Famously, “It's difficult to make predictions, especially about the future.” An outbreak of volcanic eruptions or some unprecedented change to global conditions could alter Lewis' timeline.
However, the major uncertainty is us. Lewis found that so much heat has already been added to the system that, even with drastic action on carbon emissions we probably cannot avoid reaching a point where 2015 conditions are the new normal. However, she found that not only can we delay that grim day, but for many regions we can prevent this outcome entirely, if we are willing to get serious about climate action.
Explaining why the global fate may not apply everywhere, Lewis told IFLScience: “At a regional level natural climate variation is more important than globally. In a single city temperatures might vary 10 degrees from one day to the next, but for the whole of Australia that might be one degree, and for the planet as a whole it would be tiny.”
As important as it is from a scientific viewpoint to consider the averages, Lewis stressed to IFLScience that this was not the whole story. “When a record hot season becomes average it means we will have summers that are much hotter still, and the impacts of those will be severe,” she said.
Anticipated dates for regions to hit the point where 2015 is the new normal vary, but many are frighteningly close. Lewis et al/ Bulletin of the American Meteorological Society