
1.1, Temperature Trends in the Lower Atmosphere: Steps for Understanding and
Reconciling Differences.
DOUGLASS, David H., Benjamin D. Pearson, and S. Fred Singer. 2004. Altitude
dependence of atmospheric temperature trends: Climate models versus observation.
Geophysical Research Letters 31: L13208, doi:10.1029/2004GL020103,
ESSEX, C., and R. McKitrick. 2002. Taken by
Storm, Key Porter Books, Ltd., Toronto,
320pp.
ESSEX, C., R. McKitrick, and B. Andriesen. 2007. Does a Global Temperature
Exist? J. Non-Equilib. Thermodynamics 32, 1-27.
IPCC. 2007. Contribution of Working Group I. Fourth Assessment Report:
www.ipcc.ch.
LEE, M.-I, M.J. Suarez, I.-S. Kang, I. M.
Held, and D. Kim. 2007. A Moist Benchmark Calculation for the Atmospheric
General Circulation Models. Journal of Climate [accepted].
LINDZEN, R.S. 1990. Some coolness concerning global warming. Bull. Amer. Met.
Soc. 71, 288-299.
MOENE, A. 2006. Measurements show no increase of the global greenhouse effect.
Lecture presented at the annual meeting of the Norwegian Geophysical Society.
ORESKES, N. 2004. The scientific consensus on climate change. Science 306,
1686.
SANTER, B.D., M.F. Wehner, T.M.L. Wigley, R. Sausen, G.A. Meehl, K.E. Taylor,
C. Ammann, J. Arblaster, W.M. Washington, J.S. Boyle, and W. Bruggemann. 2003.
Contributions of anthropogenic and natural forcing to recent tropopause height
changes. Science 301, 479-483.
SPENCER, R. W., W. D. Braswell, J. R. Christy, and J. Hnilo. 2007. Cloud and
radiation budget changes associated with tropical intraseasonal oscillations.
Geophysical Research Letters 34, L15707, doi:10.1029/2007GL029698.
THORNE, P. W., D. E. Parker, B. D. Santer, M. P. McCarthy, D. M. H. Sexton, M.
J. Webb, J. M. Murphy, M. Collins, H. A. Titchner, and G. S. Jones. 2007.
Tropical vertical temperature trends: A real discrepancy? Geophysical Research
Letters 34: L16702, doi:10.1029/2007GL029875.
WINSTON et al. 1979. ref. Adrian E. Gill: Atmosphere-Ocean Dynamics. Academic
Press International Geophysical Series 30.
