Scientists study future changes and impacts of the climate using climate models based on an understanding of physical processes. These models have improved over the years as knowledge of the earth’s climate system has developed and the speed and power of computers have increased.
Scientists model a range of future possible climates using different scenarios. Each scenario makes different assumptions about factors such as how the world's population may increase and use energy supplies, what technological innovations there may be and how our behaviours may adapt to future changes. They can give us a reliable guide to future climate change although some uncertainty remains.
If future emissions follow the ‘business as usual’ projection, then CO2 concentration in the atmosphere will more than double over the next 100 years
If global emissions remain at current levels, concentrations would still go on rising
If global emissions were cut in half, concentrations would still increase
Even if we stopped releasing any more CO2 into the atmosphere today, the world's climate is still predicted to warm in the future. This is because of the 'residence' time of CO2 which lasts about 100 years in the atmosphere.
As CO2 emissions have been rising, so has the global temperature. Since 1900, the average temperature of the earth’s surface has warmed by 0.6°C. All of the ten warmest years on record since 1861 have occurred since the beginning of the 1990s. 1998 was the warmest year on record and 2005 was almost as warm. The global average temperature measurements are taken from thousands of weather stations across the world on land, from ships at sea and more recently satellites.
Some activities in some parts of the world could initially benefit from climate change, for example Northern Europe could experience less demand for heating so using less energy. There could also be a longer growing season for crops for farmers. But higher temperatures are also likely to increase the number of heat waves, severe storms and flooding through sea level rise and the melting of large ice sheets in Greenland, the Arctic and Antarctica.