Interesting article by the man that invented the email that email contributes to climate change. (I've used the term global warming in the headline as it's more emotive, sorry).
If we take the example, where just replying "thank you" to emails creates 16,433 tons of carbon every year, just think about what happens with the 100 million emails that Google alone traps everyday as spam.
Lancaster University’s Prof Mike Berners-Lee — brother of web inventor Tim — estimates that the energy used to process 64 million emails creates 23,475 tons of carbon a year. If each adult sent just one fewer a day, it could save 16,433 tons a year.