China, for instance, could slap an export tarif on goods sold to the US. (What would we do, start making widgets here? That'd be downright anti-American!) Then use the revenue from the tariff to fund climate research. Imagine how much could be raised by tariffs applied by every nation that sells to the US...

Sure, Trump could, and perhaps would, apply an import tariff on the very same goods, the revenue from which he'd probably turn over to the domestic coal industry. But I can only imagine the panic that would ensue as Americans watched prices skyrocket on all items marked "Made in XXXX," where XXXX != USA.