To ask Her Majesty's Government what assessment they have made of the reasons for the stable or declining global average temperatures since 2001; and how these will inform their policy on climate change mitigation. [HL2104

The short-term decrease in global average temperature that occurred between 2001 and 2008 resulted from natural, internal processes in the climate system. These cause temperatures to fluctuate from year to year and from decade to decade. Temperatures were lower in 2007 and 2008 than in previous years, for example, due to a La Nina event in the Pacific Ocean, which caused cold water at depth to rise to the surface. Over short periods, this natural variability is larger than the changes expected due to global warming, so it can easily result in the temperature trend being constant or negative over a period of a decade or so, as has happened on occasion during the 20th century.

The effect of greenhouse gases on the climate system is evident in the long-term temperature trend, which is upward (as demonstrated by the fact that the 10 warmest years on record have all occurred in the past 12 years). As long as greenhouse gas emissions continue, global average temperatures will continue to rise in the long-term, with potentially dramatic implications for food and water supplies, human health, national security and the global economy. For this reason, the slight decline in global average temperature since 2001 will not affect the UK Government's policy on climate change mitigation. Rather, this policy will continue to be based on the latest scientific evidence regarding the impacts of greenhouse gas emissions on the climate system.