The medieval warming period was at least 2.5 degrees warmer than today. That number is the revised number, revised by the climate alarmists of today. The original number was estimated to be 5 degrees warmer. Why was it revised? According to Michael Mann and a few of the other frauds, the period of warming between 950 ad and 1250ad was regional not global. How do they know this? Hey, they're experts!
Why did they revise it? Because the Medieval warming period was a time of prosperity. Humans flourished. Food was abundant. This conflicts with their predictions of gloom and doom from a 1.5 degree temp increase. If island nations were not covered by oceans after a 5 degree temp increase, then how could an increase half that amount cause a calamity for humanity?
How do we know the climate alarmists are wrong? That's is easy. During the warming period much of the ice covering Greenland disappeared and human began to farm the land. Snow caps that normally covered European mountain tops receded and farmers began growing grapes and other crops at higher altitudes. These thing would not be possible today. So clearly the temperature increase of that time had to far more than what they claim we have experienced in this era.
Climate change is real. The climate is always changing as the earth is always changing. But global warming is a myth, a hoax.