It's not. Ice core isotope evidence gives you resolution all the way down to a year or two. We're seeing a first derivative of temperature that is simply unattested in any of that data. Or any other data source, honestly.
It's true that over thousand year timescales the earth has seen excursions larger than this. We have no evidence anywhere for anything happening this fast in the climate other than large impact events.
It's true that over thousand year timescales the earth has seen excursions larger than this. We have no evidence anywhere for anything happening this fast in the climate other than large impact events.