The intergovernmental panel on climate change (ipcc) is the world’s leading authority on global burning and it uses computer models of the climate to formulate predictions about future climate change. These models, known as general circulation models (gcm), contain many deficiencies which decrease the accuracy of their predictions. These deficiencies include:-

At present it is not possible to feed climate models with all the facts about the current state of the Earth’s climate. A large proportion of such facts are not known. It is not known how many facts about the climate would be sufficient to get a good representation of the climate.

For example: the oceans store far more heat than the atmosphere. However, the impact of the heat absorbed by the oceans on the Earth’s climate depends upon its distribution between the various layers of the oceans. If there is an even distribution of heat within the oceans then, because of the vastness of the oceans, the impact would be insignificant. However, if the distribution is confined to the surface layers then the impact on the climate could be substantial, "The ability of the oceans to store heat is 1000 times that of the air. The extent of greenhouse gas heating will greatly depend upon how much of the added heat is distributed in the oceans. If all of the predicted rise in surface temperature were mixed in with the oceans uniformly, there would be no perceptible rise in surface atmospheric temperature during the next century or so." If the additional heat accumulated in surface layers of the ocean this could disturb ocean circulation causing a major change in the climate, "Peter killworth said the top few metres of the oceans store more heat than the whole of the atmosphere. They were expected to absorb heat arising from global warming, but if the warming causes ocean circulation to change the heat could be released instead."

Humans are not merely boosting global burning, they are also moderating global burning. Unfortunately, it is not yet possible to determine the strengths of these opposing factors.

A number of atmospheric pollutants contributing to the greenhouse effect could not be quantified and had to be left out of the ipcc’s 1990 computer model, "Ground level (tropospheric) ozone makes a significant contribution to global warming, but is very difficult to quantify. For this reason the ipcc did not include it in its estimates of the contribution that various greenhouse gases make to global climate change."

Although there is evidence that humans are boosting global burning there is much less evidence concerning the positive feedback processes which could send the climate spiralling out of control. In 1990 the ipcc scientific working party identified a number of positive feedback factors boosting global burning, "The main feedbacks which have been identified are due to changes in water vapour, sea ice, clouds and the oceans." But, it had to conclude .. "many of the feedback processes are poorly understood ..." The ipcc concluded these feedback processes are likely .. "to increase, rather than decrease, greenhouse gas concentrations in a warmer world."

Perhaps the most fundamental consequence of scientists’ lack of information about the Earth’s life support processes is their inability to balance the Earth’s Carbon budget, "There remains at this time a significant gap in climatologists' and geophysicists' ability to balance the global carbon cycle budget. The discrepancy between model requirements (climate models treat the biosphere as neutral!!!) and land-use based estimates has led to speculation about additional carbon sinks not presently accounted for." Climate modellers .. "would be the first to admit that their model representations of the atmosphere are far from able to include the full effects of the clouds. They would confirm their greater inability to include the effects of the internal climate of the oceans, and almost complete inability to take in the changing and responding ecosystems at the surface of the Earth."

Scientists are able to incorporate many geophysiological processes into their computer models of the climate, "Meteorologists have built supercomputer models (which) take into account all of the atmospheric gases and their greenhouse effects and also the effects of land and sea surface temperatures, ice cover, and the effects on winds of mountain ranges." However, even the most advanced computers cannot represent all climatic processes. Many have to be left out of computer models.

"Meanwhile, in February we learned that the demonstrably-warming Arctic tundra has transformed from a CO2 sink into a significant source of CO2. Biogeochemical feedbacks like this, however, are omitted from most climate models. The dreadful rates of warming the IPCC forecasts may in fact be underestimates."

"Rising temperatures could reduce the oceans’ ability to absorb Carbon dioxide by as much as 50%, leaving the greenhouse gas in the atmosphere to heat the Earth further. Until now, climate models such as those by the ipcc, have assumed that the oceans’ capacity to remove CO2 from the atmosphere will stay constant as the world warms."

