"When it goes from zero to even a very small charge, it can feel very bad," said Dan Ariely, an economics professor at Duke University. "It creates a very small financial burden but a very big emotional reaction."
That quote from an interesting article in The New Republic that talks about the success of the Washington, DC plastic bag tax. On 1/1, stores began charging shoppers a tax of a nickle per plastic bag and bag use has gone down 50%. The article then makes the connection to a carbon tax and how even a tiny fee is better than no fee because of reason Ariely states above.
The article also mentions a failed $0.20 bag tax in Seattle that potentially reached too high. Nickle bag tax for everyone!