Read here. Pro 'cap & trade' profiteers and climate alarmist scientists like to claim that modern warming is "unprecedented" and is having a large impact on the current climate. Based on actual empirical paleo-climate evidence across the globe, previous warming and cooling periods had much larger impacts on climate than the modest and short warming that has occurred since the mid-1800's.
As the U.S. climate agency's own data shows, the MWP had a huge impact on climate as this graph of annual precipitation represents - for several centuries the MWP generated extensive drought conditions, often referred to as 'mega-droughts'. This data is from Mono Lake in the Sierra Mountains of eastern California. (click on image to enlarge)
"The occurrence of these droughts is validated by an independent lake-level record from the neighboring Sierra Nevada Mountains. The timing of coinciding low lake levels from the Mono Lake record (Stine 1994) is shown....Droughts of this character, were they to occur today, would clearly have a devastating impact."