There seems to be less information about the Earth's oceans than there is about the atmosphere. Climate modellers .. "would confirm their greater inability to include the effects of the internal climate of the oceans ..."; "The speed and timing of climate change strongly depends on how the oceans respond. The uppermost layers of the oceans interact with the atmosphere every year and so are expected to warm along with the earth's surface. But it takes over 40 times as much energy to warm the top 100 m of the ocean as to warm the entire atmosphere by the same amount. With ocean depths reaching several kilometres, the oceans will therefore slow down any atmospheric warming. How much they slow it down depends on how deeply the warming penetrates. The latest climate models are only just beginning to represent the processes which exchange energy between the atmosphere and ocean depths, so this remains an important source of uncertainty."

Climate modellers .. "would be the first to admit that their model representations of the atmosphere are far from able to include the full effects of the clouds." James lovelock points out that, "But the clouds, though included in the models, are usually treated as more or less fixed entities unable to vary much with the changes of climate. (A later model includes more responsive clouds)."; "Clouds reflect sunlight, implying that more clouds would have a cooling effect. But most clouds, particularly those at high altitudes, also have an insulating effect: being very cold, they shed energy to space relatively ineffectively, thus helping to keep the planet warm. So the net cloud feedback could go either way. Clouds are the main reason for the large uncertainty about the size of warming under any given emissions scenario."

"Neither of these (ipcc) models yet take account of the cloud-algae connection .."; "According to a climatologist at the university of east anglia, who prefers to remain anonymous, "If you took away this plankton-clouds effect, you could see a warming of the order of maybe 5C in the southern ocean.""

"Nor can they (the ipcc models) fully mimic the largest year-on-year variability in the natural climate system, the el Nino oscillation in the pacific ocean. A greater natural variability in climates might make it harder to discover a genuine human signal."

The most important deficiency of the ipcc's computer model may be the failure to incorporate the planet's biota, "Today's (climate) models do not account fully for the removal of CO2 from the atmosphere by land plants, but may overstate the oceans' ability to absorb it."; "Current general circulation models (GCMs) of the climate contain the key geophysical climate feedbacks, such as changes in water vapour, clouds and sea ice albedo, but biogeochemical feedbacks such as changes in methane emissions, ocean CO2 uptake and vegetation albedo are generally neglected."; "The damage done to certain species of plankton by increased ultra-violet radiation .. was highlighted recently by the ozone trends panel of the UNEP but ignored by the IPCC."; "Several atmospheric feedback processes are well defined in global climate models but those relating to ocean productivity are not yet sufficiently well understood to be included."; "Treating the biosphere as neutral has been a common assumption in climate modelling exercises not only because of model calibration difficulties, but also because these exercises focused on scenarios of growing fossil fuel consumption. In that case, biospheric releases do become less important, though positive feedbacks from forest die-back could still make a large contribution." Bunyard has pointed out, "Models used to justify a business-as-usual approach are fundamentally flawed because they treat the Earth’s land surface as it would be had we not destroyed great tracts of natural vegetation. The models therefore ignore the impact of global agriculture on the climate ..." Scientists have so many problems incorporating the planet’s biota that their models are regarded as only ‘atmosphere-ocean general circulation models’ (AOGCMs).

According to gregg easterbrook, "Today’s greenhouse computers do not acknowledge the effects of the living world on climate trends. Current greenhouse models take into account only one biological effect - the negative human action of generating carbon dioxide through combustion."; "The general circulation models, although vastly improved in recent years and based on excellent science, do not come close to evaluating the true impact of our activities on global climate."; "Also the possibility of other human activities such as deforestation, desertification, ozone depletion, and the indirect effects of sulphate aerosols exerting a significant influence have yet to be addressed (by gcms)."; "Yet, by their own admission ‘the model describes the potential natural vegetation that would exist without interference by humans, such as the recent rainforest fires."

