CLIMATE CHANGE 2001:
THE SCIENTIFIC BASIS
THE SUMMARY FOR POLICYMAKERS: AN APPRAISAL
by Vincent Gray
INTRODUCTION
The final draft of the Third Assessment Report (TAR) of Working Group I of the Intergovernmental Panel on Climate Change has now been issued to contributors and reviewers. It is expected to be published as "Climate Change 2001: The Scientific Basis" early next year, after the meeting in Shanghai from 17-20 January 2001, when there will an acceptance of the full report and a line-by-line approval of the Summary for Policymakers.
The text of the full report is expected to remain unchanged, but there could be some final amendments to the Summary for Policymakers.
The whole report has, on every page, the injunction "Do Not Cite. Do Not Quote", but the report has already been "leaked" to the press, and to organisations, and parts of it cited, quoted and published. Prominent participators have spoken of its content to the media and in lectures. The full report is available on the Internet, provided you know the password. In response to all this partial publication it is desirable that the public should know what is in the report and what conclusions, if any, it has reached. This paper makes no apology for joining the others in commenting on the "Summary for Policymakers" (SPM) which summarises the most important material from the whole report.
CLIMATE CHANGE: A PHILOSOPHICAL QUAGMIRE
The report, and indeed the whole process behind the investigation of "Climate Change" suffers from irreconcilable philosophical contradictions.
The whole subject for investigation is Climate Change rather than Climate Science
According to a footnote on the first page of the SPM, The Framework Convention on Climate Change "refers to" climate change as "a change of climate that is attributable directly or indirectly to human activity that alters the composition of the global atmosphere and that is in addition to natural climate variability observed over similar time periods"
The implication here is that "change" is different from "variability"; that "variability" is always "natural", and that "change" is always caused by humans.
The confusion is compounded by the first sentence of the footnote on page 1 "Climate Change in IPCC Working Group I usage refers to any change in the climate over time, whether due to natural variability or as a result of human activity"
The IPCC still seem to make a distinction between "variability" when it is "natural" and "change" caused by humans, but in contrast to the Framework Convention on Climate Change both of them are considered as "change".
The "Glossary of Terms" at the end of the report gets even more confused
"Climate Change" is said to "refer to a statistically significant variation in either the mean state of the climate or in its variability, persisting for an extended period (typically decades or longer)."
The definition of "Climate" is as follows:
"Climate, in a narrow sense, is usually defined as the "average weather", or more rigorously, as the statistical description in terms of the mean variability of relevant quantities over a period of time ranging from months to thousands or millions of years"
"Climate variability" is defined as follows
"Climate variability refers to variations in the mean state and other statistics (such as standard deviations, the occurrence of extremes . etc.) of the climate on all temporal and spatial scales beyond that of individual weather events."
"Detection and attribution" begins "Climate varies continually on all time scales". But does it "change"?
The "mean state" of the climate seems to depend on the time period chosen for deriving it and is therefore indefinite.
It does not seem to occur to anyone that "change" might be "natural", or that "variability" might be "anthropogenic".
Since "variability" and "change" interpenetrate, and cannot be distinguished from one another if the time scale is undefined, the identification of a climate effect as solely caused by humans seems impossible.
The IPCC skate over this problem by switching time scales in an arbitrary fashion. "Annual" or "decadal" change or variability is regarded as "natural" whereas "centennial" or "millennial" change is "suggested " as being "anthropogenic" and even "unprecedented". Presumably change or variability which is millionennial" or "billionennial" (pace ice ages or downfall of dinosaurs) reverts to being "natural" In Chapter 1 (The Climate System: an Overview) there is the statement: "The fact that the global mean temperature has increased since the late nineteenth century and that other trends have been observed does not necessarily mean that an anthropogenic effect on the climate system has been identified. Climate has always varied on all time scales, so the observed changes may be natural. A more detailed analysis is required to provide evidence of a human impact." This paragraph accepts that "change" may be "natural" and that "variability" can occur on "all time scales". Therefore even a "centennial" or a "millennial" change" might be "natural" How can "more detailed analysis" prove otherwise?
