I have been reading a blog called Behind The Black by Robert Zimmerman for some time now. I find we have some things in common. He posts cool stuff about space! Plus a whole host of other stuff ranging from awesome college football plays to interesting comments on topical issues. Unfortunately I must disagree with his stance on climate change. As level headed as he seems when it comes to understanding the intricacies of NASA contracts and how they will effect the emerging private space sector is a stark contrast to his blind devotion to climate change denial. I have for the most part refrained from making arguments against his position. It's his blog and his opinion. Though I will correct the more egregious paraphrases and misinterpretations. But for the most I keep my opinion to myself.
But in a recent post he asked questions, and I decided to answer them. I would suggest going to the original post to get the background. I am posting my comment below the break.
Our understanding of how certain chemicals, most notably CFCs, effect our atmosphere began during the fifties, with measurements of atmospheric ozone. The ozone was stable until about 1970, when there was a noticeable downturn in global ozone levels. This was about 40 years after CFCs first began to see industrial use, and right about when you would expect to see such depletion due to CFCs breaking down into chlorine in our upper atmosphere. In 1974 Mario Molina put forward his ozone depletion hypothesis. This lead to several studies being conducted across the globe, most notably the launch of the TOMS and SAGE-1 satellites in the late 1970's, with a suite of studies coming in the mid 1980's. The data was clear by the time of the Montreal Protocol, and has become increasingly clear ever since. CFCs destroy our ozone.
The Antarctic is significantly colder than the arctic, and this has a big role to play in ozone depletion rates via CFC contamination. During the polar summer CFC is broken down by UV light into chlorine monoxide radicals (ClO). NOx (term for both NO2 and NO) can react with ClO to form either chlorine nitrate or hydrochloric acid (HCL) and nitric acid. During the winter months the nitric acid can freeze, providing a surface for chlorine nitrate and HCL to react to form molecular chlorine and nitric acid (latter of which freezes to create more surfaces for this reaction to take place on). Molecular chlorine (CL2) does not react with ozone, but it is easily broken down by UV light. Come spring the sun turns CL2 into two CL molecules, which are what react with ozone to create CLO and O2. The CLO combines with another CLO, (unless otherwise combined with NOx) and is then broken down again by UV to form two CL molecules and an O2 molecule. The CL is then free to repeat the process. The antarctic, being significantly colder, forms much more nitric acid ice and that ice hangs around a lot longer. So the amount of CFCs generated in the north has not previously been enough to cause an ozone hole (though there is noticeable depletion of the ozone in the arctic, as compared to pre-1970 levels), while the colder temperatures in the antarctic facilitate the breakdown of CFC into CL, which in turn breaks down O3 (Ozone) into O2.
The Montreal protocol had specific phase out dates. By 1992 the participating nations agreed to keep their CFC production under 150% of 1986 levels. It isn't until 1996 that all CFC production was halted, and it won't be until 2015 that HCFC production will be halted. CFC can hang out in the atmosphere for up to 150 years, and the resultant chlorine can hang around equally long. There seems to be some confusion between the signing of an agreement and the implementation of the things agreed to. The Protocol was enforced on January 1, 1989, 23 years ago. But the first phase began in 1991 and the last phase ended in 1996. (Neglecting HCFCs, which have yet to be phased out) There have been significant declines in CFCs in the atmosphere, measured both directly and by rising ozone levels. However, not all CFCs are out of the atmosphere, and dangerous levels are expected to persist until about 2050.
As Blair pointed out, the greenhouse gases in our troposphere trap heat, preventing it from warming up the stratosphere. The warming of the troposphere is generating a net loss of heat in the stratosphere. As CFC levels drop (as was achieved by the Montreal Protocol) and ozone levels rise, the stratosphere will warm due to the interaction between ozone and UV light. But this will only mitigate part of the cooling due to tropospheric heat trapping. This stratospheric cooling means that more nitric acid ice can form above the arctic, resulting in the new arctic ozone hole. The role of CFCs in our atmosphere is well understood.
"In the first sentence they admit that they really don’t understand why the temperatures have cooled recently in the Arctic stratosphere."
"There is considerable uncertainty if and to what extent past cold Arctic winters have cooled and there is even more uncertainty as to how this will evolve in the future."
Your statement is similar to what you were referring to, but it was not equivalent to it. The sentence referred to makes two statements. The first is that they are uncertain if and how much past arctic winters have cooled. The second statement is in regards to the uncertainty in how this new development will shape the future of arctic temperatures. Neither statement is about understanding why these temperatures have fallen in the past decade. They did not admit that they really don't understand why the temperatures have cooled recently.
There are two things happening to cool the stratosphere. As ozone gets depleted it lets through more UV light. But it's ozone's absorption of UV light that warms the stratosphere in the first place. Thus, less ozone means lower temperatures. Furthermore, greenhouse gases trap heat in the lower atmosphere, exasperating the cooling from ozone depletion. This happens because in an essentially non-radiating body like the Earth (We do generate some heat from internal processes, but these are negligible in comparison to the energy received from the Sun. Old Faithful heats the world up a lot less than the Sun does) the total energy level of that planet is derived from external bodies, like a nearby star. We get only so much energy from the Sun, and so if some of that energy is being trapped as heat in one part of the atmosphere, there must be a corresponding drop in temperature in another part of the atmosphere. Conservation of energy. The ozone layer is recovering, but it is not fully healed. But even if it were at the stable levels measured before 1970, that warming would not be enough to counteract the stratospheric cooling caused by the tropospheric warming that is due to man made greenhouse gases.
Their third sentence is I believe in relation to atmospheric waves, especially the mostly biennial sudden stratospheric warmings. It seems that they are saying that as the climate changes we will see increased atmospheric wave activity. This will intensify current wave activity, such as the sudden stratospheric warmings, resulting in higher temperatures during these events, a more chaotic schedule for the events, and potentially a greater frequency of these events. But these events generally last only a few days, and so would not lead to higher overall arctic temperatures. Unfortunately I cannot be sure that this is what they are referring to as your reference paper is behind a paywall, but that seems the most likely assumption from what I was able to research. I would like to point out that global warming is a somewhat misleading term for a complex event. While yes, the general trend will be towards higher temperatures on the ground, the term global warming neglects certain factors like stratospheric cooling or the chaotic change from one climate to another. Which is why the term climate change has been growing in popularity. Yes, the planet will get warmer. But not all at once and everywhere at the same time. The climate is changing.
I should like to note that the Montreal Protocol has successfully reduced atmospheric concentrations of CFCs, with a corresponding rise in ozone levels. The Montreal Protocol is working, which is why it has been hailed as one of the most successful international agreements in history. Such a high level of international cooperation is not a thing to be scoffed at.