Some critics of the ipcc point out that, "The (ipcc) models’ errors are not so surprising. As barnett points out, they do not yet include the effects of ‘forcing’ mechanisms that alter temperature, such as solar cycles and volcanic eruptions."; "Climate models omit many sources of variability that could also cause apparent long-term trends. Current model-based estimates of natural variability do not include the effects of volcanic eruptions, which can cool the global climate temporarily by several tenths of a degree. They are also only beginning to include the effects of long-term changes in the power output of the sun. The sun may have been responsible for relatively cool periods during the 16th, 17th, and 19th centuries (the so-called "Little Ice Age") when the northern hemisphere may have been about 0.5oC colder than it is today. Some of the warming over the past century (about 20-30% of it, according to some recent model results) may still be a recovery from that time."; "So, in the search for greater precision, our forecasts would need to include predictions of solar activity on all timescales. Beyond this we will need to include the tidal effects of the sun, the moon and of other planets in the solar system, notably the pull of the giant planets on both the Earth and the sun."

It has been suggested that the ipcc left out seven of the most important factors influencing the climate, "Uncertainty led to 7 of the potentially most alarming factors being left out of the UN's final report."

At present, even the most powerful supercomputers, using the most sophisticated computer software, can aggregate climatic conditions only over thousands of cubic miles and can handle only a limited number of variables. The lack of computing power and software sophistication is compounded by a more mundane problem - cost, "Supercomputers cost a great deal to run, and so, in the interests of keeping the computation time manageable and within budget, the models have to cut down on the detail by using a larger grid spacing and by lengthening the time intervals between successive computations."

The limitations of climate models are so serious that even when the facts about a particular climatic phenomena are known they cannot always be reproduced in these models. It has to be suggested there is something highly suspicious about scientists who make prognostications about the Earth’s climate when their models can’t incorporate the facts about the geophysiological processes contributing to the climate. Climate models are unable to reproduce a number of climatic facts:-

"At ground level, the model results underestimate the recent warming over northern eurasia and eastern north america, as the models fail to predict fully the strong westerly circulation in the northern hemisphere in the winter half of the year, which is a major factor in the warming trend since around 1970."

"Paleoclimatologists often snicker at gcms because greenhouse computers are stumped by ice ages. When pleistocene conditions are plugged into climate models, no ice sheets appear. The precise causes of ice ages are unknown and therefore hard to simulate."

There are huge amounts of data about el ninos but climate modellers cannot reproduce such extreme climatic conditions in their models, "Nor can they (the ipcc models) fully mimic the largest year-on-year variability in the natural climate system, the el Nino oscillation in the pacific ocean."

Climate models are limited not merely by inadequate computing power, inadequate software, lack of money, and a lack of scientific evidence but by the scientific theories underlying these models.

Climate models can represent changes in the Earth’s climate only by linear extrapolations. They are not able to represent quantum leaps. A part of this problem is that scientists do understand the climate’s threshold points or points of no return e.g. where the destruction of a particular habitat becomes so extensive the entire ecological system collapses. Ipcc scientists are unable to incorporate in their climate models a danger highlighted by james lovelock - that an ecological system is likely to collapse if more than a certain proportion of it is damaged, "To a planetary physician, by far the most dangerous malady afflicting the Earth is that of exfoliation - destruction of its living skin. In human medicine the loss of skin from whatever cause is a serious threat to life: the loss of more than 70% of the skin by burning is usually fatal. To denude the Earth of its forests and other natural ecosystems and of its soils is like burning the skin of a human. And we shall soon have destroyed or replaced with inefficient farmlands 70% of the earth's natural land surface cover." Another example of a possible threshold point is the possibility that a rise in global temperatures could slow down the ocean conveyor belt system and trigger off an ice age.

William james burroughs argues, "The current generation of computer models are not capable of providing reliable estimates of how the incidence of tropical cyclones will be altered by global warming."

The most fundamental theoretical deficiency of climate models is that scientists do not know the concentration of greenhouse gases, and the scale of the Earth’s Forest cover, needed to stabilize the Earth’s climate.

Whilst the ipcc pointed out that to return the concentration of greenhouse gases in the atmosphere to the level prevailing in 1990 there needed to be global reductions in greenhouse gases of 60-80%, they made no attempt to determine national reductions in these emissions. As far as the ipcc is concerned, responsibilities for reducing greenhouse emissions is a political matter over which they have no jurisdiction.

The previous few sections reveal that what prevents scientists from representing the climate is not merely what they feed into computer models - it is the prejudices of the scientists themselves. The political nature of the ipcc scientific working group goes far beyond refusing to state what needs to be done to stabilize the climate i.e. refusing to determine the global scale of Forest cover and national reductions in greenhouse gases.

