HOW DOES THE EARTH STABILIZE THE CLIMATE?

It has been estimated that the sun was formed approximately five billion years ago. Many commentators propose that since then there has been a linear increase in the sun's luminosity, "Some estimates for the increase in solar luminosity over the past history of the Earth are as much as 100%; most astronomers apparently accept an increase of at least 25% over 4.5 billion years ..." Other commentators believe the increase in solar radiation has lessened over the last 600 million years, "Most scientists believe that the solar luminosity has increased about 30% since the formation of the Earth some 4.5 billion years ago, 5% of that in the past 600 million years." One commentator has argued solar radiation has levelled off over the last few aeons, "Solar input was weaker in the beginning, but the solar radiation increased logarithmically some three billion years ago, and became more or less constant during the last two billion years."

It is believed that solar radiation will go on increasing for many more billions of years before the sun turns into a ‘red giant’ and, eventually, collapses into a white dwarf the size of venus, "By astronomical reckoning, the sun has a total life span of only about 10 billion years. After all the sun’s hydrogen burns up as a fuel, nuclear reactions that convert lighter to heavier atoms are expected to take over. As the radiating sun expands into a red giant, our dying star will shine as it has never shone before. The luminous body is expected to generate such immense heat that oceans will boil and evaporate."

Although solar luminosity has increased significantly since the formation of the Earth there has been no corresponding increase in the Earth’s average temperature .. "the sun has warmed some 30% over the last 4.5 aeons of the Planet’s existence .. The Earth’s mean surface temperature has (not) risen anywhere near the 50-60C that the sun’s warming would imply." As lovelock has pointed out, "If the Sun were to cool so that its output was 25% less than now, then the mean temperature of the Earth would not be 14C like now but would fall to somewhere below freezing. By the same argument, if the Earth 3.6 billion years ago was as warm as it is now, then a 25% increase in solar output would have raised the mean temperature above 30C, far too hot for comfort."

The Earth was formed four and a half billion years ago and its first atmosphere contained no oxygen but colossal quantities of Carbon - in the form of Carbon monoxide, Carbon dioxide and methane. If this concentration of Carbon had persisted in the atmosphere over the aeons then the sun's increasing luminosity would have boosted global warming - and the Earth's climate is likely to have become too hot for the survival of most forms of life. The main reason that increasing solar radiation did not overheat the Earth is because Photosynthesizers extracted Carbon from the atmosphere and thus reduced the greenhouse effect, "Lovelock and the microbiologist Lynn Margulis had long argued that were it not for life, the Earth would have had a predominantly CO2 atmosphere (this) implied a greenhouse strong enough to have created searing Earthly temperatures - some 60C warmer than now."

The amount of Carbon extracted from the atmosphere has been prodigious. The concentration of Carbon dioxide in the atmosphere has fallen over the Earth's lifetime from 30% to 0.04%. The history of the Earth has been the process of extracting Carbon from the atmosphere through Photosynthesis thereby keeping the Planet cool and maintaining climatic stability. The fact that the Earth has been able to offset a substantial increase in solar radiation reveals its extensive powers for stabilizing the climate. Thus, despite the seemingly all important role played by the sun in determining the Earth's climate it seems the Earth’s own role has been of greater significance. For the vast majority of the Earth’s history, Photosynthesis has seemed to act cybernetically - the greater the solar radiation, the greater the amount of Carbon removed from the Earth’s atmosphere through Photosynthesis.

If there were no Photosynthesizers on Earth most of the Carbon would still be in the atmosphere. Only relatively small amounts of Carbon would have been deposited on the seabed via the lengthy process of diffusion, "Were life not present, the Carbon dioxide from the atmosphere would have to reach the calcium silicate of the rocks by slow inorganic processes like diffusion." In other words, purely geological factors wouldn’t have been able to remove CO2 quickly enough from the atmosphere to combat increases in solar radiation and, without Photosynthesis, the Earth’s temperature would have approached what it should be for a planet between venus and mars.

Over the aeons, the extraction of Carbon from the atmosphere has brought dramatic changes on Earth. The vast bulk of the Carbon originally in the atmosphere now covers the surface of the land and large sections of the ocean floor. Correspondingly, the Earth’s atmosphere currently contains huge quantities of oxygen but only trace quantities of Carbon.

Throughout the bulk of the Earth’s history Photosynthesizers have played a critical role in countering the sun’s increasing luminosity by extracting Carbon from the atmosphere, reducing global temperatures, and thus stabilizing the climate. Without Photosynthesizers the Earth’s average temperature would soar. The role of the Earth’s Photosynthesizers is to cool the Earth. This is one of the basic geophysiological facts of life.

During the early stages of the Earth's history when the planet was covered by a global ocean, marine Micro-organisms were responsible for removing Carbon from the atmosphere. Over the following couple of aeons, as continents began to form, the role of marine Photosynthesizers was supplemented by terrestrial Photosynthesizers. It wasn’t until the latter half of the Palaeozoic that Trees emerged. Lovelock believes that, at the start of the miocene period, about 10 million years ago, Photosynthesizers had extracted so much Carbon from the atmosphere this led to the emergence of new Photosynthesizers which could survive such conditions, "Not surprising is the emergence in the miocene, some 10 million years ago, of a new type of green Plant able to grow at lower Carbon dioxide concentrations. These plants have a different biochemistry and are called C4 plants to distinguish them from the mainstream C3 Plants. The C4 Plants are able to Photosynthesize at much lower Carbon dioxide levels than older C3 Plants. The new C4 Plants include some, but not all Grasses, whereas Trees and broad leaved plants generally use the C3 cycle." C4 Grasses function more efficiently than C3 Plants (which includes Trees) in low Carbon atmospheres. During the miocene period, Grasses have played an increasingly significant role in the Earth’s biosphere.

