The Scientific Case against the Global Climate Treaty
by S. Fred Singer
|
The Scientific Case against the Global Climate Treaty by S. Fred Singer |
A Report from
The Science & Environmental Policy Project
Fairfax, Virginia
July 1999
TABLE OF CONTENTS
EXECUTIVE SUMMARY
Climate is Forever Changing
Computer Models Don't Work
Other Human Influences Have Been Ignored
Rising Temperatures Could Have Positive Effects
Higher CO2 Levels May Not be "Dangerous"
Drastic Reductions in Energy Use…
… And Huge Economic Burdens on the Poor
Adapting to Climate Change
Farming the OceanTHE UNDERLYING SCIENCE.
There is No Detectable Anthropogenic Warming
The Climate Treaty Goal
Natural Climate Variations
Human Influences
Explaining the Discrepancy
Satellite vs. Surface Data
Climate Observations vs. Computer Results
Historically, a Modest Warming is Beneficial
Control of Atmospheric CO2
Adjusting to Climate ChangeUPDATE(1999)
Update on Climate Science
Economic Benefits from Global Warming: A Post-IPCC Re- Evaluation
The Kyoto Protocol is Ineffective
The purpose of this essay is to demonstrate the absence of a sufficient scientific basis for the Global Climate Treaty or for the kind of hasty and drastic bureaucratic "solutions" arising from the December 1997 Conference of the Parties (COP-3) in Kyoto, Japan.
During more than two dozen seminar lectures presented in the United States and Europe during the past two years, I found that audiences - both scientists and non-scientists - responded most favorably when they could see the actual data supporting some of the major scientific conclusions about climate change. Those conclusions are that:
· There is no current global warming and little to be expected in the future.
· The past, both recent and geologic, has seen large and rapid natural changes in temperature.
· Any onset of warmer temperatures would be expected to produce a drop in sea level, not a rise.
· The science of climate change is not "settled" or "compelling," and there is hardly any consensus within the informed scientific community.
At this point, policymakers who promote the Kyoto Protocol appear determined to impose severe economic hardships on much of the world's population through energy taxes and energy rationing. The United States Senate, which ultimately must be persuaded to ratify the Protocol, has voted 95-0 against such schemes, in the absence of scientific justification. Many labor unions, industries and thoughtful citizens appear to agree with the Senate.
It is my hope that readers, after examining the evidence for a manmade climate change - or rather the lack of it - will reach the same conclusion.
S. Fred Singer, Ph.D., July 1999
The announced objective of the 1992 Global Climate Treaty (officially known as the United Nations Framework Convention on Climate Change) is to "achieve stabilization of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system" (emphasis added).
The problem for policymakers is that no one knows what constitutes a "dangerous" concentration of greenhouse gases. There exists, as yet, no scientific basis for defining such a concentration, or even for knowing whether it is more or less than current levels. Just the same, efforts are now underway to establish a protocol for reducing emissions of greenhouse gases, focused mainly on carbon dioxide (CO2) from the burning of fossil fuels by industry, electric power plants, home heating and cooking, automobiles, and other road and farm vehicles.
To effectively reduce CO2, such an emission control scheme, with its legally binding targets and timetables still to be decided, will be extremely costly and have a detrimental economic impact on much of humankind. It risks ruining national economies, driving manufacturing and other industrial operations into less regulated countries (with the perverse effect of harming the environment in those countries), and ultimately costing citizens hundreds of billions of dollars.
Regulatory costs, although initially borne by industrial and agricultural producers, will eventually be passed along to consumers in the form of higher prices. The loss of jobs, combined with a higher cost of living, will cause severe hardship, especially for the poorest among us. Such economic sacrifices cannot be justified by current scientific evidence. Indeed, scientists continue to put forth new theories to explain why global temperature is not rising, even though greenhouse theory says it should.
The Global Climate Treaty, signed at the 1992 "Earth Summit" in Rio de Janeiro, rests on three propositions that are either questionable or demonstrably false.
1: The Climate Treaty supposes that a human influence has been detected in the climate record of the last hundred years, thereby validating the computer-generated predictions of a major future warming. But the climate has not warmed significantly over the last half-century, and not at all over the last 20 years, in contrast to theoretical predictions.
2: It further supposes that any future warming would produce catastrophic consequences, including droughts, floods, hurricanes, rapid and significant sea level rise, the collapse of agriculture, and the spread of tropical disease. But the climate record of the past 3,000 years appears to contradict all these assertions. Historically, warmer temperatures have been beneficial for human welfare and the development of civilization.
3: It presumes - with no scientific definition - to know which atmospheric levels of greenhouse gases are "dangerous" and which are not. To stabilize CO2 concentration at present levels, 30 percent above pre-industrial values, would require a drastic reduction of emissions and of energy use - more than 60 percent worldwide. But again, the historical record indicates that higher levels of CO2 - and they have been much higher in the past - may in fact provide benefits. Some scientists, including the late Roger Revelle, known as the father of greenhouse warming, have speculated that some of these benefits have already turned up in improved agricultural yields.
Let's take a broader look at these points. The main conclusion of the UN-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." This artful but essentially meaningless phrase has been misread by policymakers as proof that computer models predicting a warming of 1 to 3.5 degrees Celsius by the year 2100 have been validated. Such confusion is understandable. The IPCC Policymakers Summary juxtaposes that phrase with the results of climate model calculations of future warming, even though such a connection is specifically denied in the body of the 1996 IPCC report (p. 434).
Such misinterpretations to the contrary, the global temperature record of this century, which shows periods of both warming and cooling, can best be explained in terms of 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. [Fig. 1]
The weather satellite record of global temperatures, now spanning nearly twenty years, shows no global warming trend, much less one of the magnitude that computer models have led us to expect. The discrepancies between satellite observations and conclusions drawn from computer calculations are so large as to throw serious doubt on all computer-modeled predictions of future warming. Yet this discrepancy is never mentioned in the IPCC Policymakers Summary; indeed, the Summary does not even admit the existence of satellites.
Extrapolate the maximum allowed temperature trend from satellites to the year 2100 - the "worst-case" scenario - and one might estimate an increase in global average temperature of close to 0.5 degree Celsius - one-half the very lowest IPCC estimate. But 0.5 degree C is barely detectable and completely inconsequential.
Moreover, any calculated warming will be reduced by the cooling effect of volcanoes. Even though we cannot predict the occurrence of a volcanic eruption, we have sufficient statistical information about past eruptions to estimate their average cooling effect; yet this is one of several factors not specifically considered by the IPCC.
Are warmer temperatures necessarily bad? History shows us that human health and human activities, especially agriculture, thrive during warm periods and falter during cold ones. Infectious diseases are not related to temperature, but to poor hygienic practices, lacking public health services, and, ultimately, poverty. A warming trend should lead to a reduction in severe storms as the equator-to-pole temperature differences diminish. Also, new research indicates that warmer temperatures would likely cause sea levels to fall, not rise, as ocean evaporation increases precipitation over the poles and thickens the ice caps of Greenland and Antarctica.
With climate change - and climate has often changed - the traditional route
for humankind has been simply to adapt. What is more, if it should become advisable
to limit the increase of atmospheric CO2, it might be more cost-effective to
speed-up CO2 absorption into the oceans than to resort to energy rationing.
Recent successful experiments in fertilizing the ocean with micronutrients indicate
that in the near future it may be possible to not only draw down CO2 but to
increase phytoplankton and fish populations at the same time, thereby deriving
commercial benefits from what was once considered a problem.
Fig. 1 Global temperature versus time, as determined from surface measurements.