Scientists are increasingly working in more and more specialized fields which makes it difficult for them to discuss a broader view of their subject. The problem with climate scientists is not that many of them are too absorbed in their own field to learn more about related fields but that there are barriers preventing them from publicly discussing issues beyond their particular specialism. There seem to be few scientific endeavours which are more riven by departmentalism and intellectual discrimination than climatology, "The textbook view of life is that it comprises millions of independent beings that inhabit inanimate surroundings. Meteorologists still state that they do not even consider the chemistry or the biology of the Earth. Atmospheric chemists claim meteorology lies beyond their territory. Neither science refers much to biology. Such territoriality is inimical to understanding the planetary body." This unhealthy state of affairs leads lynn margulis to argue, "The greatest hindrance to the study of gaia is the fragmentation of science into a proliferating number of disciplines, departments, buildings, journals, and societies."

Another major flaw in the work of ipcc scientists has been their refusal to formulate a worst case scenario. After the publication of their first report in 1990, jeremy leggett, scientific director of greenpeace international’s climate campaign, demanded that ipcc scientists should explore the scenario of a self-perpetuating, global burning disaster, "Greenpeace’s criticisms of the IPCC scientific assessment focused, then, as now, on the fact that the worst case analysis arising from this conclusion was not spelt out for policymakers. The worst case analysis is, in principle, amplification of warming, by the kinds of feedbacks alluded to here, to a point of no return, beyond which might lie a point where emissions resulting from feedbacks would cancel out any anthropogenic emissions reductions, hence engendering essentially unstoppable warming." Leggett criticized the ipcc for failing to warn political leaders about the possible dangers of a spiralling global burning disaster, "The scientists of the ipcc have undersold the worst possibilities outlined in their analysis of global warming."

There are two, contradictory, conclusions which might be drawn from the inadequacies and limitations of computer models of the Earth’s climate.

Some commentators believe the deficiencies in gcms tend to over-estimate the threat posed by global burning.

Easterbrook pointed out that the ipcc’s climate models have an inbuilt bias towards global warming because they cannot create ice ages .. "the lack of ice ages in ice-age simulations leads some researchers to believe that climate models contain fatal biases in the direction of warmth." In typically optimistic vein, easterbrook argued that the more information acquired about the climate, the more that computer models have started to predict that global burning will not become a significant problem, "As climate-simulating computers become more sophisticated, most worst case predictions become less worrisome."; "Greenhouse projections are being revised downward partly on the basis of evolving knowledge about the climate." In other words, the more factors that gcms take into account, the more realistic they become, and the more evident it is that global burning will not become a significant problem! His conclusions about gcms were developed in the early 1990s before the extraordinary global warming trend of the 1980s and 1990s became apparent.

Another group of commentators argue that the multitude of deficiences in the ipcc’s computer models are likely to grossly underestimate the rise in global temperatures. By ignoring the Earth's biotic and biological processes the ipcc scientists may be seriously underestimating the dangers posed by global burning.

In 1992, in the run up to the Earth summit, leggett polled 400 climate scientists about their views on a worst case scenario. "By the end of january, 113 had replied; 15 had professed that the runaway scenario was probable, 36 that it was possible, and 53 probably not."

In the late 1990s leggett came to believe that there were indications that ipcc scientists were on the verge of creating a worst case scenario, "Finally, it seems, scientists are losing their reluctance to articulate the worst case analysis. As steven schneider told new scientist, "We used to discuss these scenarios privately. Now we are being more open’."

Bunyard has been another proponent of the need for a worst case scenario, "We might be misled into thinking that the modellers have shown us the worst scenarios. Yet, by their own admission ‘the model describes the potential natural vegetation that would exist without interference by humans, such as the recent rainforest fires.’ The actual situation is therefore fundamentally different from the one they are modelling."