Lovelock has estimated that in about a hundred million years time, even C4 Grasses will become redundant as the last remnants of atmospheric Carbon disappear, "Eventually, and probably suddenly, these new Plants (the C4s) will take over and run an even lower Carbon dioxide atmosphere to compensate for the increasing solar heat. But it will serve only temporarily, because in as short a time as 100 million years, assuming nothing else has changed, the sun will have warmed up enough to require a zero Carbon dioxide atmosphere to maintain the present temperature."

In the future, when the Earth’s atmosphere has no Carbon in the atmosphere, the role of Photosynthesizers in stabilizing the climate will become redundant and the Earth will have to adapt a new, non-Photosynthetic, cooling system - whatever this might be. Easterbrook, who seems to know little about the Earth’s climate history, doesn’t believe there will be such a crisis in the Earth’s climate stabilization system, "Taking these factors into account, kasyting and caldeira estimated the life expectancy of the current biosphere at 900 million to 1.5 billion years. After that the sun will have become so hot the oceans will boil."

Firstly, some commentators believe this is the first ice age to have fluctuated between ice ages and inter-glacials, "The present oscillations to and from a glacial state are recent: up until 2 million years ago, the climate was much more constant."

Secondly, the rapidity of the changes between ice ages and inter-glacials has been unusual, "The pleistocene is remarkable not just for the alternation of warm and cold phases but for the scale and rapidity of the changes. At least 20 glacial/interglacial cycles are known to have occurred ..

Thirdly, each ice age in the quartenary period has lasted for only a very short period compared to previous ice ages. Even if the whole of the quartenary period is counted as one continuous ice age it is still much shorter than previous ice ages, "At least eight previous ice ages are known ranging through geological time from the jurassic, around 150 m years ago, to the pre-cambrian, 2,300 million years ago and beyond. Significantly, all of these earlier ice ages lasted for longer - up to 50 m years - than the two million years of the quaternary ice age."

The duration of quartenary ice ages has varied between 40,000 years and 100,000 years, "Ice ages tend to last for 100,000 years. The spell between them, usually, lasts for 10,000 years." There have been 10 in the last million years.; .. "four million years ago when humans were evolving in east africa, the climate began to change dramatically and the Earth not only began to have permanent ice at the poles but underwent periodic cycles between one glacial period and the next. The cycles have changed in length as time has passed. Several million years ago they lasted 40,000 years; more recent cycles appear to have lasted 100,000 years, with the glacial part of the period taking up nine-tenths of the whole." The last ice age started 130-120,000 years ago and ended a mere 10,000 years ago.

In the geological past, the Earth seemed to have little difficulty in perpetuating ice ages because solar radiation wasn’t substantial. However, during the quartenary period, the increase in solar radiation has reached an intensity which significantly shortens the duration of ice ages. As will be seen, despite the Earth’s ability to increase the scale of Photosynthesis causing a deepening of ice ages, Photosynthesizers haven’t been powerful enough to ensure the continuation of these ice ages.

Since the emergence of Photosynthesis, the Earth’s Photosynthetic capacity seemed to act cybernetically - cooler temperatures caused a decline in Photosynthesis leading to a rise in the concentration of atmospheric Carbon and thus a rise in global temperatures. However, this meant the Earth’s Photosynthetic capacity had a diminishing capability for provoking and maintaining ice ages as a means for countering the sun’s increasing output of solar energy. As the sun’s luminosity increased, the Earth’s Photosynthetic capacity extracted Carbon from the atmosphere to cool the Earth only to find the smaller scale of Photosynthesis allowing the accumulation of Carbon in the atmosphere to push the climate out of the ice age. As a result of increasing solar radiation and the cybernetic behaviour of Photosynthesis, ice ages would have lasted for shorter and shorter periods of time until, eventually, the Earth would have been unable to create any more ice ages and would have started to burn up. Fortunately for the Earth, the ice ages of the quartenary period did not bring about a decline in global Photosynthesis.

Given that Photosynthesis declines when temperatures fall, it seems anomalous that global Photosynthesis increased as the Earth’s climate got colder. Lovelock tries to explain this anomaly, "Laboratory experiments show that land Plants and marine Algae grow best when the temperature is about 22C, well above the Earth’s mean temperature of 15C. Further heating should therefore lead to more growth and consequently a negative feedback on temperature. The reason it does not is because the ideal temperature for the superorganism, Gaia, is not the same as that for plant growth, but lower." According to lovelock, the Earth’s current ideal temperature is 10C. This is significantly below the Earth’s current average temperature of 15C. It is also 12C below maximum Photosynthetic efficiency under laboratory conditions. Perhaps the simplest way of explaining how Photosynthesis increased during the quartenary ice age is by making a distinction between the rate, and the scale, of Photosynthesis. The former concerns the efficiency of Photosynthesis at different temperatures whilst the latter concerns the spread of Phytomass around the Earth.

It has just been pointed out that lovelock believes that the point of maximum Photosynthesis occurs under laboratory condition at 22C. However, the point of maximum Photosynthetic efficiency in the real world is different from that under laboratory conditions. In a laboratory, soils can be kept moist to provide the right growing conditions for Plants whereas outside the laboratories, as temperatures rise, soils begin to dry out thereby reducing Photosynthesis. In the real world, maximum Photosynthetic efficiency tends to occur at around 18C. According to peter bunyard, "Terrestrial vegetation will lose its ability to regulate the climate once the average surface temperature reaches around 18C ..."

The rate at which the Earth’s Photosynthetic capacity carries out Photosynthesis increases until global average temperatures reach 18C. Thereafter the rate declines. Conversely, the colder global temperatures are, the less efficient Photosynthesis becomes. Geophysiologically, this means the rate of Photosynthesis has a cybernetic role in stabilizing the Earth’s climate. As the Earth’s temperature rises up to 18C, there is an increase in the rate at which Photosynthesis extracts Carbon from the atmosphere and this decreases global temperatures. Conversely, as the Earth’s temperature falls there is a decrease in the rate of Photosynthesis which allows the build up of Carbon in the atmosphere thereby boosting global temperatures.

