Original message (edited to preserver identities):
A friend of mine sent me the link below to a video with claims against currently accepted ideas concerning global warming. Although I think I have answers to some of the objections in the video, I thought that you are far better informed to know where the claims are wrong:
I assume the claim that most sources of CO2 are natural can easily be answered by noting that what matters is not the total amount of CO2, but how it is changing and who is changing it.
However I never heard about the 800 year lag between increase of temperature and increase of CO2, did you ever heard of that?
Thank you in advance!
Here's the video segment:
So here goes...
I got about 30 seconds into it, and immediately I know it's bullshit. The second guy on the video is arguing that the atmosphere needs to increase temp with altitude is just plain wrong. Cooling high altitude atmosphere is a symptom of more IR radiation being absorbed at the surface. This is perfectly well predicted by physics. And it's actually evidence FOR global warming, not against it.
As for the 800 year lag... there is a lag in the sense that it takes time for the CO2 we've added to the atmosphere to fully absorb all the radiation it can, but I don't know what the number is. The problem is that this makes global warming scarier. There is no sharp moment in time where we aren't warming and then, bang, 800 years later, the temperature spikes. We are warming from the first moment CO2 is added. And even if we stabilize our current CO2 levels, the lag means the temperature will keep going up. You can't say that we are warming now as a result of something that happened 800 years ago. If we had been warming, and then it stopped, that would be a sign that the CO2 had absorbed all the IR it could.
Global warming has been studied since 1895 (it was first proposed as a theory then). It's not like it's a back of the envelope calculation from some grad student ten years ago.
Their understanding of global warming is absolutely false. It's hard not to make this any clearer.
They also try to argue that CO2 comes after the warming. The models are pretty clear about how this works. Warming can be triggered by other factors, but once warming begins, there is a positive feedback between warming and CO2 release, and water vapor release that further drive warming. The CO2 is released from ices, permafrost, frozen biomatter, etc. CO2 wasn't the initial cause of the warming in the past, but it did drive the warming to increase rapidly. Naturally, it is normally triggered by orbital changes. The problem they are missing is that CO2 absorbs infrared. This is just a matter of chemistry/physics. The CO2 absorbs the IR radiation/heat and then emits it, but instead of it heading straight out into space, it sends it off in a random direction, where it hits another CO2, and on and on, until it randomly, eventually, makes it out of the atmosphere. But it takes so much more time to get out, that the effect is to heat the atmosphere with all the extra energy bouncing around. The more IR absorbers in the atmosphere, the longer it takes, and the more we heat up. O2 and N2 are transparent to IR radiation, so they have no impact. Some molecules like methane are more significant greenhouse gases because they absorb more wavelengths of IR.
They talk about how the temp has "only" gone up half a degree C in 150 years. The problem here is that there is no evidence in the ice cores or in tree rings or paleobotany, or via any other means, that the temperature has EVER risen this fast, this quickly. It seems slowly on a human lifespan, but geologically, it's the blink of any eye.
But the thing it, it doesn't matter where in the cycle you get started. If you start heating the Earth, great, we get warmer, the CO2 goes up as it's released from the soils and such, and we get still warmer. Or, you add the CO2 first, and then we get warmer, and then more CO2 or methane or water vapor gets added because it's warmer, and so it gets still warmer. (Never mind the albedo effects.) Ignoring the fact the CO2 absorbs IR is to reject most of particle physics and modern chemistry.
The fact that we aren't the "main source" of CO2 is beside the point as well. What matters is that without manmade CO2, the atmosphere had been in equilibrium. The balance of CO2 (and this can be measured in ice cores, etc.) was stable for tens of thousands of years. The animals and volcanoes, etc., etc., put CO2 in the atmosphere, and the plants and the ocean, and other carbon sinks, etc., etc., were taking it out at about the same rate it was going in. What we did was disrupt that equilibrium. We started adding it faster than it was coming out. The ocean was able to absorb some of it, but it's not doing such a good job now that it's been absorbing for 150 years, and we increased the acid level of the ocean while we were at it. But we've been doing it too much and too fast, and it adds up. The video likes to pretend it so small compared to the mass of the atmosphere, or how much CO2 is in the carbon cycle, but it doesn't matter. What matters is how much the difference between what was happening before and what it is now is compared to the CO2 in the atmosphere. It's not insignificant. We've increased it by like 60%. The underlying greenhouse effect on Earth, keeps up from being about 0C. It's pretty strong, and we are making that much stronger. It doesn't matter than the small amount is being added. It matters that it accumulates. And the increase in CO2 is accelerating.
And dare I point out that the ocean is an carbon sink. This whole discussion about oceans adding to CO2 in the atmosphere may be true when the atmosphere isn't changing. But there is no mechanism for getting the ocean to release CO2 in the amounts that we've seen given the conditions. The guy on the video himself says that you have to cool the ocean for it to release CO2, but the oceans are warming, which doesn't make ANY sense.
And the claims that there was warming until the 40s but not since, is more complete bullshit. That's why seven of the ten warmest years on record were all in the 1990s. Sure. The climate has many forces acting on it. There is no requirement that global climate go up in a straight line. There will be years where it's cooler or years where it is warmer. El Nino, La Nina, sunspots, volcanoes, etc., etc. But if you look at the temperature record over the last 150 years, the trend is pretty clear; and if you look at decadal averages, it's even more clear.