About ten thousand years ago, the ice sheets covering large parts of the northern continents began to retreat leaving behind them large areas of land bereft of life. These areas were rapidly covered in Forests. Other areas of the Earth which were deserts at the end of the ice age, also became covered in Vegetation as the climate changed, "In the Sahel, Kalahari, High Plains of North America, the Argentine pampas, western Siberian steppes, Indus valley plain and the semi-arid areas of Australia, the landscape and soils were formed during periods of intense aridity at the conclusion of the ice age. Each region is predisposed to desertification during drought by the nature of its soil and landforms. When one considers that these areas produce the great majority of all the surplus food in the world, then one realizes the importance of understanding the relationship between the processes that formed the landscapes and those that in the future may transform them, when assisted by man's alteration of the environment to meet his needs." It has been estimated that the greening of the Earth after the ice age was extensive, "Forests once covered about 90% of the surface of the Earth."

It might have been expected that the widespread destruction of Forests, Peat Bogs, Coral reefs, and Grasslands, and the considerable increase in the concentration of greenhouse gases in the atmosphere, would have produced a noticeable increase in global temperatures. Surprisingly, however, this has not been the case, "Since the end of the last ice age, about 10,000 years ago, global surface temperatures have probably fluctuated by little more than 1%."; "The Earth has enjoyed a rather steady climate over the last 10,000 years in the current interglacial .. " Despite the vast changes which have happened since the end of the last ice age, the Earth’s climate has been fairly stable. However, this doesn’t mean that humans cannot destabilize the climate and provoke a rapid increase in global temperatures.

There are various explanations for the stability of global temperatures during the industrial revolution.

Although humans have damaged the Earth’s life support system throughout their existence, much of the damage happened during the industrial revolution. To be more precise, most of the damage has occurred only since the second world war. More damage has been done to the Earth’s life support system over the last half of the 20thc than during the whole of ooman history. It may be there is a time lag before the climate responds to the large scale damage which humans have inflicted on the Earth in recent decades.

A second factor constraining a dramatic rise in global temperatures is astronomic forcing pushing the Earth toward a new ice age. It is possible astronomical changes have offset, to an extent, an anthropogenic rise in global temperatures.

A number of commentators believe that if the Earth was evolving according to its own tendencies, the next ice age would be on the horizon:-

"The Earth is anyway moving steadily towards a position on the Milankovich cycle where solar heating is low and an ice age due."

"Left to its own devices, the climate cycles show, the world would now be beginning to settle down for the next ice age .... human activities are going against the natural trend."

Easterbrook believed the Earth will eventually move back into an ice age, "If the observed cycles hold, Earth will descend toward its next deep freeze sometime between 1,000 and 2,000 years from now. Incidence of sunlight falling in summer on the high latitude glaciers of the northern hemisphere, a key natural influence acting in opposition to ice sheets, peaked around 9,000 years ago .. Summer sunlight falling in the north has been declining since."

"We are sliding into another ice age which will reach its nadir in 23,000 years. But .. there is no way of knowing whether this cooling will take place smoothly, or in a series of sudden shifts."

"Thus the observed increase (0.3 to 0.6C over the last 100 years) could be largely due to this (natural) variability; alternatively this variability and other human factors could have offset a still larger human-induced greenhouse warming."

One commentator suspects the Earth’s climate started slipping back into an ice age during the medieval period (when, for example, the thames froze over on a number of occasions), "As Gribbin has pointed out, there is the real possibility that the enhanced greenhouse effect is preventing the onset of the next ice age. It is also pertinent to examine the possibility that it may have already done so. There is widespread evidence for cooling during what is generally recognized as the ‘Little Ice Age’ of the fourteenth to the early 19C. While it is unequivocal that interglacial environments were characterized by climatic variation .. there is no precedent for cold periods similar to the ‘Little Ice Age’ in earlier interglacial periods."; "In the view of some it (the little ice age) could have represented the initiation of post-holocene cooling towards the next glaciation whether interrupted by human intervention or natural variability ..." It is possible this return to an ice age was stalled by the widescale devastation of european Forests.

