I've taken my time in responding to the latest slew of links and videos not because of the level of difficulty (although it was difficult) but by who presented them.
I am primarily responding to this link and the video links included therein.
Denis Rancourt is a published physicist who is also by most accounts a pretty good teacher. So when someone of substance states that AGW is a crock and goes on to present evidence that seemingly demonstrates that I have to take my time and consider the evidence carefully.
To begin, I am not a physicist, my higher level math skills are sorely lacking. So I will be the first to admit when confronted by an accomplished physicist I feel I am out of my depth.
I started off with the video links where he outlines the very basis of the physics of climate change. I will say my estimation of him as a teacher rose considerably because how he illustrated the basic equation that governs how hot the earth is based on energy input from the sun, I grasped immediately. I watched through the video two more times to make sure I understood the implications.
The basic equation is as follows (Is)=(a)(Is) + (E)(Is)oT^4 where (Is) is Intensity from the sun, (a) is albedo of the earth and (E) is emissivity of the earth and T is the temperature.
The equation must balance. Energy going into the system must equal energy going out otherwise T will rise or fall accordingly to make it balance. If (Is) increases and all other factors of (a) and (E) remain the same then T will increase.
He agrees that the atmosphere provides a greenhouse effect of a net increase of roughly 33 degrees Celsius. He agrees that a doubling of CO2 in that atmosphere will in the worst case scenario increase the temperature 1.4 degrees C.
1.4 degrees C 42 minutes in.
Keep in mind that is lower than the lowest estimate of what the impact of doubling CO2 will have (1.5 to 4C). But let's go with that for now.
@43:58 changing (a) or (E) has a much bigger effect. 100 times or 2 orders of magnitude. What could be a bigger change of land use than the disappearance of our ice caps? Droughts that are brought about changes in the hydrological scale that precipitate wildfires that devestate our forests and accelarate the creation of deserts.
I agree with him that CO2 alone isn't enough to raise the temperature to the levels of the geologic historical average of 22C. No climate scientist I know of has said that CO2 is the only driver of climate, not even that it is the main driver of climate.
It is a very basic acknowledgement that the sun is the main driver of climate.
CO2 is however, one of the levers of climate that we have out hands on. And all things being equal, this is what is driving the warming we are seeing right now.
Looking at the problem in isolation, it is perfectly rational to conclude that CO2 by itself will never have a significant impact on our climate. But from Denis's own presentation of the formula and by his own words there are other aspects that would have way more impact. Albedo for example. From his own words he thinks that land use which impacts the reflective/absorptive properties of the earth would have a far greater impact than CO2. As we know when we are talking a 1 or 2 degree increase in global average temperature we are not saying that the temperature increase will be equal across all latitudes. It will in fact be disproportionately higher in the extreme northern and southern polar regions in comparison to the equatorial regions. A large enough increase in which we see a significant reduction in old ice sheets which have a coincidently large impact on the albedo of the region. If the northern and southern poles of our world which were historically the air conditioner of our planet experienced warming which reduced the extent of the ice sheets, what happens to the (a) in the equation. What happens to albedo? It reduces, reflecting less (Is) and thus further raising T. Which starts to further reduce (a) which increases the amount of (Is) that remains and thus increases T. This is called a positive feedback loop. Of course there is an upper limit that (a) will decrease with the disappearance of the ice sheets, but I would ask Denis who is a superior mathematician to calculate what the increase in T would be from that. After we figure out that increase, what other positive feedback loops kick in at that new level of T? The release of methane from the clathrates from the ocean? Which would then change (E).
Yes the atmosphere does have some cooling effects, but we both agree that the net effect of the atmosphere is warming. Change the (E) of the atmosphere then you end up retaining more heat than you radiate away into space.
Another part of his article I have some difficulty accepting is the graph he uses showing the historical temperature plotted against CO2 across geologic time (at 47:40). CO2 has been as high as 6000ppm in the past and the average temperature has been 22 degrees Celsius. Much warmer than today with much higher CO2 levels. Then he makes the statement that life did just fine. This is misleading for a number of reasons.
