The Paris Climate Agreement seeks to keep global warming well below 2 degrees Celsius relative to pre-industrial temperatures. In the best case scenario, warming would go no further than 1.5 degrees.
Many scientists see this as an impossible goal. A recent study by Peter Cox et al. postulates that, given a twofold increase in atmospheric carbon dioxide, there is only a 3% chance of keeping warming below 1.5 degrees.
But a study by Richard Miller et al. provides more reason for hope. The Miller report concludes that the 1.5 degree limit is still physically feasible, if only narrowly. It also provides an updated “carbon budget”—a projection of how much more carbon dioxide we can emit without breaking the 1.5 degree limit.
Dr. Joeri Rogelj, a climate scientist and research scholar with the Energy Program of the International Institute for Applied Systems Analysis, co-authored the Miller report. For Rogelj, the updated carbon budget is not the paper’s most important point. “Our paper shows to decision makers the importance of anticipating new and updated scientific knowledge,” he says.
Projected “carbon budgets” are rough estimates based on limited observations. These projections need to be continually updated as more data becomes available. Fortunately, the Paris Agreement calls for countries to periodically update their emission reduction pledges based on new estimates. Rogelj is hopeful “that this paper has put the necessity for a strong [updating] process on the radar of delegates.”