As far as the scale of Photosynthesis is concerned, however, the outcome is quite different. When global temperatures start moving towards, or dipping below, 10C there is an increase in the spread of Photosynthesizers around the Earth. But when global temperatures rise towards, or above, 10C there is a decrease in the spread of Photosynthesizers. The warmer the climate, the smaller the scale of Photosynthesis around the Earth, the greater the boost to global warming. Whilst the rate of Photosynthesis acts cybernetically to stabilize the climate, the scale of Photosynthesis has a destabilizing impact on the climate. This seems to defy common sense. How does the scale of Photosynthesis increase when global temperatures are declining and decrease when global temperatures are rising?

As the Earth gets colder, ice sheets spread across the amero-euro-asian continents, "During this period (the last ice age) the whole of scandinavia, north germany, poland, north-west soviet union and most of britain were covered in ice and at the height of the glacial period, about 20,000 years ago, the ice sheets moved even further south. The area to the south of these ice sheets was one of permafrost and a tundra type vegetation. It supported a wide variety of Animal life dominated by herds of Reindeer, woolly Mammoth, Bison and wild Horse together with smaller numbers of woolly Rhinoceroses, giant Elk and saiga Antelope." The growing ice sheets cause a substantial drop in sea levels around the Earth and expose more and more land along coastal areas in the tropics. Whilst ice sheets obliterate Forests across a huge expanse of the northern hemisphere, a large number of Forests begin to grow along the coastal fringes emerging in the tropics. The area of Forests gained in the tropics by the drop in the level of the oceans is greater than the area of Forests lost by the spread of ice sheets across the northern continents. This produces a net increase in the scale of global Photosynthesis which increases the amount of Carbon extracted from the atmosphere and brings about a further fall in global temperatures .. "the low Carbon dioxide during the glacials can be explained by the presence of a larger or more efficient biota. There must have been more living organisms on Earth; how else could the Carbon dioxide have been so low? If more organisms were doing the pumping, where were they? At first thought it might seem that the ice sheets would leave less room for life as it covered much of what is now, or was before humans, forested land. However, as water was used to form the land based glaciers, the level of the sea could have fallen by some 100 meters, exposing vast areas of land on the continental shelves ready for colonization by Plants. A glance at a map of the continental shelves reveals that much of the new land would have been in the humid tropics, such as in present day southeast asia. It could have covered an area comparable with that of africa now, and could have supported extensive Plant growth."

The second geophysiological factor boosting the scale of Photosynthesis when global temperatures fall towards and below 10C, is the growth in marine Algae. This is caused by the increase in the supply of nutrients reaching the surface of the ocean. Lovelock argues that when the Earth is warm, the oceans stratify into layers of warm and cold water which prevent nutrients rising from the ocean bed to the surface where marine Algae live. The warmer the Earth, the more pronounced oceanic temperature gradients become. When the Earth cools these gradients disappear and nutrients rise to the surface stimulating Algal growth. The rise in marine Photosynthesis extracts more Carbon from the atmosphere, further boosting global cooling, "Algal ecosystems of the oceans grow best when the sea surface temperature is 10C. Not necessarily because the ocean organisms are different in their temperature response to land Plants, but because for geophysical reasons the ocean surface layers tend to form a stable inversion, the thermocline, when the heat flux increases. In practice, the thermocline forms when the surface layers exceed about 10C. When this happens the cooler, nutrient rich, waters below the thermocline can not mix with the surface water and the organisms starve. Satellite views taken to show surface temperature, Algal density, and cloud cover, reveal dense Algal growth to be limited to ocean regions where the surface temperature is near or below 10C; these are also the regions of maximum cloud cover .."

Marine Algae also provide another boost to global cooling by releasing a gas called dimethyl sulphide (dms). This triggers the formation of clouds thereby reducing global temperatures .. "the rapid oxidization of dimethyl sulphide in the air over the ocean could be the source of the nuclei needed for the condensation of water vapours to form clouds. Small droplets of sulphuric acid are ideal for this purpose, and over the open oceans there is no other significant source of condensation nuclei from which to form clouds."; Dms is converted in the air to particles of sulphuric acid, "DMS oxidises in the air and produces tiny droplets of sulphuric acid onto which the cloud droplets form." Clouds reflect sunlight back into space reducing global warming. Other commentators concur, "How is Carbon dioxide removed from the air when the world cools? .. marine algae thrive, increasing the cloud cover of the Planet - and clouds reflect away some of the heat of the Sun."; "Sulphur dioxide.. could possibly damp down the greenhouse effect by encouraging cloud formation."

Lovelock finds confirmation of his view that the ideal temperature for the growth of marine Algae is below 10C by pointing out that, "What we do know is that the greatest effect (of Algae releasing dimethyl sulphide) seems to be in the arctic and antarctic oceans. Here Algal growth is dense and the ocean surface is often covered by a low lying blanket of marine stratus cloud, a cloud form that has the greatest cooling effect. Cold waters favour Algal growth because they are well supplied with nutrients. Warm and tropical waters are stratified so that a warm-layer, the thermocline, overlays the nutrient-rich water below. In addition to these effects of temperature on Algal growth, cloud formation is also temperature dependent. The reflecting marine stratus clouds form most readily in cold regions." According to lovelock, Algal growths in european waters are on a par with sulphur pollution from industry .. "the emission of this gas from phytoplankton blooms at the surface of the oceans around western Europe is large enough to be comparable with the total emissions of sulphur from industry in this region."

