Get Out Your Thimbles

James Hansen thinks we only need thimblefuls to prevent the coming ice age.

"If there were no humans on the planet, the long term trend would be toward colder climate. Another ice age cannot occur unless humans go extinct, or unless humans decide that they want an ice age. However, ‘achieving’ an ice age would be a huge task. In contrast, prevention of an ice age is a trivial task for humans, requiring only a ‘thimbleful’ of CFCs (chlorofluorocarbons), for example."
http://www.columbia.edu/~jeh1/2007/IowaCoal_20071105.pdf

What you can do:
1. Get out your thimbles
2. Fill them with CFCs
3. Throw them up in the air