Global Warming (AGW)
Leonard Weinstein, ScD,
April 23, 2009
A theory has been proposed that human activity
over about the last 150 years has caused a significant rise
in Earth’s average temperature. The mechanism claimed
is based on an increased greenhouse effect caused by anthropogenic
increases in CO2 from burning of fossil fuels, deforestation,
cement manufacture, and also from increases in CH4 from
farm animals and other causes. The present versions of the
theory also include a positive feedback effect due to the
increased temperature causing an increase in water vapor,
which amplifies the effect. The combined result are used
to claim that unless the anthropogenic increases of CO2
are slowed down or even made to decrease, there will be
a continuing rapid increase in global temperature, massive
melting of ice caps, flooding, pestilence, etc.
In order to prove a theory, specific predictions
need to be made that are based on the claims of the theory,
and the predictions then need to happen. While the occurrence
of the predicted events is not proof positive of a theory,
they increase the believability of the claims. However,
if the predictions are not observed, this tends to indicate
the theory is flawed or even wrong. Some predictions are
absolute in nature. Einstein’s prediction of the bending
of light by the Sun is such a case. It either would or would
not bend, and this was considered a critical test of the
validity of his theory of general relativity. It did bend
the predicted amount, and supported his theory.
Many predictions however are less easily
proved. For example weather forecasting often does a good
job in the very short term but over increasing time does
a poor job. This is due to the complexity of the numerous
nonlinear components. This complexity has been described
in chaos theory by what is called the butterfly effect.
Any effect that depends on numerous factors, some of which
are nonlinear in effect, is nearly impossible to use to
make long-range predictions. However, for some reason, the
present predictions of “Climate Change” are
considered by the AGW supporters to be more reliable than
even short-term weather forecasting. While some overall
trends can be reasonably made based on looking at past historical
trends, and some computational models can suggest some suggested
trends due to specific forcing factors, nevertheless, the
long term predicted result has not been shown to be valid.
Like any respectable theory, specific predictions need to
be made, and then shown to happen, before the AGW models
can have any claim to reasonable validity.
The AGW computational models do make several
specific predictions. Since the time scale for checking
the result of the predictions is small, and since local
weather can vary enough on the short time scale to confuse
the longer time scale prediction, allowances for these shorter
lasting events have to be made when examining predictions.
Nevertheless, if the actual data results do not significantly
support the theory, it must be reconsidered or even rejected
as it stands.
The main predictions from the AGW models
The present CO2 level is high
and increasing. It should be fairly easy to
show the consequences of AGW predictions if they are valid.
Figure 1. Global average temperature from 1850 through 2008.
Annual series smoothed with a 21-point binomial filter by
It should be noted that the largest part of
the last 150 year increase in CO2, which is blamed on human
activity, did not occur until after 1940, so the largest
temperature rise effects should have occurred in that time.
The proponents of AGW have generally used the time period
from 1970 to 2000 as the base line for an indicator of the
rapid warming. In that base line period, the average temperature
rose about 0.50C, which averages to 0.160C per decade. The
claim was then made that this would accelerate due to continuing
increases in CO2 level. However if we look at the temperature
change from 1940 through 2008, the net increase is only
0.30C. This is due to a drop from 1940 to 1970 and a slight
drop from 2000 through 2008. Now the average rise for that
period is only 0.040C per decade. If the time period from
1850 through 2008 is used as a base, the net increase is
just under 0.70C and the average rise is also 0.040C per
decade! It is clear that choosing a short selected period
of rising temperature gives a misleading result. It is also
true that the present trend is down and expected to continue
downward for several more years before reversing again.
This certainly makes claim 1 questionable.
The drop in temperature from 1940 to 1970
was claimed to have been caused by “global dimming”
caused by aerosols made by human activity. This was stated
as dominating the AGW effects at that time. This was supposed
to have been overcome by activity initiated by the clean
air act. In fact, the “global dimming” continued
into the mid 1990’s and then only reduced slightly
before increasing more (probably due to China and other
countries increased activity). If the global dimming was
not significantly reduced, why did the temperature increase
from 1970 to just past 2000?
A consequence of global dimming is reduced
pan-evaporation level. This also implies that ocean evaporation
is decreased, since the main cause of ocean evaporation
is Solar insolation, not air temperature. The decreased
evaporation contradicts claim 2.
Claim 3 has been contradicted
by a combination of satellite and air born sensor measurements.
While the average lower Troposphere average temperature
has risen along with near ground air temperature, and in
some cases is slightly warmer, nevertheless the models predicted
that the lower Troposphere would be significantly warmer
than near ground at the lower latitudes, especially in the
tropics. This has not occurred!