Recent research reinforces lovelock’s thesis, "Coccolithophores which form huge blooms covering areas up to 500,000 square kilometres in the relatively nutrient poor open oceans, produce about a hundred times as much dms as some other algae - such as diatoms, which thrive on the continental shelves but produce very little dms. Charlton’s original idea was that waters heated by greenhouse warming could encourage algal production, leading to more dms and hence more cloud. This would lead to more solar energy being reflected which would in turn lower the Earth’s temperature. (Ice core) results suggest that concentrations of sulphate aerosols derived from dms and msa are lower during warm interglacial phases and higher during ice ages. This is the opposite of what could be expected if the dms-derived aerosols were acting as a damper on climatic change." However, the intergovernmental panel on climate change is more cautious about the climatic role of marine Algae, "One group of plankton, the Coccolithophorids, are apparently a major source of DMS and their bloom processes would most likely respond, although in uncertain ways, to changes in ocean-atmosphere exchanges resulting from climate change."

There are also other reasons for the increase in Photosynthesis during an ice age. John gribbin asks, "How is Carbon dioxide removed from the air when the world cools? During an ice age the world is dry. Winds blow the dust from the arid land out over the oceans, where the iron in the dust helps marine organisms to grow. One effect of this is that Plankton thrive, absorbing Carbon dioxide, turning it into Carbonates in their shells, and dropping it onto the sea floor when they die." Gribbin's hypothesis is supported by another commentator, "If iron controls the productivity of the oceans and thereby the natural level of atmospheric CO2 it follows that iron supply to the oceans could affect global temperatures through the heat trapping properties of CO2. Iron in the surface ocean comes mostly from dust in the atmosphere, soaked up from deserts or other arid regions. Measurements from ice-ages in Antarctica show that levels of wind blown dust were regularly higher during the ice ages which would explain why the atmospheric carbon dioxide levels were substantially lower then"

Lee klinger believes Peatbogs also play a role in boosting global cooling. He argues they are more important than Forests for determining the concentration of atmospheric Carbon. Peatlands exist on a massive scale around the world and thus have the potential to play a major role in driving down temperatures, "Peatlands cover about 5m square kilometres of the Earth, ranging from the tropics up to the frozen tundra of Siberia, going down to a depth of 60 feet in places, holding up to 100 times as much carbon per hectare than tropical rainforests."; "Peat bogs are a giant natural store of carbon, holding between 500 and 1000 gigatonnes of the element - more than the amount stored in the world’s trees and similar to the 700 gigatonnes held in the atmosphere. Peatlands cover about 5 million square kilometres of the Earth’s surface, ranging from frozen tundra to tropical bogs. Large Peatbogs in sumatra and borneo have accumulated peat to a depth of 20 metres over 8000 years, and hold up to 100 times more Carbon per hectare than the surrounding tropical Rainforest."

A fall in global temperatures stimulates Peatbogs to extract Carbon from the atmosphere, thereby enhancing global cooling .. "peatlands could have been an important part of the biological mechanisms that many believe have helped plunge the Planet into and out of glaciation. Alterations in the extent of peat bogs would change the concentration of Carbon dioxide in the atmosphere by up to 20%. Global cooling would encourage the growth of Peatbogs, at the expense of Forests. Over thousands of years, the Peatbogs would extract Carbon from the atmosphere and store it, so reducing the natural greenhouse effect and driving temperatures still lower."; "Cooling encourages the growth of peat bogs. They extract Carbon from the atmosphere and store it, so perpetuating the cooling ..."; "Peat bogs could be the real driving force of climate change and the global carbon cycle."; "These are potential mechanisms that could initiate ice ages," says Lee Klinger."; "Lee klinger .. argues that the humble sphagnum moss may have been responsible in large measure for bringing about past ice ages .. Klinger has followed Plant succession in alaska and concludes that, slowly but surely, dense coniferous Forest yields to coniferous Bog Forest and finally to moss-sedge Bogs, which may last for thousands of years. Bog Plants tend to acidify the soil through the release of sulphides which form acids when they are oxidized. Acidity favours mosses against other Plants, not only stimulating the growth and spread of sphagnum, but also favouring the accumulation of peat by preventing the bacterial decomposition of organic matter - thus locking up huge quantities of Carbon and helping to cool the climate. The result is a self-reinforcing process, with cooler conditions favouring the advance of peatlands ..."

In conclusion, lovelock argues that during an ice age there is an increase in terrestrial, and marine, Photosynthesis which exacerbates global cooling. The cooler the Earth’s temperature, the greater the Photosynthesis, the greater the global cooling. These views are shared by others, "Since the major agents of fluxes between the atmosphere, the terrestrial and oceanic pools of Carbon dioxide are living organisms, the astronomical forcing factors must somehow promote or demote organic productivity. The implication is that during ice ages organic productivity was higher than during interglacials .."; "Ice ages .. are periods of greater marine biological activity than the warm periods in between." Schneider points out that evidence from the greenland ice cores suggests that, during the last ice age, Photosynthesis acted as a positive feedback factor, boosting cooling, whilst in the past it had acted as a negative feedback factor, "What is important for our discussion (is) the fact that the feedback appears positive. This is different from what we inferred from studying the one- to two- billion year long transition from the high CO2 .. atmosphere of the archean to the era of great biological evolution about half a billion years ago .. the negative feedback implicit in the Gaia hypothesis." The increase in marine and terrestrial Photosynthesis during ice ages are both powerful influences on the Earth’s climate. It seems that as temperatures fall the increase in the scale of Photosynthesis has a bigger impact on global temperatures than the decline in the rate of Photosynthesis.

