Top 10 Global Warming Myths
In an article intended to raise pubic consciousness about the
threat of global warming, environmental writer Bill McKibben mentioned reports that, in
northern Russia, venomous snakes had appeared for the first time.... Well, venomous snakes will certainly get
peoples attention. (This is reminiscent
of the old college poster ploySEX SEX SEX! Now
that I have your attention, my Western Civ textbook is for sale.)
Much to our dismay, McKibben never
did expand on the global warming/snake connection. But
his article did proceed to list his favorite fallacies about the theory and consequences
of climate change.
In the interest of public education,
we present our top 10 fallacies about global
warming and climate change.
McKibben, B. (1995).
Hot? Welcome to the 21st century.
Commentary, Los Angeles Times, Aug. 15.
CLIMATE SCIENTISTS AGREE THAT DISASTROUS GLOBAL WARMING IS HERE
We frequently read that, the
vast majority of climate scientists agree that....
To get most scientists to agree that water is wet would be difficult enough,
but consensus on something as complex as anthropogenic climate change would be downright
Few recent surveys of active
climatologists have addressed greenhouse warming and its impact. One, after the release of the first report from
the Intergovernmental Panel on Climate Change in 1990, demonstrated that there is a wide
range of opinion on critical issues. For
example, most survey respondents agreed that the climate models do not accurately depict
the ocean-atmosphere system. Similarly, a
majority agreed it was not possible to attribute the observed warming of about 0.5°C
since 1890 to human impacts. Five years
later, scientists still cant agree on how much of this warming was caused by humans.
In reality, one should be careful
about giving too much weight to the majority opinions of scientists on any given topic at
any given time. Science generally advances
through revolution of ideas, not by popular opinion.
Singer, S.F. (1991).
No Scientific Consensus on Greenhouse Warming,
Wall Street Journal, Sept. 23. p.
MYTH #2IN THE
UNITED STATES, RECENT YEARS HAVE BEEN THE WARMEST ON RECORD
Because of problems with temperature
records, the worst place to look for global warming may be in the surface temperature
history. Nevertheless, most discussions of
greenhouse warming focus on temperature trends.
After removing biases caused by
urbanization, thermometer relocations, instrument changes, and so on, it is clear that
there is no trend in mean annual temperatures in the last 65 years. Apart from a sharp rise from 1915 to 1930, when
trace-gas concentrations were low, the trend is essentially zero.
Figure 1. Temperature departures (°C) in the United States.
Karl, T.R., et al.
(1994). Global and hemispheric temperature
anomaliesland and marine instrument records. In
Trends 93: A Compendium of Data on Global
Climate Change. U.S. Dept. of Energy. 984pp.
#3NORTHERN HEMISPHERE TEMPERATURE INCREASES OVER THE LAST CENTURY CORRESPOND TO
Based on the best available
temperature records, the Northern Hemisphere has warmed about 0.65°C since 1860. However, we werent producing much CO2
prior to 1945, so the greenhouse effect should have been most prevalent in the last 40
years. But most of the temperature increase
occurred prior to 1945. Why then? The most scientifically defensible position is
natural climate variation. There has been
little or no trend after 1945, when two-thirds of the greenhouse gases were released.
Figure 2. Temperature departures (°C) in the Northern
Jones, P.D., T.M.L.
Wigley, and K.R. Briffa (1994). Global and
hemispheric temperature anomaliesland and marine instrument records. In Trends
93: A Compendium of Data on Global Climate Change.
U.S. Dept. of Energy. 984pp.
CO2 YIELDS MUCH HIGHER SURFACE TEMPERATURES
The global climate is a complex and
poorly understood system of positive and negative feedbacks. Increasing trace gases will absorb more radiation
from the earth and re-emit it back, enhancing the natural greenhouse effect. But the climate system is much more complicated
than that. And it is impossible to alter one
aspect of the system without affecting the others.
For example, more atmospheric CO2
may enhance growth of plants, which may then transpire more water. What if surface temperatures warm and thus cause
more evaporation? Will this produce more
clouds? If so, will they be low (water) or
high (ice) clouds? Do clouds have a net
cooling or warming effect? How about changes
in cloud brightness related to sulfates?
General circulation climate models
try to mathematically calculate all of these interactions, but they have yet to
sufficiently (or even remotely) duplicate current climatic reality. Why, then, should we trust their predictions of
#5CLIMATE MODELS ARE CORRECT BUT ARE
LIMITED BY COMPUTER TECHNOLOGY
Our ability to predict climate is
exceptionally poor because we dont yet understand the climate system and how it
varies. This is demonstrated by the inability
of general circulation models to reproduce current climatic conditions. If the atmospheric physics were better understood,
large-scale climate models would be more accurate.
