I have no expertise in environmental science, and have never made an intensive study. I realise that what I write here is so simple as to be taught to a six year old. But there is a reason I write it.

I am however trained as a historian. That mankind has changed the levels of carbon dioxide in the atmosphere is indubitable from a moment’s consideration of the evidence.

Early man lived in an earth covered by vast forest. Cultivation brought a cutting down of forest for clearings. Industrial development brought a cutting down of forests for fuel and raw material. We know this for certain because the process continued into historic times, and has never stopped but simply spread into lesser developed parts of the world, and because of the unlimited numbers of tree throws discovered by archaeologists in areas of prehistoric settlement.

The burning of the trees released carbon dioxide, but this process was greatly accelerated by the industrial revolution, where the start of intensive use of fossil fuels released the stored carbon dioxide of millennia. At the same time, of course, the destruction of the forests reduced the capacity to absorb carbon dioxide and replenish oxygen.

The Earth is big, but not that big. I’ve been round it a few times. The incredible scale is of human activity. It is impossible for an honest rational man to believe that the destruction of the forests and burning of fossile fuels on an ever accelerating scale has not had an effect on the atmosphere. Carbon dioxide is of course not the only pollutant involved.

Now I do not claim to understand the complex science of the interaction between man made atmospheric change and the natural processes of climate change. But plainly, as we change the atmosphere it is going to have some effect on the movement of gases and vapours within the atmosphere, which we call weather, and might perfectly well affect the extent to which the atmosphere absorbs or reflects energy from the sun.

I doubt that the processes are fully understood. But the argument seems to me unanswerable that mankind should seek to minimise its effect on the environment that bred us, for obvious reasons of self preservation.

We should also seek to reduce the astonishing rate at which we squander non-renewable resources. I view most of the opposition to the Copenhagen process as missing the point entirely – be it from the ultra-rich fossil fuels lobbies, scientific dissidents [I don’t despise them; all accepted science was once dissidence, including global warming], those who think anything agreed by governments must be a plot against us, or those who just want to keep on personally enjoying the fruits of untramelled consumption. The point they miss entirely is that we should stop polluting anyway.

I can’t say I fully support the Copenhagen process because it is too timid, the “cuts” offered by the US are derisory, and the oil producers should also be paying much more to the developing world. Carbon trading and its derivatives show we have still, despite the banking collapse. not learnt that inventive greed is not the best motivator.

But thirty years ago I never thought we would have this much agreement by governments to an environmental agenda. The broad direction is better, and Copenhagen must succeed to keep the dynamic going.