“presents some of the issues and ideas that have emerged since the close of research for consideration by the IPCC Fourth Assessment Report over three years ago. Focusing on work that brings new insights to aspects of Earth System Science at various scales, it discusses findings from the International Polar Year and from new technologies that enhance our abilities to see the Earth’s Systems in new ways. Evidence of unexpected rates of change in Arctic sea ice extent, ocean acidification, and species loss emphasizes the urgency needed to develop management strategies for addressing climate change.”
The UNEP summarises the findings of the report as:
“The pace and scale of climate change may now be outstripping even the most sobering predictions of the last report of the IPCC … many predictions at the upper end of the IPCC’s forecasts are becoming ever more likely.”
One of the most important sections of the report deals with sea-level rise – an area of considerable research debate since the IPCC Fourth Assessment Report was released.
The IPCC Fourth Assessment Report could affirm only 18–59 cm rise in global sea levels over the 21st century based largely on thermal expansion of the oceans. Critically, it excluded contributions to sea level rise from dynamic ice changes, such as from melting of glaciers, because no consensus could be reached based on the published literature available at that time.
The new UNEP report concludes based on recent research publications that:
“Introduction of realistic future melt and discharge values … suggests that plausible values of total global average sea-level rise, including all land-ice sources plus thermal expansion, may reach 0.8 to 2.0 metres by 2100, although no preferred value was established within this range …
Immediate implications are already challenging … for every 20 cm of sea-level rise the frequency of any extreme sea-level of a given height increases by a factor of about 10. According to this approach, by 2100, a rise of sea level of 50 cm would produce events every day that now occur once a year and extreme events expected once during the whole of the 20th Century will occur several times every year by the end of the 21st.”
The UNEP report’s reference list provides a helpful compilation of the leading climate change research since 2007.
McMullen, C.P. and Jabbour, J. (2009). Climate Change Science Compendium 2009. United Nations Environment Programme, Nairobi, EarthPrint (Link to PDF)