If there is a hard data gap for this period, then Cato has done a positive service (for once) by pointing out that Warming Island might also have been disconnected from the land in this period... thus deflating the landmark's «poster child» status as an indication of unusual climate change. (dotearth.blogs.nytimes.com)
These previous mass extinction events (also known as the «Big Five») are hypothesised to have been caused by combinations of key events such as unusual climate change, changes in atmospheric composition, and abnormally high stress on the ecosystem (except in the case of the Cretaceous, which was caused by an asteroid impact and subsequent effects). (treehugger.com)
There are additional risks related to commodity investments due to large institutional purchases or sales, and natural and technological factors such as severe weather, unusual climate change, and development and depletions of alternative resources. (proshares.com)