Climate modelers manage to get around
this problem by using parameterization (estimates of unknown quantities) and
fudge factors (tinkering with mathematical constants and coefficients until
results resemble reality).
Last spring, scientists determined
that clouds absorb 30% to 50% more sunlight than was previously believed. The numbers that atmospheric scientists have
plugged in next to the arrows in Figure 3 had gone relatively unchanged for decades.
Solar radiation drives the
earths weather and climateits distribution is the starting point for most
models. Time for some Reparameterization!
Figure 3. Schematic radiation balance for the earth. Lines represent various emissions and re-emissions
Pilewskie, P. and
F.P.J. Valero (1995). Direct observations of
excess solar absorption by clouds. Science, 267, 16261629.
FORECASTS ARE CORRECT BUT CONFOUNDED BY SULFATES, VOLCANOES, ETC.
It is convenient to blame climate
model errors on rare eventsvolcanoes, El Niño, solar flares, etc.factors not
explicitly accounted for in the models. However,
these models dont do a good job of handling rudimentary atmospheric variables such
as temperature, precipitation, and winds.
Precipitation, for instance, is the
result of processes occurring at a variety of scales, from large-scale low pressure
systems and fronts to cloud formation. Models
that duplicate observed global rainfall probably have a lot of the physics right.
Well, they dont. All of the models severely underestimate
precipitation in the tropics, the region with the heaviest rainfall. The modeled values are off by almost 50% in some
regions. Conversely, most models show the
polar regions as wetter than they are in reality.
Figure 4. Total precipitation errors by latitude band
produced from two of the leading global climate computer models.
Legates, D.R. and
C.J. Willmott (1992). A comparison of
GCM-simulated and observed mean January and July precipitation. Paleogeography,
Paleoclimatology, Paleoecology, 97, 345363.
#7MELTING OF THE POLAR ICE CAPS WILL CAUSE SEA LEVEL TO RISE
In Antarctica, there is absolutely no
evidence of increasing temperatures since the mid-1960s (see also Vol. 1, No. 1 of the Report). Even if a trend were present, temperatures
wouldnt be hot enough to melt ice.
test the effects of global warming on sea-level rise from melting North Polar ice, do a
little experiment. Put some ice cubes in a
glass and then fill it to the rim with water. Then,
let the ice melt and see how much overflow there is.
The amount of water on your kitchen counter is proportional to sea-level
rise from melting of the ice cap on the North Pole.
Figure 5. Temperatures measured at the South Pole.
Sansom, J (1989). Antarctic Surface Temperature Time Series. Journal of Climate. 2, 11641172.
CLIMATE WILL BE MORE EXTREME
While this is another great
attention-getter, it is difficult to justify based on prevailing theories or models. In most ways, a greenhouse world would
actually be less extreme than the current
Despite large differences between
global climate models, one area of complete agreement is that the largest warming should
occur in the high latitudes in winter (see Myth #7).
This, coupled with little or no warming in the tropics, will reduce the
temperature difference between the equator and the poles.
The magnitude of this temperature difference is related to the strength of
the jet stream.
The jet stream is stronger and moves
farther south (or equatorward) in the winter, when strong storms influence most of the
United States. A
greenhouse-warmed world should have winters that are more summerlike, with
fewer strong storms, milder temperatures, and polar air masses that are not so cold and do
not travel so far south.
Figure 6. Schematic of the influences of greenhouse warming
on the jetstream.
#9SUMMERS WILL BE EXTREMELY HOT AND DRY
Newspaper accounts of this
summers heat wave suggested these high temperatures were a sign of things to come,
in perfect agreement with climate model forecasts. But
in dispelling Myth #7, we see that most of the warming is predicted to be over the poles
during winter. So the popular image of a
dust bowl caused by greenhouse warming is not even the consensus of the
It is now generally accepted that
most of the warming would occur at night. There
is some evidence of this in hemispheric temperature records that show nighttime warming
but no change in afternoon high temperatures. This change also increases the length of the
Furthermore, there has been no
significant trend in summer precipitation (see Vol. 1, No. 4). So the imagery of expanding desert wastelands is
supported by neither models nor observations.
Karl, T. R., et al.
(1991) Global warming: Evidence for asymmetric diurnal temperature change. Geophysical Research Letters, 18, 22522256.
BAD WEATHER IS EVIDENCE OF GLOBAL WARMING
All sorts of bad
thingshurricanes, droughts, fires, floods, even blizzards and insect plagues (not to
mention venomous snakes)have been blamed on global warming.
remember: before you accept at face value any pronouncement regarding global warming, see
if its in our Top 10.