economist A summary of what the IPCC report said yesterday. This is a chart currently circulating in Deutsche Bank Research.
source: Jim Reid, Daily Chart, Deutsche Bank, August 9, 2021.
The entire IPCC summary for policymakers is here.
I had hoped to contribute to how to evaluate the predictive accuracy of the IPCC report, but it was more difficult than I thought (in an easy-to-understand language).So I pass on some informal ideas that have been circulated among some people in the know, and my colleagues are related to me Greg Nemet.
- The global average temperature is the most basic forecast, so it deserves attention
- Every IPCC assessment (2000, 2007, 2014, 2018, 2021/2…) will update the temperature forecast based on the most recent temperature observations.
- The clearest way to reveal any changes is in the “carbon budget”, that is, how many tons of carbon dioxide can be emitted into the atmosphere before reaching a temperature change of +2 degrees.
- The carbon budget in the 2014 report has been expanded because the model has been “hot” compared to observations
He also pointed me out Twitter thread from Zeke Hausfather (I usually don’t link to tweets, but I am an exception here). This topic describes how they use results and predictions to narrow the “range of sensitivity”, which is the range of possibilities. Using my prediction language (which may not be the correct way to describe the statistics accurately), the point prediction is relatively unchanged, but the prediction interval is smaller.