The temperature changes are referred to an arbitrary baseline. Three different
compilations are shown: IPCC [1996]14, GISS [Hansen and Lebedeff, 1987] and
Hasselmann [1997]27. While all three records show the remarkable warming before
1940, likely a natural recovery from the cooling of the "Little Ice Age,"
the records differ considerably after 1940. The differences between these records
illustrate some of the uncertainties in the "global" climate record
caused by the selection and treatment of the data.
We start with the observation that climate is forever changing, in many cases for reasons we do not yet understand. External changes are brought about by the variability of the sun, by volcanic eruptions, and, more rarely, by impacts of large asteroids or comets. But on the time scale of years and decades, the most important changes arise from complicated interactions between the atmosphere and the ocean; the El Niño events that cause global changes in temperatures and rainfall are a good example.
On a longer time scale, the Earth has experienced some seventeen glacial episodes - Ice Ages - in the last 2 million years. The variability of this past climate can be demonstrated by examining tree rings, ice cores, and ocean sediment cores, all of which show evidence of large and rapid temperature changes, even in recorded history - i.e. during the past 3,000 years. "Global" thermometer records have been available only since about 1880, and much of the world (particularly in Asia and Africa) temperature data were logged only sporadically, if at all. Even today large portions of the southern hemisphere and the oceans are not monitored regularly. It is only in the last 20 years that we have had truly global temperature data of the lower atmosphere from weather satellites.
Here is what the temperature data tell us: There has been a sharp warming from about 1880 to 1940, which is generally assumed to be a natural recovery from the "Little Ice Age," a period of much colder temperatures that began around 1450. After the 1940 peak, temperatures fluctuated, generally declining till about 1975 when there may have been a sudden increase [Fig. 1]. Surface thermometers show such an increase lasting into the middle 1980s; satellite data, however, backed up by observations from balloon-borne instruments, show no increase whatsoever since 1979, and even a slight cooling.
There is still fierce debate about the discrepancy between surface data and satellite temperature trends, but there is considerable evidence that the surface-based thermometers, generally located at airports near cities, have been contaminated by the "urban heat island" effect, which produces warmer temperatures locally. Climate records corrected for this effect show maximum temperatures occurring around 1940, rather than in the 1980s.
Computer Models Don't Work
Three-dimensional climate models that run on fast computers, the so-called General
Circulation Models (GCMs), have become much more sophisticated but still do
a poor job of representing the atmosphere. Their results differ widely, some
showing a warming of 1.5 degrees C or less, others of 4.5 degrees C or more.
Because these models suffer from poor spatial resolution - about 300 km - and
an incomplete knowledge of cloud physics, computer modelers cannot depict actual
clouds but must instead "parameterize" cloudiness, which accounts
for much of the wide range of GCM results. The GCMs also implicitly incorporate
a positive feedback from atmospheric water vapor (the most important greenhouse
gas), which greatly amplifies the effect of a CO2 increase. In reality, the
feedback may well be negative, instead of positive.
The UN Intergovernmental Panel on Climate Change has tried to explain the discrepancy between observed and calculated temperature changes. In its first assessment, in 1990, it simply ignored the satellite data and pronounced the observations and calculations to be "broadly consistent."
The second and most recent assessment, published in 1996, no longer uses this phrase. Instead, the IPCC tries to explain the difference between observations and theory by introducing the cooling effects of anthropogenic sulfate aerosols, i.e. particles derived largely from sulfur pollution produced by burning coal. It reduces the calculated "best" warming trend from 0.3 C down to 0.2 C per decade, which is still in disagreement with the satellite results. The IPCC also appeals to a supposed similarity of observed and calculated temperature patterns and concludes that "the balance of evidence suggests a discernible human influence on global climate." This ambiguous phrase has been widely used to argue that the climate models produce results validated by observations. The models are still inadequate in representing the real atmosphere, however, and no such validation has occurred.
Just a year after the IPCC published its 1996 report, it has become apparent, on the basis of recent computer studies, that the discrepancy between observations (showing no warming trend) and theory (projecting a 0.2 to 0.3 C temperature increase per decade) can no longer be explained by the assumed cooling effects of sulfate aerosols.
So what could be causing the gap? One set of explanations relies on effects internal to the models, principally their inadequate treatment of clouds and water vapor. It is thought that, if the models are improved, the positive feedback from water vapor would be reduced, or even reversed, resulting in a climate sensitivity (i.e., temperature increase for a CO2 doubling) of perhaps less than 1 degree C. Such temperature changes would be barely detectable in view of the noisiness of the natural variations, and would be quite inconsequential in their impact on climate.
The other set of explanations relies on external effects, principally caused by the 11-year cyclical variations of solar ultraviolet radiation, or on the corpuscular emission from the sun, the so-called "solar wind." Ultimately, these solar variations produce changes in cloudiness or in atmospheric ozone, which can more directly affect the climate.
These two sets of explanations have very different consequences, and call for very different policy responses. With the science largely unsettled, there is urgent need for further research.
Other Human Influences Have Been Ignored
There are other greenhouse gases, in addition to carbon dioxide from burning fossil fuels: nitrous oxide from agricultural fertilizers, various halocarbons, and methane from oil and gas operations, cattle raising and rice growing. International control efforts focus almost exclusively on CO2, yet methane has increased more than 100 percent in the past century and, on a per-volume basis, is 20 times more potent as a greenhouse gas than CO2.
Aside from raising the level of greenhouse gases, an expanding population is changing the ratio between cropland and forests, and thereby the reflecting power ("albedo") of the surface. Growing air traffic is changing the chemical composition of the lower stratosphere and may be producing sufficient contrails and cirrus clouds to show climate effects. Even the diversion of river water can affect ocean circulation, and thereby climate.
It is the task of research scientists to decide which of the many human influences are important enough to be incorporated into climate models. For example, if the Aswan Dam, by reducing the flow of the Nile, increases the already high salinity of the Mediterranean, can its outflow through Gibraltar disturb the North Atlantic circulation and affect North American and European climate, as has recently been suggested?
Rising Temperatures Could Have Positive Effects
Possible climate changes from human activities need to be considered from the perspective of natural changes. The geologic record shows natural changes that were larger and more rapid than those predicted by many computer models, and certainly larger than can be expected on the basis of extrapolation of observed temperature trends. Nevertheless, one should examine the potential impact of even a moderate temperature increase.
Judging from the climate record of the last 3,000 years of human history, climate consequences of a greenhouse warming should be generally beneficial. One would expect severe weather to be less frequent because of (calculated) reduced equator-to-pole temperature gradients. In fact, the frequency and intensity of hurricanes have decreased over the past 50 years, although the reason for this is not known.
The most feared consequence of global warming has been a catastrophic rise in sea level, resulting in coastal flooding and the disappearance of some islands. But new research indicates that increased ocean evaporation would lead to more rain--and therefore to more ice accumulation in the polar regions. As such, sea levels may actually drop. An empirical study of sea level change and sea-surface temperatures of the past century appears to point in that direction.
As far as agriculture is concerned, the combination of warmer weather and increased CO2 would be beneficial. More CO2 promises rapid plant growth and, at the same time, reduced water consumption because of reduced evapo-transpiration from leaves. The climate warming that has been calculated would be most noticeable at higher latitudes, primarily in the winter and at night, and would result in fewer frosts and a longer growing season. Farmers can adjust to local climate changes - as they have in the past - with improved technology and proper crop selection.
Higher CO2 Levels May Not Be "Dangerous"
One of the often expressed concerns has been that ongoing atmospheric changes could reach a "dangerous" level that might cause climate to become extremely unstable, or precipitate a sudden switch to a new climate state that would be detrimental to human existence.