As the Earth warms, the amero-euro-asian ice sheets retreat and there is a rise in ocean levels. Forests begin to reappear in the regions of retreating ice sheets, whilst the Forests on the coastal shelves of the tropics are drowned under the rising oceans. The net result is a decline in the scale of the Earth’s Forest cover. This boosts the greenhouse effect. As regards marine Photosynthesis; the rise in the Earth’s temperature produces an increase in oceanic stratification preventing nutrients from the ocean floor from reaching marine Algae on the surface of the ocean, "The model (created by lovelock) operates on the principle that as the oceans warm, the thermocline layer spreads and becomes a greater barrier to the mixing of deep and surface waters. On land, as temperatures increase, plants find themselves increasingly suffering from the drying out of soils and water stress. In both instances, rising temperatures take their toll on growth. The model clearly shows that life in the oceans is more vulnerable to higher temperatures compared to life on land. The thermocline barrier is a feature of oceans when the surface waters are warmer than about 12C. On land, water stress becomes a widespread phenomenon once the average surface temperature reaches 20C." This reduces the amount of Carbon extracted from the atmosphere; decreases marine cloud cover; and reduces sulphur’s fertilization of terrestrial Phytomass - all of which boost global warming. Overall, then, when global temperatures rise, there is a decrease in the scale of Photosynthesis which boosts global warming and contributes to the destabilization of the climate.

Conversely, when global temperatures rise above 10C, the decline in the scale of Photosynthesis around the Earth is more substantial than the increase in the rate of Photosynthesis. The net effect is a drop in the total amount of Photosynthesis carried out on Earth which thus boosts global warming. Once the Earth’s temperature rises above 10C the climate develops a momentum towards increasing global warming - a destabilization of the climate.

As the Earth’s temperature rises above 10C, it is not known whether there is a linear decline in the scale of Photosynthesis i.e. the greater the rise in global temperatures, the greater the net decrease in the area of land covered by Forests, and the greater the degree of oceanic stratification. Similarly, it is not known whether there is a linear increase in the scale of Photosynthesis when the Earth’s temperatures fall below 10C. It is possible the changes in the scale of Photosynthesis do not take place in a linear fashion but through spasmodic convulsions. Logically, if the Earth’s Photosynthetic capacity does not change evenly then, to a limited extent, there may be times at which the cybernetic role of the rate of Photosynthesis would play a more noticeable part in the climate. However, there is no evidence for this.

When the Earth’s average temperature rises above 10C there is an increase in the rate of Photosynthesis but a decrease in the scale of Photosynthesis. However, when the Earth’s average temperature reaches 18C, the rate of Photosynthesis also begins to decline and many of the Earth’s terrestrial Photosynthesizers start to die off. According to lovelock and kump .. "the contribution from land to the stabilizing of global temperatures is from vegetation drawing down Carbon dioxide. As temperatures increase, so Plants suffer from drying out of soils and from water stress. Their efficiency in taking Carbon dioxide out of the atmosphere is thereby significantly reduced. Terrestrial vegetation will lose its ability to regulate the climate once the average surface temperature reaches around 18C - ipcc estimates that a century from now, the Earth will have temperatures close to that critical point." It is predicted that if global temperatures rise above 18C both the scale and the rate of Photosynthesis would go into decline giving a double boost to global warming and thus increasing the destabilization of the climate. Global warming could accelerate out of control. In other words, given that global average temperatures are currently 15C then human civilization is just 3C away from the point where the Earth’s main climate stabilizing factor starts destabilizing the climate, "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."

Lovelock’s analysis suggests that the scale of Photosynthesis has far more of an influence on the Earth’s climate than the rate of Photosynthesis. This is crucial because whilst the rate of Photosynthesis has a cybernetic relationship with the climate, the scale of Photosynthesis does not. For aeons, Photosynthesizers have helped to stabilize the climate but now that the scale of Photosynthesis has such a dominant influence on the climate it virtually turns the climate moderating role of Photosynthesizers inside out so that instead of stabilizing the climate they destabilize it. Paradoxically, however, if the increasing scale of Photosynthesis did not destabilize the climate by boosting global cooling, the Earth would have no way of combating the sun’s increasing heat. In effect the climatic ‘instability’ created by the scale of Photosynthesis, in so much as it reinforces the fall of global temperatures, helps to stabilize the Earth’s climate. In other words, the Earth counters the sun’s increasing output by ‘destabilizing’ the climate.

The tendency of the Earth’s Photosynthetic capacity to reinforce falling global temperatures and destabilize the climate is a serious breech in the geophysiological theory that life stabilizes the climate, for although the fall in global temperatures counters the sun’s increasing luminosity and stabilizes the climate, the scale of Photosynthesis increases only because of two ‘accidental’ factors, the rise and fall of the oceans and oceanic stratification. If the oceans did not rise and fall, the scale of terrestrial Photosynthesis would not change; and if oceanic stratification did not occur then the scale of marine Photosynthesis would not change either.

According to lovelock, given the current intensity of solar radiation, the Earth’s climate is at its most stable when global temperatures are around 10C i.e. during an ice age. This point of climatic stability is not, however, like a centre of gravity for all the geophysiological factors influencing the climate. On the contrary, once global temperatures move away from this point i.e. towards global warming or global cooling, the Earth’s Photosynthetic capacity reinforces these trends. If global average temperatures are rising, the scale of Photosynthesis boosts the momentum of global warming. On the other hand, if global average temperatures are falling this boosts the momentum of global cooling. Either way, the scale of Photosynthesis forces the Earth’s climate into greater instabilities. The only way that a change in the scale of Photosynthesis can be stopped from destabilizing the Earth’s climate is if it is countered by external i.e. astronomical forces or by other, more powerful, geophysiological factors.

