Why Did the Mongol Army Retreat from Conquering Europe?

Why did the victorious Mongol army suddenly retreat from Central Europe in 1242? Using data analysis of tree rings and historical documents, a study by Nicola Di Cosmo, Luce Foundation Professor in East Asian Studies in the School of Historical Studies, suggests that Europe could have been rescued by its own bad weather. Read more via New Scientist http://ow.ly/wIiZ300EBLv