If you use a computer and can read this newsletter, you'll have no doubt heard about global warming.

You've probably heard different stories about what could be causing global warming and what it'll do to us, ranging from the effect that CFC gases have on the ozone layer to global warming being nothing more than a natural occurrence as our planet continues to emerge from the last "Little Ice Age". But just how much do you know about either of these subjects? And how are they affecting you?

The Effect of CFC Gases

First of all, in order to understand how CFC gases might be affecting the ozone layer, it's important to understand what the ozone layer actually is.

Ozone is a form of oxygen, one of three forms that can be found in our Earths atmosphere. Without ozone, our planet would be a very different place because it shields us all against harmful radiation from the Sun (ultraviolet (UV) radiation), life—or at least, life as we know it—wouldn't exist.

If the ozone layer breaks down, UV rays will be able to reach the Earth's surface, with the result being a dramatic increase in the number of cases of skin cancer and eye cataracts.

The affect on the food chain could also be disastrous. Because UV rays kill plankton in the sea, the fish and whales that live off of plankton would eventually starve and disappear. This would then affect the next link in the chain - those creatures that live off of fish - and so it would continue throughout the chain.

It's just as well we're not dependent on meat for survival - a few carrots, a handful of potatoes and a cabbage a day should suffice.

Anyway, let's move on to look at how CFC gases affect the ozone layer. Those who did chemistry at school will know what this is all about.

Any compound that contains chlorine will lead to the decrease in natural ozone levels by removing one oxygen atom from the ozone molecule, thus converting it into oxygen.

As you can imagine, there's no natural occurrence of such compounds in the upper atmosphere, but vast amounts have built up over time due to our increased use of man-made chlorine based compounds, of which CFCs (Chlorofluorocarbons) are the most common.

When we first starting using CFCs back in the 1930s—primarily to cool fridges—we thought they were safe. When you don't know better, you can't be blamed for making a mistake, can you?

We know now that CFCs rise from the surface of the Earth and into the stratosphere where they're bombarded by UV light. We know that this releases the chlorine atoms that react with the ozone molecules and we know that before long, ozone becomes oxygen and we're left with less protection.

While most countries have banned the usage of CFCs in aerosols, these gases are still found in refrigerators and in some types of foam packaging.

How much this will affect our generation is uncertain - it depends entirely on how quickly the ozone layer is depleted - but what is certain is that it will have an effect on future generations.

The selections we make today will affect the future of the planet. It's up to us to make the right ones. What's great is that we have the knowledge to make the choices that will give our descendants the chance of a good life too.

Is global warming all about the ozone layer though?

There is a theory that doesn't involve the ozone layer at all, and that's that our planet is becoming warmer because oceanic tides are driving climate change.

Evidently, the coldest water found at the deepest points of the ocean is generally transported to the surface by tides that cause the water to mix, thus lowering the temperatures in the air. But thanks to changes in the way the tides work, less cold water is mixing with the warmer upper layers of water, with the result being warmer periods on Earth.

According to scientists at Scripps Institution of Oceanography- part of the University of California, the way the ocean deals with cold water is controlled by the alignment of the sun, moon and earth. Right now we're experiencing less and less cold water being forced to the surface, so the planet is heading for its warmest peak.

When will this happen? Well, the last "Little Ice Age" was during the 15th century, when the Vikings perished on Greenland after having enjoyed a temperate climate there during the 14th century. This was about 1,800 years after the previous "Little Ice Age" of 1300 AD. With known hot periods also being spaced at about 1,800 years apart, it's pretty safe to assume that the next hot peak would have been around the 30th century- but due to the depletion of the ozone layer, this will have changed, but by how much? Your guess is as good as anybody's.

How hot will it be? Unfortunately it appears that the answer to that is also anybody's guess. What is for sure, however, is that it will be too hot to sustain life as we know it long before the Earth's temperature reaches its peak.

If the answer really is a matter of the inevitable, the least we should do is get out there and enjoy the good weather while we have it. Just make sure you remember to wear your sunscreen.

Copyright (c) 2008 Mervyn Rees