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Global warming and the greenhouse effect

There has been much publicity about Global warming and the greenhouse effect and it is really important to understand what these words mean and what effect they may have on the future of the planet.

We live as it were on a knife-edge as fart as the temperature of the planet is concerned. If the Earth was closer to the Sun the temperature at the Earth's surface would rise and if it was further away the temperature would fall.

Being too cold is as bad as being too hot. The Earth's atmosphere plays a vital part in keeping the planet at a temperature where life as we know it can exist. Take the atmosphere away and we would have temperatures like those on the Moon which has no atmosphere to 'protect' it. During the lunar night the equatorial temperature on the Moon's surface falls to -184 oC while at mid- day it can rise to as much as 101 oC! Imagine these temperatures on the Earth and you can see why the atmosphere is so important. It is changes in our atmosphere that are of so much concern at present.

Venus is a planet much the same size as our Earth but only about two thirds of the distance from the Sun. Because of this you would expect the surface temperature of Venus to be higher than that on Earth. However Venus is covered with a thick atmosphere and it may surprise you to find that the average temperature at the surface of the planet is a staggering 467 oC! Over 96% of this atmosphere is carbon dioxide with about 3% of nitrogen and minute traces of water vapour, oxygen, carbon monoxide, helium, and sulphur dioxide.

Venus is an example of an extreme example of global warming and the greenhouse effect.

So what is the greenhouse effect and how can it contribute to global warming and should we worry if it does?

During the day the radiation from the Sun falls on the surface of the Earth the energy at ground level is roughly 800 J per second on every square metre of the Earth's surface. This radiation is spread over the wide range of wavelengths but because the Sun is a very hot body (the surface of the Sun has a temperature of about 6000 oC) a lot of this radiation is of fairly short wavelength. The Earth warms up so that the ground reaches say 20 oC at the latitude of London. The ground the radiates some of this energy back into space but because the surface of the Earth is so much colder than the surface of the Sun this radiation has a much longer wavelength much of it in the infra red region of the spectrum. It is this balance between incoming radiation from the Sun and outgoing radiation from the Earth that keeps the surface temperature of the planet stable and allows life to continue. Too much radiation escaping from the Earth and we would freeze, too little and we would 'fry'! The atmosphere absorbs some of this outgoing radiation and so helps to keep the planet 'warm'.

This is where the greenhouse effect comes in. The glass of a greenhouse acts just like the Earth's atmosphere allowing short wavelength radiation in from the Sun but preventing some of the longer wavelength radiation from the ground from leaving so the inside of the greenhouse warms up.

Not all gases absorb infrared. The most important absorbers are the so- called "Greenhouse gases" such as carbon dioxide, water vapour, methane, sulphur dioxide, nitrous oxide and the chlorofluorocarbons (CFCs). At present some 100 000 million tons of carbon dioxide every year are produced from biological processes.

However people are now adding a further 5000 million tons due to emissions from factories, cars and aircraft. This massive extra amount of pollution is absorbing more of the outgoing radiation and so that planet is warming up global warming. In Britain we emit just over three tons of greenhouse gases per person per year as compared with nearly seven tons per person per year by the people of the USA.

The destruction of the rain forests removes a most important absorber of carbon dioxide - trees.

The results of global warming may be a radical change in the climate of our planet and steps must be taken to prevent this. The raising of the mean sea level due to the melting of the south polar ice cap is just one effect, and this would result not only in the flooding of many major cities that are sited at "sea level" but also the disappearance of low lying islands.

The following two photographs show the change in the Upsala glacier in Patagonia. The first was taken in 1928 and the second in 2004.

In case you think these are a bit remote from your experience have a look at the photograph that I took of the Athabasca Glacier in British Colombia, Canada in 2008. Notice the sign showing where the ice was in 1992 - only sixteen years earlier. See how far it has receeded - we really do need to be concerned!

Storms and unseasonable temperatures have also been predicted.

If you want to see the effect of global warming vist the following site: Glaciers - global warming

What can we do?
(a) Use nuclear power stations or renewable energy sources as an alternative to coal burning power stations.
(b) Attempt to reduce the carbon dioxide emissions from all forms of transport.
(c) Try to preserve the forests of the planet especially the equatorial rain forests
(d) Attempt to recycle as much waste as possible by supporting recycling programmes

It remains to be seen just how accurate these prophecies are!

Concentrations of carbon dioxide in the atmosphere are naturally regulated by a number of processes known as the "carbon cycle". This is shown in the following diagram. You can see that the balance of carbon in our atmosphere has been upset by the 6.3 billion tonnes released due to the burning of fossil fuels.

Further topics to consider

Banning diesel cars
Using hydrogen as a fuel for all transport
Reducing air travel
The improvement in air quality in cities such as Beijing during the corona virus pandemic of 2020.

© Keith Gibbs 2020