El gran debate sobre el calentamiento global (segunda parte)

The video discusses the natural climate cycles and historical warming periods, highlighting the medieval warming era. It addresses skepticism about global warming, emphasizing the need for direct temperature evidence. The video explains the use of climate indicators, like tree rings and ice sheets, to map historical temperatures, leading to the creation of the hockey stick graph by Michael Mann. Despite skepticism about the graph's accuracy, it shows no period in the last 1000 years as hot as the late 20th century. The video concludes with a consensus on recent warming trends.

What methods do scientists use to calculate historical temperatures beyond the last century?

What is the significance of the hockey stick graph in the context of climate change?