They talk in the video about how there were no cars when the warming started. Trouble is there WAS industrialization. Coal power plants, and coal trains and deforestation. Cars are hardly the primary source of CO2. They are big now, but power plants are bigger. They are trying to distract viewers with this stupid argument.
And if it's not CO2, they have to have an alternative explanation. And the argument that it's the sun is another complete bullshit argument. There is no evidence whatsoever that the sun is doing anything over the long term that is different than what it was doing 400 years ago. They start talking about sunspots at the end, but there is an 11 year sunspot cycle and we are currently in an exceptionally low and long minimum right now. Does it affect daily weather? Probably. But have the last 20 sunspot cycles been doing anything exceptional compared to the 20 before that? Nope. And we have satellites in orbit of the sun studying it very closely, and there is absolutely no mechanism to support this wild claim. James Hansen works for NASA, for heaven's sake. If there was such data, it'd be available to him.
I've seen the whole video before, and it's filled with this kind of nonsense. This was actually the video that first made me hate BBC science coverage because it's become really, really poor and just into sensationalism.
Did I miss anything? :)
A few days later, my friend writes back:
Thank you for your instructive comments about the BBC video on global warming. Unfortunately my friend keeps sending me more links to materials casting doubts about the current scientific consensus on the matter. I did not want to bother you asking more questions about each fine detail of that material, but there is a question about which I would like to know your opinion.
We can consider the surface of the Earth as a complicated dynamical system with many variables - level of CO2 and other gases, temperature, ice caps surfaces, etc. They interact in a very complicated way, but the oscillating shapes of those variables in the past seem to show that the whole system remains in the neighborhood of a stable equilibrium point, so if the system is slightly perturbed it should tend to go back to equilibrium. However some of your remarks seem to indicate that the equilibrium should be unstable, e.g.: "once warming begins, there is a positive feedback between warming and CO2 release, and water vapor release that further drive warming".
What has prevented that process from running away in the past (at times when the warming was started by natural causes)?
The thing about a system as complex as this is that there are many stable equilibria. We had been stable in one for around 20,000 years. Another stable equilibrium was in the ice age many degrees cooler globally before the last natural warming period began. When the system was forced, it was driven to the current stable point by positive feedbacks. When in the past the system finally got knocked out of this high stable point, it crashed back to the low one again. What we are doing is forcing the system out of the stable point. If we stop soon enough, we will return to the current equilibrium (we hope because the natural cycle says it's actually about time for another ice age from the background orbital dynamics). However, what scientists fear is that we will drive up the CO2 high enough and warm up enough that we will cause several factors to push us into a higher stable state, by reducing albedo in the polar regions (absorbing more heat), increasing water vapor (absorbing more heat), and potentially causing an outgassing of addition CO2 from the permafrost and releasing methane from methane ices on the ocean floor (which will absorb still more heat). Methane is a greenhouse gas with 20 times the IR absorption of CO2 and releasing all that methane into the atmosphere would not only drive the temperature up, but make it very hard for it to come back down again. During the period of the dinosaurs, for instance, CO2 was much higher, and it stayed high for millions of years, despite the same orbital dynamics. The thresholds for these different equilibria are referred to as turning points in the press. So, yes, there is some stabilizing influence, but once we get too far away from the current stable point, we will stabilize to an entirely different equilibrium.
That having all been said, people forget the kind of time frames are talking about for "stable". CO2 remains a part of the active carbon cycle for hundreds or thousands of years (the number I'm familiar with is about 5000 years before the CO2 in the cycle actually decreases and can reset, but this is likely an estimate). Even if we stopped today, the CO2 already in the atmosphere would continue to warm and it would take a very long time to wring it out of the atmosphere using natural processes (plant growth actually is temporary and keeps the CO2 in the carbon cycle--we are talking about rocks). On geologic scales, this is nothing at all, but on the scale of a human lifetime, that's a very long time indeed. Deniers have a habit of figuring this is ten or twenty years, but it's nothing of the sort. And the more out of kilter it is, the longer it takes to swing back.
It should also be pointed out that there is another potentially dangerous side to the swing back to equilibrium. Systems out of whack tend to approach equilibrium in oscillating systems by swinging way past the mark and then come back again. If we wait long enough to let the natural systems try to pull us back, they may very well take us from very hot to very cold, and once there, again, the system is dynamic and complex, there is no guarantee that it won't pull us back past the equilibrium we want and send us directly into an ice age if we scrub too much CO2 from the atmosphere. Dynamical systems are sometimes well behaved and sometimes somewhat chaotic. Our current equilibrium may be stable in one direction, but not another. I rather doubt that there is enough computer resources in the world, though, to run these systems long enough to see what would happen in 5000 years or 10,000 years, or for some other radical scenarios. Most models are only run to the end of this century which is more than enough to produce some pretty scary scenarios and run the risk of passing several possible turning points, all of which would make it that much more difficult to go back to the stable point we started at.
Apparently, none of this convinces deniers, but facts are facts. And just a word to any deniers who come across this and want to argue with my statement of the facts, don't send me to your bullshit website. You want to argue with anything, you send me a research article in a peer reviewed journal. Anything else will be dismissed out of hand.