(last updated 9:05 a.m. 9 December 2009).

I get so many questions from readers about a variety of global warming issues that I thought I would whip up some Q&A for those who want to understand the views of skeptics a little better. I will try to update these with links and additional answers as time permits.

Climate science is complex and the study of it is highly specialized. Nevertheless, there is a common theme that runs through the claims of the global warming establishment, from Al Gore’s movie An Inconvenient Truth, to the UN’s Intergovernmental Panel on Climate Change (IPCC): Weather and climate events that happen naturally are being increasingly blamed on the activities of humans. So, causation is at the root of most beliefs about global warming and climate change.

As one digs further into the science, the direction of causation also emerges as a key theme, and it is one that can totally change the degree to which it appears humans affect the climate system. In my own area of research I have found that mixing up cause and effect when examining how cloud cover varies with temperature has greatly misled the scientific establishment regarding how sensitive the climate system is to our addition of greenhouse gases to the atmosphere.

Not all skeptics believe the same things, though, so some skeptics will object to some of what I have listed below. These represent my opinions, not all of which are necessarily ascribed to by other skeptics. Additional details on many of these issues can be found throughout this website, including a Q&A list I published on April 19, 2009.

The following list, in no particular order, are my responses to common claims and accusations about global warming skeptics. If other scientists or laypersons want me to add to the list, or want to argue for changes, email me and I will update it as appropriate. Please be sure to check back for the latest update (posted above).

1. Skeptics deny global warming. No, we deny that warming has been mostly human-caused.

2. Skeptics are paid by big oil. The vast majority of skeptics have never been paid anything by Big Oil (me included).

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. Kevin Trenberth has now famously admitted as much in one of the Climategate emails, where said it’s a “travesty” that we don’t know why warming has stopped in the last 7 to 10 years. For century-time-scale changes, some believe it is cloud cover being modulated by cosmic ray activity, which is in turn affected by sunspot activity. A few others think it is changes in the total energy output of the sun (possible, but I personally doubt it). In my opinion, it is internal, chaotic variability in the ocean and atmosphere circulation causing small changes in cloud cover. Since clouds are a natural sunshade, changing their coverage of the Earth will cause warming or cooling. The IPCC simply assumes this does not happen. If they did, they would have to admit that natural climate change happens, which means they would have to address the possibility that most of the warming in the last 50 has been largely natural in origin.

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! Yes, I agree. But the direct warming effect of moré 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.

11. But we can’t keep pumping CO2 into the atmosphere forever! No, and we won’t. Assuming fossil fuels will be increasingly difficult to find and access in the coming decades, the continuing demand for energy ensures that new energy technologies will be developed. It’s what humans do…adapt.

12. But we shouldn’t be interfering with nature! Actually, it would be impossible to NOT interfere with nature. Chaos theory tells us that everything that happens, naturally or anthropogenically, forever alters the future state of the climate system. I predict that science will eventually understand that more CO2 is good for life on Earth. This doesn’t mean it will be good for every single species…but when Mother Nature changes the climate system, there are always winners and losers anyway. In the end, this is a religious issue, not a scientific one. Interestingly I have found that the vast majority of scientists also have the religious belief that we should not be impacting nature. I believe this has negatively affected their scientific objectivity.