> Lots of well-informed stuff. It's nice to have someone on
> tap that actually knows the science involved. I have a
> question you can probably answer. One of the stock
> objection of greenhouse skeptics (like Herb Schmertz or his
> epigone that's still writing advertorials for Exxon now
> that they've become ExxonMobil) is that there have been
> large variations in global temperature over the last 3
> millennia, and that variation during the "medieval warm
> period" (circa 1000 years ago) and the "little ice age"
> (circa 400 years ago) were both more extreme and happened
> more quickly than the variation we've experienced over the
> last century. The implication is that there are chaos-like
> structures leading to global temperature variation that are
> as yet unaccounted for in our theories, and that might well
> swamp the effects of human industry -- in which case, if
> we have to spend billions of dollars either way, we are
> better off spending them adapting to climate chage than
> trying to prevent it. Is there any truth to this position?
> Does it have an obvious flaw?
I'm not an expert. I'm a former physicist turned technical translator turned lexicologist turned linguist turned computer programmer trying to turn into a cognitive scientist, with a bizarre interest in economics. All that I've got that most people don't have is that I have absolutely no fear of technical scientific literature or heavy duty math.
I'm not a climatologist, but I read their papers. :^)
As I understand it, there is some truth to that argument, but it sidesteps the issue to some extent. There has been climate variation, some of it pretty severe, and the causes are not well understood. It is possible that what we are currently experiencing is in part natural climate variation. However, there is strong evidence that the climate changes over the last century are at least in part caused by humans.
The logic goes something like this:
We know as certainly as anything can be known in science, that increasing the amount of carbon dioxide in the atmosphere will raise the amount of heat the atmosphere retains. This is an uncontrovertial result of simple chemistry. We know that a significant part of the carbon dioxide currently in the air comes from burining fossil fuels - that too is easy enough to check. The conclusion that global warming is therefore happening at least in part due to human activities shouldn't be too controvertial.
The question of how much of that warming can be positively attributed to human means discussing climate modeling. The current models are pretty good at predicting year to year climate variation. How good "pretty good" is depends on your expectations. The current set of models predicts, within a fair margin of error, current average temperatures and precipitation. All of those models point to human emissions as the source of most of the post 1970 warming, not natural variation.
Now, a lot of the criticism of global warming that I've seen comes from criticising modelling as an approach to science. All I can tell you is a that physics, chemistry and biology have come to rely on modelling as a method. Even though computer modelling is a fairly recent development, it has been instrumental in the progress made in all those fields over the last decade. (It's even beginning to make progress in linguistics, but that's another post.)
Modelling isn't certain, but obviously waiting to see how well the models predict long term climate change isn't an option either.
Now, I imagine that a case can be made that we would be well advised spending money learning to deal with climate change, but I can't see how that eliminates the need to deal with emissions. When you have a polluter pouring sulfuric acid into a river, getting the neighbours a new water supply is an excellent idea, but that doesn't mean you don't tell the polluter to stop pouring acid into the river.
Less carbon dioxide in the air may not be able to prevent global warming, but it can only make it less pronounced than it would otherwise be. The one thing that is certain, even without discussing climate modelling, is that more CO2 means more global warming in the long run.
Scott Martens
---
Envoyé par Moncourrier.com Vous aussi obtenez gratuitement votre adresse électronique sur Moncourrier.com