What is climate change?

Our planet is surrounded by a blanket of gases which keeps the surface of the earth warm and able to sustain life. This blanket is getting thicker, trapping in heat as we release greenhouse gases by burning fossil fuels for energy and as we cut down forests and replace them with agricultural land. As a result, our climate is starting to change.

Scientific research indicates that, because of climate change, we may experience more intense and more frequent extreme weather events. A gradual increase in temperature also has major implications for ecosystems, growing seasons, animals and their habitats.

Some changes to the climate are inevitable – even if we stop emitting gases now, the gases we have already released will have an effect. However, we must do everything we can to avoid further changes and to adapt to the new situation we find ourselves in.

• What is the 'climate'?
• What causes climate change?
• What effects will climate change have?
• What can we do about climate change?
  

What is the 'climate'?

The term 'climate' normally describes the average weather we get over a long period of time. When our climate changes, the weather we experience locally day to day can also change.

Over the millions of years of the earth's existence, the climate has changed many times. However, when we use the term 'climate change' now, it is to describe shifts in temperature over approximately the last 100 years and the next 100 years or so.

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What causes climate change?

There will always be some degree of uncertainty in understanding a system as complex as the world's climate. However, there is now strong evidence and almost unanimous agreement that significant global warming is occurring. It is also likely that most of the recent warming can be attributed to human activities.

Natural causes

Some changes to the earth's climate are caused by the effects on each other of the sun, land, oceans and atmosphere. These often occur over very long periods of time.

Human causes

Human activity has changed the concentration of greenhouse gases in the atmosphere in two important ways. First, we have cut down forests to develop land for agriculture. Trees absorb carbon dioxide so, with fewer trees, more carbon dioxide builds up in the atmosphere. Also, the agriculture that replaces the forests can often be a source of emissions.

Second, by burning fossil fuels like coal, oil and gas for energy, we release greenhouse gases. Currently, burning fossil fuels emits about 6.5 billion tonnes of carbon dioxide into the atmosphere each year. Since before the industrial revolution, which began in the 18th century, concentrations of greenhouse gases have increased by 30 per cent.

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What effects will climate change have?

Even if we stop burning fossil fuels and cutting down forests today, the world's climate will still warm in years to come. There is a time lag between when the emissions occur and when we begin to feel their effects, so we have yet to experience the impact of the greenhouse gas emissions from the last 30–40 years.

Scientists have identified some of the likely effects of this warming.

Rainfall

Some regions will experience more extreme rainfall while others will experience drought.

Sea level

The sea level could rise by more than 40 centimetres by the end of the century. There are two reasons for this. First, as the water in the oceans warms, it expands. Second, ice from the polar caps and from glaciers is melting into the sea. Rising sea levels will completely swamp some small, low-lying island states and put millions of people in low-lying areas at risk.

Water

There will be less water available for irrigation and drinking because there will be less rain, and salt from rising sea levels will contaminate ground water in coastal areas. Droughts are likely to be more frequent. Three billion more people could suffer increased water shortages by 2080. Northern Africa, the Middle East and the Indian subcontinent will be the worst affected.

Harvest

As temperatures increase and rainfall patterns change, cereal crop yields are expected to drop significantly in Africa, the Middle East and India.

Disease

As temperatures increase, the areas that harbour diseases such as malaria, West Nile disease, dengue fever and river blindness will shift. It is predicted that 290 million additional people could be exposed to malaria by the 2080s, with China and Central Asia seeing the biggest increase in risk.

Rainforests

Higher temperatures and reduced rainfall could mean the loss of large areas of Brazilian and southern African rainforest – on top of the forest that we are cutting down to clear land for agriculture. These forests currently act as a 'sink' by absorbing large amounts of carbon dioxide which would otherwise be released into the atmosphere.

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What can we do about climate change?

We can't stop the effects of the greenhouse gas emissions that have already taken place. But we can influence the future.

The majority of scientists agree that to avoid radical changes of temperature in the future, action is needed now.

Many believe that emissions of greenhouse gases, which are continuing to rise, must begin to decline over the next 10–20 years to avoid extreme changes to our climate.

Carbon dioxide is the main greenhouse gas that causes climate change. Every tonne emitted into the atmosphere commits the world to more warming. But every tonne we avoid emitting helps reduce the risk.

The good news is there are lots of ways we can tackle climate change. Many of them will bring other benefits, such as new jobs, improved local environments and economic growth.

But the first step is to increase people's awareness and understanding of what's happening. Despite research showing that in the UK most people have heard of 'climate change' and 'global warming', the understanding of what causes climate change remains low.

By communicating climate change successfully, we'll be able to make sure that there is widespread support for the goal that together this generation will tackle climate change.

Now that climate change is in the news on an almost daily basis it is easy to think of it as something new. In fact, the first research that has helped us understand climate change dates back to the 18th century. However, it is only relatively recently that the full severity of the possible effects of climate change – and how urgently we need to act – have emerged.