Ten things you need to know about climate change
by
Bob Ward (February 2008)
1. Carbon dioxide and other gases in the atmosphere naturally create the greenhouse effect by letting the Sun’s rays through to warm the Earth and preventing a lot of the heat from escaping. As a result, the average temperature of the Earth is about 15°C instead of -18°C due to the effect of the greenhouse gases in the atmosphere.
2. Humans have been emitting large volumes of greenhouse gases since the start of industrialisation about 250 years ago. The main greenhouse gas from human activities that has increased is carbon dioxide. It has been calculated that more than 1,156,584,000,000 metric tonnes of carbon dioxide were released into the atmosphere between 1751 and 2004 by the burning of oil, gas, coal and other fossil fuels, and through the production of cement. As a result, levels of carbon dioxide have risen by more than a third in the atmosphere since the Industrial Revolution.
3. According to the latest calculations, more than 29,000,000,000 metric tonnes of carbon dioxide were emitted across the world in 2004 by cement production and the burning of fossil fuels. This figure was nearly 25 per cent higher than that for 1994. The United States was the largest emitter of carbon dioxide, accounting for more than a fifth (6,050,000,000 metric tonnes) of total emissions, and the United Kingdom ranked eighth (587,000,000 metric tonnes) in the world league table of emitters. When population size was taken into account, Qatar was the biggest emitter (79.3 metric tonnes per capita) of carbon dioxide from fossil fuels, with the United States (20.6 metric tonnes per capita) in ninth place and the United Kingdom (9.8 metric tonnes per capita) in 37th place. Mainland China (3.8 metric tonnes per capita) ranked 92nd and India (1.2 metric tonnes per capita) was 129th, while Chad (0.04 metric tonnes per capita) was bottom of the 207 countries. However, it is important to note that greenhouse gases do not just stay in the atmosphere above the place that they are emitted, and instead contribute to global concentrations.
4. The increase in levels of greenhouses gases in the atmosphere has caused the Earth to warm – the global average temperature has risen by about 0.7°C in the last 100 years, and the eleven warmest years since records began in 1850 have all occurred in the last 12 years. The change in global average temperature may seem small compared with the differences in temperature in any one place from day to day, but it is significant trend – the average temperature today is only about 5°C higher than it was during the last Ice Age.
5. The rise in global average temperature has been accompanied by a rise in global sea level by about 7 centimetres in the last 40 years (as glaciers and ice sheets have melted and sea water has expanded as it warms) and changes in climate that vary from region to region. For instance, there have been changes in the amount of snow and rain fall, and shifts in the frequency, intensity and geographical distribution of some extreme weather events, such as droughts and floods.
6. Researchers use powerful computer models to simulate the world’s climate. These models are now very good at reproducing the past and present climate, and can be used to explore possible future changes. They can be used to calculate how global average temperature and its associated effects may change in response to further increases in the amounts of greenhouse gases in the atmosphere during this century. Although there are many uncertainties in making such estimates about the future, the computer models all show that rising greenhouse gas levels will lead to further increases in global average temperature, perhaps by as much as 6˚C by the end of this century if no action is taken to reduce emissions, and potentially major changes in climate.
7. Whatever happens to greenhouse gas emissions in the future, climate change will continue for the next few decades because carbon dioxide and many of the other greenhouse gases stay in the atmosphere for a long time, and the Earth takes time to adjust to increased concentrations. Therefore, human populations will need to adapt to the direct and indirect effects of climate change, some of which will be potentially beneficial (such as a reduction in deaths from cold weather as extremely low temperatures become less common) and others which will be potentially harmful (such as an increase in deaths due to more frequent and intense heatwaves). Populations in poor countries are likely to find it more difficult to adapt to climate change, for instance by constructing buildings that are more resistant to strong winds and flood waters, or by relocating to areas that are less exposed to extreme weather, and they will be therefore more likely to be affected by the adverse impacts.
8. The most extreme effects of climate change can be averted through mitigation, which means reducing greenhouse gas emissions so that levels in the atmosphere stop increasing and reach a stable level. There is no agreement about what the threshold is for greenhouse gas levels beyond which climate change will be dangerous. However, to stabilise the concentration of carbon dioxide at a level that would not cause global average temperature to eventually be 2˚C or more higher than in pre-industrial times worldwide total emissions would have to be 50 to 85 per cent lower in 2050 than they were in 2000. The UK Government has committed the nation to reducing its carbon dioxide emissions by at least 60 per cent by 2050 compared with 1990 levels.
9. Greenhouse gas emissions can be reduced in many ways, such as decreasing the amount of fossil fuels that are burnt by changing to alternative sources of energy and using energy more efficiently. At present, coal, oil and natural gas provide more than 80 per cent of the world’s primary energy supply. Alternative sources of energy that emit little or no carbon dioxide include solar panels, wind turbines and nuclear power plants. However, there are many potential challenges in changing completely to these sources of energy from fossil fuels. It might also be possible to capture and store carbon dioxide that is produced by the burning of fossil fuels.
10. Climate change has the potential to affect every person in the world, and similarly can be tackled if every person in the world helps to reduce greenhouse gas emissions. Straightforward measures can make a difference, such as improving the insulation of homes and turning off electrical appliances and lights when they are not in use.
Bob Ward is Director of Global Science Networks at the Risk Management Solutions, the world's leading provider of models for the quantification and management of the risk of natural and man-made catastrophes such as hurricanes, earthquakes and terrorism. He is also a member of the executive committees of the Association of British Science Writers and the World Conference of Science Journalists 2009, and is a member of the board of the Science Media Centre. Until September 2006, Bob was Senior Manager for Policy Communication at the Royal Society, the UK national academy of science, where his duties included heading the media relations team. He was previously a policy manager at the Society, with responsibility for the defence, energy and science base portfolios. He has also worked as a science reporter, and has a degree in Geology and an unfinished PhD thesis on experimental rock deformation.
With thanks to Stuart Franklin for permitting the use of his photographs in this article.