For the bulk of the Earth’s history the most important way in which the Earth stabilized its climate has been through the Photosynthetic extraction of Carbon from the atmosphere preventing the Earth from overheating. But, there has never been an exact correlation between the sun’s increasing luminosity and the extraction of Carbon from the atmosphere. There have always been far more Photosynthesizers on Earth than was needed to extract Carbon from the atmosphere to counter increasing solar radiation. Even in the early stages of the Earth’s history, Photosynthesizers could have extracted all the Carbon from the atmosphere in a relatively short time which would have meant the Earth’s main problem would not have been global burning but global freezing, "A biosphere one hundredth as active as the one today could have removed all of the Carbon dioxide in a few million years." It was decomposers which came to the rescue and released most of the Carbon back into the atmosphere. Although there has not been a linear increase in the extraction of Carbon from the atmosphere to match the linear increase in solar radiation, Photosynthesizers and decomposers have combined to maintain climatic stability preventing the extremes of global freezing or global burning from eradicating life on Earth.

Lovelock’s theory is based on the assessment that the oscillating nature of the pleistocene ice ages are unique in comparison to the Earth’s earlier ice ages. However, one commentator has suggested this is not the case, "Although not all in one area, the burial of swamp vegetation covered a period of almost 100myears, in all of which there are not occasional thick coals but dozens, even hundreds. (They have ) "a mixed periodicity for several coal basins, involving cycles around 100,000 and 40,000 years. These correspond to the faint astronomical forcing of climate due to changes in the Earth’s rotational and orbital characteristics. The planet went again and again through cycles of glaciation and deglaciation very like those of which we are certain for the last 2.5myears.." If drury is correct, that such oscillations have existed before, then this implies that lovelock’s interpretation is wrong and that they do not indicate a fundamental instability in the Earth’s climate.

Other commentators believe the current series of ice ages didn’t start during the pleistocene period but started many millions of years earlier. Jd macdougall believes the origins of the current series of ice ages can be traced back 55-50 million years ago .. "temperatures on the earth have been dropping since early in the Eocene epoch." Macdougall believes the antarctic was formed about 35 million years ago, "The record in the rocks shows that the permanent Antarctic ice cap formed as early as about 35 million years ago, and permanent northern glaciers were present nearly three million years ago, well before the pleistocene began." However, even he admits that .. "for the past several million years the planet has been colder, on average, than it has over much of its history." The fact that the ice ages might have started a lot earlier than the quartenary period does not necessarily undermine the lovelock’s theory. Lovelock has pointed out that there was a dramatic development in the Earth’s Photosynthetic capacity when a new type of Photosynthesizer, the C4, emerged during the miocene period so the effects of the decline in atmospheric Carbon began to appear a lot earlier than the pleistocene period.

A number of commentators dispute lovelock’s assertion of an increase in tropical Rainforests during ice ages, "In the world at the height of the last glaciation, about 18,000 years ago, the global water tied up and useless in a frozen state led to arid conditions in the tropics. The tropical forests shrank to an area less than they occupied just after the last ice age and just before humans became farmers. It is not hard to see how the larger mammals of australia and madagascar with their adaptations to tropical forest living would have been pushed to the edge of extinction, and often past it, by the encroaching deserts, while the forest animals in the rest of the tropics would find themselves squeezed into shrinking refuges where scarcity might force direct competition and extinctions. The term ‘ice ages’ therefore distracts attention from the chief agent of change. The drying of the tropics may have had a much more profound effect on mammalian evolution and extinctions than the freezing of the ice sheets."; "Another general lesson of past climate is that cold, high latitudes accompany dry tropics."

Surprisingly, a gaian also disputes lovelock’s views. Bunyard states that about twenty thousand years ago .. "mile high ice sheets covered much of northern Europe and north America. Tropical forests contracted ..." He argues that during the last ice age there was .. "a much drier climate in the lower latitudes. Savannah rather than rainforest covered much of the amazon basin." If it is true that the warmer the climate the wetter it is, "When the greenhouse effect warms the Earth, it accelerates the hydrologic cycle, more water moves around in the atmosphere, and rainfall increases in many places." then the converse must hold.

Lovelock believes the reason for the succession of ice ages and interglacials during the pleistocene is that the Earth’s climate is in a highly unstable state at the end of its current stabilization system. The concentration of Carbon in the atmosphere is so low it is getting more and more difficult for Photosynthesizers to reduce the greenhouse effect to maintain an ice age. Conversely, the decreasing contribution of the greenhouse effect to global warming means the climate is far more vulnerable to even small releases of Carbon emissions: a major Forest fire or a huge volcanic eruption could trigger other geophysiological phenomena to release enough Carbon to significantly boost the greenhouse effect thus, once again, making it far more difficult maintaining an ice age. Paradoxically, the stroke of luck that enabled the scale of Photosynthesis to increase during an ice age only heightens the problem - taking more Carbon out of the atmosphere reduces the contribution made by the greenhouse effect even further.

As far as lovelock is concerned the point of climatic stability is approximately 10C i.e. when there is an ice age. Conversely, it is in an unstable and unhealthy state during inter-glacials, "Geophysiology suggests that to regulate the climate in the face of increasing heat from the sun, glacials are the normal state and the inter-glacials like now, are the pathological one." Lovelock looks upon the present inter-glacial as an aberration, "The present interglacial warm period could be regarded as a fever for gaia and that left to herself she would be relaxing into her normal, comfortable for her, ice age." "The recurrent warm spells now experienced are the pathology of a form of Planetary senescence."; "If I am right that self regulation proceeds most efficiently at glacial temperatures, then the interglacials like the present one represent some temporary failure of regulation, a fevered state of the planet for the present ecosystem. How do they come about? Active systems of regulation or control are well known to exhibit instability when close to the limit of their operating range."

Whilst for lovelock an ice age is imperative to counter increasing solar radiation, for other commentators, most of whom are deeply embedded in the current political and scientific status quo, the Earth’s current inter-glacial is ‘normal’ whilst ice ages are a frightful anomaly, "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."

