It seems that the usual state of Earth is for a climate warmer than the present one. The Earth has been ice free at the poles for most of its existence. Astrophysicist John Gribbin in Science A History says: "The now well understood... geological record tells us that the natural state of the Earth throughout most of its long history has been completely ice free (except for the tops of high mountains)... But occasionally, as the scars of ancient glaciations reveal, at intervals separated by hundreds of millions of years, one or other hemisphere is plunged into a period of cold lasting for several million years" (P481). There was an "Ice Epoch" 250 million years ago during the Permian Period, which lasted 20 million years. Then there were 200 million years of warmth, followed by gradual cooling which set in around 55 million years ago. By 10 million years ago the glaciers had returned, first in the mountains of Alaska, and soon afterwards in Antarctica. The north pole then cooled, ringed as it was by continents, which prevented warm currents melting the ice. A pattern of alternating ice ages with warm interglacials then followed, beginning about 3.6 million years ago, just at the time when mankind's ancestors were living in Africa's Rift Valley.
For the last 400,000 years the climate has followed a broadly regular pattern. There has been a succession of ice ages, each of which has ended rapidly, to be followed by a warm interglacial period lasting about 10,000 years. During the most recent ice age, and especially during its latter stages, the weather could change dramatically and quickly. 15,000 years ago Greenland temperatures varied by up to ten degrees centigrade in a few years.
With the ending of the last ice age, about 15,000 years ago, temperatures increased and steadied, and then for a short while plunged again.This might have been due to huge amounts of fresh water from melting glaciers disrupting North Atlantic currents, though there is some debate. Following this severe but relatively short lived event, temperatures increased and climate entered the extraordinarily steady state in which it has continued for the last ten thousand years. Of course there have been some fluctuations. 6000 years ago Britain was warm enough for trees to grow up to three hundred meters above the present timberline. There have been times of lower temperature, such as the so-called Little Ice Age which took place in Western Europe roughly between the sixteenth and nineteenth centuries. But relatively speaking temperatures have been remarkably stable. It could be suggested that the development of the modern world has been a result of this benign situation. A stable climate was needed for human civilisation to develop. This of course brings us round to current concerns about recent increases in average temperature. It seems that temperatures rose in the late twentieth century at a rate which is unprecedented for at least the last thousand years.
As a non expert I am not able to comment on man's role in climate change, or how the climate will change. It is only clear how we have viewed these things up until now.
Looked at historically it is clear that mankind has deeply ingrained preconceptions about the weather and its changes. Humanity has always tended to see unhelpful changes in the weather as some kind of judgment on itself. Flood myths which occur in many cultures illustrate the way people tend to blame climate changes on themselves and their "sins". The Epic of Gilgamesh, one of the earliest recorded flood myths, tells of the King of Uruk, ruling a kingdom on the Euphrates. A great flood ordered by the gods destroys Uruk. The gods decide to save only the king and his wife. The king is warned to build a boat, which is loaded with gold, silver and representatives of all the world's animals. Flooding lasts seven days, and Uruk's ordeal only ends when his boat lodges on a mountain top, and birds fly out to find dry land. This story dates to about 4700 years ago, and predates Genesis by at least a thousand years, a story which of course contains a very similar account of the gods punishing mankind by flooding.
It is possible that these flood myths have their roots in a massive flooding event that took place 8,400 years ago. Melt water from glaciers over what is now Canada had formed vast lakes. Eventually ice dams holding back the water failed, and it is estimated that 163,000 square kilometers of water poured through the Hudson Strait into the Labrador Sea. People at this time would have tended to live near the sea or along river estuaries where they could supplement their diet with fish. On gently sloping continental shelves the sea could have immediately advanced a kilometer inland, and over the following year advances might have reached ten kilometers. It is also possible that rising waters breached a small strip of land running between the Mediterranean and a lake we now call the Black Sea, and in doing so inundated an important area of human civilisation. Within a few years 100,000 square kilometers of land disappeared.
All of these dramatic events were the result of climate changes at the end of the last ice age, which were not influenced by man. And yet people, self centred as always, saw these events as a judgment on themselves. This view of the weather has endured throughout human history. Former British government climate scientist William Burroughs describes in his book Climate Change In Prehistory the attitude to weather in ancient Egypt. Egypt enjoyed a very stable climate, with the huge Nile watershed tending to iron out fluctuation. The main job of Egyptian priests was to intercede with the gods to maintain this stability, and to ensure regular flooding of the Nile which re-invigorated the soil every year. If flooding did not happen, then it was the priests' fault. If changes to drier weather were dramatic then priests were lucky to escape with their lives. This view of weather as a judgment continued, cropping up frequently in history. Terry Jones in Who Murdered Chaucer describes how one unfortunate peasant pointed out that once the fearsome Henry IV came to the throne it seemed to rain more. Henry had the poor man executed, the king resenting, and fearing, a suggestion of judgment by God expressed through weather. In more recent times, the nineteenth century saw the New York Tribune running a story about inhabitants of a Mexican town "which had issued an edict saying that if rain did not return in eight days, they would not go to mass or say prayers; if after another eight days adequate rain had not fallen they would tear down the churches and chapels...; and if relief had not arrived after a further eight days all priests, friars, nuns and saints would be beheaded. Fortunately for the Church heavy rain fell within four days " (Climate Change in Prehistory P 247). Today we don't tend to mention angry gods directly, but there is often a moral element to discussion of climate change. It is suggested that mankind has been greedy and profligate with the earth's resources and is paying the price. There also seems to be a replacement for the angry gods of times gone by in the form of Gaia, the embodiment of a self regulating earth. Gaia is sometimes portrayed as being angry with mankind, and will pass sentence by way of climatic disaster and wide spread flooding. The most financially successful film of all time, Avatar (2009) is an ecological fable which sets contemporary concerns on the planet of Pandora. Pandora is presided over by a nature god in the shape of a tree. And of course in the end this god turns on the mining company which threatens to destroy the natural world of Pandora. In many ways age old religious impulses have found a new home in global warming concerns.
