Thank you for soliciting my testimony on the science of climatechange as it pertains to the Kyoto Protocol to the United NationsFramework Convention on Climate Change.
Nearly ten years ago, I first testified on climate change in theU.S. House of Representatives. At that time, I argued thatforecasts of dramatic and deleterious global warming were likely tobe in error because of the very modest climate changes that hadbeen observed to that date. Further, it would eventually berecognized that this more moderate climate change would beinordinately directed into the winter and night, rather than thesummer, and that this could be benign or even beneficial. Itestified that the likely warming, based on the observed data, wasbetween 1.0 and 1.5°C for doubling the natural carbon dioxidegreenhouse effect.
The preceding paragraph was excerpted verbatim from my lasttestimony before this House, on November 6, 1997. Since that lasttestimony, new scientific advances have been published in therefereed literature that have now proven the validity of thisposition. The key findings include:
- Documentation that observed climate change is severaltimes below the amount predicted by the climate modelsthat served as the basis for the Framework Convention on ClimateChange (Hansen et al., 1998),
- Documentation that observed changes are largely confined towinter in the very coldest continental airmasses of Siberia andnorthwestern North America (Balling et al., 1998),
- Documentation that the variation, or unpredictability, ofregional temperatures has declined significantly on a global basiswhile there was no change in precipitation (Michaels et al.,1998),
- Documentation that, in the United States, drought has decreasedwhile flooding has not increased (Lins and Slack, 1997),
- Documentation that carbon dioxide is increasing in theatmosphere at a rate below the most conservative United Nations'scenarios, because it is being increasingly captured by growingvegetation (Hansen et al., 1998),
- Documentation that the second most important human greenhouseenhancer-methane-is not likely to increase appreciably in the next100 years (Dlugokencky et al., 1998),
- Documentation that the direct warming effect of carbon dioxidewas overestimated (Myhre et al., 1998), and
- Documentation that the Kyoto Protocol to the United NationsFramework Convention on Climate Change will have no discernableimpact on global climate within any reasonable policy timeframe(Wigley, 1998).
In toto, these findings lead inescapably to the conclusion thatthe magnitude and the threat from global warming is greatlydiminished. They should provoke a re-examination of the need forthe United Nations Framework Convention on Climate Change, and thesubsequent Kyoto Protocol.
Ten years ago, on June 23, 1988, NASA scientist James Hansentestified before the House of Representatives that there was astrong "cause and effect relationship" between observedtemperatures and human emissions into the atmosphere. His testimonycoincided with a very hot, dry period (much worse than the summerof 1998), and subsequent polls showed that, as a result of histestimony, the public believed that the 1988 drought was caused byhuman-induced global warming.
At that time, Hansen also produced a model of the futurebehavior of the globe's temperature, which he had turned into avideo movie that was heavily shopped in Congress. That model wasone of many similar calculations that were used in the FirstScientific Assessment of the United Nations Intergovernmental Panelon Climate Change ("IPCC", 1990), which stated that "when thelatest atmospheric models are run with the present concentrationsof greenhouse gases, their simulation of climate is generallyrealistic on large scales."
That model predicted that global temperature between 1988 and1997 would rise by 0.45°C (Figure 1). Figure 2 compares this tothe observed temperature changes from three independent sources.Ground-based temperatures from the IPCC show a rise of 0.11°C,or more than four times less than Hansen predicted. Loweratmosphere temperatures measured by ascending thermistors onweather balloons show a decline of 0.36°C and satellitesmeasuring the same layer (our only truly global measure) showed adecline of 0.24°C.
The forecast made in 1988 was an astounding failure, and IPCC's1990 statement about the realistic nature of these projections wassimply wrong.
This failure did not surprise me. On a 100 year time scale, themodels were predicting a warming of about 1.5° by 1988. Theobserved change was 0.5°C. That the models continued to fail inthe last ten years at the rate that they were failing in theprevious century was strong evidence for my original thesis. Howmuch might we have saved, including the notorious Kyoto Protocol,if we had just listened to nature instead of a manmadecomputer?
By 1995, in its second full Assessment of climate change, theIPCC admitted the validity of its critics' position: "Whenincreases in greenhouse gases only are taken into account...most[climate models] produce a greater mean warming than has beenobserved to date, unless a lower climate sensitivity [to thegreenhouse effect] is used...There is growing evidence thatincreases in sulfate aerosols are partially counteracting the[warming] due to increases in greenhouse gases."