Again, looking at the climate record, there have been many large climate fluctuations, but nothing that would lend support to the idea of a climate "surprise." If anything, the variability of climate was greater during the last Ice Age, when CO2 levels were less than 200 parts per million, than during the most recent 10,000 years of the warm interglacial (the Holocene), with CO2 levels at 280 ppm.
The geologic record does not indicate that CO2 levels higher than the present level (of 350 ppm) would be "dangerous." In fact, some 500 million years ago the planet experienced CO2 levels as high as 15 times the present level: they have been declining ever since, reaching a secondary peak of about 1500 ppm some 200 million years ago.
If we cannot tell whether higher levels of carbon dioxide are better or worse than present or pre-industrial levels, there is little point to mounting elaborate schemes to control CO2 emissions.
Drastic Reductions in Energy Use...
The IPCC has determined that maintaining the present atmospheric concentration would require that CO2 emissions be reduced by well over 60 percent worldwide and kept at that value. Any lesser reduction would only slow down the ongoing increase of CO2 in the atmosphere. But even a politically more palatable target of 550 ppm, much talked about in the IPCC report, would require a CO2 reduction of some 50 percent, with a corresponding reduction in the use of energy.
When the Conference of Parties to the Framework Convention on Climate Change
(Global Climate Treaty) held their first meeting in Berlin in 1995 (COP-1),
it was decided to exempt, or at least defer, developing countries from the obligation
to stabilize or reduce CO2 emissions. But since their emissions will very rapidly
exceed those of industrialized countries - by the year 2010 - emission control
schemes become purely a political exercise without any scientific basis.
This is quite evident from the fact that there is no scientific guidance on how to define and avoid a "dangerous" level of CO2 - the announced goal of the Climate Treaty.
...And Huge Economic Burdens on the Poor
Reducing the emission of CO2 - or even stabilizing CO2 at the present level - would put huge economic burdens on the industrialized nations and their citizens. If an emissions trading scheme is put in place, which allows industrialized nations to buy unused permits from developing nations, it may do little to reduce global emissions. Depending on how national emission quotas are set, emission trading may simply develop into a giant scheme to transfer wealth between nations, or - as some have put it - taking from the poor in the rich countries and giving to the rich in the poor countries.
It is, of course, obvious that oil-exporting nations will suffer economic losses if demand is reduced by industrialized countries. It is less well known that developing countries, relying on trade and foreign investments, may also incur losses if the economies of the industrialized nations falter .
There is considerable concern, particularly in the United States Senate, that imposing energy restrictions will not only raise energy prices to consumers, but cause industries to transfer operations to nations that do not incur these restrictions. The current U.S. administration has attempted to reassure the Congress that economic losses will not occur or will not be too severe if they do. But if it becomes apparent that a global warming could produce net benefits rather than net losses, it may be difficult to construct a benefit-cost analysis to convince the public and the Congress to go along with restrictions on energy use through what amounts to a hidden energy tax.
The recommended policy to meet any consequences of growing atmospheric greenhouse gases is to rely on human adaptation to any climate change, coupled with a "no-regrets policy" of energy conservation and increased energy efficiency. ("No-regrets" energy policies are those that make economic sense even if no climate change occurs.) Common sense is the key. Over-conservation can waste energy if it destroys energy-imbedded capital stock that requires new energy expenditures to replace.
Adaptation has been the traditional method of meeting climate changes; it has worked over thousands of years for human populations that were not as technologically advanced nor as materially endowed as those at present. The resources saved by not restricting energy use through rationing or taxing can be applied to make human societies more resilient to climate change, whether manmade or natural. After all, any effects from climate change over the next century will be minor compared to societal changes brought about by new technology, rising incomes and population growth.
In spite of the absence of observed global warming, and in spite of the expectation that warm temperatures would likely produce net benefits, governments may still feel politically compelled to reduce the ongoing increase in atmospheric carbon dioxide. As an alternative to controlling emissions, the idea of sequestering CO2 from the atmosphere by creating tree plantations has been widely discussed.
An equivalent scheme - potentially much more effective and with much lower cost than controlling emissions - would speed up the absorption of excess CO2 into the ocean. It has been successfully demonstrated recently that fertilizing certain regions of the ocean with micronutrients, like iron, can significantly increase the populations of phytoplankton. In addition to enhancing a basic food source for fisheries, ocean farming can also serve to absorb atmospheric CO2. In short, it may soon be possible to turn excess CO2 into a resource, making it no longer a menace.
There is no Detectable Anthropogenic Warming
The fear has often been expressed that anthropogenic release of greenhouse gases could cause a temperature increase that is 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 [Fig. 2] shows many changes. The CO2 concentration was about 15 times the present level 500 million years ago. It diminished rapidly as CO2 was removed by weathering, and reached its lowest level about 300 million years ago. The concentration of CO2 then rose to a secondary peak of about 4 to 5 times its present level and has been diminishing ever since, with considerable fluctuation. Clearly, there was no problem with plant growth at these higher levels; concerns have been raised, however, that too-low a CO2 level would endanger the survival of plants .
Temperature: Observations have shown that climate varies on all scales, both in time and in space. The paleo-temperature records from ocean sediments and from Greenland and Antarctic ice cores have established the existence of some 17 Ice-Age 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 an earlier medieval "climate optimum," a strong warming
around 1000 AD. Even larger and more rapid temperature variations, certainly
not caused by human activities, can be found in high-resolution ocean-core data
[Fig. 3], going back 3,000 years. Abrupt climate transitions occurred simultaneously
at the equator and at both polar regions around 8,000 years ago, suggesting
that such changes were worldwide. These findings contradict the oft-quoted IPCC
claim that a human-caused greenhouse warming would lead to temperature changes
greater and/or more rapid than anything experienced up until now.
Fig. 2 A compilation of carbon dioxide concentrations (as multiples of the pre-industrial value of 280 ppmv) [Berner, 1997] . In spite of considerable uncertainties, one can discern a rapid downward trend starting about 450 Myr ago, and an ongoing downward trend that began about 200 Myr ago. The recent anthropogenic increase would be difficult to notice.
Fig. 3 Detailed temperature variations of the past 3,000 years (during recorded
history), as determined from ocean sediment studies in the North Atlantic. [Keigwin,
1996] . Note the rapid variations, as well as the much warmer temperatures 1,000
and 2,500 years ago.
The climate record gives little guidance as to what levels of atmospheric CO2 could produce "dangerous interference with the climate system," although the announced purpose of the Global Climate Treaty is to avoid such levels. We don't know how climate variability depends on CO2 concentration, or if it does at all.
Rapid variations in temperature were quite prevalent during the most recent Ice Age, when the atmospheric CO2 concentration was only about 200 parts per million (ppm), well below the pre-industrial value of 280 ppm. Stager and Mayewski suggest that the warmer Holocene was "relatively more stable than the late Pleistocene." If this observation is supported by further data, it could be argued that we should be striving to increase the CO2 level in the atmosphere to gain climate stability.
An attempt was made recently to place the "dangerous" CO2 level in the range of 350-400 ppm . The authors, however, simply posited that a 2 degree C increase would be "dangerous"; even more dubious is their assumption that the present level of CO2 would lead to such a large temperature increase.
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 palatable level of 550 ppm, double the pre-industrial value. But without scientific guidance, the goal is entirely arbitrary, and any stabilization level - or none - will serve the purpose.
The cause of natural climate variations is largely unknown, their future course unpredictable. Many climate scientists believe in the existence of irregular, quasi-periodic oscillations based on purely internal interactions between atmosphere and ocean, which models cannot yet simulate. Another school of thought holds that solar variability is the main cause of climate variations. Observers have noted striking correlations between sunspot cycles and climate [Fig. 4]. Unfortunately, we do not have a clear idea as yet how the rather small variations in solar radiation can influence climate so effectively - although there are now a number of different candidate mechanisms.
