The Earth’s climate is varied and has always changed, archaeology shows that the Sahara was not desert but grassland just 6,000 years ago. At about the same time, Devon was too cold for oak trees. Some people wonder why it is such a hot (pun intended) topic today.
As far as we know, our planet is the only one in the Solar System to support life. This is because our atmosphere moderates the solar radiation and keeps much of the surface at a temperature where life can exist. The planet Mercury has no atmosphere to do the same; daytime temperatures there soar to 800o, but it plunges to -330o at night. If the atmosphere is too dense it is like a winter duvet in summer, the planet retains too much heat. Venus is further from the Sun than Mercury but its very dense atmosphere keeps most of the planet at about 400o.
Rather than a blanket, this phenomenon is sometimes called the greenhouse effect. Inside a greenhouse it is warm during the day because much of the Sun’s energy comes in as light but converts to heat energy which is trapped by the glass. The atmospheric greenhouse effect is not a new idea. 160 years ago, physicists Eunice Foote and John Tyndall, working separately, showed that carbon dioxide and water vapour played an important part in trapping energy. Analysis of air bubbles trapped in the ice caps shows that the amount of carbon dioxide in the atmosphere has increased since the industrial revolution. It is now at the highest level since the last Ice Age.
In 1896, Svante Arrhenius calculated the temperature change that would be linked to changes in atmospheric carbon dioxide. The atmosphere is a complex system and Arrhenius’ calculations have been updated and refined over the years. A further problem is that a warmer atmosphere will hold more water vapour which increases the effect. We now know that other gases such as methane also play a part, but the basic principle is well established, if you increase carbon dioxide, the atmosphere will warm.
As this has always happened, some people say it doesn’t matter, 2o isn’t much, why the fuss? That figure is a worldwide average, some places will heat up much more, other places might cool down. Devon has mild winters because of warm ocean currents. Arctic warming and the melting icecap might change the ocean currents and Devon could experience winters like the North Sea coast in future.
Two current problems are the speed of change and the growth of human population. Oak trees became established in Britain through natural migration because our treescape adapted to a slow process. The climate is changing at a faster rate now than at any time since the meteor strike 66 million years ago which precipitated a huge global temperature drop that wiped out most of the Earth’s species.
As the land-based ice caps warm, their melt water enters the ocean and global sea level will rise. Sea levels have varied across geological time. The difference now is that many world cities have been built on the coast. People complain that governments are forcing them to change their lifestyles, the reality is that nature will force much more significant changes if things carry on as they are.
Climate change has always been with us, but humans are speeding up the change. Global action is needed but we can play a part. No single act will affect climate change but, if enough people do something individually, many small actions will have a large impact which is the principle behind the environmental work of the Sid Valley Biodiversity Group. We will be collecting climate change pledges at our stall in the parish church on October 16. Please come along.
This article just skates on the surface of this very important issue, do find out more about climate change, but you have to be careful. There is a lot of misleading information available, cross check anything you read, including this article.