High-consequence outcomes and internal disagreements: tell us more, please

This article is one of several in this special double-issue that reports the views of “users” of IPCC reports. I am a user in the sense that I advise the policy-making community and rely on the IPCC reports to provide me with authoritative views on the state of the science. My principal recommendation for making the IPCC more helpful to the policy-making community is to strive in the Fifth Assessment Report (AR5) to communicate fully what the climate science community understands and does not understand about high-consequence outcomes. This will require the AR5 authors to provide vivid information about future worlds where high-consequence outcomes have emerged. It will also require the AR5 authors to reveal any disagreements persisting among them after the give-and-take of the writing process has run its course. In the Fourth Assessment Report (AR4) the presentation of high-consequence outcomes had shortcomings that can be rectified in AR5.