IPCC is presenting two alternative hypotheses: Either the basewarming was simply overestimated, or, some other anthropogeneratedemission is preventing the warming from being observed. IPCComitted a third source for the error: Perhaps the greenhouse gaseswere not increasing at the projected rate.
As evidence comes in, the first and third reasons appear to becarrying the day. The direct warming effect of carbon dioxide wasoverestimated (Myhre et al., 1998). Carbon dioxide is notaccumulating in the atmosphere at even the lowest rate estimated byIPCC in 1992 (Hansen et al., 1998), and the the second mostimportant greenhouse emission, methane, began to decrease its rateof increase in 1981 (Etheridge et al., 1998), some 15 years beforethe recent IPCC report that projects an increased rate ofemissions for the next 50 years.
Only the sulfate hypothesis allows the exaggerated notion ofclimate change any credibility. It is not surprising that this isthe one that IPCC continues to champion because it raises thespectre of "dangerous" interference in the climate system, which iswhat the Framework Convention on Climate Change was designed toprevent. If there is no "dangerous" interference, there is no needfor the Convention, or the subsequent Kyoto Protocol, and the IPCChas failed in its mission. The U.N. General Assembly, more than tenyears ago, directed the IPCC to provide the basis for theConvention.
Why did it not warm as predicted?
a. The sulfate hypothesis
Are sulfate aerosols responsible for the now-admitted dearth ofwarming? In previous testimony I have shown how poorly thisargument stands the critical test of the data. Suffice it to saythat the entire record of three dimensional atmospheric temperaturedoes not appear consistent with this hypothesis. Instead ofrepeating that argument, I would simply point out that the southernhalf of the planet is virtually devoid of sulfates, and should havewarmed at a prodigious and consistent rate for the last twodecades. Unfortunately, we have very few longterm weather recordsfrom that half of the planet, and almost all come from therelatively uncommon landmasses. However, we do have nearly twodecades of satellite data (Figure 3). They show a statisticallysignificant decline in temperature-exactly the opposite to what thesulfate hypothesis predicts.
b. Was the sensitivity overestimated?
If sulfates do not explain the lack of warming, one option isthat the sensitivity to climate change was overestimated. The largewarmings predicted by the failed models that back the FrameworkConvention rely on a roughly threefold amplification of carbondioxide warming by increased atmospheric moisture. Yet Spencer andBraswell (1997) have found that the expected moisture is notthere.
Perhaps even more remarkable is that amount of direct warming bycarbon dioxide was also overestimated (Myhre et al., 1998).This is the basic driving force behind the entireissue!
c. Was the increase in greenhouse gasesoverestimated?
Dlugokencky et al. (1998) recently demonstrated that theconcentration of methane in the atmosphere-currently 30% of thehuman greenhouse potential-is rapidly stabilizing. It has done thisbecause its concentration is coming into chemical equilibrium withother atmospheric reactants. His calculations strongly suggest thatthe concentration will remain stable in the future. The IPCCassumed that, without any controls, the methane warming effectwould double by 2050 and increase by 125% by 2100.
Hansen et al. (1998) recently calculated that the concentrationsof carbon dioxide in the atmosphere are increasing at approximately60% of the rate that is normally projected. Notably, he argues thatthe biosphere is absorbing CO2 at a rate much faster thananticipated, as he wrote that "Apparently the rate of uptake by CO2sinks, either the ocean, or, more likely the forests andsoils (our emphasis) has increased."
DECLINING PROJECTIONS OF GLOBAL WARMING
In the ten years since my first testimony, estimates of globalwarming to the year 2100 have declined. When the latest findingsare factored in, the projected warming is now at the lower limit Inoted in 1989. Following is a summary of that decline in medianprojected warming for the next century:
IPCC 1990 initial estimate: 3.2°C
IPCC revised 1992 estimate: 2.6°C
IPCC revised 1995 estimate: 2.0°C
After allowing for overestimation of direct CO2 warming:1.7°C
After allowing for flattening of Methane concentration:1.4°C
After allowing for decrease in carbon dioxide accumulation:1.0°C
The Nature of Observed Change
Greenhouse physics predicts that the driest airmasses shouldrespond first and most strongly to changes induced by humanactivities. These, in fact, are generally the coldest airmasses,such as the great high pressure system that dominates Siberia inthe winter, and its only slightly more benign cousin innorthwestern North America. When the jet stream attains a properorientation, it is this airmass that migrates south and killsorange trees in Florida.
