How to predict the future climate of the planet

Predicting climate change in general terms must be the one of the hardest things for climate scientists to do. You need massive computer processing power, huge amounts of data and most importantly some reasonably accurate assumptions upon which to base your predictions. With these tools you can do one of the hardest things in your job description – predict general climate trends in the future.

Money can buy all the processing power you need and as a climate scientist you can get the money if you have a compelling enough story to tell. If you can prevent the planet from being destroyed (or persuade people that you can) then you have a compelling story to attract taxpayers’ money from the government.

Climate data has been collected for many places for several centuries. It is expanded each day with more people measuring more temperatures in an ever increasing variety of places, from towns to small fields, from mountain tops to the bottom of deep seas and thousands of metres above mean sea level.

In addition to actual real time measurements all sorts of other things are being measured to help build up the climate change data. Ice compacted for hundreds of thousands of years can be extracted and small pockets of air trapped in the ice can be analysed for greenhouse gases. Trees rings can be counted and measured and ancient pollen can be found and studied. Yes there is a great deal of data out there and if we look hard enough we can extract layers of data. In fact there is so much data that you need to compile data about the data.

You need to make assumptions. As far as assumptions are concerned you can factor in various climate theories. The most widely accepted amongst scientists is the theory of global warming by manmade greenhouses gases. So many find this persuasive, so many now in fact that even the politicians believe in anthropogenic climate change now. In some quarters this theory is being treated as a religion.

Scientific theories make poor religions because religion requires belief and scientific theories require disbelief. When a theory is disbelieved it either ends up proved or discarded. With religious belief there is no requirement to prove that the belief is true.

If you do not like the concept of anthropogenic climate change there are others. I must admit that I do think that it is probably true and if I went into a bar and had to order one climate change theory I would order the anthropogenic theory of global warming. All the theories have been around for roughly the same length of time, give or take a decade. Greenhouse gas global warming makes sense to me, but I do not believe it is the only influence on our climate but I do believe that it is the faster driver of global warming. I could be wrong. I devoutly hope that I am but fear that I am probably right.

If human made greenhouse gas changes the climate theory is not to your taste, then you can choose from a number of other climate theories that may suit you better. You can believe that sunspots influence climate and change the climate in a way that makes the climate colder where there are fewer sunspots. You can believe that the reversal of polarity changes the climate and makes it cooler. There is a theory centred on magnetism. You can believe that from time to time a huge asteroid crashes into the earth and the dust emitted from the crash fills the atmosphere with dust and that prevents light from warming the earth, thus cooling it. You can believe that aliens squirt special rays at the earth through green jelly tentacles and the rays heat us up from time to time as part of an inter-stellar multi dimensional heat chess game.

These are all very respectable theories apart from the one about aliens – I made that up.  These theories are all credible and need to be examined. For example sun spots might well create climate changes and be the sole influence of global warming and cooling – no one knows for sure but then again we know so very little for sure. If you want you can read about most of these theories on these post using the blog search facility.

It is likely that all the respectable theories play some part in climate change. That means you before you click “start” on your computer you must to attach appropriate weight to each theory and feed that theory and its weighting and individual time frame into your computer model.

So having chosen your poison (or cocktail of poisons) you have to superimpose the known and estimated effects of the poisons on the planet Earth. Now Earth is not a simple or stable environment. It is a roughly spherical object that is subject to radiation from the outside while having a hot core that emits heat from time to time through the surface. The earth is covered with deep oceans, shallow seas, hills and mountains of a diverse nature.

Each physical feature on our planet and each place has its own heat or climatic characteristics so your model must take these into account and also allow for the “knock on” effect which happens when one region becomes hotter or cooler or drier or wetter than its neighbours. You must also try to predict how your model will cover the changes on the known climate influences that we get from ocean currents, like the Gulf Stream, and weather events like El Nino.

Then you have to make assumptions for human population growth and the way in which that will affect the climate, and then make assumptions about economic growth; it is all very well having the Kaya Identity but economists cannot even predict how growth will occur over an short economic cycle so what assumptions can you as a climate scientist make for your modelling with any degree of certainty?

It is quite astonishing that in these circumstances anyone thinks that they can model future climates with any success at all. It is perhaps even more astonishing to understand why anyone gets paid to do it. That is why we cannot expect to have any faith in predictions of climate scientists about the future climate that we and our descendants will enjoy or suffer. However, that does not mean that the money spent on climate research is wasted or pointless – quite the reverse in fact. I shall explain why in tomorrow’s post.

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