Pointed out above, he'd turn into a rotting corpse which emits CO2 and Methane which is much more powerful.
Which by the way, is what marks the point of no return, - since temperature in enough quantity will unleash the methane stored in the Siberian territories, there will be so much greenhouse gases around that what we humans emit is like a toothpick in Hell. Then BAM, hit the boiling point at certain areas (for Farenheit people that is 100 degrees celcius), and there will be no turning back.
So, is it worth a fight?