To what extent should scientists differentiate in their role as ‘pure’ scientists and their role as public educator, advocate, activist, or whatever other public role they may want to assume? James Hansen is not afraid to voice his political opinion. As expected, he is viciously attacked for that by political opponents, but others, even if not in agreement on everything he sais, give him credit for differentiating clearly between talking science and providing a personal opinion. I definitely do.
Roger Pielke Jr frequently takes issue with how scientists blur these roles. He often charges that scientists (especially those from RealClimate are a frequent target) “argue politics through science”, i.e. pretending to talk only science, but in the meantime providing a value-laden political stance. Now that all depends on what he means by “politics”.
Climate scientists more and more speak out about the need to (drastically) reduce emissions. IMHO, they do so based on an understanding of the science. Of course, it is also based on a value judgement, that the risks posed by unmitigated climate change are undesirable. Roger’s point (I think) is that this value judgement is not widely shared. He may be right in that, but I think that the vast majority of people opposing the need to curb emissions do so for reasons other than science, and then rationalize that decision by twisting the science around so that it fits their pre-conceived wish not to curb emissions. There are preciously few people who really accept the science, and still strongly argue against emission reduction.
Consider the analogy of a lifelong smoker who goes to see his doctor for breathing problems. The doctor may say: “All the indications point towards your lung function deteriorating. This is very likely related to you having smoked for X decades. In order to minimize the risk to your health, I urge you to quit smoking.”
That is what I see Gavin Schmidt and many other climate scientists doing. And I find it perfectly legitimate, even desirable, that scientists (as well as doctors) share their knowledge about risks with those who need to know.
If the doctor were to say as the last sentence instead “(…) I urge you to take these nicotine patches” he would act as a stealth advocate, since there are many more options to quit smoking that the patient may want to chose from.
If the patient is so hooked to his cigarettes, and would rather continue smoking than extend his statistical life expectancy by X months, he is free to do so. If however he rationalizes that decision by claiming “smoking isn’t bad for your health at all. My dad was 96 when he died in a car accident, and he chain-smoked his whole life!”, the doctor would be right to reply: “You’re mistaken. Smoking is definitely bad for your health. If you keep smoking, your life expectancy will be X month less than if you quit smoking, and you will have more breathing problems. It is your choice whether or not to quit smoking, but you should make your choice in the full knowledge of these consequences”.
This highlights a different problem. One could argue that by continuing to smoke, the patient really only impacts his own health negatively (and those who breath the second hand smoke; likely not the doctor). If the majority of people, and especially the people in power, decide to ignore the problem and not change the trajectory society is on, it is everybody who suffers. Even worse, those in different parts of the world, and those who have yet to be born, will suffer the most. That makes it much more difficult to just say “I don’t care if you quit smoking, as long as you realize the risks”.
So climate scientists could perhaps be more specific about this, by saying e.g.: “You’re mistaken. Unabated CO2 emissions will very likely cause substantial climate change, with serious consequences. So you should decide your course of action based on this knowledge. If you don’t care about these risks, that is your perogative. However I do. Please find yourself another planet to experiment on.”