Whatever the cause, the General Circulation Models (GCMs) used to predict future climate increases are not able to account for the natural fluctuations of climate. Even the most sophisticated GCMs, using coupled atmosphere-ocean computer models, are as yet unable to predict the El Niño-Southern Oscillation (ENSO), the North Atlantic Oscillation (NAO), and other quasi-periodic variations of climate.
Fig. 4 Solar activity, in terms of sunspot cycle length (broken line), shows
a strong correlation with global temperatures (solid line) [Friis-Christensen
and Lassen, 1991] . The author extended the correlation back to 1500 by using
proxy data [Lassen and Friis-Christensen, 1995] .
Human Influences
The existence of natural climate variability makes it difficult to detect any "signal" due to human activities. In the 1996 IPCC report, the lead authors of Chapter 8 claim that they can discern a human influence gradually emerging from the "noise" of natural climate fluctuations, as the concentration of CO2 increased with time. They show a correlation coefficient between observed and computed geographic climate patterns that appears to increase with time [Fig. 5]. In a contemporaneous research publication, however, some of the same authors express a different opinion [Box 1].
Human Influences
Box 1: Is There a Discernible Human Influence on Climate?
Here are two views by the same researchers:
"...there is evidence of an emerging pattern of climate response to forcings
by greenhouse gases and sulphate aerosols….from the geographical, seasonal
and vertical patterns of temperature change….These results point towards
a human influence on global climate."
B.D. Santer, T.M.L. Wigley, T.P. Barnett, E. Anyamba. IPCC Climate Change 1995:
The Science of Climate Change, Chapter 8 Summary, p. 412., 1996
"Estimates of...natural variability are critical to the problem of detecting
an anthropogenic signal.…We have estimated the spectrum.…from palaeotemperature
proxies and compared it with.…general circulation models….None of
the three estimates of the natural variability spectrum agree with each other....Until....resolved,
it will be hard to say, with confidence, that an anthropogenic climate signal
has or has not been detected."
T.P. Barnett, B.D. Santer, P.D. Jones, R.S. Bradley and K.R. Briffa, The Holocene,
vol. 6, pp. 255-265, 1996.
trends.GIF)
Fig. 5 a) From Santer et al., 1995 . As can be seen, the correlation coefficient
between calculated and observed temperature patterns is rather small and shows
strong variations. It decreases during the period of rapid warming (before 1940)
and does not increase during the past 25 years when atmospheric CO2 level rose
greatly. b) In the 1996 IPCC report (Fig. 8.10b, p. 433) only the increasing
50-year trend line is shown; the zero and negative trend lines were omitted
by the authors for reasons that were not explained.
There are several additional problems with the claim of a "discernible
human influence":
§ The "natural" variability is derived from computer runs of General Circulation Models, rather than from observations, and is certain to be different from the true value, and likely to be smaller. [Box 1]
§ The computed climate pattern includes, of course, the (positive) radiative
forcing 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
[Fig. 6].
Fig. 6 Global-mean radiative forcing for greenhouse gases and particulates.
Note the huge uncertainties shown by the vertical lines, especially for the
indirect effects of aerosols. The total forcing could even be negative, but
there is little reality to a "global mean" because of the large geographic
and temporal changes of particulates [Schwartz and Andreae, 1996] .
"Climate sensitivity" is defined as the temperature rise calculated by GCMs for a doubling of CO2-equivalent greenhouse gases; the 1990 and 1996 IPCC reports quote values between 1.5 and 4.5 degrees C. The clearest demonstration that current GCMs are inadequate comes from a comparison between their "best" predicted warming of 0.3 degrees C per decade and the actual observations. Surface measurements with thermometers show a warming of 0.13 degrees C per decade since 1979, while global satellite measurements using a microwave sensor actually show a slight cooling of the lower troposphere, about minus 0.04 degree C per decade [Fig. 7]. Thus there are really two separate problems:
a) To explain the difference between surface and satellite measurements.
b) To explain the difference between observations and computer model results.
Here one has several possible causes, each with quite different implications:
(i) External man-made causes: aerosols, ozone changes; (ii) External natural
causes: solar variations, volcanoes; and (iii) Internal (to the models) causes,
i.e. inadequate representation of clouds, water vapor distribution, atmosphere-ocean
interaction.
Fig. 7a Ground-based temperatures and satellite-observed temperatures show quite
different trends. Surface data shows a slight positive temperature trend while
satellite data shows a cooling trend. Fig. 7b The difference is large, statistically
significant, and growing. Fig. 7c The independent balloon radiosonde data support
the satellite data. [Michaels, P.J., World Climate Report, vol. 1, Jan. 22,
1996].
The IPCC report and individual investigators 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 work for a short time, but it is untenable if 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 claim to have found an error when different satellite records are joined together; they assert that the reported cooling trend is an artifact. Against this, one notes that the balloon record of the lower troposphere agrees almost exactly with the satellite record, but not with the trend in the surface record [Fig. 7]. Furthermore, the surface observations are subject to an "urban heat island" effect [Fig. 8]. As population grows in the vicinity of weather stations, an artificial warming trend is introduced that is difficult to eliminate.
The urban heat island effect has been demonstrated in the United States and in other regions where there is a dense network of weather stations. After correcting for the heat island effect, the years around 1940 emerge as the warmest years of the century in both the U.S. and European records [Fig. 9].
Climate Observations vs. Computer
Results
The discrepancy between observations and computer model results is even more serious. Even if the satellite data are corrected for the cooling effects of El Niño and volcanic eruptions, the growing discrepancy in trends indicates that the GCMs are not adequately simulating atmospheric processes.
Attempts have been made to "fix" the discrepancy by introducing
into the GCMs the effects of sulfate aerosols that are supposed to cool and
counteract the positive radiative forcing of greenhouse gases.
Fig. 8 Warming trends since 1910, as observed by California stations. The top
curve is for counties with populations of more than 1 million, the middle curve
is for populations between 0.1 and 1 million, and the bottom curve for counties
with less than 0.1 million inhabitants. Note the increased warming trend for
populous counties, indicating an urban heat island effect [Goodridge, 1996].
Fig. 9 After correcting for the urban heat island effect (UHI), the years around
1940 emerge as the warmest years of the century in both the US record (top)
[Karl and Jones, 1989] and European record (bottom) [Balling, 1997].
More recent modeling experiments, however, indicate that the aerosol effect
is minute and ascribe the lack of troposphere warming to a cooling trend of
the stratosphere, presumed to be caused by an ongoing depletion of stratospheric
ozone.
Trying to reconcile temperature observations of the northern and southern hemispheres also shows that aerosols cannot account for the discrepancy. Human-induced sulfate aerosols are restricted almost entirely (about 90 percent) to the northern hemisphere and thus should have opposed or slowed greenhouse warming mainly in the northern hemisphere. Yet recent re-analyses of southern-hemisphere land data (which are more credible and also predicted to change more than sea surface temperatures) have cut the observed rate of warming to about half that of the northern hemisphere.
Fig. 10 Temperature trends vs. latitude (1979 to 1995) for surface and satellite
data. A fairly conclusive piece of evidence against the importance of aerosols
comes from the observation of a strong (zonal) warming trend in northern mid-latitudes.
[Michaels, P.J., World Climate Report, vol. 1(2), pp. 1995].Aerosols, which
are supposed to cool climate, originate mainly in the Northern Hemisphere at
middle latitudes.