A further philosophical dilemma arises with "detection" and "attribution". All scientists suffer from the dictum of the philosopher David Hume that there is never absolute certainty in prediction. We can only assert a probability that, say, the sun will rise tomorrow. The probabilities get a lot lower when you are dealing with simulation of the climate by models. Even if a correlation coefficient of 100% is found, there is no certainty that a cause and effect relationship has been established. Much effort is exerted by the IPCC in attempting to simulate the amalgamated surface temperature record by means of mathematical models based on the greenhouse effect, but they have not even reached the stage of calculating correlation coefficients or of considering obvious alternative explanations, let alone the philosophically unattainable task of "attribution"
THE QUANTIFICATION OF UNCERTAINTY
The Third Assessment Report is much more preoccupied with uncertainty than previous reports. "Climate Change 1990" proudly asserted that the models were "broadly consistent" with the surface temperature record , and that there would be a great effort to "reduce uncertainty". Unfortunately the levels of uncertainty, in quantitative terms, have never been calculated or stated, so it is not possible to tell whether they have been reduced. The effectiveness of models is invariably described in purely qualitative terms. We are forever being told how "confident" they are in their effectiveness, and how the models are "improved" (over what?), with "considerable progress" being made. The models may even be "impressive" or "robust", or "consistent with" climate data. But these are mere opinions of the creators, undoubtedly partisan. There are no actual figures to back up these claims. There is still no scientifically based validation procedure, and thus no model which can be regarded as a reliable simulation for any climate process to a level of accuracy that could justify the use of the model for future projection.
This does not, of course, deter the IPCC from making future projections, but it does mean that the projections have no scientific basis.
In footnote 3 to page 1 of the SPM is the following:
"the following words have been used to indicate approximate judgmental estimates of confidence: virtually certain (99% chance that the result is true); very likely (90-95% chance); likely (66-90% chance): medium likelihood (33-60% chance): unlikely (10-33% chance): very unlikely (1-10% chance): exceptionally unlikely (less than 1% chance)"
This attempt to put quantitative figures on subjective judgements is futile when it is not backed up by real quantitative statistical studies.
The admission of uncertainties pervades the report
"Many of these trends (of climate changes) are now established with high confidence: others are far less certain."
"the estimates of radiative forcing (of the indirect effect of anthropogenic aerosols) remain very uncertain"
"Nevertheless, the accuracy of estimates of the magnitude of anthropogenic warming, and particularly of the influence of the individual external factors, continue to be limited by uncertainties in estimates of internal variability, natural and anthropogenic radiative factors, in particular the forcing by anthropogenic aerosols, and the climate response to these factors"..
"Many factors continue to limit our ability to detect, attribute and understand current climate change and to project what future changes may be."
Figure 2, which gives estimates for radiative forcing of the climate since 1750, shows from the "error bars" that there is a fair chance that the net radiative forcing since then was zero.. The "error bars" are however rendered valueless by "Levels of Scientific Understanding" which, for many of the factors are characterised as "Very Low", so the error bars should be increased in size. The Figure does not even mention indirect aerosol negative forcing effects, which, according to Chapter 5, could alone cancel out the positive effects of greenhouse gases, or even cause a net negative forcing.
.Chapter 7 "Physical Climate Processes and Feedbacks" which includes amongst its lead authors RS Lindzen and KE Trenberth goes to considerable lengths to demonstrate that the uncertainties associated with every conceivable climate parameter or relationship are much greater than is assumed by the climate models, without daring to place figures on them. The uncertainties of the models and their simulations are probably so great that any climate sequence can be simulated by a model, merely by the right choice of parameters and relationships. Models are therefore universally successful, but practically useless.
GLOBAL TEMPERATURES
The amalgamated surface temperature record is promoted as the only acceptable evidence of global temperature and the global temperature measurements from weather balloon, satellite, and proxy records are played down, denigrated and obscured.. Chapter 2 has 10 Figures devoted to the surface record, whereas the weather balloon and satellite records are jumbled together in Figure 12a which tries to show that they are compatible with the surface record provided you do not look too closely.
The minuscule 0.6°C rise in surface temperature over the last 140 years is raised to the level of a major catastrophe, and its "unprecedented" character is "suggested" as "unlikely to be entirely natural in origin".
The exceptionally high temperatures in 1998 due to a strong El Niño Southern Oscillation, have been recruited throughout the report to provide phoney evidence of permanent global warming and to claim that weather balloon and satellite measurements confirm, or partly confirm, the rise in surface measurements. As this transient ocean-based event subsides it has already become abundantly clear that temperature measurements made remote from human habitation (weather balloons, satellites, tree rings, remote weather stations) show no evidence of warming, so the cause of warming in the surface record must be subtle long-term changes in the thermal conditions surrounding many weather stations.
