One is higher taxes, to make polluters pay the full cost of their anti-social behaviour.

ECONOMIST: When children should be screened and not heard

Governments increasingly accept the need to put a price on the damage carbon does, and make polluters pay that price.

ECONOMIST: Cleaning up

Maybe you could look at the ethics of "free riding" or possibility of introducing measures that make polluters pay rather than take advantage of the conscientious?

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The legislation would force about 500 of the biggest polluters to pay for each tonne of carbon dioxide they emit.

BBC: Australia parliament passes divisive carbon tax