30 July 2010Introduction
What is climate?
Why is climate change happening?
What are the Greenhouse Gases?
Measuring the Global Warming Potential
Climate Change myths
Climate Change is also known as Global Warming because the average global temperature is increasing or warming.
The earth's climatic systems work together to reduce this overheating, just as our bodies work to reduce our temperature when we have a fever. This results in changes in the local, regional or global climate. This increase in the global temperature is the result of the Enhanced Greenhouse Effect.
For further information, visit the brief history of climate change section on the Directgov website, the Met Office's Warming – climate change the facts (
PDF File 1067KB file details) or for detailed information, the International Panel on Climate Change's frequently asked questions ( PDF File 7341KB file details).
It is important to recognise the difference between weather and climate. Weather is the temperature, precipitation (rain, hail, sleet and snow) and wind, which changes hour by hour and day by day. Climate is the average weather and the nature of its variations that we experience over time.
Weather and climate are closely related but it is more difficult to predict weather which can vary daily than to predict changes in climate which are made using long term average weather and changes in atmospheric composition.
Even if we experience a colder period of weather this can still mean that the climate is heating up as there are always cooler periods of weather in a warmer climate.
Why is climate change happening?
Climate change is being caused by the Greenhouse Effect which occurs naturally and without it life on earth would be very cold with an average temperature of -19°C instead of +14°C.
Greenhouse gases gather above the earth and form the equivalent of a pane of glass above the lower atmosphere. This traps some of the heat from the sun that would otherwise return to outer space. The image below describes how the Greenhouse Effect occurs.
.gif "Climate change process")
Image - Source IPCC, 2007: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change [Solomon, S., D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M. Tignor and H.L. Miller (eds.)]. Cambridge University Press, Cambridge.
Since the industrial revolution human activity has been gradually added to these naturally occurring gases, creating a thicker layer of gas causing more heat to be trapped in the atmosphere.
To learn more about the causes of climate change, view the causes of climate change section on the Directgov website.
What are the Greenhouse Gases?
The main greenhouse gases responsible for this Greenhouse Effect are water vapour (H2O), carbon dioxide (CO2), methane and nitrous oxide. For a full list of greenhouse gases visit the Department for Energy and Climate Change website.
All of the greenhouse gases are measured by their Global Warming Potential (GWP)
Measuring the Global Warming Potential (GWP)
Each greenhouse gas will stay in the atmosphere for a measurable amount of time, for CO2 this is between 50 to 200 years. This means that CO2 will be present in the atmosphere for at least 50 years before it is absorbed. It also means that CO2 emitted into the atmosphere today could cause global warming for up to two centuries to come.
The other greenhouse gases are provided a GWP which is defined as the warming influence they exert over a set time period relative to that of CO2.
You can obtain more information by visiting the greenhouse gas emissions page on the DEFRA website. When the warming effect of current greenhouse gas emissions over the next 100 years is calculated, the CO2 will be responsible for about two thirds of the expected future warming.
As CO2 is emitted from the burning of fossil fuels many of our daily activities such as driving your car, heating your home and even switching on a light contribute to climate change. This is why we need to move to a low carbon future ensuring that all energy is used efficiently and using non fossil fuel sources of energy.
If you would like to find out the amount of greenhouse gas you are responsible for emitting (also known as your annual carbon footprint) please visit the Act on CO2 website.
There are several myths and misunderstandings about climate change. To find out more, visit the Directgov website section covering the most common climate change misconceptions and the facts behind them.
See also guide by the Royal Society, A guide to facts and fictions about climate change ( PDF File 131KB file details).
