Conservatives seem to be allergic to “big government” in any form,

This is a feature of conservativism, not a bug. :-)

but the plain fact is that without major policy change — i.e. ending massive subsidies to fossil fuel companies and passing strong enough regulatory bills and tax incentives to give corporations the incentive to stop externalizing costs and reduce their massive carbon footprint, nothing will be done till it is far too late.

Odd comment, in view of the facts. Per capita carbon emissions in the US are at their lowest levels since 1950.

Fact is that there are a lot of adaptations that conservatives would be amenable to accepting which (a) would continue the per capita decrease in US emissions AND (b) do not lead to big government. Yes, SPENDING of tax dollars into the economy is involved, but all that needs to be done is make adaptations economically desirable instead of being economically UNdesirable. Pretty simple stuff, that.

And, if you do THAT, you don’t need to touch the oil companies; these are some of the best run businesses in our economy, and if they see serious profits moving into alternatives, they’ll be all over it. Exxon, for example, has made serious investments into biodiesel and natural gas, which is certainly not their core exploration and production business.

The “free market” of itself will do anything at all to increase their bottom line

True. Again, a feature, not a bug. The mission of good governance is, like a good race horse, to train it and reap benefits when they win, not hook the horse up to a plow and hobble its potential.

Only a government that serves the public interest — that is, a LIBERAL government —

Now, you’re just being silly. You and I both know that there’s no such thing as a liberal party in the US. We have two conservative parties; it’s just that one is honest about their conservatism, and the other pretends to be liberal to attract the votes of the uninformed and idealistic.