Wednesday, December 9, 2009

Global Warming Skepticism 101

Global Warming Skepticism 101

Informative summary From Dr. Roy Spenser 12/9/09

A few excerpts from Spenser with [my notes]:
1. [AGW]Skeptics deny global warming.
No, we deny that warming has been mostly human-caused. [Scientists should be skeptical, even of skeptics. Science is not pitch a view, it is to advance understanding].

2. Skeptics are paid by big oil.
The vast majority of skeptics have never been paid anything by Big Oil (me included). [It's not as easy to get a grant as an AGW skeptic. Note: several recent revelations show big oil is pandering to AGW folks.]

3. Skeptics don’t publish in the peer reviewed literature.
Wrong…but it is true we do not have nearly as many publications as the other side does. But it only takes one scientific study to destroy a scientific hypothesis, which is what anthropogenic global warming theory is.

4. Skeptics are not unified with an alternative explanation for global warming. Well, that’s the way science works in a field as immature as climate change science. The biggest problem is that we really don’t understand what causes natural climate variability.........

5. But the glaciers are melting!
Many glaciers which have been monitored around the world for a long time have been retreating since the 1800’s, before humans could have been responsible. A few retreating glaciers are even revealing old tree stumps…how did those get there? Planted by skeptics?

6. But the sea ice is melting!
Well, the same thing happened back in the 1920’s and 1930’s, with the Northwest Passage opening up in 1940. It was just as warm, or nearly as warm, in the Arctic in the 1930’s. Again, this is before humans could be blamed. There were very low water levels in the Great Lakes in the 1920’s too, just as has happened recently. We have accurate measurements of sea ice cover from satellites only since 1979, so there is no way to really know whether sea ice cover is less than it was before.

7. But we just had the warmest decade in recorded history!
Well, if thermometer measurements had started in, say 200, AD (rather than in the 1800’s), and it was now 850 AD, the same thing might well have been said back then. The climate system is always warming or cooling, and the Industrial Revolution (and thus our carbon dioxide emissions) just happened to occur while we were still emerging from the Little Ice Age…a warming period.

8. But the Antarctic ice shelves are collapsing!
Well, sea ice around Antarctica has been expanding since we started monitoring by satellite in 1979….so which do we use as evidence? There is no convincing evidence of warming in Antarctica, except in the relatively small Antarctic Peninsula, which juts out into the ocean. Just as glaciers naturally flow to the sea, ice shelves must eventually break off. It is very uncertain how often this happens through the centuries, and what has been observed in recent years might be entirely normal. Similarly, it was warmer in Greenland in the 1930’s than it has been more recently.

9. But the sea levels are rising!
Yes, and from what we can tell, they have been rising since the end of the last Ice Age. Again, the more recent rise might be just a consequence of our emergence from the Little Ice Age, which bottomed out in the 1600’s.

10. But we keep emitting carbon dioxide, which we know is a greenhouse gas!
But the direct warming effect of morĂ© CO2 is agreed by all to be small…and I predict that when we better understand how clouds change in response to that small warming influence, the net warming in response to more CO2 will be smaller still. This is the “feedback” issue, which determines “climate sensitivity”, the area of research I spend most of my time on. I and a minority of other scientists believe the net feedbacks in the climate system are negative, probably driven by negative cloud feedback. In contrast, all twenty-something IPCC climate models now exhibit positive cloud feedback.