I did not see the ABC special the other night on climate, but I am told that as a skeptic of the extreme global warming scenarios, I was compared to both a holocaust denier and a tobacco executive. Boy, you gotta love free scientific inquiry!
One of the tricks of all debaters, not just climate folks, is to create a straw man opponent who is easy to knock down. Now apparently this show did not even bother to interview a skeptic at all, but they chose as their straw man "people paid off by the oil companies who believe man has no effect on climate."
Well, gee, I certainly can see how with current state of knowledge it is getting tougher to credibly sell the "no impact at all" argument, but I would say that with climate and all its vagaries its still a position that a person can stake out and not be a wacko.
There is, though, a middle ground of skepticism that falls somewhere between "man has no effect" and "temperatures will rise ten degrees and the world will end unless we make Al Gore our economic dictator."
One of the things they never explain on shows like ABC's is that most
climate scientists agree that when other variables are held constant
(more in a minute), increases in CO2 will only increase global
temperatures by 1-2 degrees, some of which we have already seen. It is
seldom mentioned in the press that there is a strong diminishing return
relationship between CO2 levels in the atmosphere and warming (leaving
everything else equal for a moment). So, the next doubling in CO2
concentrations will have substantially less impact on global
temperatures than the last doubling. This is something that most
reputable climate scientists will agree with.
So, how do climate researchers get 6-8 degress of additional warming or
more in their models? They get it from positive feedbacks. Most of
Nature's processes are negative feedbacks -- push a pendulum one way,
nature tries to bring it back to the center. Positive feedback is like
a rock balanced on the top of a mountain -- one little push and it
starts rolling faster and faster.
Climate scientists posit (but as yet have not observed and can't prove)
a number of feedback processes that might tend to amplify or dampen the
effect of increase atmospheric CO2 on global temperatures. The easiest
to understand is the effect of water. As temperatures rise due to CO2
concentrations, one might expect clear air humidity to go up worldwide
(as higher temperatures vaporize more water) and you might expect cloud
cover to increase (for the same reason). If water vapor goes mostly to
humidity, then global warming is accelerated as water vapor in clear
air is a strong greenhouse gas. One to Two degrees of warming from
increased CO2 might then become four or six or eight. If instead vaporized water mostly
goes to cloudcover, the effect of CO2 is instead dampened since more
clouds will reflect more sunlight back into space.
Generally, one can make two observations about how most of the climate models
that make the news treat these positive and negative feedback loops:
- Climate scientists tend to include a lot of positive feedback
loops and downplay the negative feedback loops in their models. Some
skeptics argue that the funding process for climate studies tends to
reward researchers who are most agressive in including these
- The science of these accelerating and decelerating effects is
still equivocal, and their is not much good evidence either way between
positive and negative feedback. We do know that current models with
heavy positive feedback loops grossly overestimate historic warming.
In other words, when applied to the past, these positive-feedback-heavy
models say we should be hotter today than we actually are.
My much longer article on the same topic is here, where I also address other things that may be happening in the climate and reasons why a poorer but colder world may be worse than a warmer and richer world. I recommend to your attention this article, which is the best statement I can find of the skeptical middle ground.