why is the climate changing?

Adding carbon dioxide (and a number of other industrial gases) into the atmosphere causes the sun's heat to be trapped - incoming solar radiation still reaches the earth, but reflected heat (which has a longer wavelength) can no longer escape into space. This is known as the greenhouse effect, as it is the same reason why heat is trapped in greenhouses.

Using ice core data, scientists have proved that the concentration of greenhouse gases has increased tremendously over the past 250 years due to human activities and now far exceeds pre-industrial values.

The greenhouse gases include carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) but the most important out is carbon dioxide accounting, responsible for around 75% of the greenhouse effect. This is why people often refer to the greenhouse gas emissions as carbon emissions or simply CO2 emissions. Although methane, and the other lesser contributors by volume, account for a much lower proportion, their greenhouse effect is much more potent than carbon dioxide (they are often converted to a CO2 equivalent).

According to the Intergovernmental Panel on Climate Change (IPCC), set up to investigate the problem, greenhouse gas emissions due to human activities have grown significantly since pre-industrial times. Between 1970 and 2004, the annual CO2 emissions, which come mainly from the burning of fossil fuel for the generation of energy, have grown by about 80% with a growth rate during 1995-2004 much higher than during 1970-1994.

Fossil fuels such as oil, coal and gas where formed millions of years ago by the decay and decomposition of plants and animals. The use of those fuels for our energy needs is currently releasing around 21 billion tonnes of CO2 per year into the atmosphere. However, only half that amount can be reabsorbed by the earth's natural cycles, which means that there is an additional 10.5 billion tonnes CO2 in the atmosphere every year.

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how is it affecting us?

The effect of the increased concentration of greenhouse gas in the atmosphere will take several decades before the full impact upon the climate is realised.

Over the next 20 years, a rise of about 0.4°C can be expected. This increase in temperature will potentially have global climate impacts similar to those observed to date but it is envisaged that they will be more extensive and of greater intensity. These will probably include:

• Warming, especially over land and in Northern latitudes
• A decrease in snow cover and the ice sheet over both the Arctic and Antarctic will contract considerably
• Rise in sea level
• Heat waves and heavy precipitation will become more frequent
• Tropical cyclone intensity will increase; coupled with higher wind speeds
• Increase of precipitation in high latitudes with decrease of precipitation over subtropical regions

Such changes would in turn quite likely have the following effects:

• Risk of extinction of about 20% to 30% of plant and animal species
• Significant changes in ecosystem structure and function
• Decrease of crop productivity in some areas with changes of crop variety in others
• Erosion of the coastal region and increase of flooding
• Industries close to the coast and flood plains would become at risk
• Poor communities would also become more vulnerable
• Millions of people could be affected by malnutrition, disease, and injury, even death, due to the extreme weather
• Major stress on water resources as the physical, chemical and biological properties of the freshwater in lakes and rivers changes

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where will be most affected?

Click on the interactive map above to find "hot spots" where climate change is expected to have the greatest adverse effect. The map above was produced by the Meteorological Office on behalf of DECC in advance of the December 2009 Copenhagen meeting, and shows the most likely scenarios as a result of an average 4°C global temperature rise - the level that might occur by 2100 under a Business As Usual assumption.

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can we combat climate change?

Even if we stopped emitting greenhouse gases now, due to the complexity of the climate system, changes in the climate would continue for many years.

There is therefore a need to prepare for this change and adapt our environment and the way we go about our lives (infrastructure, lifestyle, etc) to cope with effects of climate change that are already inevitable but not unmanageable. This is known as adaptation.

However, continued carbon emissions at or above the current rate will lead to more serious climate changes than those observed over the past decade. If we are to reduce the change of catastrophic long term climate changes, we must begin to make real inroads to reducing those emissions now.

Adaptation

Even if we cut CO2 emissions today, there are likely to be some changes that we will need to live with. Adaptation will require policies and actions that will ensure countries, regions, districts organisations and every one of us have the capacity to respond and adapt to the impacts of climate change. Examples of adaptation include the design and construction of buildings with deeper and/or raised foundations to prevent subsidence and minimise the risk of flooding and which are capable of providing a comfortable environment during higher temperatures without the need for mechanical cooling and air-conditioning. These measures will reduce significantly our vulnerability to climate change.

The costs of adaptation will increase as the impacts on the environment worsen, so by delaying action we will make it harder and more expensive to combat the effects of climate change. The Government commissioned Stern Report (2006) emphasised that money spent now in reducing carbon emissions to 'safe' levels would be a fraction of that required to adapt in the future if we carried on with 'business as usual'.

Mitigation

In order to reduce the rate of change to manageable (and ultimately sustainable levels), we must significantly reduce the amount of carbon emissions that is currently being released into the atmosphere. Studies from the IPCC show that if adequate policies were implemented, a significant reduction of carbon emissions could be achieved which should stand to stabilise the climate in the long term.

Mitigation measures include:

• The promotion of lifestyles less dependent on fossil fuels - making choices that release less carbon;
• Using energy more efficiently - reducing waste and avoidable losses;
• Widespread use of renewable energy as an alternative to fossil fuels.

There are many ideas about mitigation on the climate change and you section of the thimkagain website.

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