In his final testimony submitted to the Iowa Utilities Board on the proposed coal-fired power plant in Iowa, NASA’s James Hansen used a very provocative metaphor about the trains that deliver coal:
If we cannot stop the building of more coal-fired power plants, those coal trains will be death trains — no less gruesome than if they were boxcars headed to crematoria, loaded with uncountable irreplaceable species.
The President and CEO of the National Mining Association wrote Hansen a letter (posted here by Hansen with his response) complaining:
The suggestion that coal utilization for electricity generation can be equated with the systematic extermination of European Jewry is both repellent and preposterous…. I believe you owe the hard-working men and women of the coal mining and railroad industries an apology and respectfully request that you refrain from making such comments in the future.
Hansen’s reply was:
There is nothing scientifically invalid about the above paragraph. If this paragraph makes you uncomfortable, well, perhaps it should.
I have a slightly different view of the metaphor.
Now the head of the Intergovernmental Panel on Climate Change has moved up the deadline. In announcing the IPCC’s final report on Nov. 16, Rajendra Pachuari warned, 
Language Intelligence: Lessons on persuasion from Jesus, Shakespeare, Lincoln, and Lady Gaga
