What is climate change?

• the Earth’s surface has warmed by about 0.754°C on average since around 1900 and by around 0.4°C since the 1970s

·         human activity is the main cause of global warming observed over the last 100 years, particularly over the last 50 years

•     over 30 billion tonnes of CO2 are emitted globally each year by burning fossil fuels

·                            atmospheric concentration of CO2 is now higher than at any time in at least the the last 800,000 years

·                            average global temperatures are likely to rise between 1.1°C and 6.4°C above 1990 levels by the end of this century

Climate is the average weather experienced over a long period. This includes temperature, wind and rainfall patterns. The Earth’s climate is not fixed, and in the past has changed many times in response to a variety of natural causes. However, the Earth’s surface has warmed by about 0.754°C on average since around 1900 and by around 0.4°C since the 1970s.

The 2007 Fourth Assessment Report (AR4) of the Intergovernmental Panel on Climate Change (IPCC) leaves no doubt that human activity is the main cause of the warming observed over the last 100 years, particularly over the last 50 years.

The main human influence on global climate is the emission of so called greenhouse gases, such as carbon dioxide (CO2), methane and nitrous oxide. As these gases build up in the atmosphere, they strengthen what is known as the ‘“greenhouse effect’”. At present, over 30 billion tonnes of CO2 are emitted globally each year by burning fossil fuels, and another 7 billion tonnes by changes in land use, mainly deforestation. Atmospheric concentration of CO2 is now higher than at any time in at least the the last 800,000 years.

According to the AR4, average global temperatures are likely to rise between 1.1°C and 6.4°C (with a best estimate of 1.8 to 4°C) above 1990 levels by the end of this century, depending on our future greenhouse gas emissions. This will result in global sea levels rising by at least26 to59cm by the end of this century, continued melting of ice caps glaciers and sea ice, significant changes in rainfall patterns and intensification of tropical cyclones such as hurricanes.