The final reason why global temperatures have not increased dramatically during the industrial revolution is that humans have not merely been boosting global temperatures they have also been moderating them. There are a number of ways in which humans have been inadvertently moderating global burning:-

In 1990, the ipcc stated there had been an increase in global temperatures over the past century of roughly 0.5C but concluded there was no proof that humans were responsible for this increase. Easterbrook made the valid point that the greater the natural variability of the climate the more difficult it is for scientists to state categorically that anthropogenic factors are responsible for climate change, "A greater natural variability in climates might make it harder to discover a genuine human signal."

In december 1995 ipcc scientists announced they had detected a discernible human influence on the climate, "The ipcc has now agreed that man-made global warming is under way." Since this announcement, despite the political fears of upsetting their paymasters, climatologists have hardened their views about humans’ role in boosting climate change.

In january 1998 the american geophysical union talked about human-induced climate change leaving little doubt that they believed humans were responsible for global burning, “After months of internal discussion, the american geophysical union (agu), a prominent international scientific body of 35,000 Earth and planetary scientists, made a bold move into the public global warming debate last january by unveiling a strongly worded position statement on climate change. The paper (noted that) “there is no known geologic precedent for the transfer of carbon from the Earth’s crust to the atmosphere” in amounts comparable to fossil-fuel burning, without simultaneous changes in the climate system. While acknowledging significant uncertainties, the statement stresses that the “present level of scientific uncertainty does not justify inaction in the mitigation of human-induced climate change.”

"The anomalous warmth of several recent years appears likely to be related to human influences on climate.""

In april 1998, herman zimmerman, programme director at the national science foundation's atmospheric sciences division, argued, "The balance of evidence now firmly supports an important human influence on the global climate system."

In november 1998, a group of climatologists made an even more dramatic announcement, "A leading team of climate modellers has strengthened its claims that humans have contributed to global warming. The hadley centre, part of Britain’s meteorological office, says new research shows that industrial greenhouse gases have contributed significantly to warming over the past 50 years. This, says geoff jenkins, head of the centre’s climate prediction programme, is a much tougher statement on the issue than its previous ones, which talked of "the balance of probability""

At the end of the millennium, two senior scientists made it clear that humans were responsible for global burning. They delivered what sounded like an apocalyptic plea for action to curb anthropogenic global burning, "Global warming is now changing the world's climate rapidly, and humanity faces a 'critical' position because of it, the chief meteorologists of britain and the u.s. warn today in a remarkable joint statement. Peter ewins, head of the uk meteorological office, and james baker, his u.s. counterpart, confront climate-change sceptics head on .. The statement from such senior figures breaks a tradition of caution by scientists involved in climate research, who have been providing evidence for a decade of global warming, but have left the conclusions to politicians. The letter from ewins and baker is the most definitive statement yet by senior scientists on global warming." In their letter they stated, "The rapid rate of warming since 1976, approximately 0.2C per decade, is consistent with the projected rate of warming based on human induced effects. In fact, scientists now say that they cannot explain this unusual warmth without including the effects of human-generated greenhouse gases and aerosols. Our new data and understanding now point to the critical situation we face: to slow future change, we must start taking action soon. Ignoring climate change will surely be the most costly of all possible choices, for us and our children."

"If we fail to take prudent, sensible steps to address the problem [of climate change] now, our children and their children will simply be overwhelmed. Rising seas, rising temperatures, the threat to public and economic health around the world, the prospect is very real. In the end, failure is not an option. The consequences of global warming are that severe."

There are a range of nay-sayers seeking to downplay global burning. Some deny there has been a rise in global temperatures; some deny that humans are responsible for the increase in global temperatures; others argue the rise is of no significance in comparison to warmer periods in the past; whilst others suggest, a little more plausibly, that global burning is but a prelude to global cooling. The following sections highlight some of these denials and attempt to expose their flaws.

There are a small number of scientists who deny there has been a rise in global temperatures. They point out that satellites have not found an increase in global temperatures.

There are far more denialists who dismiss humans responsibilities for the rise in global temperatures.