I will agree that CO2 historically has been much higher with seemingly less sensitivity when it comes to climate. I was curious as to why and in my research it turns out that 500 million years ago our suns output was a few percent less. This falls in line with stellar evolution of main sequence stars. As stars age, they burn hotter and output more energy.
Going back to Denis' equation at the beginning (Is) was smaller, so CO2 sensitivity is reduced proportionately. It could be much larger without turning Earth into Venus.
Now let's address what 22 degree Celsius means. It would mean for much of Earth's history, beings that could thermo regulate were at a disadvantage. To put it plainly, while Denis' is correct that life flourished, we have to look at what life flourished, the only animals that were of any great size were animals that were not warm blooded. You had snakes the size of school buses, but of our distant ancestors you only had mammals the size of mice. That was the only size that had the surface area to mass ratio appropriate to be able to thermoregulate in those temperatures. I encourage Denis to look up "wet-bulb" temperatures. These are temperatures at which animals our size, cannot get rid of excess heat even at rest, fully naked in strong winds. These are lethal to our kind of life. So yes, that is what we are saying, we couldn't survive that.
@52:52 it is the large mammals that are the most susceptible to extinction. The large ones are really endanger.
I couldn't agree more. We are large mammals.
This isn't an either/or proposition. It is not 'it is climate change OR habitat destruction'. It is climate change AND habitat destruction. Talking about immediate human impact on environment in no way lessens the importance of climate change and conversely climate change does not lessen to importance of our immediate impacts on environments through habitat destruction, pollution, and deforestation. They are additive, the causes do not substitute for each other. To speak of it as an either/or proposition is a red herring. Yes there are other actions we are responsible for, but it doesn't abrogate our responsibility for climate change.
@6:23 into part 2. About papers on how they got it so wrong.
If we go back to Denis' equation all those papers are trying to explain is where the (Is) went if it didn't raise T to the extent they thought it would. They are just balancing the equation. This would be the very same question Denis' would ask if he couldn't see that (Is) was reflected back into space through an increase in (a) or radiated out into space due to an increase in (E). If neither of those variables changed, (Is) has to end up somewhere.
Denis refers to ocean measurements as hauling water up and putting thermometers into it. This practice was supplanted by satellite measurements that started in 1967, well before climate change was on the scene. That this method is still in use has been perpetuated by Monckton and is very much false.
Basically part two devolves into one debunked myth after another (ie climategate, no access to raw data, scientists trying to protect funding over doing good science, etc). Which a few minutes on Google can set you straight so I'm not going to bother.
His argument then becomes that nature is too complicated to find any relationships between cause and effect. For which I wonder why is he a physicist at all, if he feels he can never truly know if a cause is truly a cause. I can agree that trying to model natural systems can be complicated, but as Denis showed us in the beginning, the basic formula can be scaled up to be as complicated as you need it to be (as you find more variables to model).
Denis' disdain for peer review is obvious. This can be traced back to his difficulties with the administration of U of O. Denis' does not hold any authorities body in good esteem so it is no surprise that he sees the peer review process in a similar light. His charge that scientists do not care about the truth anymore has no foundation. Any scientist that proposes to be an expert in their field is going to make sure that any paper they quote actually supports the science that they are doing, and I am not referring to any ambiguous political support, but technical and mechanical support of their work. This is how knowledge is built up. Previous scientists do the groundwork and those scientists that come after build upon it. It is a house of cards, if the base science doesn't support their work then all the work that follows is useless (or at least illustrates an unfruitful path). It is imperative that scientists understand what supports their work before continuing down the same path.
I've done much the same thing throughout this article. When Denis' has made a claim I've investigated the source to see if 1) it has merit 2) has it been misconstrued. For me to make an assertion that Denis is wrong without actually looking at the sources I would be doing exactly what Denis is accusing the vast majority of scientists of doing. However it is in my best interest to know the facts and speak only to those, to do otherwise weakens my argument. The same can be said of scientists, it is in their best interest to be sure that the work that has been done before actually supports their own work, for if it is knocked down (like a metaphorical house of cards) that does significant damage to their reputations as serious scientists and in the final analysis that is all any scientist has; their reputation.