Why? Well, warm periods have occured in the past, and if not the medieval period, then probably the last interglacial (120,000 years ago), certainly the Pliocene (3 million years ago), without question the (Eocene 50 million years), and in particular the Paleocene-Eocene Thermal Maximum (55 million years ago), and so on. Current theories of climate change do not rely on whether today’s temperatures are ‘unprecedented’. Instead they examine the physical causes of climate change and match up what we know about their physical effects and time history and see which of the multiple drivers or combination can best explain the observations. For the last few decades, that is quite clearly the rise in greenhouse gases, punctuated by the occasional volcano and mitigated slightly by the concomittant rise in particulate pollution.
The Climate of Gavin
2 hours ago