A fairly conclusive piece of evidence against the importance of aerosols comes
from the observation of a strong zonal warming trend in northern mid-latitudes,
rather than an expected cooling. It can be seen in surface as well as balloon
and satellite data [Fig. 10]. Its cause is suspected to be a positive radiative
forcing from cirrus clouds produced by the rapidly increasing air traffic in
the vicinity of the tropopause.
It is therefore surprising that efforts are still underway to explain the discrepancy between observations and climate models in terms of the direct effects of aerosols . The confident 1996 IPCC conclusion that "...the balance of evidence suggests a discernible human influence on global climate" seems no longer supportable [Box 2].
Box 2: Doubts about the IPCC Conclusions
Klaus Hasselmann, 1997: "uncertainties 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 ". [See Ref. 27]
Richard Kerr, 1997: "Many scientists say it will be a decade before computer models can confidently link the warming to human activities." [See Ref. 28]
Benjamin Santer (as quoted by Kerr), 1997: "We say quite clearly that few scientists would say that the attribution issue was a done deal." "It's unfortunate that many people read the media hype before they read the [IPCC] chapter [on the detection of global warming]." [See Ref. 28]
Brian Farrell (as quoted by Kerr), 1997: "There really isn't a persuasive case being made for detection of greenhouse warming ... the error bars are as big as the signal." [See Ref. 28]
Thomas Crowley, wishfully, in the New York Times, July 2, 1997: "...statistical studies suggest that we are already on the verge of detecting a greenhouse warming."
Solar variability in the ultraviolet region of the spectrum and through the
solar wind could also modulate the Earth's climate. One possibility is the climate
influence of the well-known 11-year cycle of stratospheric ozone thickness,
which could in turn affect atmospheric circulation.
Another possibility is that the solar-modulated 11-year cycle of cosmic-ray intensity influences climate. Several quite different mechanisms have been discussed: the generation of nitrogen oxides, depleting stratospheric ozone ; ionization by cosmic rays that affect the rate of freezing of supercooled water in high-level clouds ; changes in the vertical air-earth current density affecting atmospheric dynamics ; changes in cloud cover correlated with cosmic-ray intensity [Fig. 11].
Fig. 11 Changes in cosmic ray intensity at Climax, Colorado (thick line) and
cloud data sets from four satellites (triangles are Nimbus 7 data, squares are
ISCCP.C2 data, diamonds are DMSP data, crosses are ISCCP.D2 data) [Svensmark
and Friis-Christensen, 1997]. The data are smoothed using a 12-months running
mean.
It is likely, however, that the discrepancy between observations and computer
model results is due to the inadequate treatment of internal effects within
the models themselves, rather than external factors like changes in aerosols
or ozone. Possible internal effects include a negative feedback from increased
cloudiness or from a possible reduction of upper troposphere water vapor, either
by an intensification of the Hadley circulation or by mesoscale drying mechanisms
related to cloud dynamics.
It is too early to tell which of the many feedback possibilities can account for the shortcomings of the current GCMs, although satellite infrared and microwave observations may settle the issue. But it is clear that until validated by actual climate observations, the model results should not be used as a basis for developing policy. Contrary to the confident assertions by politicians that climate science is "settled," it appears that climate science is still "unfinished business."
It is quite important to understand the reason for the discrepancy between theory and observations. If it is due to aerosols, then the ongoing growth of greenhouse gases will eventually win out, because of the short atmospheric lifetime of aerosols - a few days - compared to the lifetime of CO2. If the discrepancy is due to solar variations, then the enhanced greenhouse effect should again win out, because solar variations are presumably periodic and should average out to zero over the long term. On the other hand, if the discrepancy is due to internal effects, leading to reduced or even negative feedbacks, then the climate sensitivity itself is greatly reduced and any future warming is likely to be unimportant.
Historically, a Modest Warming is Beneficial
We already know from recorded human history that warm periods are beneficial
for human populations and that cold periods bring disaster in the form of crop
failure and disease. More specifically, however, observations indicate, and
theory suggests, that weather should improve as a result of global warming.
If greenhouse warming serves to reduce the equator-to-pole temperature gradient,
as predicted by models, then mid-latitude storms should diminish in intensity
. North Atlantic hurricanes have diminished in both frequency and severity in
the past 50 years [Fig. 12]. Precipitation on a global scale has decreased in
the past 40 years [Fig. 13], a result that is contrary to the expectations from
greenhouse theory.
The most-feared consequence of global warming has been the possibility of a
catastrophic sea-level rise. The ongoing rise, averaging about 1.8 mm/yr, cannot
be explained in terms of climate warming and is thought to be of tectonic origin.
It is virtually impossible, however, to predict (purely from theory) whether
sea level rise will accelerate or slow as climate warms. On the one hand, melting
glaciers and thermal expansion of ocean water will lead to a rise. On the other
hand, increased evaporation from the oceans and subsequent precipitation and
accumulation of ice on Greenland and especially Antarctica would lower sea level.
The only way to settle this issue is by examination of data. As can be seen in Fig. 14, both global average temperature and tropical average sea-surface temperature are anti-correlated with fluctuations of sea level rise. Ice accumulation on polar ice sheets also anti-correlates with sea level rise. Results from GCM calculations suggest that Antarctic ice accumulation will outweigh thermal expansion and glacier melting. Thus, a possible future warming would slow down the ongoing rise in sea levels, rather than accelerate it.
Fig. 14 Sea-level rise change (SLR) (after subtracting the linear rise), global
average temperature (GAT), and tropical average sea-surface temperature (TASST).
Note that the correlation is inverse, suggesting that global warming could slow
down, rather than speed up sea-level rise [Singer, 1997b]. (All plots are 10-year
running means of yearly values.)
Fig. 12 Time series of mean annual maximum sustained wind speed attained in
Atlantic hurricanes [Landsea et al., 1996]. Linear trend shown as dashed line
[IPCC, 1996].14
Fig. 13 Record of "global" annual precipitation anomaly (with respect
to 1961-1990 mean) observed over land areas in latitude interval 55ES to 85EN.
Note the general decline since about 1955 [IPCC 1996, p. 155]14.
As far as agriculture is concerned, a modest global warming based on increased
CO2 levels - as seems likely over the next 100 to 200 years - is bound to be
beneficial for a number of reasons. The predicted rise in average temperature
comes mainly from a rise of night-time and winter temperatures, in other words
from a reduction in the diurnal and annual temperature range. Thus, greenhouse
warming should lead to fewer frosts and longer growing seasons. In addition,
the increased CO2 will stimulate plant growth, while at the same time reducing
the need for water. A "greening" of the Earth has already been reported,
as well as an earlier spring growing season. What is more, farmers are quite
capable of adjusting to climate changes.
Recently, concerns have been raised that warmer temperatures would spread insect-borne tropical diseases. This neglects the fact that insect control and public health are the primary determinants of such diseases, and that, with cheap and rapid mass transportation, the human vector is becoming increasingly important. One is reminded that frequent epidemics of malaria and yellow fever occurred in the United States and even Northern Russia when the climate was much colder. And it's worth noting that wealthy Singapore, situated at the equator, does not share the widespread tropical diseases prevalent in poverty-stricken Africa.
With the residence time of atmospheric CO2 variously estimated as between 50 and 200 years, its current excess over its pre-industrial value will eventually be absorbed by biota on land and in the ocean. But even if a future warming is negligibly small and on the whole beneficial, there may still be political pressure to control CO2 levels. The standard approach, and the one most appealing to international negotiators, has been to control CO2 emission rates; for example, the 1990 IPCC report pointed out that maintaining the current level of CO2 (350 ppm) would require a worldwide emission reduction of more than 60 percent from 1990 rates, with a corresponding reduction in energy use.
