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Hot Talk Cold Science
Global Warming's Unfinished Debate
By S. Fred Singer
The Independent InstituteCopyright © 1999 S. Fred Singer
All rights reserved.
The Scientific Case Against the Global Climate Treaty
A driving force behind the push for a global climate treaty has been the United Nations' Intergovernmental Panel on Climate Change (IPCC). Through a series of well-publicized reports — co-authored by teams of scientists and policy specialists — the IPCC has come to be viewed by many governmental agencies, environmental policy organizations and the media as the leading source of scientific information on climate change. It is for this reason that I focus much of my attention on reports issued by this esteemed organization.
The major conclusion of the United Nations' Intergovernmental Panel on Climate Change (IPCC WG-I 1996) — that "the balance of evidence suggests a discernible human influence on global climate" — cannot and should not be used to validate current Global Circulation Models (GCMs). The growing discrepancy between weather satellite observations, backed by balloon radiosonde data, and the results of computer models, throws doubt on the models' adequacy to predict a future warming. An earlier IPCC (1990) conclusion that observed and calculated temperature changes are "broadly consistent" is no longer accepted; the current IPCC explanation of the acknowledged discrepancy in terms of cooling effects from anthropogenic (man-made) sulfate aerosols is being increasingly disputed. There exist different, competing views about the cause(s) of the discrepancy — including exogenous factors like solar variability, and endogenous factors like clouds or water vapor distribution — all inadequately treated by current computer models. The models do not include a variety of human influences, ranging from possible climate effects of air traffic to the diversion of fresh water from the Mediterranean.
Even if a moderate warming were to materialize, its consequences would be largely benign — for other climate parameters, for sea-level changes, and for agricultural production. The goal of the Global Climate Treaty — avoiding a "dangerous" level of greenhouse (GH) gases — cannot as yet be scientifically defined; higher GH gas levels may well produce a more stable climate. Therefore, the prudent course is to practice a "no-regrets" policy of conservation and efficiency improvements and rely on adaptation to meet any damaging effects of climate change. At the same time, building on successful initial experiments, the capability of ocean fertilization to draw down atmospheric CO2 should be demonstrated.
The chief points of this overview are as follows:
1. The major conclusion of the 1996 report of the U.N.-sponsored science advisory group, the Intergovernmental Panel on Climate Change (IPCC), is that "the balance of evidence suggests a discernible human influence on global climate" (IPCC WG-I 1996, Chapter 8). This innocuous but ambiguous phrase has been (mis)interpreted to mean that computer models predicting a future warming have now been validated. But such a connection is specifically denied in the body of the IPCC report (IPCC WG-I 1996, p. 434) — although not in the politically approved IPCC Summary for Policymakers (SPM).
On the contrary, the global temperature record of this century, which shows both warming and cooling, can best be explained by natural climate fluctuations caused by the complex interaction between atmosphere and oceans, and perhaps stimulated by variations of solar radiation that drives the Earth's climate system. The satellite record of global temperature, spanning nearly twenty years, does not show a global warming — much less one of the magnitude predicted by General Circulation Models (GCMs). The gap between the satellite observations and existing theory is so large that it throws serious doubt on all computer-modeled predictions of future warming. Yet this discrepancy is never mentioned in the IPCC report's Summary — nor does the SPM even admit the existence of satellites (Singer 1996).
If one were to extrapolate the maximum allowed temperature trend from satellites to the year 2100, allowing for a further increase in atmospheric carbon dioxide and other greenhouse gases (GHG), one might estimate the increase in global average temperature at about 0.5 C (U.S. General Accounting Office 1995) — about one-fourth of the "best" IPCC value — hardly detectable and completely inconsequential.
Any future warming would be reduced further by the cooling effects of volcanoes — a factor not specifically considered by the IPCC. Even though we cannot predict the exact dates of future volcanic eruptions, we have sufficient statistical information about past eruptions to estimate an average cooling effect.
2. Even if global warming were to occur, it would most likely lead to positive benefits overall rather than to disbenefits. Human activities, especially agriculture, have always thrived during warm periods and faltered during cold periods (Moore 1995). A greenhouse warming should lead to a reduction in severe storms. Furthermore, it seems likely that a global warming will lower, rather than raise, sea levels, because more evaporation from the ocean would increase precipitation and thereby thicken the ice caps of Greenland and Antarctica (Singer 1997a).
3. Finally, no credible attempt has been made to define what constitutes a "dangerous" level of atmospheric CO2; thus the goal of the U.N. Climate Treaty (the Framework Convention on Climate Change-FCCC) is arbitrary. If one chooses as the target the present concentration, about 30 percent higher than the preindustrial CO2 level of 280 parts per million by volume (ppmv), emission rates must be cut by over 60 percent on a worldwide basis, according to IPCC modeling (IPCC WG-I 1990, p. xi).
