"This statement is simply incorrect. While it is true that the globe’s temperature varies over the course of thousands of years as a result of Milankovitch cycles and other causes, there has not been any time in the past 650,000 years when the global average temperature has been higher than it is today. What the author is most likely referring to is the Medieval Warm Period (800-1300 AD). During this time, the average temperature was higher than normal in the European region and perhaps part of northern Asia. However, when you compare the average global temperature of both the Medieval times and current day, the average temperature today is much higher than it was back in Medieval times."

You assume that proxy measurements are correct. However there is no reason to believe this is the case as no one has used a time machine to go check if proxy measurements actually match real temperatures. However the accounts from the medival warm period provide direct evidence indicating that the proxy measurements are garbage.