---

Climate Change: Greenhouse Gases

Answer

The Intergovernmental Panel on Climate Change (IPCC) has developed a methodology for calculating the relative climate effects of different greenhouse gases. This provides the relative contribution of a tonne emission of each gas, relative to the effect ofa tonne emission of carbon dioxide integrated over a fixed time period. A 100-year time horizon has been chosen in view of the relatively long time-scale for addressing climate change. This factor is known as the global warming potential (GWP). GWPs are given in the table below for carbon dioxide, methane and nitrous oxide. These were published by the IPCC in its third assessment report.

Gas	GWP
Carbon dioxide	1
Methane	23
Nitrous oxide	296

The GWP values used for calculating national greenhouse gas emissions reported to the United Nations framework convention on climate change are by international agreement taken from IPCC's second assessment report and differ slightly from the values shown in the table. Taking account of GWPs and the level of emissions of different gases, the UK greenhouse gas inventory shows that in 2004 carbon dioxide accounted for about 84 per cent of UK greenhouse gas emissions. Methane and nitrous oxide contributed about 8 per cent and 6 per cent respectively. Research conducted by the Hadley Centre takes account of the detailed effects of these gases on the climate including the interactions between the gases, the oceans and the terrestrial biosphere.

Secondary information

Type

Written question

Reference

217; 687 c91-2WA

Session

2006-07

Subjects

Climate change Carbon dioxide Research Methane Nitrous oxide

Contains statistics

Yes

Link

View this Written question on www.publications.parliament.uk