JW: What we realized is that our climate system is capable of changes in temperature of magnitude equal, for example, to changing the climate of Minneapolis into the climate of Atlanta in four years, less time than it takes to get through high school. How do we know this? Because it actually happened a number of times in the past. Not frequently, and not recently — 20,000 years ago is the last instance of such abrupt change — but we know for sure that kind of change is a characteristic of earth’s climate system.
Such a dramatic change — several degrees on average rise or fall in 4 years — would also change