Many people in positions of power -- and not just global warming skeptics -- believe the following two things:
- Economic growth is an engine driven by fossil fuels. Remove all restrictions on fossil fuel use, growth surges. Restrict fossil fuel use, growth slows.
- "Doing something about global warming" means restricting or capping carbon dioxide emissions, which means restricting fossil fuel use.
The inevitable conclusion is that the only way to fight global warming is to slow down and possibly cripple the economy. Thus you get calls for "certainty" about exactly how much damage global warming will do, so it can be weighed against the damage of mitigating global warming.
This picture of the situation is grossly distorted. Here's why, in a nutshell: