UNEP’s newly released Climate Change Science Compendium 2009 is an excellent, if not sobering, potential student reading on current and potential impacts of climate change. The Compendium serves as an update of our current state of climate knowledge from the 4th Assessemnt Report in 2007. It reinforces a theme that I often emphasize to my students: as our scientific knowledge in the field of climate change deepens, our projections of impacts in most contexts become more serious, accentuating the need for an extremely precautionary approach. Here’s some of the key take-aways from the report:

• We are now likely committed to a one meter rise in sea level by the next century and 5-10 times this rise in the following centuries;
• We are now committed to an additional increase in temperatures of 1.6 degrees C, which combined with the 0.6-0.7C increase we’ve already witnessed over pre-industrial levels, we now appear inevitably committed to exceeding the 2C “guardrail” that virtually everyone agrees will visit extremely serious impacts on human institutions and natural systems;
• In the context of Earth ice dynamics:
  • Glacial melting has accelerated in recent years, including massive losses in Europe, the Himalayas, and in a region we often don’t think about glacial melting, Africa;
  • Arctic ice melting has accelerated, suggesting a record low volume by the end of summer 2008, and a much hire incidence of first year ice, which is prone to melt more quickly than thicker multi-year ice. In 2009, ice older than two years accounted for less than 10% of ice cover;
  • More than 75% of marine-terminating outlet glaciers in the Greenland Ice Sheet are thinning, with potentially very serious implications for sea level rise given the mass of this ice body;
  • Portions of Antarctica are also losing ice, including an increased loss of ice by 60% in the last decade. Observed cooling in the interior may be attributable to ozone layer diminution, which is likely to be reversed in upcoming decades, potentially bringing even warmer temperatures and more dynamic ice conditions
• In terms of the world’s oceans:
  • The report reminds us that a large portion of warming inertia in the system is attributable to the storage of heat in oceans, potentially delaying surface temperature response from 10-100 years;
  • Ocean acidification is proceeding apace, including water that can coorde aragonite (one form of calcium carbonate) now along the California coastline, a phenomenon that may also occur in 2050, if not sooner in many high latitude regions;
• In terms of the Earth’s ecosystems:
  • Amplification of natural variability intensities “introduces a new urgency” for understanding the biological consequences of climate extremes;
  • There is already substantial evidence of phenological changes in many parts of the world;
  • The southwestern United States is moving rapidly to a point where “drought becomes the region’s new climatology;”
• The report may also be helpful for its suggestions of systems management. It includes an extensive (and pretty unique) discussion of adaptation strategies for natural systems, including controversial propositions, e.g. assisted colonization, and a good discussion of potential adaptation for agricultural systems;
• The study does also briefly discuss some of the potential geo-engineering responses, as well as prospects for biochar; however, this section almost seeks like an afterthought.

Overall, this study should increase the urgency of the Parties to the UNFCCC and Kyoto as they near the finish line for COP15.

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