The statement, referring to the temperature measurements from weather balloons, that "the overall global temperature trends of the lower atmosphere and near-surface air temperature are similar (0.1°C per decade)." can only be claimed by the use of the aforesaid jumbled diagram, and with major emphasis on the temperature rise in 1998 shown by both records, but now lost, particularly from the weather balloon record.
The satellite record from the MSU (microwave sounder units) is also claimed to be rising, thanks to 1998, but it cannot now be claimed that it is consistent with the surface record, as was attempted in the first draft of this report. The 1998 El Niño temperature rise has now disappeared from the satellite record, which has reverted to its customary zero value, showing that the lower atmosphere, where the greenhouse effect is supposed to happen, is not warming.
Claims in the paragraphs on snow cover and sea ice also depend on a warm 1998 which is compared with cool 1950s or 1960s to claim a warming trend from two points on a graph.
SEA LEVEL
"Tide-gauge data show that global-average sea level rose between 0.1 and 0.2 meters during the 20th century". John Daly's analysis (Daly 2000) has shown that this was only after manipulation of the tide gauge data by models based on only a small part of the globe, and whose validity is doubtful.
The next sentence has become rather tentative. "It is very likely that this is at least partly due to thermal expansion of sea water and widespread loss of land ice associated with 20th century warming". They should be more tentative still, as this "very likely" "partly due" explanation is purely theoretical, based on the assumption that measurements of "warming" in the ocean are genuine.
"Global-ocean heat content has increased since the late 1950s" Another example of two points on a graph; dependent on the 1998 El Niño exceptional heat increase. The heat content has already gone down again.
There is no mention of the TOPEX satellite measurements (Figure 11.8), recent extensions of which to 2000 show no increase in mean sea level since 1993, with the transient increase of 1997- 1998, due to El Niño now firmly over. As satellites have already proved that the background climate is not warming, so, now, satellites are proving that the mean sea level is not rising either.
PRECIPITATION
The report makes a big thing of the discovery that precipitation, and extreme values of precipitation have increased in some places and decreased in others. They have, however, failed to show whether this is "natural variability" over whatever time scale, or some consequence of human influence.
SMALL MERCIES
"No significant trends of Antarctic sea-ice extent are apparent.. (since the 1970s)"
"The observed intensities and frequencies of tropical and extra-tropical cyclones, and severe local storms show no clear long-term trends". Actually Figures 2.37 and 2.38 show that the intensity and frequency of hurricanes and tornadoes are going down.
KEEPING US IN THE DARK ON GREENHOUSE GASES
The report is supposed to be about the possible effects of emissions of greenhouse gases and aerosols and of their influence on atmospheric composition, yet information on these subjects is concealed or distorted.. There is no mention at all of emissions in the SMP. Chapter 3 (The Carbon Cycle and Atmospheric CO2 ) does not mention carbon dioxide emissions in the text until page 23. It states that global carbon dioxide emissions reached "a maximum of 6.6PgC/yr in 1997", but you have to go to Figure 3.3 to discover that they have fallen since then and to deduce the actual figures from the graph. It later says "The average value of emissions in the 1990s was 6.3±0.4Pg/yr" but will not enlighten us on trends.
It is characteristic of the IPCC that when any trend is upwards it is publicised, even if it happens only for a year or so, like that 1998 El Niño heating. When the trend is downwards, like the emissions for 1998 and 1999, it has to be concealed. It is interesting that these figures for 1998 and 1999 have not yet become publicly available from the Carbon Dioxide Information and Advisory Center The falling emission figures foul up the new set (SRES) of emissions scenarios (see below) which all assume emissions for the year 2000 as 6.8 to 6.9 GtC, whereas the likely figure for 2000, from Figure 3.3, is 6.3 GtC.
Chapter 3 evades discussion of trends in the components of the carbon cycle by giving global CO2 budgets based on decadal averages. A comparison between the average of the 1980s and the average of the 1990s cannot establish a trend. Emissions of the other greenhouse gases and aerosols are also not mentioned in the SPM. Chapter 4 (Atmospheric Chemistry and Greenhouse Gases) and Chapter 5, on Aerosols also give minimal information on emissions and none on trends.
Information on concentrations is also distorted. There is a grudging admission that "The rate of increase of atmospheric CO2 concentration has been about 0.4%/yr over the past two decades " (more like three), but this does not stop the modellists from assuming an increase of 1% a year in most of the models, or for most of the emissions scenarios from assuming that the long established rate of 0.4% a year will suddenly increase dramatically, beginning in the year 2000.
