Sunday, September 29, 2013

You Decide

Editors note: This post was updated on 24 January 2017 to include the new, updated link for the Summary for Policy Makers (the old one had expired). 

The Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment Report (referred to by scientists as the AR5) consists of four reports:
  1. Working Group I report on the physical science basis of climate change
  2. Working Group II report on impacts, adaptation, and vulnerability
  3. Working Group III report on mitigation of climate change
  4. The Synthesis Report
The final draft of the Working Group I report, which attempts to provide a snapshot of current understanding of climate change, will be released and available at tomorrow.  The Summary for Policy Makers was approved and released on Friday.  

Below is a Cliff Notes version of the key figures, provided with as little commentary as possible.  Perhaps we will take a closer look at key findings and areas requiring further research in future posts.  

Observed Global Temperature Change during Historical Record
Source: IPCC

Other Changes to the Climate System
Source: IPCC

Carbon Dioxide Concentrations
Note: Trends in other greenhouse gasses not included in the Summary for Policy Makers but should be included in the full report issued tomorrow.
Source: IPCC

Estimated Changes in Radiative Forcing since 1750
Note: Radiative forcing can be thought of as a shift in the Earth's energy balance.  A basic description is available here.  
Source: IPCC

Simulations of Recent Climate Change with and without Anthropogenic Forcings
Source: IPCC

Climate Model Projections
Note: RCP2.6, RCP4.5, RCP6.0, and RCP8.5 are scenarios for future concentrations of greenhouse gasses and other climate forcing agents with RCP2.6 representing a highly aggressive mitigation scenario designed to limit the increase in global mean temperature to 2ÂșC and RCP8.5 representing the most extreme scenario. 
Source: IPCC
Source: IPCC


  1. What's there to decide? Unless of course you're talking to someone with a counterfactual argument and we know what they are going to say.

  2. CMIP - Is this a coupled model (ocean+atmosphere) ensemble?

    1. CMIP stand for the Coupled Model Intercomparison Project. Yes, this is a multi-Earth System Model ensemble. More details at