A look at the trends in the satellite data-our only truly globalrecord of lower atmosphere temperature-is remarkably revealing.While there is no overall global warming trend, there is apronounced warming trend in the coldest winter regions.
Balling, Michaels, et al. (1998) examined surface temperaturerecords since 1945 and found also that warming was largely confinedto the coldest winter airmasses, in agreement with the satellite. Awarming of the coldest, driest airmasses, is by definition, arelative warming of the nights compared to the days. And, byextension, this is the type of climate change that slightlylengthens the growing season, as the coldest temperature occurs atnight.
Michaels et al. (1998) recently examined the surface temperaturehistory in order to answer three questions:
Is the temperature becoming more variable fromyear-to-year? We found a statistically significant decline ininterannual variability worldwide (Figure 4) .
Is the variation from day-to-day increasing? We foundno statistically significant change.
Are the number of record high or low temperaturesincreasing? We found no statistically significant change.
In summary, here is what the climate has done during thegreenhouse enhancement: The most notable change is that the coldestairmasses of winter in Siberia and North America have warmedslightly. The only change in weather variability has been atendency towards reduced year-to-year variability.
Our results should be integrated with a recent study of U.S.streamflow by Lins and Slack (1997). In an investigation ofundisturbed sites, they found no change in the frequencyof highest flow (flood) events, but a decrease in the lowest flow(drought) events.
We are not entering a world of increased variability,unpredictability and peril, but rather the opposite. If this is ahuman interference in the climate, it is hardly "dangerous."
The Kyoto Protocol: How Much Warming isPrevented?
This analysis assumes the IPCC's "consensus" estimate of2.0°C of warming by the year 2100 in the absence of substantialemissions stabilization. Please note that my testimony indicatesthis is a considerable overestimation.
The Kyoto Protocol requires that the United States reduce itsoverall greenhouse gas emissions by a remarkable 43% for the2008-2012 average, compared to where they would have been if wecontinue on the trajectory established in the last two decades. Theeconomic costs are enormous, they are but not the subject of thishearing. What are the climate benefits?
Wigley (1998) recently calculated the "saved" warming, under theassumptions noted above, that would accrue if every nationmet its obligations under the Kyoto Protocol. According to him, theearth's temperature in 2050 will be 0.07°C lower as a result.My own calculations produced a similar answer. Wigley is a SeniorScientist at the U.S. National Center for Atmospheric Research.
0.07°C is an amount so small that it cannot be reliablymeasured by ground-based thermometers. If one assumes the morelikely scenario that warming to the year 2100 will be approximatelyhalf of the IPCC estimate, the saved warming drops to 0.04°Cover the next fifty years.
This is no benefit at an enormous cost.
In conclusion, the observed data on climate and recent emissionstrends clearly indicate that the concept of "dangerous"interference in the climate system is outmoded within anyreasonable horizon. This makes the Kyoto Protocol a uselessappendage to an irrelevant treaty. It is time to reconsider theFramework Convention.
Balling, R.C., Jr., et al., 1998. Cli. Res.,9, 175-181.
Dlugokencky, E.J., et al., 1998. Nature,393, 447-450.
Etheridge, D.M., et al., 1998. J. Geophys. Res.,103, 15979-15995.
Hansen, J.E., et al., 1988. J. Geophys. Res.,93, 9341-9364.
Hansen, J.E., et al., 1998. Proc. Nat. Acad. Sci.,95, 4113-4120.
Intergovernmental Panel on Climate Change, 1990. ClimateChange: The IPCC Scientific Assessment.
_____, 1996. The Science of Climate Change.
Lins, H. and J.R. Slack, 1997. Amer. Geophys. Union, SanFrancisco. Abstract. 12/8/97.
Michaels, P.J., et al., 1998. Cli. Res.,10, 27-33.
Myhre, G., et al., 1998. Geophys. Res. Lett.,25, 2715-2718.
Spencer, R.W. and W.D. Braswell, 1997. Bull. Amer. Met.Soc., 78, 1097-1106.
Wigley, T.M.L., 1998. Geophys. Res. Lett.,25, 2285-2288.