The methane story is even worse. In the second draft of the TAR the rate of increase in atmospheric methane concentrations is shown to have been falling steadily for the last 17 years, with a final fall about to pass the level of zero concentration increase. In the final draft, Figure 10 in the Technical Summary and Figure 4.1 in Chapter 4 show a very slight upturn from the brink, not available from the NOAA/NCDC website, but the figures continues to indicate, that from the trend of the past 17 years of -0.09% a year in the rate of increase, the concentration of methane in the atmosphere will become stable in the year 2005, and will fall thereafter. The SMP conceals this fact by claiming that the concentration "continues to increase". And that the annual increase "has become slower and more variable". The SRES scenarios all assume that this trend downwards in the rate of concentration increase of the past 17 years will suddenly, this year, turn upwards and continue upwards for the next hundred years.
"The atmospheric concentration of nitrous oxide has increased by 16% since 1750" But they do not reveal that it is currently increasing at the much lower rate of 0.2% per annum. Amazingly, most SRES scenarios project that the rate of NO2 increase will fall. "The observed depletion of the stratospheric ozone layer over the past two decades has caused a negative radiative forcing (-0.15 Wm-2)". So the depletion of the ozone layer, including the ozone "hole", is beneficial! Perhaps the global cooling will supply more benefits than the handicaps of the slight additional ultraviolet radiation?
AEROSOLS
"significant progress has been achieved in better characterising the direct radiative roles of types of aerosols other than sulphate, including black carbon (soot), organics, mineral dust and sea salt. There is much less confidence in the ability to quantify the total aerosol effect, and its evolution over time, than for the gases".
It is worse than that. According to Chapter 5 "The largest estimates of negative forcing due to the warm-cloud indirect effect may approach or exceed the positive forcing due to long-lived greenhouse gases". In other words, the net greenhouse effect could be negative. The indirect effects of aerosols are not mentioned in Figure 2 on radiative forcing. and they are not considered in the future projections of the SRES scenarios.
There are very few past figures for sulphate levels, or for aerosol emissions or concentrations, so the SRES emissions scenarios have a free hand to speculate for the future. They have chosen to assume that sulphate-based aerosols will become less in many scenarios, so boosting the upper temperature figures of their "projections". The rather astounding statement "The most important climate feedback is sea salt" in the second TAR draft, has mercifully disappeared.
THE SUN
"Mechanisms for the amplification of solar effects on climate have been proposed, but lack a rigorous theoretical or observational basis". In contrast, it would seem, with the greenhouse effect!
MISPLACED CONFIDENCE
"Confidence in the ability of models to project future climates has increased". No model has ever been shown to simulate climate to a satisfactory level of accuracy, so what is the basis for "confidence", or why it should have increased.?
"understanding…….has improved" "Some recent models produce satisfactory climate simulations" "Several models have reproduced the observed warming" "Some aspects of model simulations of ENSO etc have improved"
These are all subjective judgements made by the models' creators, unsubstantiated by any scientific or statistical evidence.
HUMAN INFLUENCE
"The SAR concluded -
"The balance of the evidence suggests a discernible human influence on global climate"
"There is now stronger evidence for a human influence on global climate than at the time of the Second Assessment Report"
"Emissions of greenhouse gases and aerosols due to human activities continue to alter the atmosphere in ways that affect the climate system"
These statements fail to specify in what way " human influence on global climate" is "discernible" or in what respects "greenhouse gases and aerosols due to human activities continue to affect the climate system". In particular they do not state that human influence affects global, or regional temperature. There are human influences on the climate that are undisputed.. There is convincing evidence that sulphate-based and other aerosols are influencing the climate. It is also agreed that cities cause increases in local temperature or "heat islands". But where is the evidence of an influence from greenhouse gases?
"Detection and attribution studies consistently find evidence for an anthropogenic signal in the climate record of the last 35 years." Again no mention of greenhouse gases or of temperature change. "Detection" involves correlation but this does not mean cause and effect. "Attribution" is impossible. Which climate record are we talking about? "Furthermore, model estimates of the rate of anthropogenic warming are consistent with observations in the majority of cases" "Consistency" with selected observations, especially when not quantified, is not reliable evidence.
