Climate change

Life on Earth relies on oxygen and water, and crucially also on the temperature. Over long periods of history, temperature changes have dramatically affected life. The ice ages are the most well known examples. We are now at a point in history when it is clear that a significant temperature increase has started to happen. Earlier changes in temperature were caused by natural events. This time, the forces driving the change are widely accepted to be the result of human activity.

This is good news – it means that by changing human activity, we can affect how far and how fast the global temperature changes, and limit it so that the effects are tolerable.

But if we don’t tackle the problem, the consequences will be severe. Changes to the climate from increasing global temperatures will disrupt the basics of life for millions, then billions of people. Food and fresh water supplies will start to fail; extreme weather conditions will cause flooding and other damage. Ultimately, rises in sea level will inundate coastal areas, submerging many urban and rural communities. There will be mass displacement and migrations of peoples from the worst affected areas. Those living in ‘safer’ areas will not be immune – global trade in commodities and manufactured goods will be severely disrupted. Animal and plant life will also be adversely affected, with many species becoming extinct.

The climate is a very complex system. No-one can predict with 100% certainty how it will behave. But the majority of scientists who work in the relevant areas, accept that the climate is changing, and that the changes we are seeing now are due at least in part to human activity. They also believe that as the temperature rises, certain events – ‘tipping points’ could be triggered, that cause the temperature to rise even faster. Examples are the melting of peat bogs in Siberia, releasing huge quantities of methane, a gas that has a major warming effect in the atmosphere; and the melting of polar ice that currently reflects heat from the sun back into space.

The temperature of the Earth is regulated by the atmosphere and by the amount of energy generated by the Sun. (Solar activity does vary, but the global temperature changes now being seen are not consistent with observed levels of solar energy.)

Some energy from the Sun is reflected back into space when it hits the Earth, some is absorbed. The more that is absorbed, the higher the global temperature. How much is absorbed is controlled by the atmosphere. In this respect the Earth’s atmosphere acts like an insulating blanket. Without this effect the Earth’s surface would be 20 to 30°C colder and much less suitable for life

Different atmospheric gases trap differing levels of heat – carbon dioxide; methane; nitrous oxide; hydrofluorocarbons (HFCs); perfluorocarbons (PFCs); and sulphur hexafluoride. Water vapour and ozone are also potent greenhouse gases.

Over millennia, the concentration of carbon dioxide in the atmosphere has fluctuated in the range 200 – 300 parts per million. Natural cycles maintain this balance - CO2 is absorbed by growing plants and micro-organism in the oceans, and is emitted by decaying plant and animal remains and by animal respiration. Warm areas of the sea also give up dissolved carbon dioxide.

Human activity over the last two centuries in particular has significantly increased the levels of carbon dioxide in the atmosphere. By 2006 the level had reached 380ppm and was continuing to increase. Burning fossil fuels for heating, transport and electricity generation, and chemical processes like the production of cement and agricultural fertilisers, all create CO2 to an extent that has upset the natural balance of the gas in the atmosphere. Change of land use, most notably conversion of natural forests to agricultural land, and draining of peat bogs has reduced the natural environment’s capacity to absorb CO2 and remove it from the atmosphere.

Human activity, primarily agriculture, but also natural gas extraction, is contributing to increased atmospheric levels of methane. Methane is present in much lower overall concentrations than Carbon Dioxide, but it has a much greater greenhouse gas effect.

As greenhouse gas (GHG) concentration levels increase, global average temperatures rise. The Intergovernmental Panel on Climate Change (IPCC) believes that we should be aiming to limit global temperature rise to a maximum of 2 degrees Celsius above pre-industrial levels. To achieve this, GHG concentrations cannot carry on increasing – some commentators suggest they need to fall from the current level of 380ppm, but consensus (in early 2007) is that they should

The implications for a society based on cheap energy from fossil fuels are significant and wide ranging. Not only do we have to reduce GHG emissions, we have to do it quickly.

We in the developed world have already benefited from abundant fossil fuel energy. Now we have realised the damage this is causing, and that the damage that will fall disproportionately on poorer nations, the moral imperative is inescapable. In the first place, we in the developed world must drastically reduce our greenhouse gas emissions over the next few decades; and secondly, we must use our wealth and our skills to assist poorer countries to develop in a way that does not contribute to climate change.

The developing world has aspirations to match our material quality of life, and the quickest and cheapest way for them would be to build economies based on fossil fuels.

Tackling climate change requires action at all levels of society – personal, community, business and government; and across all activities – work, leisure, education etc. In order to reduce greenhouse gas emissions, we need to:

• Reduce consumption and be less wasteful
• Use less energy to run our lives
• Use non-polluting sources of energy

With its planned Climate Change Law, the UK government is intending to set a policy framework to achieve GHG emissions reductions of at least 60% by 2050. Delivering on this objective will require attitude and behaviour changes across society as well as urgent acceleration of the deployment of energy efficiency measures in homes and offices and rapidly increased availability of clean energy supplies.