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What is happening to our weather?
When I first got into farming I quickly got to understand the critical connection between climate and human survival. But it took me a little longer to understand just what a delicate and unstable thing our climate is. The following is what I have learnt from the many expert people with whom I have worked over the last few years. Unlike some who seem to have a lot to say about this subject, the people that I know appear to have no axe to grind, unless it is the survival of humankind.
One prime influence on our climate is our distance from the sun but another is the nature of our atmosphere. For example our moon, which is pretty much in the same location as earth, but has virtually no atmosphere, has surface temperatures that range from minus 153degC to 134degC. At the other end of the scale our neighbour Venus, of similar size to us but with an atmosphere almost entirely made up of carbon dioxide, has a mean surface temperature of 480degC, more than hot enough to melt lead. Carbon dioxide is one of the “greenhouse gases,” so called because they trap solar energy making a climate warmer than it would have been without them.
Our planet has not always enjoyed a climate that has allowed human occupation; in fact there is really no such thing as a stable natural climate on earth. About 4600 million years ago, when the earth was formed, it was a very hot place, so hot that it took another 4200 million years for the first plants to arrive. At that stage our atmosphere, like Venus, was pretty much all carbon dioxide, and it was still far too hot for anything like humans.
Plants “breathe in” carbon dioxide, retaining the carbon within their structure while releasing the oxygen back into the atmosphere but this process reverses when they die and decompose. However some of those early plants became buried when they died and the carbon remained underground, eventually becoming coal. That meant that oxygen levels went up while carbon dioxide levels went down and as that happened the world got slightly cooler, so encouraging even more plants to grow.
Eventually, the whole landscape of the earth changed from one of virtually bare rock to lush forest and animals began to appear. Like the plants some of the animals became buried and became oil and natural gas. By these processes, over millions of years, most the carbon dioxide that was almost entirely our atmosphere became stored safely out of it, either in great forests or under the surface of the earth and the climate became even more benign.
About 3 million years ago conditions became right for humans. At first humans did not have much of an impact on the climate. They may have cut down a tree to burn, so raising carbon dioxide levels temporarily, but they generally let another grow in its place which removed it again. But, as humans became more numerous and needed bare land for growing food, they cut down the forests at a far greater rate than they could regrow. And then humans found the coal and a little later oil and burnt that as well.
Because of this releasing of massive quantities stored carbon dioxide temperatures have begun to rise quite quickly. Right now the concentration of CO2 is about 25% more than it was pre industrial revolution times and it is increasing more rapidly as time goes on. The climate changes that we have been experiencing are quite consistent with those changes.
What this means in practical terms is that, if we do not modify our ways, someone being born today is most unlikely to die in a world that resembles the one we enjoy right now, but might be heading to be one more like Venus. Another more immediate danger is the conflict that will no doubt arise as conditions deteriorate.
In the twinkling of an eye we are well on the way to undoing what nature has so painstakingly created for us over aeons, that is, the very climate and conditions that have allowed us to survive in the first place.
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