"natural forcings may play a role in the observed warming in the first half of the 20th century, but fail to explain the warming in the latter half of the century". This refers only to the surface observations. Warming is not observed in the lower atmosphere in the latter half of the century.
"The effect of anthropogenic greenhouse gases over the last 50 years can be identified, despite uncertainties in other forcings" Identified how? Correlation again. Effect on what? On surface temperature records? But which ones? Again, a correlation is not an identification. "the sulphate forcing is negative over this period (50 years)". Nowhere is it mentioned that this implies that the Southern Hemisphere should be warmer than the Northern Hemisphere; the opposite of the observations. "It is likely that increasing concentrations of anthropogenic greenhouse gases have contributed substantially to the observed warming over the last 50 years". At last an admission of a "likely" ( 66-90% probability?) relationship between the "observed" warming (by only one system; but 50 years eliminates the others?), with a "substantial" contribution (without a probability level) from "anthropogenic greenhouse gases". This sentence, which appears in the middle of the SPM, is regarded by many as its "conclusion", yet no convincing evidence is presented to justify it. It depends on the studies which show that the 0.6°C rise in the past 140 years is "unprecedented" over the millennium, and that it cannot be entirely explained by volcanoes, solar effects or El Niño, using the crude calculations available. The fact that this rise is not observed in locations far from human habitation does indicate that humans may be responsible, since there is no observed warming in the lower atmosphere it must be due to local thermal changes around the surface measurement equipment not to "increasing concentrations of greenhouse gases".
The lack of confidence in the SPM "conclusion" can be judged by the next sentence, which is worth quoting once more. "Nevertheless, the accuracy of estimates of the magnitude of anthropogenic warming, and particularly of the influence of the individual external factors, continues to be limited by uncertainties in estimates of internal variability, natural and anthropogenic radiance factors, in particular the forcing by anthropogenic aerosols, and the climate response to these factors." "Likely" and "substantial" do not seem well founded.
FORECASTING (OR PROJECTING?) THE FUTURE
The Report utilises a new set of future emissions scenario which are described in detail in a separate, published report from IPCC Working Group III (Special Report on Emissions Scenarios (SRES), Nakecenovic et al 2000). The IPCC do not like to admit it, but the old set of scenarios (IS92) which began in 1990, had to be abandoned because all of them failed so miserably in predicting climate, sociological and economic facts for the year 2000 (Gray 1998)
The scenarios are supposed to be "neither predictions nor forecasts". They are merely consequences of a range of assumptions about possible futures. The Scenarios Report states:
"No judgement is offered in this Report as to the preference for any of the scenarios and they are not assigned probabilities of occurrence, neither must they be interpreted as policy recommendations"
It would seem that although all the scenarios are equally probable, some are more equally probable than others. The above limitations are ignored even by the scientists and routinely disregarded altogether by politicians and "activists" who invariably treat them as predictions and interpret them as policy recommendations.
This Third Assessment Report gives an incomplete view of the Special Report on Scenarios, spread amongst various chapters, but accompanied by a set of SRES Tables for assumptions (on greenhouse gases only) as Appendix II.
416 possible future emissions scenarios were submitted to the Special Report Committee .The Committee attempted to limit the possible number of scenarios by concocting four "storylines" (A1, ,A2, B1, B2 ) of possible future development. 40 scenarios resulted from the four "families" of this exercise, from which six "illustrative" scenarios were "selected" (A1B, A1T, A1F1, A2, B1, B2) as shown in Figure 4 of the SPM. Appendix II adds three others ( A1p, A2p, B1p, and B2p).
As with the previous IS92 scenarios, there is no provision for updating the scenarios as the years go by. My paper (Gray 1998) showed that all of the IS92 scenarios, begun in 1990, overestimated most climate and social data, as measured for the year 2000
However, the IPCC, in wishing to compare the current scenarios with IS92 have felt compelled to update IS92a, not only once, but six different times! The old IS92a appears in the Tables under the title "SAR". This makes for confusion as it is often impossible to work out which version is being used.. Further confusion ensues from the fact that all the scenarios start in 1990, but many of the figures start in 2000.
Since the old IS92a was intended to line up with the older SA90, the "Business As Usual Scenario" it means that the IPCC is still trying to pretend that carbon dioxide, or "equivalent carbon dioxide" is increasing at 1% a year, in defiance of the facts that the rate of increase of carbon dioxide has been 0.4% a year for 30 years, and the rate of increase of methane is about to reach a constant value.
