The Earth's climate is in a state of continuous but very slow change and has changed or fluctuated many times in the last 4,000 million years. The evidence for this can be found in rocks, fossils and old landforms, such as glaciated mountains, fossil sand dunes, and coal deposits which are the relics of ancient tropical forests. Until very recently it was the opinion of most scientists that major climatic changes, such as the retreat of the ice at the end of the last ice age some 10,000-20,000 years ago, were slow and gradual. It was also though that, while the climate might fluctuate over short periods of 30-100 years, this was around an average or norm not very different to that of the last 4,000 years.

Recently, doubt has been cast on these assumptions and the subject of climatic change has become a matter of great concern. Firstly it is believed that humans may now be responsible for causing significant changes of climate with harmful consequences. Secondly, it is now known that past changes of climate, such as the onset of ice ages, occurred more rapidly than had at one time been thought; namely over less than a century rather than over several hundred years.

There is no reason to believe that over the next ten to twenty years, the climate in particular parts of the world will be very different. Occasional extreme events or spells of weather such as occur at present, may well mask any longer-term change and make human influence on the weather difficult to detect for some time to come. One extreme winter or summer does not necessarily make for a change of climate. Yet such changes are though to be occurring and will be increasingly evident in the next fifty years. Even if drastic and immediate action is taken by the countries of the world to mitigate the effects of harmful pollutants such as CO2 and CFCs the consequences of the present levels of damage may be apparent for the next hundred years.

Recently on the Earth a new temperature record (only existing since 1500s) shows that the planet has warmed distinctly from the 1500s and especially from the 1960s to the present day. A number of factors are thought to contribute to this: atmospheric pollution from manufacturing and cars and the increasing deforestation from logging and forest fires. By combining all of these factors - the temperature records, the increase in carbon dioxide and our climate models we are able to show much of this change in climate is due to increasing greenhouse gases. We can forecast for the future that the trend will continue unless greenhouse gases are curbed.