Climate system

Climate science in context

4 November 2013

The Intergovernmental Panel on Climate Change (IPCC) published the first part of its Fifth Assessment Report (AR5) in September 2013. As one of the world's leading climate research centres, the Met Office has been a central contributor to AR5 and is a key adviser to the IPCC.

The eagerly awaited report is a comprehensive assessment of the state of scientific, technical and socio-economic knowledge on climate change, its causes, potential impacts and response strategies. The report, which forms the evidence basis for policymakers over coming years, revealed that on the ground, in the air and in the oceans, global warming is without doubt.

Temperatures have risen by about 0.8 °C since pre-industrial times; Arctic sea ice extent has declined by 4% per decade since records began in 1979, and summer extent has declined at an even faster rate; sea levels have been rising by about 3 mm a year since the early 1990s.

Each of the last three decades has been successively warmer at the Earth's surface than any preceding decade since 1850. In the Northern Hemisphere, 1983-2012 was 'likely' the warmest 30-year period of the last 1,400 years. Scientists are 95% certain that humans have been the dominant cause of the rise in temperatures since the 1950s.

Thousands of scientists from all over the world voluntarily contribute to the work of the IPCC. The assessment reports are published around every five years with the Met Office Hadley Centre's work influential in forming the content of the reports. The Met Office has a long history of involvement in the IPCC, becoming a key adviser soon after it was established by the United Nations Environment Programme (UNEP) and the World Meteorological Organization (WMO) in 1988. The Met Office contributes in a variety of ways throughout the process - including from contributing authors, use of our datasets, modelling efforts and scientific paper outputs.

Co-ordinating the global research effort of the IPCC process is a complex task. There are three working groups which will all report separately before the final synthesis report is published. With around 200 authors involved in each working group, co-ordination and arranging meetings and interaction is challenging.

In trying to draw a consensus, the working groups carry out reviews of the published work from the peer-reviewed scientific journals all over the world. The published work is carefully analysed using a matrix which assesses and measures the amount of evidence and the level of agreement on certain aspects of climate change.

The reports use consistent, calibrated language, such as it 'is likely' or 'very likely'. Throughout the process, the co-Chair of Working Group I, Professor Thomas Stocker, has stressed the importance of being rigorous, robust, transparent and comprehensive.

Scientists at the Met Office have been closely involved in Working Group I which is concerned with The Physical Science Basis of Climate Change. For the first time we have lead authors in Working Group II which looks at Impacts, Adaptation and Vulnerability. Met Office research also contributes to Working Group III which is examining the Mitigation of Climate Change.

Met Office Earth System and Mitigation Science Manager, Chris Jones, was a lead author on the carbon cycle chapter of Working Group I. Chris's main focus is on analysing feedbacks between climate and the carbon cycle and looking at the long-term commitments of ecosystem changes to climate change and their implications for setting policy targets such as reducing carbon emissions.

Publication of each working group's report will attract global media interest, as well as the final synthesis report, which will be published next December. The Met Office is helping to carefully communicate the key messages from the report throughout its publication process.

Next December's final synthesis report will be a summary of all three of the working group, but it's important to realise that's not the end of the story. The Met Office and research institutes around the world will continue to drive science forward to provide in-depth information and advice to help governments, businesses and individuals make informed decisions.

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In brief