"While still uncertain about the long-term trend, a panel of scientists says there's no question the warming of the Earth - under way for a century - has accelerated during the past 20 years. The warming trend in global-mean surface temperatures over the past two decades "is undoubtedly real and is substantially greater than the average rate of warming during the 20th century," said the 11-member panel of the National Academy of Sciences in a 71 page report published January 12th 2000. Still the panel in its report hedged on whether the warming of the Earth's surface will continue or whether it is even linked to the greenhouse effect caused by manmade pollution of the atmosphere. "There is a high level of confidence among the panel members that the surface temperature is indeed rising," said John Wallace, panel chairman and professor of atmospheric sciences at the University of Washington. But, he added, that does not necessarily mean the warming is due to manmade greenhouse gases "nor are we saying it's necessarily going to continue to accelerate in the future." The 20-year record is too short to make definitive statements as to how the atmosphere is changing in the long term," he said."

Some denialists dismiss global burning by pointing out that current global temperatures are not unusual in comparison to global temperatures in earlier periods. Most climate scientists rely only on the evidence derived from the temperature record accumulated since 1860. There are only a few scientists who compare current global temperatures with those in earlier periods e.g. michael mann who argued that, "The research finds that in 1990, 1995 and 1997 average northern temperatures were the highest since at least 1400." Unfortunately, the nay sayers have been much better at persuading people about their case than the advocates of global burning.

Easterbrook is a cornucopian green and a global burning sceptic. Writing in the early 1990s he condemned the rio Earth summit because of .. "the hypothetical prospect of global warming - a troubling but speculative concern that so far has harmed no one and may never harm anyone - was put above palpable, urgent loss of lives from third world water and smoke pollution." He continued, "Never had great nations devoted so much energy to addressing an entirely speculative problem."

"From the unique perspective of the geological record, it appears that the ‘greenhouse Earth’ was a feature of the climate for up to 80% of the last 500ma, and that therefore our present glacially dominated climate is an anomaly."

If present social and economic trends continue then humans are likely to cause further increases in global temperatures. Those who are worried about global burning argue this rise is serious in comparison to past global temperatures. On the other hand, there are denialists argue that even if the climate begins to warm as dramatically as has been predicted it still won’t pose a threat to humans.

"Under the business-as-usual scenario emissions of greenhouse gases, a rate of increase of global mean temperature during the next century of 0.3C per decade (with an uncertainty range of 0.2C to 0.5C per decade. This will result in a likely increase in global mean temperature of about 1C above the present value by 2025 and 3C before the end of the next century."

"Models predict that the climate could be warmer by the end of the 21st century than it was during any previous inter-glacial period."

"Atmospheric concentrations of greenhouse gases are rising rapidly as a result of human activities and in particular, fossil fuel burning, land use change and agriculture. According to the IPCC, if current trends in emissions continue then this could cause a rate of global warming over the next century "probably greater than any seen in the last 10,000 years"."

.. "our very climate is being so transformed and destabilized that within the next forty years we will experience climatic conditions in which no human has ever lived before."

Avery dismisses concerns about the current rise in global temperatures, "They say that the earth is likely to warm by no more than 2 degrees celsius (3.5 degrees fahrenheit) during the next century. That may sound like a lot, but it isn't. The world has experienced that much warming fairly recently. And we loved it. Between 900 AD and 1300 AD, the earth warmed by some 4 to 7 degrees fahrenheit - close to current predictions for the 21st century. Historians call it the Little Climate Optimum. Predictions that we face a new global warming should be greeted with enthusiasm: the medieval experience should reassure us, and the latest scientific evidence supports such optimism. Global warming scaremongers have also claimed that a warmer world would suffer more extreme weather events. This too is unlikely. With or without warming, we can expect a peak population of approximately 8.5bn people around the year 2035. That peak will be followed by a slow, gradual decline through the rest of the 21st century."

"Should it occur this increase would surely disrupt climate patterns but still leave the land environment notably cooler than through most of the planet’s history."; "Such an increase surely would be significant but would still leave the Earth starkly cooler than has been its condition for most of the span in which mammals have existed."

Those warning of the threats posed by global burning claim not merely that there has been a rise in global temperatures but that this rise is taking place more rapidly than has been the case in the past. As far as is known, the rate at which global temperatures are currently rising is unprecedented. In the past, changes in global temperatures of 1C have occurred over hundreds, usually thousands of years. But, at present, humans are threatening to bring about changes of between 1-4C within a century - and given the rate of increase that has occurred over the last couple of decades, the rise is more likely to be closer to the latter range than the former. However, scientists’ willingness to speculate about rapid rises in global temperatures became commonplace only in the late 1990s.

