Carbon dioxide - part 1

If human made CO₂ has an effect it could equally be that it actually constrains natural global warming rather than the opposite?

No. This could certainly not equally well be the case. It is well‐understood and experimentally proven that CO₂ enforces the greenhouse effect. The feedbacks in the climate system makes it hard to say exactly how much warming this increased greenhouse effect will lead to, but both from the record of past climate change and our physical understanding of CO₂ and its effects, nothing points to that increasing CO₂ levels would imply cooling or inhibit warming.

-- Sune O. Rasmussen, post doc