5 Degrees Celsius

A leaked draft of the Fifth Assessment Report (AR5) of the Intergovernmental Panel on Climate Change (IPCC) mainly reflects even greater confidence that human activities are responsible for most of the warming since the 1950s.  If greenhouse gas emissions are not reduced, the world is on track for 5 degrees Celsius of warming by sometime around the end of the century.

Update (August 19):  It's interesting to note that while the upcoming AR5 makes an effort to explain why land surface temperatures have been steady for the past ten years, research not included in the assessment demonstrates that warming in the oceans has accelerated over the past 15 years.  90 percent of overall warming of the planet goes into heating the oceans.

Update (September 23):  As the IPCC gets closer to publishing AR5, the climate change deniers are coming out in force.

Update (September 27):  The Summary for Policymakers is now available with more to come.

Update (January 16, 2014):  Further leaks of the IPCC report suggest that, in the worst case, the cost of preventing climate change could exceed the cost of adapting to it.