UPDATE, 2022. This post, this question has been out for over twelve years, and yet still remains as valid as ever. — Jo
The all important question that rises above and before ALL other questions is the one of evidence.
Is there any evidence that carbon dioxide causes major warming?
In science, “evidence” has a very specific meaning and for a very good reason. In a court of law or a game of football, the label “evidence” can be plastered all over the place. If 500 footballers signed a petition to change a rule, that would be “evidence” the rule needed changing. But if 5 billion people signed a petition to make it rain in Mumbai on Thursday, that’s a waste of paper.
Science is only about the natural world. That’s why human opinions are irrelevant.
Scientific evidence for the theory that human emissions of carbon dioxide are the main cause of global warming needs to be:
- Empirical – That which we can see, hear, record, or write down. A measurement of some sort. An observation of the natural world.
- Related to CAUSE and EFFECT. That means evidence that shows that our extra carbon caused most of the recent warming. Not just evidence that the world has got warmer (which could be due to some other reason).
- Evidence that shows carbon has a major role, that doubling the level of atmospheric carbon dioxide would cause, say, 2 – 10 degrees of warming. If doubling carbon only causes 0.5 degrees of warming, who cares?
It doesn’t matter how many associations, unions, or Nobel-Prize-winning Saints believe in a theory. If they claim there is evidence, by thousands of scientists in peer reviewed papers, then it should easy for them to provide it. The problem is, all those thousands of papers are either not empirical, not related to the cause of the warming, or do not show carbon has a major role.
When we talk about the “Major Role”, we’re talking about Feedbacks. Nobody who is anybody believes doubling carbon on it’s own will warm us by much more than one degree C. The Pachuri-Gore-Hansen Team ($$) believe this warming will then cause changes in other factors (like humidity) which will then cause much more warming.
The history of humanity is full of people who were absolutely dead-set sure, and completely wrong. Climate models are not evidence: they are imperfect “simulations” of the climate, not the climate itself. Our global atmosphere is a messy algorithm, with oceans, clouds, rain, water vapor, solar wind, magnetic fields, forests, ice-cover, glaciers, volcanoes, heat from below, and moving dust clouds of soot. It’s just not possible to simulate the real atmosphere without making assumptions, estimates or decisions on which parts to simplify or omit. Since all those things rely on the opinions of the modelers, no matter how well intentioned or educated they are, a model is a glorified opinion.
When people claim they have lots of evidence, notice closely whether they can back that up.
This thread is for discussing papers that may fit the bill above. A lack of evidence (or even a mass of evidence that points the other way) will not win us the PR war. That’s a different debate.
IMAGE Credit: Thanks to Taw for the image I manipulated.