Nope, the tree huggers are not proposing to tax chocolate as a way to slow global warming, the global warming deniers are raising the price of chocolate because of their insistence that we do nothing to combat global warming. According to an article in the Washington Post, cocoa production in the Ivory Coast and Ghana, which account for 70 percent of world production, has declined in recent years as a result of dry weather and the spread of a fungus.
Is this due to global warming? Well, we can only have probabilities, but we have to act on probabilities all the time. For example, we invaded Iraq ostensibly because there was a high probability that Saddam Hussein was developing weapons of mass destruction. (Some of us did know the probability was near zero, but no reason to go there.)
Anyhow, when we get people crying tears over the harm that will be done to people if carbon taxes or other restrictions on greenhouse gas emissions raise their energy prices we have to ask where are their tears when people pay higher prices for chocolate or other foods due to the effects of global warming? Or when they have to pay more taxes to pay for the damage from storms like Sandy?
When costs rise the economy doesn't care whether it was due to a government imposed tax or the impact of human caused global warming. The effects are the same. If the former is "job-killing" so is the latter.