Last week’s release of the IPCC Working Group I’s contribution to the Fifth Assessment Report (AR5) prompted a moment of self-reflection for the climate community.

It reported incremental gains in the scientific community’s confidence in its findings, with a few important tweaks to past findings. For example, it is now extremely likely (rather than just very likely) that human influence has been the dominant cause of observed warming since the mid-20th century (see C2ES’s table of increasing certainty). The Working Group also significantly revised the upper bound of their sea level rise estimates (see Nature’s News Feature on this topic).

However, there is a feeling that we have reached a point of diminishing returns in our current lines of inquiry. As a recent Nature editorial pointed out, comprehensive assessments of climate science may no longer represent the best use of our resources; continued investment in the IPCC process as it stands may result in smaller policy-relevant returns over time. We should feel a great sense of achievement and satisfaction at having reached this point. However, we may also need to sit back in our chairs, grab some old-fashioned writing implements, and reframe our questions.

Let’s think for a moment about the audience for the IPCC. Mitigation and adaptation policymakers around the world are struggling to address two big questions: How do I evaluate my policy options and how do I act in the absence of certainty?

As a community, our most pressing issue is not how to resolve the remaining uncertainties in climate science, but rather, how to make sound decisions based on the information we do have.

This is a big question. However, to take advantage of this moment of self-reflection, I’ve begun a “wish list” of items for the IPCC to consider addressing as it grows and changes. Each of these items requires the rigorous involvement of the science community, but is aimed more explicitly at enabling decisions and action.

CPI will be updating this policy “wish list” over the course of the IPCC AR5 releases. In the spirit of WG1, these first items offer suggestions for climate science that is “policy-ready.”

  1. Uncertainty: We need rigorous thinking and aggregation across disciplines about how to productively make decisions in the face of uncertainty. For example, adaptation policymakers often use scenario planning to bracket uncertainty about the future. The IPCC’s Representative Concentration Pathways (RCPs), which replace the older Special Report on Emissions Scenarios, provide a common starting place for these exercises. How can we develop and share improved methods of managing uncertainty?
  2. Targets and indicators: Multiple options for global climate change targets exist, such as global mean temperature, atmospheric greenhouse gas concentrations, and cumulative emissions (see, for example, CPI’s work on tracking emissions and mitigation actions). In addition, there are many datasets that could (and do) serve as indicators of how well or poorly we are managing climate change.  Which targets and indicators are best suited for specific policy needs?

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