The essential injustice of global warming is that the poor will suffer the worst effects while contributing far less to carbon emissions than the rich. So here's a radical solution: divide greenhouse-gas emissions by population, and give everyone in the world the right to emit the same amount of carbon—a personal carbon allowance.
Essentially, allowances are a cap-and-trade scheme for individuals. They set a clear target and let the market work out the details. Bike to work and live beneath your allowance, and you can sell your carbon credits to energy spendthrifts who refuse to give up their SUVs. The balance of your allowance might be recorded on a sort of carbon-debit card, so if you buy that SUV, you'll be spending carbon too. If you want to keep living as if it's 1989, all you have to do is pay for it.