The climate of the Earth is always changing. In the past it has altered as a result of natural causes (think oceans, atmosphere, orbits and volcanoes). Nowadays the term “climate change” is generally used when referring to changes in our climate that have occurred over the last 100 years or so. The climate changes we've seen over recent years and those that are predicted over the remainder of this century are thought to be mainly as a result of the influence of human behaviour rather than due to natural changes.

For more than 200 years we have been burning increasing amounts of fossil fuels like coal, oil and gas, primarily to generate heat, power and light. However, what we didn’t know until relatively recently was that along the way we have been creating a bit of a problem. This is because fossil fuels contain carbon and when we burn them carbon dioxide (CO2) is released. Too much CO2 is not so good for the climate. So here’s some commonly used terminology explaining why…

The Greenhouse effect

The “greenhouse effect” is very important when we talk about man-made climate change. It is a natural effect. A thin layer of gases (what we term greenhouse gases) in the upper atmosphere act naturally to keep the Earth at a habitable temperature by trapping some heat (primarily from the sun) – a bit like a duvet. The thicker the layer, the warmer the duvet. The six main greenhouse gases, often termed the ‘basket of 6’, are:

• Carbon dioxide (CO2);
• Methane (CH4);
• Nitrous oxide (N2O);
• Hydrofluorocarbons (HFCs);
• Perfluorocarbons (PFCs); and
• Sulphur hexafluoride (SF6)

CO2 is one of the biggest constituents of this layer and scientists have figured out that the CO2 content thus has a big influence on the climate.

Global Warming

It is the extra greenhouse gases (primarily CO2) that we have released over the last 200 years and continue to release (through power stations, cars and planes for example) which are now known to pose the problem. Our activities have bulked up the duvet by approximately one third of it’s volume and  too much heat is now trapped in the system – thus the term “global warming”.
This warming (due to past emissions) is already stressing the Earth’s climatic system creating more extreme weather, melting of the ice caps, floods and droughts. It’s a bit like leaving a winter weight duvet on the bed in summer – things are going to get pretty uncomfortable underneath…

Carbon Sinks

The Earth has a number of natural carbon “sinks” and it is estimated that these have actually absorbed more than half of C02 emissions over the last 200 years. This has mainly occurred in oceans but also on land through the soil and forests.

Scientists believe, however, that excess levels of CO2 can lead to these carbon sinks becoming less effective and that planting more trees is not enough to mitigate global warming. There are other side effects too. Higher CO2 leads oceans to become more acidic – enough to bleach coral the world over.

Feedback Effects

Added to this there are so-called “feedback effects” in climate change.

An example of negative feedback is the “Ice Albedo” Effect. Ice reflects solar radiation back into the atmosphere whereas water absorbs solar radiation and gets warmer (like the Solent in summer – not that we’ve noticed though!). So as the Earth gets warmer and more ice melts there is less ice to reflect radiation and a greater expanse of water to absorb radiation. This magnifies the global warming effect.

In simple terms...

The Earth’s natural systems don’t grow in the same way as our activities on Earth. Thus we are putting stress on these systems. One of the ways this is manifested is in man-made climate change.

Want to find out more and see some nice diagrams?

Here are some useful links:

More on climate change and the greenhouse effect from BBC Weather:

http://news.bbc.co.uk/weather/hi/climate

Several websites have very good descriptions of the different kinds of carbon sinks and mention some of the problems such as acidification of the ocean:
http://www.fern.org/campaign/carbon-trading/what-are-carbon-sinks
http://www.nerc.ac.uk/research/issues/climatechange/carbon.asp
http://www.ieta.org/ieta/www/pages/index.php?IdSitePage=124

An explanation of the different feedback effects, including the Albedo Effect, can be found on the website of a local NGO based in Eastleigh – carbon-info.org
http://www.carbon-info.org/carboninfo_029.htm

A greenhouse effect simulators:
http://warmcast.blogspot.com/

http://phet.colorado.edu/en/simulation/greenhouse

Lots more on climate change from climate change scientists at Real Climate. The linked page below allows you to adapt your reading to your existing level of knowledge so don’t be intimidated by the word scientist!

http://www.realclimate.org/index.php/archives/2007/05/start-here/

And finally myths…
No not urban myths! You can find them elsewhere on the web... We are talking climate change myths and controversies.

Rather then drone on about these we suggest you look at the guide produced by the Royal Society at:

http://royalsociety.org/Climate-change-controversies-a-simple-guide/