A meeting of the Intergovernmental Panel on Climate Change in Stockholm 21-27 September is due to finalize a summary for policymakers of a comprehensive assessment of the physical science basis of climate change.
The summary for policymakers, an accompanying technical summary and a 14-chapter assessment form the contribution of Working Group I on the physical science basis to the IPCC’s Fifth Assessment Report. Working Group II’s contribution on impacts, adaptation and vulnerability and Working Group III’s work on mitigation of climate change will be published in March and April 2014 respectively. The synthesis report of the Fifth Assessment report will be considered in October 2014.
The IPCC is co-sponsored by the World Meteorological Organization (WMO) and United Nations Environment Programme.
WMO Secretary-General Michel Jarraud told the Working Group I opening session that the degree of scientific confidence about climate change has grown since the Fourth Assessment Report in 2007.
“Today few would dispute the important changes observed in the climate system over more than half a century. The temperature of the atmosphere and of the ocean has increased, the ice sheets and glaciers of the world have diminished, and the global mean sea level has risen. But the last decades have also been characterized by a high frequency of extreme weather events: heat waves, heavy rain and floods, drought, and tropical and extra-tropical storms,” Mr Jarraud said in a video address.
“But these changes have today dire impacts on our most vulnerable societies and remind us that climate action cannot be further postponed. It is therefore particularly welcome that the Fifth Assessment Report pays particular attention to the regional scale, with greater emphasis on the socioeconomic aspects of climate change and their implications for sustainable development,” said Mr Jarraud.
"To assess how much can be attributed to human activities, further assessments and projections are needed. This reaffirms once more the importance of IPCC and the need for its continuity," he said.
The Working Group I report was developed by an international team of scientists who were selected in May 2010. It went through a multi-stage review process involving expert reviewers and governments. A total of 209 lead authors and 50 review editors from 39 countries and more than 600 contributing authors were involved.
The Working Group I report includes an assessment of observations of the climate system, with separate chapters covering changes in the atmosphere and surface, the ocean and the cryosphere, as well as information from paleoclimate archives. There are chapters covering the carbon cycle, the science of clouds and aerosols, radiative forcing and sea level change. Coverage of climate change projections is extended by assessing both near-term and long-term projections.
Climate phenomena such as monsoon and El Niño and their relevance for future regional climate change are assessed. An innovative feature of the Working Group I report is the Atlas of Global and Regional Climate Projections, which is intended to enhance accessibility for users and stakeholders.
The summary report will be reviewed on a line-by-line basis in Stockholm and the approved version presented on Friday 27 September.