FeatureWorld Climate Report
intdots.gif (546 bytes)
Home
white1.GIF (834 bytes)

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 people’s attention.  (This is reminiscent of the old college poster ploy—SEX 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.

Reference:

McKibben, B. (1995). “Hot?  Welcome to the 21st century. —Commentary,”  Los Angeles Times, Aug. 15.

MYTH #1—MOST 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 impossible.

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 0.5C since 1890 to human impacts.  Five years later, scientists still can’t 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.

Reference:

Singer, S.F. (1991). “No Scientific Consensus on Greenhouse Warming,”   Wall Street Journal, Sept. 23. p. 14.

MYTH #2—IN 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 (7399 bytes)

Figure 1.  Temperature departures (C) in the United States.

Reference:

Karl, T.R., et al. (1994).  Global and hemispheric temperature anomalies—land and marine instrument records.  In Trends ’93: A Compendium of Data on Global Climate Change.  U.S. Dept. of Energy.  984pp.

MYTH #3—NORTHERN HEMISPHERE TEMPERATURE INCREASES OVER THE LAST CENTURY CORRESPOND TO HUMAN-INDUCED WARMING

Based on the best available temperature records, the Northern Hemisphere has warmed about 0.65C since 1860.  However, we weren’t 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 (8050 bytes)

Figure 2.  Temperature departures (C) in the Northern Hemisphere.

Reference:

Jones, P.D., T.M.L. Wigley, and K.R. Briffa (1994).  Global and hemispheric temperature anomalies—land and marine instrument records.  In Trends ’93: A Compendium of Data on Global Climate Change.   U.S. Dept. of Energy.  984pp.

MYTH #4—MORE 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 future conditions?

MYTH #5—CLIMATE MODELS ARE  CORRECT BUT ARE LIMITED BY COMPUTER TECHNOLOGY

Our ability to predict climate is exceptionally poor because we don’t 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 earth’s weather and climate—its distribution is the starting point for most models.  Time for some Reparameterization!

Figure 3 (7509 bytes)

Figure 3.  Schematic radiation balance for the earth.  Lines represent various emissions and re-emissions of energy.

Reference:

Pilewskie, P. and F.P.J. Valero (1995).  Direct observations of excess solar absorption by clouds. Science, 267, 1626–1629.

MYTH #6—MODEL FORECASTS ARE CORRECT BUT CONFOUNDED BY SULFATES, VOLCANOES, ETC.

It is convenient to blame climate model errors on rare events—volcanoes, El Nio, solar flares, etc.—factors not explicitly accounted for in the models.  However, these models don’t 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 don’t.  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 (10873 bytes)

Figure 4.  Total precipitation errors by latitude band produced from two of the leading global climate computer models.

Reference:

Legates, D.R. and C.J. Willmott (1992).  A comparison of GCM-simulated and observed mean January and July precipitation.  Paleogeography, Paleoclimatology, Paleoecology, 97, 345–363.

MYTH #7—MELTING 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 wouldn’t be hot enough to melt ice.

 To 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 (18301 bytes)

Figure 5.  Temperatures measured at the South Pole.

Reference:

Sansom, J (1989).  Antarctic Surface Temperature Time Series. Journal of Climate. 2, 1164–1172.

MYTH #8—THE 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 climate.

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 (8786 bytes)

Figure 6.  Schematic of the influences of greenhouse warming on the jetstream.

MYTH #9—SUMMERS WILL BE EXTREMELY HOT AND DRY

Newspaper accounts of this summer’s 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 models.

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 growing season.

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.

Reference:

Karl, T. R., et al. (1991) Global warming: Evidence for asymmetric diurnal temperature change. Geophysical Research Letters, 18, 2252–2256.

MYTH #10—ALL BAD WEATHER IS EVIDENCE OF GLOBAL WARMING

All sorts of bad things—hurricanes, droughts, fires, floods, even blizzards and insect plagues (not to mention venomous snakes)—have been blamed on global warming.

Just remember: before you accept at face value any pronouncement regarding global warming, see if it’s in our “Top 10.”