Having highlighted the importance of the role played by Photosynthesis in determining the Earth’s climate over the last few aeons, it needs to be pointed out that astronomic forcing is responsible for triggering off the quartenary oscillations between glacials and interglacials. This has happened not because astronomic forces have been so strong they have over-powered the Earth’s climate regulation system but because the latter is so weak ("close to the limit of their operating range") that even minuscule astronomical changes have a considerable impact on the climate. The consequence of the increasingly feeble state of the Earth’s climate stabilization system is that the climate has become increasingly vulnerable to astronomical changes. Over the last couple of million years the Earth’s enfeebled state has enabled the minor ebbs and flows of astronomical forcing to push the climate between ice ages and inter-glacials, "That the system is stressed is evidenced by the fact that even the small additional flux of heat that occurs when the milankovich effect brings the Earth closer to the sun, is enough to destabilize the healthy glacial state and bring on the fever of an interglacial."

Some commentators believe the quartenary succession of ice ages-interglacials is due solely to changes in the Earth’s orbit around the sun. They argue that when astronomic changes cause a decrease in the solar radiation reaching the Earth this pushes the climate towards an ice age, whilst an increase in solar radiation produces interglacials. The astronomic theory of climate change implies the Earth has little responsibility for regulating its climate. Lovelock does not support this theory. Although he believes that astronomic factors currently push the climate in the direction of glacials and inter-glacials (which they are able to do because the Earth’s climate stabilization system is so unstable during the pleistocene period) he estimates they are still not powerful enough by themselves to force the climate into a glacial or inter-glacial. Astronomic factors initiate the changes but it is geophysiological changes which bring about ice ages and interglacials. Astronomical forcing provides the initial change in the direction of the climate but not the momentum, "So what causes the fever (of an interglacial period)? The short-term answer is geophysical. The milankovich effect certainly explains exactly the timing of the interglacial warm periods .. But it is an incomplete explanation on two accounts. Firstly, the change in temperature is larger than would be expected from the small change in solar heating, and secondly, there is a period in between the interglacials when the Earth is warmed by being nearer to the Sun and yet nothing happens."; "Milutin milankovich .. proposed a link between glaciations and astrophysical effects. The magnitude of these variations in solar heat received by the Earth is not enough in itself to account for the flip from glacial to interglacial, but the synchronicity between the orbital cycle and the glacial one does suggest that the milankovich effect is the trigger."; "We do not yet know the cause of the glaciations .. The magnitude of the change in warmth received from the Sun is not in itself enough to account for the range of temperature between the glacials and the inter-glacials, but it could be the trigger synchronizing the change from one state to another." This view has other supporters, "Changes in radiation receipt over the 100,000 year periods are small compared with the scale of climatic changes so that other factors operating within the Earth’s environment must have amplified the cycle’s effects." Paradoxically some commentators believe the weakness of astronomic factors is evidence that other, non-geophysiological, factors are responsible for changing the climate, "Calculations now show there simply isn’t enough energy difference in solar-insolation fluctuations to deactivate a worldwide freeze. The increased sunlight that falls on the northern glaciers when milankovitch cycles end works out to only a few watts per square meter, about the heat of a penlight."

Lovelock’s theory of climate change is thus distinct from the astronomic theory of climate change. He accepts that astronomic forcing plays a considerable role in reversing the direction of the climate but believes geophysiological factors still play the major role in shifting the climate from one extreme to the other. Changes in the scale of Photosynthesis can’t initiate changes in the direction of the climate, they can boost only the direction it is going in. The view that the scale of Photosynthesis does not trigger off changes in the direction of global warming/cooling but only boosts their momentum suggests that it is only astronomic changes which have prevented the Earth from relapsing into a global warming/cooling disaster.

In the quartenary period, the increase in the scale of Photosynthesis during glacial periods has saved the Earth from burning up because of increasing solar radiation but the price that has had to be paid for this is that the direction in which the climate moves is determined by astronomical forces. This means the Earth has been gradually losing its climate stabilization role. Astronomical forcing may be useful in pushing the climate in the direction of global cooling and thereby combating the sun’s longer term increase in solar heating, but the danger is that it can also end up pushing the climate out of an ice age and, if it then goes into an inter-glacial period, the Earth’s life support system is even more vulnerable to increasing solar radiation. The Earth’s climate stabilization forces are currently too weak to maintain a perpetual ice age and have to rely on astronomical factors to initiate changes away from increasing global burning. This is yet a further example of the current demise of the geophysiological climate regulation system. Lovelock has made a marvellous discovery about the Earth’s capability for stabilizing its own climate at a time when it is becoming increasingly ineffectual.

The climate has become increasingly unstable over the last two million years or so because the Earth has failed to establish a permanent ice age to offset long term solar heating. Ignoring the role played by humans, the problem is unlikely to have been too serious because at present whilst ice ages last for about a hundred thousand years, interglacials last only approximately 10,000 years, "Ice ages tend to last for 100,000 years. The spell between them, usually, lasts for 10,000 years." But, as these proportions are reversed, the situation would become increasingly serious for life on Earth. Lovelock believes the climatic instability caused by oscillations into, and out of, ice ages is indicative of the Earth’s need to develop a new climate stabilization system. However, humans disruption of this succession of ice ages and inter glacials makes the situation far more serious because there is now even less time for the creation of a new climate stabilization system.

