Dramatic change

The changes to our climate that are happening now are attributed to a very steep rise in the concentration of a number of gases in the air. Concentrations of these gases, known as greenhouse gases (GHGs), have risen steeply since the industrial revolution c. 1750 and so human activity - how we live our lives - is the cause.

These gases are called greenhouse gases (GHGs), because they let sunlight pass through the atmosphere to reach the earth but then trap the outgoing energy from the heated surface, which is similar to what happens in a greenhouse.

These increases were initially triggered by the change from an economy based on manual labour to one based on machine manufacture, and have continued to grow as all aspects of our lives have become mechanised.

Major GHG trends

Changes in GHGs from ice core and modern data.
AR4 (IPCC, 2007).

The graphs above from the IPCC's AR4 illustrate the evidence for the upward trend in GHG levels. They show atmospheric concentrations of carbon dioxide, methane and nitrous oxide over the last 10,000 years (large panels), and since 1750 (inset panels). Measurements are shown from ice cores (symbols with different colours for different studies) and atmospheric samples (red lines). The corresponding radiative forcings are shown on the right hand axes of the large panels (IPCC, 2007). Graphs from AR5 will be published in 2014, and will show a continuing trend.

They show a clear and dramatic increase since 1750, which lends urgency to the development and implementation of mitigation and adaptation measures on a global scale.