A policy of adaptation to a possible climate change should be considered rather than energy rationing. If it becomes advisable to limit the growth of atmospheric CO2, it might be more cost effective to speed up CO2 absorption into the ocean, rather than by reducing emissions. In fact, by fertilizing the ocean with micronutrients, it may be possible to increase phytoplankton and fish populations, and thereby derive commercial benefits from the excess atmospheric CO2 (Cooper et al. 1996).
A discussion of the underlying science will reveal the following:
1. There Is No Detectable Anthropogenic Global Warming
The fear has often been expressed that anthropogenic release of GH gases could cause a temperature increase larger and more rapid than anything experienced in human history. The geologic record gives us an important perspective on this issue.
Carbon Dioxide: The paleo record of atmospheric carbon dioxide (Berner 1997, Fig. 1) shows considerable changes. The CO2 concentration was about twenty times the preindustrial value 500 million years (Myr) ago, diminished rapidly as CO2 was removed by weathering and reached its lowest level about 300 Myr ago. The concentration of CO2 then rose to about 4 to 5 times present levels and has been steadily diminishing ever since — with considerable fluctuations. Concerns have been raised that too low a CO2 level would be catastrophic for plant growth (Idso 1989).
Temperature: Climate has always varied. The paleotemperature records from ocean sediments and from Greenland and Antarctic ice cores have established the existence of 17 ice-age (glacial/interglacial) cycles in the past 2 million years. We are now in the Holocene, the interglacial warm period that began approximately 11,000 years ago, ending the most recent Ice Age.
Historical records document the existence of a "Little Ice Age," a period of colder than average global temperatures, between about 1450 and 1850, and the "Medieval Climate Optimum" around 1000 A.D. Even larger and more rapid temperature variations, certainly not caused by human activities, can be found in high-resolution ocean-core data (Fig. 2), going back 3,000 years (Keigwin 1996). Abrupt climate transitions occurred simultaneously at the equator and both polar regions around 8,000 years ago (Stager and Mayewski 1997), giving credence that such changes were worldwide. These findings contradict the IPCC claim that a human-caused greenhouse warming would lead to temperature changes that are greater and/or faster than any experienced up until now.
The Climate Treaty Goal: The climate record gives little guidance as to what constitutes atmospheric levels of CO2 producing "dangerous interference with the climate system"; the announced purpose of the Climate Treaty is to avoid such levels. We do not know, however, whether climate variability depends on CO2 concentration. Rapid variations in temperature appeared during the most recent ice age when the atmospheric CO2 concentration was only about 200 parts per million (ppm), rather than 280 ppm, the preindustrial value during most of the Holocene (IPCC 1996). Stager and Mayewski (1997) suggest that the warmer Holocene was "relatively more stable than the late Pleistocene." If this observation is supported by further data, we should be striving to increase, not decrease, the CO2 level in the atmosphere.
Azar and Rodhe (1997) placed the "dangerous" CO2 level in the range of 350-400 ppmv, and warned that a 2 C increase would be "dangerous." Their assumption that the present level of CO2 would have an appreciable probability of producing such a large temperature increase is dubious.
Consequently, the goal of the Treaty remains scientifically undefined. While the 1990 IPCC report favored CO2 stabilization at the 1990 level of about 350 ppm, the 1996 report appears to aim for a politically more acceptable level of 550 ppm, double the preindustrial value. But without scientific guidance, the goal is entirely arbitrary, and any stabilization level — or none — will do.
Natural climate variations: The cause of climate variations is largely unknown, and therefore unpredictable. Many climate scientists believe in the existence of irregular, quasi-periodic oscillations based on purely internal interactions between atmosphere and ocean, which computer models cannot yet simulate. Other scientists hold that solar variability is the main cause of climate variations. Indeed, striking correlations have been observed between sunspot cycles and climate (Fig. 3) (Lassen and Friis-Christensen 1991). Unfortunately, we do not understand how the rather small variations in solar radiation can influence climate so dramatically — although there are now a number of different mechanisms offered as explanations.
Whatever the cause, the GCMs used to predict future climate increases are not able to account for natural fluctuations of climate. Even the most sophisticated GCMs, using coupled atmospheric and ocean computer models, are unable to reproduce the El Niño-Southern Oscillation (ENSO), the North Atlantic Oscillation (NAO), or other quasi-periodic variations of climate.