* Firstly, as lovelock has argued, when all Carbon has been extracted from the atmosphere Photosynthesis would no longer be able to decrease the greenhouse effect;

* Secondly, it is possible that as the Earth’s temperature falls the scale of Photosynthesis might not increase linearly over time i.e. if the fall in the level of the Earth’s oceans does not generate more land in the tropics than is being lost under ice sheets on the amero-euro-asian continents. This would temporarily reduce the trend of global cooling - although the trend might be resumed more forcefully later if it rebounds from such temporary constraints;

* Thirdly, it is possible that as global temperatures fall there will come a point when there is no further net increase in Forested land. This would stop any further fall in the Earth’s temperature. It is possible this factor might bring about the end of the current system of climate regulation before the removal of all Carbon from the atmosphere;

* Fourthly, there might come a point when Peatbogs no longer play a role in reinforcing global cooling. This could happen for one of two reasons. On the one hand Peatbogs boost the level of atmospheric oxygen which produces fires that destroy Peatbogs, "Klinger speculates that the cycle (of Peatbogs driving down temperatures which help to further drive down temperatures) gets broken by the very success of the sedge mosses. Thus, in the equation of Carbon dioxide drawdown and the burial of organic Carbon, oxygen gets released into the atmosphere and tends slowly but surely to rise. Higher oxygen levels mean that peatlands dry out and become more susceptible to burning, causing Carbon dioxide levels to rise and large quantities of methane to be released." On the other hand, ice sheets spreading across the amero-euro-asian continents might suffocate Peatbogs triggering off global warming, "The advancing ice of the glacial period also destroys the bogs and the process therefore become self-limiting."; "Over thousands of years, the Peatbogs would extract Carbon from the atmosphere and store it, so reducing the natural greenhouse effect and driving temperatures still lower. Eventually ice sheets would cover the bogs, perhaps helping to trigger the end of the glaciation.";

* Finally, there may be a point when the Earth’s global temperature falls so low it affects the climate in the tropics thereby reducing the rate of Photosynthesis carried out by tropical Rainforests. This would decrease the extraction of Carbon from the atmosphere and thus boost the greenhouse effect.

If humans did not exist, there would currently be little Carbon to extract from the atmosphere and, as the sun’s luminosity increased, the Earth would start to burn up. A new system of climate regulation would then be needed, "Failure of the present system will not mean the death of the Planet, only a change in the method of regulation, or more probably a shift to a new stable hot state. Nobody knows what other systems for cooling will evolve." Although in the long distant future, Photosynthesis would no longer be the primary means of stabilizing the Earth’s climate, it would still be needed because Carbon would continue to be injected into the atmosphere.

The current inter-glacial period is referred to as the holocene because it is believed that the succession of ice ages during the pleistocene has now come to an end, "The ice sheets and glaciers began to retreat about 10,000 years ago. The dating of this retreat and the concept of the ‘Great Ice age’ led to the idea that the ice age had ended. The Pleistocene Epoch, the ice age epoch, had come to an end and a new epoch had begun -called the Holocene." There are a number of commentators who believe this is not correct and thus refer to the current inter-glacial as the flandrian .. "it may be that our use of the word ‘holocene’ (or ‘recent’) is premature. Most palaeoclimatologists agree that we are presently living in an interglacial, called the flandrian, and that one day (no one can say when) this will end and there will be another ice age."; "Most geologists now believe the change of name may have been premature."

The Earth’s climate is already in a state of long term instability and humans are causing further instabilities by boosting the amount of Carbon in the atmosphere and devastating the geophysiological phenomenon which, in recent times, have stabilized the climate i.e. Forests. Given that the critical point of climatic stability is currently 10C and that the climate becomes increasingly destabilized as global temperatures move further away from this point, then the present climate is in a highly unstable state. The Earth’s current average temperature is 15C - a massive 5C beyond its point of stability. If the climate continues to warm, it will not be long before global temperatures reach 18C - the temperature at which the rate of Photosynthesis starts to decline further boosting the momentum of global burning, "Terrestrial vegetation will lose its ability to regulate the climate once the average surface temperature reaches around 18C - ipcc estimates that a century from now, the Earth will have temperatures close to that critical point."

Bunyard has converted these critical temperature points into their equivalent concentrations of atmospheric Carbon. He argues, "In lovelock and kump’s model, oceanic and terrestrial regulation operate best when the concentrations (of Carbon in the atmosphere) are approximately 200ppmv. When they reach 400ppmv the algal system collapses and surface temperatures rise quickly to another equilibrium regulated by terrestrial life. If concentrations rise to 700 ppmv then terrestrial regulation collapses." In other words, climate regulation works best at 10C (when the concentration of atmospheric Carbon is approximately 200ppmv). The current concentration of atmospheric Carbon is between 370-380ppmv so, on this basis, it will be only a decade or so before the Algal system collapses and, with it, the world’s fisheries. The Earth’s climate regulation system will collapse when global temperatures reach 18C - that is, according to bunyard, when the concentration of atmospheric Carbon reaches 700 ppmv.

Lovelock warns of the threat of runaway global warming, "Such a world is inherently unstable. If a warming trend, as by the milankovitch effect, led to a decrease of land area, then increased Carbon dioxide together with the geophysiological feedback of a diminution in the area of reflective ice and snow cover would lead to a runaway rise of both temperature and Carbon dioxide.."; "Lovelock adds his own warning. "Sadly, what mostly shows up when we include gaian feedbacks is that the system will amplify the damage we are causing, rather than opposing it." One example he believes, is that vital coccolithophorids may be emitting less dms due to global warming, leading to less cloud cover and yet higher temperatures. "If we were in the usual glacial state things would not be so serious, but the earth has a fever, and what we are doing now is like shining a lamp on a feverish patient. It’s not the right thing to do." Lovelock warns against anthropogenic disruptions to an unstable climate, "Much more serious than the direct and predictable effects of adding Carbon dioxide to a stable system are the consequences of disturbing a system that is precariously balanced at the limits of stability." Gaians thus argue that, "The Planet needs to be cooled so its biological activity may increase in order to offset the slow but steady rise in solar output. Our release of Carbon dioxide and other greenhouse gases is now overriding that trend." Paradoxically, however, despite lovelock’s warnings about the instability of the current inter-glacial, the Earth's climate has been very stable throughout the flandrian.

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THREE: AN HISTORICAL SKETCH OF THE MAIN FEATURES OF THE EARTH’S STABILIZATION OF THE CLIMATE.