The reason was a number of erupting volcanoes at various locations around the globe, the documentary says (32:10) that it cooled the global climate for almost 500 years. (notrickszone.com)
How does the heat from erupting volcanoes under the West Antarctic Peninsula's ice sheets and surrounding waters affect ice - shelf formation and break - up? (dotearth.blogs.nytimes.com)
Forget erupting volcanoes in Iceland and the meltdown of the Greek economy. (washingtonlife.com)