Lovelock was one of the few scientists who was willing to countenance the idea of rapid changes in the climate. In the 1980s he pointed out there had been a rapid rise in global temperatures at the end of the last ice age, "The rise in temperature and the rise in Carbon dioxide over a period of only a few hundred years at the end of the ice age was 3C and 100 ppm respectively. .. we have already effectively increased the greenhouse effect by as much as happened between the ice age and the interglacial that followed."

From the start of the recent concerns about global burning in 1988, most climatologists believed that changes would occur imperceptibly over long periods of time. However, results from research into the Earth’s climate carried out on ice cores samples from two sites on the greenland ice sheet, led to a dramatic reappraisal of this view. Although these results, which went back over a hundred thousand years, were not completely compatible they showed a number of rapid changes in the climate at the end of the last ice age. Since then scientists have been more willing to talk about sudden and dramatic changes in the climate than they were before. They argue that a rapid rise in global burning is feasible now and in the future because it has happened in the past. Humans are not merely boosting global temperatures they are running the risk of triggering of rapid climate change.

"The Holocene has only had one climate state, but it appears that the Eemian had three - one like the one we have now, one warmer and one colder. It appears also that a shift from one climate state to another took very little time, perhaps less than ten years."

"Whereas earlier thinking had assumed that the thermal inertia of the oceans meant that big changes in the climate took a long time, now it is possible to conceive of much more rapid and chaotic shifts."

"The rapid rate of warming since 1976 (is) approximately 0.2C per decade .."

Rather strangely, the denialists have said nothing about this proposition. This seems to be one area where global burning proponents are as yet unchallenged.

Comparing present global temperatures with those prior to the pleistocene age in order to dismiss global burning is misleading. According to lovelock, over the last couple of aeons the Earth’s Photosynthetic capacity was able to counter the long term increase in solar radiation and stabilize the Earth’s climate. However, a few million years ago the Earth’s Photosynthetic capacity had removed so much Carbon from the atmosphere it was no longer able to stabilize the climate. The climate’s loss of its stabilizing force explains the oscillations between ice ages and inter-glacials during the pleistocene period. The implication of this view of the Earth’s climatological history is that whilst high temperatures in the past may not have posed any danger to climate stability (or life on Earth) because the Earth’s Photosynthetic capacity was able to stabilize the climate, the same high temperature in the pleistocene period is much more dangerous because of the climate’s instability. It is quite true the Earth has been a lot hotter in the past than it is now but whereas in the past the Earth’s climate stabilization system was in a robust state to counter high temperatures this is no longer the case.

There are a number of criticisms which could also be made of denialists’ comparisons between current global temperatures and those during the medieval climate optimum:-

This work has presented some disturbing evidence about climate change. Firstly, whilst global temperatures have risen over the last century by a mere 0.5C, there has been a dramatic increase in recent times, "Just over the last three decades (between 1969-71 and 1996-98), global average temperature has risen by 0.44 degrees Celsius (0.8 degrees Fahrenheit)."

Whilst it is quite true that global temperatures are not at an all time high, the rate at which global temperatures are increasing is at an all time high. What this means is that global temperatures could end up as hot as some of the hottest periods during the Earth’s history. In effect, humans are creating a runaway system of rising temperatures. There is the prospect that humans could trigger off a rise in global temperatures which could continue throughout the 21st century so that instead of the predicted 1-4C rise there could be a rise of 10C. Global average temperatures could jump from their current level of 15C to 25C.

On a purely intuitive level, the small increase in global temperatures over the last century or so (0.5C since 1860) doesn’t make sense given the scale of the pollution dumped into the atmosphere and the reduction in the Earth’s Forest cover. However, most of this damage to the Earth’s life support system has occurred only over the last fifty years so this may be the reason why the rapid rise in global temperatures is only just beginning to occur. The dramatic increase in global temperatures during the last quarter of the twentieth century seems far too striking to be a purely natural phenomena.