Climate Change – an ancient perspective

 

The whole subject of climate change is not only topical and emotive, but also contested, as anyone who has read anything about it over the last ten years or so will know. Over the last 30 years scientists taking the Global Warming view have gradually won the argument in the scientific community, and therefore in the public domain too. The IPCC has become very powerful, intellectually, and the near-hysteria over the COP26 recently confirmed that the whole topic is now at the forefront of public consciousness.

I have, as readers of this blog will know, been very impressed with Prince William's Earthshot prize, and with his and David Attenborough’s excellent series of TV documentaries on the five areas we need to address in order to save the planet from environmental destruction. Only one of these five areas concerned climate change, the others ranging from re-wilding and dealing with waste to cleaning up the oceans. All are connected, and all need to be addressed. I do not have any problem with the idea that we should limit or turn our backs on fossil fuels, develop sustainable energy and so on; I have had solar PV panels on my house for more than ten years, and solar thermal heating hot water long before that. I support wind and wave turbines and new hydrogen-fuel technologies for vehicles, and so on. But I think we need to retain a sense of perspective. If we clean up the oceans, re-wild and reforest areas of environmental degradation, clear up waste (especially plastic and toxic materials) and give the planet a chance to recover, Earth’s own carbon cycle will deal with the excess carbon dioxide more effectively than we can – though of course we should lower emissions as far as possible to help with this, and to give the planet more time.

The purpose of the following whistlestop tour of geological time is merely to give that perspective. The world has been both much hotter and much colder than it is now, and no doubt will be again. Hotter and colder periods undoubtedly have profound implications for human civilizations, and we must face the fact that all abilities as human beings may be required to allow us to continue to live on the planet successfully. We must also face the fact that we have, over the Holocene period (roughly the last 10,000 years), been too successful, to the detriment of other species and the environment. We have come to believe that we are the most important species and can have things all our own way. Only recently has it begun to dawn on us that in fact all of creation is necessary for any species, including our own, to survive and flourish. We are all in this together, and unless we take steps to include all those other flora and fauna in our calculations, we shall all die together.

Over the millions of years after life was first seen on this planet, there have been periods of great warmth and period of great cold. Scientists study these via ice cores and mud cores, drilling deep to find deposits from ancient periods. The best evidence is found where a continuous core can be sampled, as for example in China where the SK Project is drilling more than 7000 metres deep. Their conclusions are of course a matter of interpretation, but broadly most paleoclimate scientists agree about the general trends. Around 145 million years ago, in the Cretaceous period, the planet was in the last so-called greenhouse period, when carbon dioxide levels in the atmosphere were high, and the climate was very warm. Dinosaurs walked the earth at this point, and continued to do so for another 80 years. Their extinction probably resulted from the catastrophic asteroid that landed 65 million years ago, creating a relatively short-lived cooling period which they were not able to adapt quickly enough to survive. Then, between 40 and 34 million years ago, the earth experienced a great cooling, in which Antarctica went from a region of extensive forests, in the Eocene, to the land of ice sheets that we know today. There have been shifts since then, but nothing as immense. Over the past million years, we have seen a number of ice ages, which occur about every 100,000 years – a time scale that suggests we are in fact overdue for another one. No one is quite sure what causes these, or what sets off the regular shift from the interglacial periods that can be quite warm (for example, about 200,000 years ago there were hippopotamuses in London) to the classic cold dry periods we refer to as ice ages, when ice sheets covered polar areas as far south as mainland Europe. Oscillations and minor wobbles in the Earth’s orbit and rotation seem to trigger these episodes, but there is also some evidence that carbon dioxide levels in the oceans were high during the ice ages, and variations in Antarctic winds prevented the process that normally releases CO2 to the atmosphere when the ocean concentration is high. This locking-in process kept atmospheric CO2 low and allowed the climate to cool. How much warming climates themselves affect these winds, and might be part of the Earth’s climate control mechanisms, is not clear. And of course no one knows what effect atmospheric and marine pollution might have on these mechanisms. But it seems clear that great variation in climate is normal for our planet.

If this is so, the task of species of all kinds, including our own Homo ?Sapiens, is primarily to adapt. We can clean up the oceans, re-wild and reforest the continents, remove the toxic waste of decades that is poisoning the world, and lower our own carbon dioxide emissions – all of which will help to undo the damage we have already done. But we will still need to adapt, using all our technological and innovative abilities, in order to survive. The idea that lowering carbon emissions will on its own cure all our problems is pie in the sky, and reputable scientists and governments have no business promoting it. The picture is much more complicated than that, in both directions – another ice age may occur imminently, for example, and all our fears of global warming will have been for nothing. But that is not an argument for doing nothing or dragging our feet on environmental matters. There is too much to do, and too much at stake.