How does Revkin try to refute some of the “uncertainties” about climate science throughout the article?

http://dotearth.blogs.nytimes.com/2014/09/26/certainties-uncertainties-and-choices-with-global-warming/

Read the essay, and answer this question: How does Revkin try to refute some of the “uncertainties” about climate science throughout the article? List all the specific points. half page.