The SRES scenarios have reduced some of the uncertainty attached to climate models, by using four models instead of one to calculate temperature change from radiative forcing, and thus increasing the range of the results. This does not go far enough as all the four models possess further considerable uncertainties in their choice of parameters and relationships which should stretch the range of the temperature estimates much further.
The scenarios still attempt to estimate positive emissions from "deforestation and land use", despite the fact that there is a net absorption of carbon dioxide by land surfaces, and that no clear distinction can be made between areas that emit carbon dioxide and those that absorb it.
The assumptions of the SRES scenarios lose credibility right from the start by assuming carbon emissions of 6.8-6.9 Gt in 2000, when the likely figure is 6.3 GtC. The projected changes 2000 to 2100 range from a fall of 30% to a rise of 320% per year.
Carbon dioxide concentrations are assumed to rise by between 32% and 195% 2000 to 2100. An extrapolation of the trend of 0.4% a year for the past 30 years would yield 40%, so the high figure is absurd.
Methane concentrations are assumed to change from 2000 to 2100 by between a reduction of 10.6% and an increase of 112% by 2100. Extrapolation of the trend of -.0094%/yr of the past 17 years would give -9.4% change by 2100..
The lowest estimates thus appear reasonable, but the highest ones are nothing short of ridiculous.
The second draft of the TAR had a paragraph on aerosols which made the extraordinary statement "The most important climate feedback is for sea salt". The whole paragraph has now disappeared, and sea salt with it. Mention of aerosols is removed from this section because it is evident that the scenarios have failed to pay proper attention to the influence of aerosols. Figure 5.11 in Chapter 5 shows assumptions that have been made for sulphate aerosols, black carbon and organic carbon, but there are evidently several other important aerosol effects that are not allowed for.
Assumptions on population increases from 1990-2100 range from 17% (after a peak increase of 44% in 2050) to 49%. steady increase. Most experts would favour the lowest alternative.
World GDP is projected to increase from 1990 to 2100 in the range of 11 to 26 times. Energy usage is projected to increase 1990-2100 in the range from 1.5 to 6.3 times. The coal industry is projected to change 1990-2100, in a range from a reduction by 76% to an increase of 10.8 times. Nobody in the coal industry could believe the latter figure.
The figures assumed by the scenarios have to be manipulated by the four climate models to give the "projections" of temperature and sea level change of Figure 4. Projected globally averaged temperature rises from 1990 to 2100 are .between "about" 1.5 and 6.0°C. Projected sea level rise is between 0.14 and 0.80 metres, despite the fact that the calculated rise in the report of 0.15 metres in the last 100 years shows no sign of accelerating.
Models predict changes in extreme events which are claimed, in Table 1, to be confirmed by observation (in the last 50 years) in many cases. The comparison is entirely qualitative, turning on what can be considered to constitute a "change".
"Atmospheric composition will continue to change throughout the 21st century". At last a forecast which may actually come true, provided "change" includes "natural variability.
"Climate change will persist for many centuries" After which, presumably, the climate will revert to its pristine, unchanged, state!
CONCLUSION
The Summary for Policymakers, and the report itself, do not have "conclusions", so readers are left to try and select them for themselves.
Partisans of the greenhouse effect have latched on to this sentence in the middle of the SPM:
"It is likely that increasing concentrations of anthropogenic greenhouse gases have contributed substantially to the observed warming over the past 50 years"
There is no convincing evidence for this a statement, and its impact is greatly reduced by the subsequent sentence on uncertainties.
They have also quoted this sentence:
"There is now stronger evidence for a human influence on global climate than at the time of the Second Assessment Report"
But none of them point out that the sentence does not implicate greenhouse gases as a "human influence".
Partisans have also quoted the future "projections" which they regard as forecasts, with the upper limit of "about 6°C" temperature rise for the year 2100, if the highly unlikely assumptions are to be believed.
Yet despite all the effort, the IPCC has not established that greenhouse gases are influencing the climate. The facts that global warming only takes place close to human habitation and that the sea level is not rising, cannot be explained away, and as the years go by they will become ever more obvious.
REFERENCES
Daly, JL, Testing the Waters: a Report on Sea Level, 2000, http://www.greeningearthsociety.org/Articles/2000/sea.htm
Gray, VR, 1998 The IPCC future projections: are they plausible? Climate Research 10:155-162
Nakicenovic, NJ, et al 2000. IPCC Special Report on Emissions Scenarios. Cambridge University Press
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