Claim 4 implies that the
higher latitudes should heat up more than lower latitudes.
This is supposed to be especially important for melting
of glaciers and permafrost. In fact, the higher latitudes
have warmed, but at a rate close to the rest of the world.
In fact, Antarctica has overall cooled in the last 50 years
except for the small tail that sticks out. See
Greenland and the arctic region are presently
no warmer than they were in the late 1930’s, and are
presently cooling! See
The overall effect of Antarctic and Greenland
are now resulting in net gain (or at least near zero change)
of ice, not loss. While some small areas have recently lost
and are some are still losing some ice, this is mostly sea
ice and thus do not contribute to sea level rise. Glaciers
in other locations such as Alaska have lost a significant
amount of ice in the last 150 years, but much of the loss
is from glaciers that formed or increased during the little
ice age, or from local variations, not global. Most of this
little ice age ice is gone and some glaciers are actually
starting to increase as the temperature is presently dropping.
For more discussions on the sea level issue look at the
following two sites: here
This indicates that claim 5 is clearly
wrong. While sea level will rise a small amount,
and has so since the start of the Holocene period, the rise
is now only 10 to 15 cm per century, and is not significantly
related to the recent recovery from the little ice age.
The claims in 6 are particularly interesting.
Figure 2 below shows the Global Brightness Temperature Anomaly
(0C) in the lower Troposphere and lower Stratosphere made
a) Channel TLT is the lower Troposphere from ground to about
b) Channel TLS is the lower Stratosphere from about 12 to
Figure 2. Global satellite data from RSS/MSU and AMSU data.
Monthly time series of brightness temperature anomaly for
channels TLT, and TLS. Data
The anomaly time series is dominated by ENSO
events and slow troposphere warming for Channel TLT (Lower
Troposphere). The three primary El Niños during the
past 20 years are clearly evident as peaks in the time series
occurring during 1982-83, 1987-88, and 1997-98, with the
most recent one being the largest. Channel TLS (Lower Stratosphere)
is dominated by stratospheric cooling, punctuated by dramatic
warming events caused by the eruptions of El Chichon (1982)
and Mt Pinatubo (1991). In these, and other volcanic eruption
cases, the increased absorption and reflectivity of the
dust and aerosols at high altitudes lowered the surface
Solar insolation, but since they absorbed more energy, they
increased the high altitude temperature. After the large
spikes dropped back down, the new levels were lower and
nearly flat between large volcanic eruptions. It is also
likely that the reflection or absorption due to particulates
also dropped, so the surface Solar insolation went back
up. It appears that a secondary effect of the volcanic eruptions
is present that is unknown in nature (but not CO2)! One
possible explanation is a modest but long-term drop in Ozone.
It is also clear that the linear fit to the data shown is
meaningless. In fact the events seem additive for at least
the two cases shown. That is, after El Chicon dropped the
level, then Pinatubo occurred and dropped the level even
more. Two months after Pinatubo, another strong volcano,
Cerro Hudson, also erupted, possibly amplifying the effect.
It appears that the recovery time from whatever causes the
very slow changing level shift has a recovery time constant
of at least several decades.
The computational models that show that the
increasing CO2 and CH4 cause most of the present global
warming all require that the temperature of the Stratosphere
drops while the lower atmosphere and ground heat up. It
appears from the above figures that the volcanic activity
clearly caused the temperature to spike up in the Stratosphere,
and that these spikes were immediately followed by a drop
to a new nearly constant level in the temperature. It is
clear from the Mauna
Loa CO2 data that the input of CO2 (or CH4)
from the volcanoes, did not significantly increase the background
level of this gas, and thus, this cannot be the cause of
the drop in the Stratosphere temperature. The ramp up of
atmospheric CO2 also cannot explain the step down then level
changes in high altitude temperature. Since the surface
temperature rise is supposed to be related to the Stratosphere
temperature drop, and since a significant surface rise above
the 1940 temperature level did not occur until the early
1980’s, it may be that the combination of the two
(or more) volcanoes, along with Solar variability and variations
in ocean currents (i.e., PDO) may explain the major causes
of recent surface temperature rises to about 2002. In fact,
the average Earth temperature stopped rising after 2002,
and has been dropping for the last few years!
The final question that arises is what prediction
has the AGW made that has been demonstrated, and that strongly
supports the theory. It appears that there is NO real supporting
evidence and much disagreeing evidence for the AGW theory
as proposed. That is not to say there is no effect from
Human activity. Clearly human pollution (not greenhouse
gases) is a problem. There is also almost surely some contribution
to the present temperature from the increase in CO2 and
CH4, but it seems to be small and not a driver of future
climate. Any reasonable scientific analysis must conclude
the basic theory wrong!!