U.N. Report Now Estimates Irreversible Global Warming of Up to 4 Degrees

Climate is Changing Faster Than Expected, Tipping Points May be Occurring

According to the new report, scientific evidence suggests important tipping points, leading to irreversible changes in major Earth systems and ecosystems, may already be occurring. The report indicates that climate change is accelerating at a much faster pace than was thought by the Intergovernmental Panel on Climate Change (IPCC) in its 2007 assessment.

World Likely Committed to Significant Warming Already

The observed increase in green house gas (GHG) concentration in the atmosphere since 1750 has most likely committed the world to a warming of 1.4-4.3 degrees Celsius, above pre-industrial surface temperatures. The equilibrium warming is expected to be 2.4 degrees Celsius - even if GHG concentrations had been fixed at their 2005 concentration levels and without any other anthropogenic forcing such as the cooling effect of aerosols.

Current Trends in Global GHG Emissions Could Lead to Unpredictable Climates

Under a high GHG emission scenario - the one that most closely matches current trends - 12-39 percent of the planet's land surface could experience "novel" climate conditions and 10-48 percent could suffer "disappearing" climates by 2100.

Key Developments Since 2007

Key developments documented in the Compendium that have occurred since the 2007 IPCC report are detailed below.

The Arctic, with implications for the globe, is emerging as an area of major concern. There is growing evidence that Arctic ice there is melting far faster than had been previously supposed. Mountain glaciers also appear to be retreating faster. Scientists now suggest that the Arctic could be virtually ice-free in September 2037 and that a nearly ice-free September by 2028 is possible. Recent findings also show that significant warming extends well beyond the Antarctic Peninsula to cover most of West Antarctica, an area of warming much larger than previously reported. Melting of the glaciers threatens the one-fifth or more of the population that depends on glacier ice and seasonal snow for its water supply.

Melting and warming of oceans could have severe consequences. Combined melting of land-ice and thermal expansion of oceans could lead to an average sea level rise of .8-2.0 meters above 1990 levels by 2100 (compared to a projected rise of between 18-59 centimeters in the 2007 IPCC report). In addition, the oceans are becoming more acidic more quickly, jeopardizing the ability of shellfish and corals to form external skeletons.

The impact on the Earth's multi-trillion dollar ecosystems is also a key area of concern. Under a high emission scenario-the one that most closely matches current trends-12-39% of the Earth's terrestrial surface could experience novel climate conditions and 10-48% could suffer disappearing climates by 2100. Ecosystems in sub-polar waters, the tropics, and semi-enclosed areas are predicted to suffer numerous extinctions by 2050. The Arctic and Southern Oceans will experience severe species invasions. Marine ecosystems may see a species turnover of up to 60%.

Rising levels of aridity are also indicated. New research indicates that by the end of the 21st century the Mediterranean region will experience much more severe increases in aridity than previously estimated, rendering the entire region, but particularly the southern Mediterranean, even more vulnerable to water stress and desertification.

Active protection of tropical forests is a cost-effective means of reducing global emissions. Reducing emissions from deforestation and forest degradation is likely to emerge as a central component of a new international climate change agreement later this year. Other innovative approaches to keeping carbon out of the atmosphere, including the use of biologically-derived charcoal mixed in soils, also warrant investigation.

Drastic measures to preserve species and food production may be needed. These measures could include large-scale translocation or assisted colonization of species and the institution of Eco-agriculture (managing landscapes to sustain a range of ecosystem services including food production) may need to replace the existing segregation of land use between conservation and production. This could help create resilient agricultural ecosystems better able to adapt to changing climate conditions.

¹The report is the result of a review of over 400 major scientific contributions to the understanding of Earth Systems and climate change that were released through peer-reviewed literature, or from research institutions, during the last three years.

The UNEP press release is available at: http://hqweb.unep.org/Documents.Multilingual/Default.asp?DocumentID=596&ArticleID=6326&l=en.

The Climate Change Science Compendium 2009 is available at: http://www.unep.org/climatechange/Publications/Publication/tabid/429/language/en-US/Default.aspx?BookID=4064.

BP's notice on the 2007 IPCC report is available at: http://www.brokerpower.com/cgi-bin/itt/itt.pl?F::ALLNEWS::2007/20070518/07051805.html.