Perhaps once again we are just reading our own concerns into the weather as we always have, thinking gods are interested in us, while the earth actually goes on its own way. In 1789 Gilbert White published his Natural History of Selborne, a book which many people see as founding the discipline of ecology. One of the many natural phenomena so wonderfully described in this book is the 1783 volcanic eruption in Norway which caused weather changes throughout Europe. There were tremendous thunder storms, a smoky haze filled the air, and the sun turned red in the sky. People began to fear judgment in these events. White wrote: "Milton's noble simile of the sun in his first book of Paradise Lost frequently occurred in my mind; and it is indeed particularly applicable, because towards the end it alludes to a superstitious kind of dread with which the minds of men are always impressed by such strange and unusual phenomena" (Letter LXV Natural History of Selborne). A superstitious kind of dread about the weather is very firmly ingrained in people. It would be unwise to think that we are now so enlightened that such instinctive reactions to the world around us have suddenly disappeared. At the end of 2009 this point was illustrated rather graphically in a series of leaked e-mails from a climate research department at the University of East Anglia. These e-mails cast doubt on objectivity of research carried out at the department. Professor Mike Hulme a reasearcher at East Anglia, and author of Why We Disagree About Climate Change wrote: "The attitudes revealed in the e-mails do not look good. The tribalism that some of the leaked e-mails display is something more usually associated with social organisation within primitive cultures; it is not attractive when we find it at work within science" (quoted in The Sunday Times November 29th 2009). Fears of judgment by gods, and self denying instincts seen in religious movements such as puritanism are part of the picture. This combination of old instincts and new science is perhaps part of the challenge we face in dealing with climate change rationally.
So if mankind has characteristically looked upon weather in terms of judgment, I'll conclude by briefly thinking about the sins that are being judged. Pollution of the environment is the modern sin, and it goes without saying that this problem is real. However, mankind is not the first "polluter" of the Earth. History shows that life and the atmosphere have always acted together, and atmospheric gases are an expression of life on the planet. It could be said that the greatest pollution event in history took place many millions of years ago. Bacteria of the ancient Earth synthesized sugar and cell-building carbon compounds from carbon dioxide and hydrogen using sunlight as energy. Hydrogen became scarce, so bacteria evolved a way of deriving hydrogen from water, with oxygen as a toxic by-product. Initially oxygen was absorbed, reacting with abundant metals and gases. These reservoirs absorbing excess oxygen were eventually exhausted and oxygen quickly built up in the atmosphere. The 2001 IPCC report suggests that in recent history carbon dioxide concentration in the atmosphere has increased from 0.0365% to 0.0452%. Compare this with the oxygen pollution crises when atmospheric oxygen rapidly increased from 0.0001% to 21%. Oxygen was highly toxic to life on ancient Earth, and much of life on Earth was immediately wiped out. A display at the Evolution House at Kew Gardens claims that ancient microbes were producing "vital" oxygen for the atmosphere. How kind we might think. In fact we are looking at the situation from our oxygen breathing perspective. At the time oxygen was the worst of pollutants, and a period of acute crisis ensued. This only ended when bacteria eventually evolved ways to exploit oxygen, consuming it for energy. And indeed with oxygen in the atmosphere more energetic creatures could evolve. As oxygen breathing creatures ourselves we are descended from those survivors of the oxygen pollution crisis. This story could be very sobering, in that it shows how dramatically the atmosphere is influenced by life on the planet. On the other hand the oxygen pollution crisis puts into perspective our own importance, which may not be what we think it is. On this important matter history suggests that we are likely to respond emotionally rather than logically, overestimating our own importance. Unfortunately the issue of climate change combines human ability in science with much older human fears and superstitions.
To explore the issues raised here why not visit the Met Office in Exeter, where there is a library and archive, open to everyone, Monday to Friday. To explore issues of conservation visit the Eden Project in Cornwall, or the Royal Botanic Gardens at Kew in Richmond and Wakehurst Place in West Sussex. The Botanic Gardens once worked to support the agriculture of Empire. Now they have found a new role in conservation research. The Eden Project, as a modern botanical garden, was conceived with the aim of researching conservation problems, and offering accessible education about them.
For information on our changing cultural attitudes to nature see pages on William Wordsworth, and John Keats, and our Nottingham Castle page which has an article on the changing nature of the Robin Hood legend.