Climate Change

Questions

Asked by

Lord Leach of Fairford
To ask Her Majesty's Government at what point during the period of warming since the little ice age they consider that an anthropogenic warming signal greater than 0.25ºC per century was observed; and what the implications are for climate change policy. [HL2726]

The Minister of State, Department of Energy and Climate Change & Department for Environment, Food and Rural Affairs (Lord Hunt of Kings Heath)
The so-called little ice age generally refers to a relatively cool period between the 17th and mid-19th centuries in the north Atlantic region. There is no evidence that this was a global event. Global average temperature has risen by approximately 0.7 degrees centigrade since the late 19th century and the long-term upward trend appears to have begun in the early part of the 20th century. The IPCC's fourth assessment report concluded that human activity was responsible for most of this warming—in particular, that it is very likely (more than 90 per cent chance) that greenhouse gas emissions were responsible for most of the warming over the past 50 years, and likely (more than 66 per cent chance) that greenhouse gases caused some of the warming during the early 20th century. The average rate of warming over the 20th century was 0.74 degrees centigrade/century and nearly double that (1.28 degrees centigrade/century) in the second half. It is not possible to identify the exact date when an anthropogenic warming signal greater than 0.25 degrees centigrade per century (or 0.025 degrees centigrade per decade) was observed without performing complex analyses, but it is clear that the anthropogenic warming signal has been significantly greater than 0.25 degrees centigrade over the past century as a whole.

Asked by

Lord Leach of Fairford
To ask Her Majesty's Government whether the rate of increase in global mean surface temperatures between 1975 and 1998 was similar to the rates of increase observed between 1860 and 1880 and between 1910 and 1940; and, if so, what the implications are for their policy on anthropogenic warming. [HL2727]

Lord Hunt of Kings Heath
Observations collated at the Met Office Hadley Centre and the University of East Anglia Climate Research Unit indicate that the rate of increase in global average surface temperature between 1975 and 1998 was similar to the rates of increase observed between 1860 and 1880 and between 1910 and 1940 (approximately 0.16 degrees centigrade per decade). This observation has no implications for our policy on anthropogenic warming.

Little can be deduced from relatively short periods in the temperature record taken in isolation from the overall picture. Temperatures fluctuate in response to both manmade factors (such as emissions of greenhouse gases) and natural factors (such as volcanic eruptions, changes in solar activity and internal variability within the climate system), and different combinations of these factors can cause temperatures to change at similar rates for limited periods of time. In its assessment of the whole global temperature record from 1860, the IPCC, in its fourth assessment report, concluded that it is very likely (more than 90 per cent chance) that greenhouse gas emissions were responsible for most of the warming over the past 50 years, and likely (more than more than 66 per cent chance) that greenhouse gases caused some of the warming during the early 20th century. The IPCC also showed that in the absence of actions to limit greenhouse gas emissions, temperatures will continue to rise through the 21st century by between 1.8 and 4 degrees centigrade. This raises the prospect of dangerous levels of climate change, which the Government remain committed to avoid through concerted international and domestic actions to reduce greenhouse gas emissions. Short-term fluctuations in the historic temperature record have no implications for this policy.

Asked by

Lord Dykes
To ask Her Majesty's Government whether they support the aim of the Government of Sweden to finalise a global climate change agreement by the end of their European Union presidency in December. [HL2818]

Lord Hunt of Kings Heath
The UK remains committed to agreeing at the UNFCCC meeting in Copenhagen in December 2009 a comprehensive, global and long-term framework for addressing climate change. The UK offers full support to the Swedish EU presidency in achieving this.