Believe it or not, global warming is not a modern event. Throughout the Earth's history, climate graphs have shown that the temperature has increased and decreased continuously, the difference today being the speed at which the warming is happening. However, what we need to focus on for the GCSE is the rapid global warming that is happening today (often incorrectly referred to as Climate Change), its causes, consequences and ways in which it can be minimised.
Okay, so you've heard about in the news millions of times. But what is actually causing global warming?
Well, global warming is caused by an increasing amount of Greenhouse gases in the atmosphere - which are Carbon Dioxide, Methane, Nitrogen Dioxide (Nitrous Oxide) and Water Vapour are greenhouse gases which cause the Greenhouse effect. Be careful when mentioning these gases, as you may be tricked into using the names of other gases.
Sulphur Dioxide is not a greenhouse gas as it does not absorb the sun's heat, but it causes acid rain. Aerosols cause depletion of the Ozone layer, and, whilst contributing to Global Warming, are of no relation to the Greenhouse Effect.
You will not need to explain why the greenhouse gases absorb the sun's heat. However you WILL need to explain that human activity is responsible for adding extra quantities of these gases to the atmosphere. Carbon Dioxide and Water Vapour are the most common greenhouse gases, as they are released from car exhausts, power stations and pretty much every other combustion reaction there is. Methane is released from rice paddies and, of course, from passing wind.
The consequences of global warming are not fully understood, however there is significant scientific evidence that it is causing Climatic Change. Be careful here, as Global Warming is the increase in the Earth's average temperature, whereas Climatic Change is when the weather changes in a certain place, so try to avoid mixing the two phrases.
In the Sahel region in Sub-Saharan Africa, over the past decade, there has been a significant decrease in rainfall and droughts are becoming commonplace. The decrease in rainfall here causes an increase elsewhere, which can increase the problem of flooding in other areas.
Another effect of global warming is the melting of the polar ice caps - the North and South Pole. A hotter termperature obviously causes the ice to melt, which will add to the level of water in the oceans - and a higher level of water means a greater risk of flooding. Throughout the world, there are many flat and low-lying countries and cities that are at considerable risk from flooding. Bangladesh is one of the most flood prone countries in the world and there will be a higher chance of floods striking the country, causing death and damage to thousands of people.