I missed that. He's still posting though.
Anyway, I totally agree that having less people on the planet would reduce climate change, if that's what you're saying. According to your Guardian article, having less Americans and Australians (who produce the most CO2) would seem particularly useful.
There are a number of organizations and charities working on reproduction control, even a UN body called UNFPA. They are trying to do something about it. And scientists are writing about it, as the Guardian article shows.