What you never hear about greenhouse warming
By Hugh W. Ellsaesser, Ph.D
We have observational data providing an
estimate of the global mean surface air
temperature since about 1870. While these
data indicate a global warming of 0.3 to 0.60C
this is significantly less than climate models
predict should have occurred by no due to
man's additions of greenhouse gases to the
atmosphere. In addition most of the observed
warming occurred before World War II,
before the bulk of the greenhouse gases had
been emitted. To argue that the model-predicted warming has been obscured by a
natural cooling cycle, requires a natural
cooling of more than 1 degree C over the past
few decades -- a cooling larger than any
observed before in the documented climate
history of Europe, which extends at some
stations into the 17th century.
Climate models predict that greenhouse warming should increase with latitude and be greatest in polar latitudes in winter. Since 1957, when regular observations began in Antarctica, neither pole has shown significantly more warming than the tropics.
Since the time of the dinosaurs, the Earth has cooled by about 10 detrees C. About 3 million years ago we entered the present ice age, marked by a series of glacial/interglacial cycles with a mean global temperature range estimated by 5 to 7 degrees C. The last seven of these cycles exhibited a glacial period of 90,000 years of staged cooling followed by rapid warming back to an interglacial lasting 10,000 to 12,000 years.. We are currently in an interglacial, called the Holocene, estimated to have begun 10,700 years ago. Thus, we are due to enter another 90,000-year period of glacial cooling at any time. Since this is our current state of knowledge, why do we not hear the argument that adding greenhouse gases to the atmosphere to delay, and thereby hopefully to prevent, the next glacial is just what man should be doing?
During the Holocene, temperature flluctuations of plus and minus 1 - 2 degrees C have been inferred from various types of data. The warmest period, the Climatic Optimum, occurred about 6,000 years ago. Around 900 AD the sea ice in the North Atlantic melted back and the Norsemen were able to colonize Iceland and Greenland. About 1350 AD the ice returned, the Greenland colony perished and the glaciers advanced over rent-paying farms and villages in Switzerland and Scandinavia. Thus we have both historical and paleoclimatological data for the "Medieval Climatic Optimum" warm period circa 900-1350 AD and the following "Little Ice Age" cold period circa 1350-1850 AD.
The least controversial explanation for the warming shown by our surface temperature observations is that it represents a return to normal from the Little Ice Age and possibly, entry into the next warm period of the Holocene. If this is what is occurring, we are now at the inflection point, or point of most rapid rise, of the temperature curve and we can look forward to a further warming of about another degree C over the next couple of centuries, regardless of what man does. Note also that the warm periods of the past have been termed "climatic optima," and so they must have appeared to the remnants of the Greenland colony circa 1350 AD.
The latest Intergovernmental Panel on Climate Change claim that "The balance of evidence suggests as anthropogenic influence on global climate" elicited much controversy. Its invalidity is now indicated by the Richard Kerr and Klaus Hasselmann articles in the May 16, 1997 issue of Science. These contain statements like the following:
"...many climate experts caution that it is not at all clear yet that human activities have begun to warm the planet -- or how bad greenhouse warming will be when it arrives." (Richard Kerr, Research News & Comment Writer for Science.)
"We say quite clearly that few scientists would say the attribution issue was a done deal." (Benjamin D. Santer, Lead Author of Section 8 of IPCC95.)
"The inherent statistical uncertanties in the detection of anthropogenic climate change can be expected to subside only gradually in the next few years while the predicted signal is still slowly emerging from the natural climate variability noise. It would be unfortunate if the current debate over this ultimately transitory issue should distract from the far more serious problem of the long-tem evolution of global warming once the signal has been unequivocally detected above the background noise." (Klaus Hasselmann, Max-Planck Institute for Meterology.)
From these acknowledgments by its supporters, it seems quite clear that the IPCC95 statement, "The balance of evidence suggests a discernible human influence on global climate," was studiously crafted. The purpose of the wording appears to have been to induce the media to broadcast to the public and policymakers of the world a message which few, if any, of the researchers, on whose work it was based, are yet willing to defend before the scientific community.
Global climate policy may reach a crescendo in Kyoto in December, but it will not be because of compelling scientific case has been made that requires action be taken to ward off environmental calamity. The theory of human-induced global warming is far from being an open-and-shut case.
While the concept of greenhouse warming is well established, its actuality on planet earth currently rests only the predictions of climate models. That the models still lack the desired precision is evident by their broad disagreement with each other and with observational data, such as their less than specific "forecast" of temperature history.
Models of global warming are especially oversimplified for the tropics due to their inability to cope with the very low humidities in the downwelling portions of the Hadley circulation. Any surface warming in the tropics will lead to acceleration of downdrafts of convectivly dried air, opening deeper and enlarged subtropical windows" for infared radiation to escape. As a result, model predictions of global warming in the tropics seem exaggerated by a factor of two to three times.
Efforts to construct a "fingerprint" of man-made global warming have also done little to enhance the credibility of gloom and doom global warming forecasts. Even the IPCC was forced to conclude: (1) "It is not possible at this time to attribute all, or even a large part, of the observed global mean warming to enhanced greenhouse effects on the basis of observational data currently available." And (2) "We do not yet know what the detailed signal [fingerprint] looks like because we have limited confidence in our predictions of climate change patterns."
Moreover, there is a consistent bias against good news. Very reputable scientists are engaged in global climate research. But their careful statements are either suppressed or ignored when they do not support dire scenarios. The United Nations, of course, has tremendous incentives to promote widespread dissemination of bad news. Global doom scenarios enhance its position as a transfer agent for massive flows of wealth from developed to developing nations.
Until global climate change models improve significantly, we do not know whether we have a serious threat to our planet, no threat, or even a beneficial outcome due to manmade greenhouse gas emissions. In short, despite pronouncements by political leaders in the United States, Europe, and elsewhere, policymakers are not being compelled to act on the basis of global warming science. Indeed, global warming science is still evolving.
(The complete scientific report from which this summary was prepared is available from Dr. Ellsaesser at 4293 Stanford Way, Livermore, CA 94550. Phone, (510) 447-3834; fax (510) 447-3003)