Stabilizing at the 550 ppm level - approximately double the pre-industrial value - requires an emission reduction of some 50 percent. It is hard to imagine broad political support for such a plan, given the disastrous economic consequences it would entail. No doubt realizing this, politicians have instead talked about more modest reductions of between 5 and 20 percent from current rates, with more to come later.
Even if these reduced rates were to be achieved on a worldwide basis, however, they would do no more than to slow down somewhat - and at great cost - the current upward trend of atmospheric CO2. Stabilizing emissions does not stabilize concentration if the atmospheric residence time is so long that CO2 accumulates.
An alternative approach to emission control is to sequester the CO2 from the atmosphere, or at least demonstrate that sequestering is technically and economically feasible. The conventional approach to CO2 sequestration has called for tree planting on a massive scale, thereby tying up CO2 for decades, to be released when the wood decays. But tree planting can be costly and impractical; it requires huge areas and great expenditures of funds to make an appreciable impact. Order-of-magnitude figures for sequestration by trees are 0.8 to 1.6 tonnes of carbon per hectare per year ; thus, to absorb the current increase of atmospheric CO2 requires about 50 million km2 (4,500 x 4,500 miles).
An equivalent, but economically far more attractive scheme is to speed up the natural absorption of CO2 into the ocean. Much of the world's ocean is a biological desert; even though many ocean areas have adequate supplies of the basic nutrients, nitrates and phosphates, they lack essential micronutrients like iron. Ocean fertilization has been widely discussed among scientific specialists, with experiments proposed by the late John Martin, and endorsed by the late Professor Roger Revelle, director of the Scripps Oceanographic Institution in La Jolla, California. With the completion and publication of the successful IronEx-II test [See also other papers in the Oct. 10, 1996 issue of Nature], it now makes sense to consider ocean fertilization as a viable candidate for sequestering atmospheric CO2.
A large-scale demonstration could prove the technical and economic feasibility for lowering the content of atmospheric CO2 at a fraction of the cost now contemplated for emission reduction. While it may never be necessary to reduce atmospheric CO2, it will be comforting to know that we have the technical capability to do so.
It is reasonably certain that any effects of human-induced climate change will be minor compared to other sources of change over the next century. Climate is important mainly because of its effect on natural resources, such as water, land, plants, forests, habitats, and other biological resources, and on human activities, such as agriculture, forestry, human settlements and recreation, which depend on these natural resources. Based upon existing assessments, human-induced climate change over the next one hundred years will be much less important to the environment than the other agents of global change, such as population growth, economic growth and technological changes.
Moreover, existing assessments tend to overestimate negative impacts of climate change, while underestimating positive ones [Box 3].
Box 3: Some Benefits of Increased CO2 Levels
Little, if any, of the $2 billion-per-year global-change research budget has been used to identify, document or quantify possible benefits of adding CO2 to the atmosphere, or of any of the other consequences of man's activities. This bias in itself has contributed greatly to public perception that these activities pose serious threats. That there are benefits from adding CO2 to the atmosphere is undeniable:
1) Fertilization of the biosphere: CO2 is essential to plant life. At the
last glacial maximum (18,000 ago) the CO2 level dropped to about 190 ppmv, which
is close to the level where plants would begin to experience propagation failure.
2) Longer frost-free growing season: Any greenhouse warming will reduce radiative
cooling of the surface, thus will be greatest in winter, at higher latitudes,
and at night. As indeed observed, minimum temperatures will be affected much
more than maximum temperatures, leading to longer frost-free growing seasons
and little, if any, additional summer-afternoon heat stress.
3) Greater water efficiency for plants: Except in the already arid subtropics,
precipitation is predicted to increase. In addition, increased CO2 allows plants
to ingest the CO2 they need with less opening of their stomata, thus making
it possible to survive with less water, since less is lost by evapo-transpiration.
4) Health: Increase of minimum temperatures with little effect on maximum temperatures
will be beneficial both in reducing cold stress and the requirements for space
heating. Idso has suggested that "the significant downturn in circulatory
heart disease experienced worldwide over the past two decades" is a possible
consequence of the 25 percent increase in CO2 in the atmosphere. Respiration
is controlled by the concentration of CO2 (rather than of oxygen) in the blood;
thus CO2-stimulated deeper breathing may have reduced the strain on the circulatory
system.
It is a fundamental principle of public policy that problems which are the most
important and can be reduced, if not eliminated, at the least cost to society
should be given the highest priority and dealt with first. Accordingly, one
must address the question: How important is a possible climate change - above
and apart from the major variations of natural origin - compared with other
agents of future global change?
It is difficult to justify major expenditures to address climate change in the presence of other unmet societal needs, such as improved health care, adequate nutrition, education, and personal and public safety. If, as has been argued here, climate change is a minor problem, then adaptation to climate change becomes the preferred option; one can then devote any resources thus saved to more important societal problems.
Adaptation to climate change is, of course, the normal response to seasonal and interannual variations of climate, and to many extreme climate events. Adaptation is generally easier for technologically advanced societies and for societies that have resources and can afford adequate housing, heating, air-conditioning, and so on. It should be noted also, that throughout human history populations have adapted successfully to large permanent climate changes; for example, when Germanic tribes migrated from the frozen north to the Mediterranean. In any case, the most serious climate threat to mankind may be the return of an Ice Age, following the end of the current warm interglacial period.
While adaptation to climate change may be problematic for natural ecosystems, the ability to adapt is, paradoxically, highest for those economic sectors and human activities which are most sensitive to climate change. Because of their sensitivity to climate, such systems have always been heavily managed and have a long history of successful and rapid adoption of technological and management innovation.
There are actions that help meet both adaptation and development goals. Besides energy conservation and the encouragement of non-fossil-fuel resources, these include increasing the productivity or efficiency (per unit of land or water) of crops, livestock, forests, fisheries and human settlements.
One needs to consider adaptation to climate change as one of the most desirable
policy options; indeed, by ignoring adaptation one systematically overestimates
the negative impacts of climate change. More importantly, strategies to limit
CO2 emission from fossil-fuel combustion--and energy use--may compromise society's
ability to cope with other global problems that require economic development.
[Box 4]
Box 4: Reasons for Avoiding Hasty Bureaucratic Action
1) We have not be able to define scientifically the goal of the Global Climate Treaty, namely the greenhouse gas concentrations that may be considered "non-dangerous." A higher CO2 level may turn out to be preferable to a lower one.
2) Postponing action by 10 years or so will not appreciably affect future temperatures.
3) A number of economic arguments have been advanced why it pays to postpone action on limiting emissions, without compromising the ability to act later. Chief of these is the fact that capital equipment can be replaced at lower cost with a more efficient unit after it wears out. Another reason is that we will learn more about the underlying climate science and be able to make more rational decisions.
Response strategies and impact assessment reports by the IPCC and other groups note that developing countries are more vulnerable to climate change. This is not because climate change is expected to be greater in those nations - in fact, climate change would be least in the tropical zone - but because of their lack of financial and technical resources. Hence, it is imperative to expand these resources. This can be done through economic growth, which will reduce poverty and eventually population growth rates, and through technological change. Encouraging the basic legal, economic and institutional framework to bring about this economic growth and technological change should be a priority.
In summary, successful adaptation to climate change requires specific actions
- many of which will also help limit greenhouse gas emissions - that will stimulate
economic growth and continued technological progress. Meeting these twin goals
is critical to ensuring that limitations on greenhouse gases, if they should
ever become necessary, result in the least disruption to society.
