In climate change science, the existence of a high degree of uncertainty seems to be the cause of anxiety for many scientists because it appears to undermine the authority of the science. One of the assertions made by the so-called sceptics against the scientific consensus on climate change is that because the science is so uncertain, there is no basis for taking action. The response of the climate change science community has been to develop in-depth analyses of uncertainty of increasing sophistication and complexity. In most areas of policy making, the normal situation is characterised by complexity, ambiguity and uncertainty. Therefore, dealing with uncertainty is not an unusual state of affairs for policy makers. However, the overemphasis given to uncertainty in theclimate science discourse by scientists working in the field has been self-defeating as it has led to confusion among the intended recipients of the policy relevant scientific knowledge and allowed room for scepticism to grow. Climate change scientists should instead communicate and engage with policy makers (and the public) on those things that we know with confidence.