Ron Bailey has a rational discussion of them, and a well-deserved slap at scientists who fancy themselves policy makers:

…a word of unsolicited advice to scientists who want to play in the public policy arena. Facts by themselves do not immediately entail the adoption of particular policies. Many of the scientific “facts” cited by activists arise from contested epidemiological data and controversial computer models. For example, if humanity is significantly warming the planet, it is entirely possible that the best policy is to encourage rapid technological progress and economic growth so that any problems caused by such warming can be dealt with more effectively and fairly in the future. And how does one make the trade-off between possibly harming a few species of birds through the use of DDT, and using the insecticide to prevent the deaths of millions of people each year from malaria? These are political decisions. Suggestive scientific data certainly help guide our decisions, but they do not mandate any particular policies