Human influences?: The existence of natural climate variability makes it difficult to detect any "signal" that may be due to human activities. In the 1996 IPCC WG-I report, the authors of Chapter 8 claim that they can discern human influence gradually emerging from the "noise" of natural climate fluctuations as the concentration of CO2 increased with time. A correlation coefficient between observed and computed geographic climate patterns that appears to increase with time (Fig. 4) was shown by B.D. Santer et al. (1995; IPCC WG-I 1996, Chapter 8). In a contemporaneous research publication, however, some of the same authors express a different opinion (Barnett et al. 1996) (see Box 2).
There are several additional problems with the IPCC claim of a "discernible human influence":
The "natural" variability is derived from computer runs of GCMs, rather than from actual observations, and therefore likely to be different from the true value (see Box 2).
The computed climate pattern (IPCC WG-I 1996) includes, of course, the effects of the rise in greenhouse gases, but only one of the cooling effects of particulates — the direct albedo effects of human-produced sulfate aerosols. Their indirect effects leading to cloud production — important but difficult to quantify — are omitted, as are the radiative effects of mineral dust and of smoke and soot from biomass burning; yet these may be the most important effects (Fig. 5) (Schwartz and Andreae 1996).
Explaining the discrepancy: "Climate sensitivity" is defined as the temperature rise calculated by GCMs for a doubling of CO2-equivalent GH gases; the IPCC reports (1990, 1996) quote values between 1.5 C and 4.5 C. The clearest demonstration that current GCMs are inadequate comes from a comparison between their "best" predicted warming of 0.3 C per decade (IPCC 1990, 1996) and the actual observations. Surface measurements with thermometers show a warming of 0.13 C per decade since 1979, while global satellite measurements using a microwave sensor actually show a slight cooling of the lower troposphere — about -0.04 C per decade (Fig. 6) (Spencer and Christy 1992; Christy 1997). Thus there are two separate problems:
a. The difference between surface and satellite measurements.
b. The difference between observations and computer model results. There are several possible causes, each with different implications:
i. External man-made causes (aerosols, ozone changes).
ii. External natural causes (solar variations, volcanoes).
iii. Internal (to the models) causes (clouds, water vapor distribution).
a. Satellite vs. Surface Data: The IPCC report and individual investigators (Hansen et al. 1995; Hurrell and Trenberth 1996) have attempted to account for the discrepancy between surface and satellite data by claiming that they are both correct but measure different quantities. This explanation might cover a short period of time, but becomes untenable when the discrepancy extends over many years and keeps growing. The temperatures of the lower troposphere and surface cannot move apart for very long.
More recently, Hurrell and Trenberth (1997) claim to have found an error created when different satellite records are joined together. They assert that the reported cooling trend is an artifact. Against this assertion is the fact that the balloon record of the lower troposphere agrees almost exactly with the satellite record, but not with the trend in the surface record. Furthermore, the surface observations are subject to an "urban heat island" (UHI) effect (Fig. 7) (Goodridge 1996). As population grows in the vicinity of weather stations, an artificial warming trend is introduced that is difficult to identify and eliminate.
The urban heat island effect has also been demonstrated in other areas where there is a dense network of weather stations. After correcting for the UHI, the years around 1940 emerge as the warmest years of the century both in the U.S. record (Karl and Jones 1989) and the European record (Balling 1997) (see Fig. 8).
b. Climate Observations vs. Computer Results: The discrepancy between observations and computer model results is very serious. Even if the satellite data are corrected for the effects of El Niño and volcanic eruptions (Christy and McNider 1994), the growing discrepancy in trends indicates that the GCMs are not adequately simulating atmospheric processes.
i. Attempts have been made to "fix" the discrepancy by introducing into the GCMs the effects of sulfate aerosols said to cool and counteract the positive radiative forcing of greenhouse gases (Taylor and Penner 1994; Mitchell et al. 1995). But a recent modeling experiment indicates that the aerosol effect is minute and ascribes the lack of troposphere warming to a cooling of the stratosphere, presumably caused by an ongoing depletion of stratospheric ozone (Tett et al. 1996). Comprehensive analysis by Hansen et al. (1997) concludes that radiative forcing by aerosols is a minor factor in climate modeling—contrary to the main thrust of the Second Assessment Report of the IPCC (1996).
Excerpted from Hot Talk Cold Science by S. Fred Singer. Copyright © 1999 S. Fred Singer. Excerpted by permission of The Independent Institute.
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Table of Contents
Foreword Frederick Seitz,
1 Overview: The Scientific Case Against the Global Climate Treaty,
2 Unfinished Business: Scientific Issues to Be Resolved,
3 Epilogue: What to Do about Greenhouse Effects,
Appendix: Mitigation of Climate Change: A Scientific and Economic Appraisal,
About the Author,