UPDATE (1999)
A number of recent developments have made an update desirable:
· Research underlying climate change has uncovered new facts, largely invalidating the evidence on which the 1996 IPCC conclusions were based. Far from being "settled," as frequently claimed, climate science has moved ahead rapidly on all fronts and is uncovering new problems.
· The economic impact of a possible global warming has been re-evaluated and found to yield positive benefits rather than losses. This new analysis, if sustained, undercuts the need for drastic mitigation policies, or even the mandatory emission cuts called for by the Kyoto Protocol.
· The Kyoto Protocol of December 1997, even if punctiliously observed, is shown to have negligible effects on any future greenhouse warming. It would require the United States to reduce carbon dioxide emission from energy-fuel use by 7% (below 1990 levels), or by about 35% around the year 2010. Other Annex-1 countries face similar problems. Kyoto is not only costly but also ineffective.
1. The radiative forcing from CO2 is now about 15% less than previously calculated
(Myhre et al. 1998). The growth rates of carbon dioxide and methane have slowed
markedly in the last few years (Hansen et al .1998) Methane levels have nearly
stopped growing (Dlugokencky et al. 1998). The cause is not well understood,
and there is no assurance that the lower rates will persist.
2. Estimates for the residence time of atmospheric CO2 continue to decrease.
About half will be absorbed into the shallow ocean within thirty years and about
80% within 100 years (Sarmiento, Orr, and Siegenthaler, 1992). A study based
on detailed CO2 data (between 1988 and 1992) has led to the discovery of a huge
carbon sink over North America, roughly equal to the amount of the fossil-fuel
carbon emitted (Fan et al.1998); the finding has provoked a lively debate.
3. Measurements with high time resolution on the Vostok ice core have established
the detailed relationship between CO2 increases and temperature increases during
the transition from an ice age to an interglacial period. During the last three
deglaciations, the CO2 increase was found to lag the temperature increase by
1000±500 years (Wahlen et al. 1999). This finding would seem to rule
out CO2 as the cause of the warming. (Methane was ruled out earlier for similar
reasons.)
4. The temperature record obtained from weather satellite data is distorted
by decay of the satellite orbits (Wentz and Schabel 1998). After applying this
correction, as well as a correction for orbit drift, the temperature trend from
1979 to 1997 is not as negative as previously reported, and is close to being
zero (Christy et al. 1999). Direct temperature measurements on Greenland ice
cores show a cooling between 1940 and 1995 (Dahl-Jensen et al. 1998), in support
of the satellite data and the (independent ) balloon radiosonde data, but not
the surface measurements (which show a warming trend that could be due to local
contamination, like urban heat islands).
5. None of the data sets, including the surface measurements, agree with the
trend expected from model results. This trend is calculated to be about 0.25°C
per decade at the surface, but rises gradually to twice that value in the upper
troposphere (Tett et al. 1996).
6. The issue of absorption of solar energy by clouds is still in dispute, as
is the feedback of clouds in climate models (Cess et al 1990, 1996). The question
of the magnitude and sign of the water vapor feedback has not been settled,
pending the arrival of better observations (Spencer and Braswell, 1997). A small
or negative feedback may explain why temperature trend observations and models
disagree.
7. The IPCC report tried to explain the discrepancy between the observed temperature
record and model calculations in terms of the cooling effects of manmade sulfate
aerosols. This explanation is no longer accepted by many. Tett et al. (1996)
showed that ozone depletion produces a much stronger impact on tropospheric
temperatures than aerosols. Penner et al. (1998), exploring the complication
of different types of aerosols, concluded that one could not explain the temperature
increase of the past century in terms of human influences. Finally, Hansen et
al. (1998) pointed to the fact that the uncertainty in radiative forcing from
aerosols exceeds the uncertainty in the climate sensitivities of the models:
"The forcings that drive long-term climate change are not known with an
accuracy sufficient to define future climate change."
8. Increasing numbers of researchers now agree that the warming during the early
part of this century is primarily a recovery from the preceding Little Ice Age.
If not completely due to solar variability, it must at least contain a strong
solar component rather than being manmade (Soon et al. 1996; Wigley et al 1997).
9. A team of investigators has produced a post-IPCC assessment of tropical cyclones
(hurricanes) and their possible relation to global climate change (Henderson-Sellers
et al 1998). They find substantial multi-decadal variability but no clear evidence
for long-term trends. Recent studies indicate that the maximum potential intensity
could increase modestly by up to 10 to 20 percent if there is global warming,
but these changes are small compared with the observed natural variations. The
broad geographical regions affected by tropical cyclones are not expected to
change significantly; the popular belief that the region will expand as the
oceans warm is a fallacy. The available evidence points to little or no change
in expected global frequency.
10. The inverse relation between global warming [or tropical sea surface temperature]
and changes in sea level (Singer 1997a) is supported by data on ice accumulation
in the Antarctic. It seems increasingly likely that a warming will increase
precipitation and ice accumulation, and thus slow down or even reverse the ongoing
sea level rise.
An up-to-date overview is given by Singer (1999).
------------------------------
Cess, R.D., G.L. Potter, et al, 1990: "Intercomparison and Interpretation of Climate Feedback Processes in Nineteen Atmospheric General Circulation Models." Journal of Geophysical Research, vol. 95, pp. 16,601-16,615; ------------- 1996: "Cloud Feedback in Atmospheric General Circulation Models." Journal of Geophysical Research, vol. 12, pp. 791-12, 794.
Christy, J.R., R.W. Spencer, and W.D. Braswell, 1999: Journal of Atmospheric and Oceanic Technology (submitted).
Dahl-Jensen, D., Mosegaard, K, Gundestrup, N., Clow, G. D., Johnsen, S. J., Hansen, A. W., and N. Balling, 1998: "Past temperatures directly from the Greenland ice sheet." Science, vol. 282, pp, 268-279.
Dlugokencky, E.J., K.A. Masarie, P.M. Lang, and P.P. Tans, 1998: "Continuing Decline in the Growth Rate of the Atmospheric Methane Burden." Nature, vol. 393, pp. 447-450.
Fan, S., M. Gloor, J. Mahlman, S. Pacala, J. Sarmiento, T. Takahashi, and P. Tans, 1998: "A Large Terrestrial Carbon Sink in North America Implied by Atmospheric and Oceanic Carbon Dioxide Data and Models." Science, vol. 282, pp. 442-446.
Hansen, J.E., M. Sato, A. Lacis, R. Ruedy, I. Tegen, and E. Matthews, 1998: "Climate Forcings in the Industrial Era." Proceedings of the National Academy of Sciences USA, vol. 95, pp. 12753-12758.
Henderson-Sellers, A., H. Zhang, G. Berz, K. Emanuel, W. Gray, C. Landsea, G. Holland, J. Lighthill, S-L. Shieh, P. Webster, and K. McGuffie, 1998: "Tropical Cyclones and Global Climate Change: A Post-IPCC Assessment." Bulletin of the American Meteorological Society, vol. 79, pp. 19-38.
Myhre, G., E.J. Highwood, K.P. Shine, and F. Stordal, 1998: "New Estimates of Radiative Forcing Due to Well Mixed Greenhouse Gases." Geophysical Research Letters, vol. 25, pp. 2715-2718.
Penner, J.E., C.C. Chuang, and K. Grant, 1998: "Climate Forcing by Carbonaceous
and Sulfate Aerosols." Climate Dynamics, vol. 14, pp. 839-851.
Sarmiento, J.L., J.C. Orr, and U. Siegenthaler, 1992: "A Perturbation Simulation
of CO2 Uptake in an Ocean General Circulation Model." Journal of Geophysical
Research, vol. 97, pp. 3621-3646.
