There are legitimate debates to be had about the relationship between carbon dioxide and global warming (although I think the debate is now overwhelmingly in favor of those arguing for a close and increasingly dangerous connection). But I know of no one who has any clue about the issue saying something like this:
Just as you shouldn't go grocery shopping when you're hungry, you probably shouldn’t discuss climate policy during a heatwave ... Because the thing about this global warming thing is that it's [sic] effects aren't global. The Southern hemisphere, for instance, is having a pretty frigid time right now, with snow in South Africa (as Kathryn pointed out yesterday) and some real 'brass monkeys' (as we'd say in the UK) in Argentina and New Zealand. And even in the US, a friend of a friend in Alaska on a fishing trip says it is so cold and stormy out there they can't get out on the water.
I would have thought that even a minimal understanding of global warming would grasp that indeed it will result in many parts of the earth getting much colder. No: increasing heat-waves in the US do not prove anything as such (they're just the latest in a mass of data pointing in one direction). But the idea that because there's a cold snap in South Africa, global warming is a hoax is, well, the kind of thing you now read at National Review.