Singer, S.F., 1999: "Human Contribution to Climate Change Remains Questionable." EOS, Transactions American Geophysical Union, vol. 80, pp. 183, 186-187.
Soon, W.H., E.S. Posmentier, and S.L. Baliunas, 1996: "Inference of Solar Irradiance Variability from Terrestrial Temperature Changes, 1880-1993." Astrophysical Journal, vol. 472, pp. 891-902.
Fischer, H., M. Wahlen, H.J. Smith, D. Mastroianni, and B. Deck, 1999: "Ice Core Records of Atmospheric CO2 Around the Last Three Glacial Terminations." Science, vol. 283, pp. 1712-1714.
Wentz, F.J. and M. Schabel, 1998: "Effects of Orbital Decay on Satellite-Derived Lower-Tropospheric Temperature Trends." Nature, vol. 394, pp. 661-664.
Wigley, T.M.L., P.D. Jones, and S.C.B. Raper, 1997: "The Observed Global
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Economic Benefits from Global Warming: A Post-IPCC Re-Evaluation
A team of economists has re-evaluated the impact of a modest warming on the US economy (Mendelsohn and Neumann 1998). The 1996 IPCC report had assembled five published estimates of damages, ranging from $55 to $139 billion per year (in 1990 dollars, including market and non-market sectors). These estimates, published between 1991 and 1995, differ greatly in details - some assigning the greatest loss to agriculture, others to flooding from sea-level rise.
The new work derives a net benefit to the US economy, rather than a net loss. In addition to including certain benefits that had been overlooked in prior studies, the new methodology considers the possibility of adaptation, as well as the beneficial effects of increased CO2 on agriculture. See Table below.
If these improved estimates are borne out, then it will no longer be possible to carry out a cost-benefit analysis for the mitigation of greenhouse warming. For if the net benefits of warming are indeed positive (adding also the appreciable benefits of a reduction in sea-level rise), then one should do nothing to oppose such a warming. Indeed, the only policy that makes sense under those circumstances is the same "no-regrets" policy that is called for if the science does not support the warming predictions of climate models: as much conservation as makes economic sense, and higher efficiencies in the use of energy and other resources.
--------------
Mendelsohn, R. and J. E. Neumann (eds.), 1999: The Impact of Climate Change
on the United States Economy. Cambridge University Press, Cambridge.
The Kyoto Protocol is Ineffective
If ratified, the December 1997 Kyoto Accord would obligate Annex-I industrialized nations to reduce greenhouse gas emissions by an average of 5.2% below emission levels in base year 1990, by the period 2008-2012. The Accord was finally signed by the United States in November 1998, over the vociferous opposition of many members of the US Senate. (In July 1997, the Senate had passed a Resolution against a Kyoto-like agreement by a vote of 95:0 -- principally because it would not include China, India, Brazil and some 130 other developing nations.)
Even if all nations were required to follow the Kyoto Accord, it would merely slow the ongoing rise in atmospheric GHG levels by some small amount. As the IPCC itself has calculated, a worldwide emission cut of 60-80% is required to stabilize CO2 at present levels.
China, now the world's third-largest CO2 emitter, has been doubling its emissions every 25 years for the past 50 years. It is likely to continue doing so even more rapidly for some time to come, as it strives to improve its living standards and modernize its industries.
Requiring China and other developing nations to drastically curtail their energy use and GHG emissions would prevent them from achieving these vital economic and industrial goals. Conversely, limiting emission cuts to only industrialized nations would create great inequities and result in economic disaster for most nations, including those that rely on trade with industrialized countries.
In any case, the climate effect of a Kyoto Accord is minute. If one were to accept IPCC figures, a 5% cut in emissions by the Annex-I nations would reduce the additional warming, predicted for 2050, of 1.39°C: from a projected increase of 1.39% to a 1.33 °C increase (Parry et al. 1998).
A 20% cut in emissions by all nations (Annex-I and Annex-II) would reduce the
predicted temperature to only 1.22°C. A drastic 30% emissions reduction
by all nations (six times the Kyoto target) would reduce the predicted temperature
increase to only 1.19°C. That is, slashing emissions by almost one-third
(and perhaps seriously damaging many nations' economies) would reduce predicted
global temperature increases by only 0.20 C.
-----------------------------
Parry, M., Arnell, N., Hulme, M., Nicholls, R. and M. Livermore, 1998: "Adapting
to the inevitable." Nature, vol. 395, pp. 741.
CREDITS AND ACKNOWLEDGMENTS
In producing this report, the author gratefully acknowledges financial support from the Atlas Economic Research Foundation and the Jacobs Family Foundation, as well as research assistance by Sean McDonald, editorial assistance by Candace C. Crandall, and general support by Douglas Houts.
The following graphs were reproduced with permission of the publications in which they originally appeared:
From Science, the journal of the American Association for the Advancement of Science: Figures 1a, 2, 3, 4, and 6.
From Bulletin of the AMS, the journal of the American Meteorological Society: Figures 8 and 9a.
From the Journal of Geophysical Research, a publication of the American Geophysical Union: Figure 1c.
From Geophysical Research Letters, a publication of the American Geophysical Union: Figure 12.
From World Climate Report: Figures 7a,b, and c, and Figure 10.
From State of the Climate: Figure 9.
All other graphs were either redrawn for this publication or appeared originally in U.S. government reports.
Hansen, J., and S. Lebedeff, 1987: "Global Trends of Measured Surface Air Temperature." J. Geophys. Res., vol. 92, pp 13345-13372
Goldemberg, J., 1995: "Energy Needs in Developing Countries and Sustainability." Science, vol. 269, pp. 1058-1059.
Montgomery, W. D., 1997: "Impacts of Annex-I Country Commitments on Non-Annex-I Countries." Workshop on the Environment, Vienna, Austria, February 20.
Idso, S.B., 1989: Carbon Dioxide and Global Change: Earth in Transition. IBR Press, Arizona.
Stager, J.C., and P.A. Mayewski, 1997: "Abrupt Early to Mid-Holocene Climatic Transition Registered at the Equator and the Poles." Science, vol. 276, pp. 1834-1836.
Berner, R.A., 1997: "The Rise of Plants and Their Effect on Weathering and Atmospheric CO2," Science, vol. 276, pp. 544-545.
Keigwin, L.D., 1996: "The Little Ice Age and Medieval Warm Period in the Sargasso Sea," Science, vol. 274, pp. 1504-1508.
Ibid.
Azar, C., and H. Rodhe, 1997: "Targets for Stabilization of Atmospheric CO2." Science, vol. 276, pp. 1818-1819.
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About the Author
S. Fred Singer, professor (emeritus) of environmental sciences at the University of Virginia, is founder and president of The Science & Environmental Policy Project, a non-profit educational and research group based just outside of Washington, D.C., in Fairfax, Virginia.
An atmospheric physicist, Dr. Singer has held many academic and governmental positions. He established and served as first director of the U.S. Weather Satellite Service. Among other positions, he was also the founding dean of the School of Environmental and Planetary Sciences at the University of Miami, deputy assistant administrator for policy of the U.S. Environmental Protection Agency and, most recently, chief scientist of the U.S. Department of Transportation. Singer is the author of numerous scientific articles and the author or editor of 15 books, including Global Climate Change (1989), Free Market Energy (1984), and Is There an Optimum Level of Population (1971). He created and developed earth satellite systems and pioneered remote sensing techniques to measure atmospheric parameters from satellites. He was also the first to recognize and calculate the anthropogenic production of atmospheric methane, an important greenhouse gas and source of stratospheric water vapor.
First Published in the United States, September 1997, and updated July 1999
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