First
We then have this:
My Thanks and Comments for Dr. Walt Meier
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Guest Post by Willis Eschenbach
First, I would like to thank Dr. Meier of the National Snow and Ice Data Center (NSIDC) for answering the questions I had posed (and had given my own personal answers) in “Trust and Mistrust”. I found his replies to be both temperate and well-reasoned. Also, I appreciate the positive and considerate tone of most of those who commented on his reply. It is only through such a peaceful and temperate discussion that we can come to understand what the other side of the debate thinks.
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Onwards to the questions, Dr. Meier’s answers, and my comments:
Question 1. Does the earth have a preferred temperature, which is actively maintained by the climate system?
Willis says that he “believes the answer is yes”. In science “belief” doesn’t have much standing beyond initial hypotheses. Scientists need to look for evidence to support or refute any such initial beliefs. So, does the earth have a preferred temperature? Well, there are certainly some self-regulating mechanisms that can keep temperatures reasonably stable at least over a certain range of climate forcings. However, this question doesn’t seem particularly relevant to the issue of climate change and anthropogenic global warming. The relevant question is: can the earth’s temperature change over a range that could significantly impact modern human society?
My comment: Since unfortunately so little attention has been given to this important question, my idea of how it works is indeed a hypothesis. Therefore, “belief” is appropriate. However, I have provided several kinds of evidence in support of the hypothesis at the post I cited in my original answer to this question, “The Thermostat Hypothesis”.
Next, Dr. Meier says that there are “some self-regulating mechanisms that can keep temperature reasonably stable at least over a certain range of climate forcings.” Unfortunately, he does not say what the mechanisms might be, at what timescale they operate, or what range of forcings they can handle.
However, he says that they can safely be ignored in favor of seeing what the small changes are, which doesn’t make sense to me. Before we start looking at what causes the small fluctuations in temperature that we are discussing (0.6°C/century), we should investigate the existence and mechanism of large-scale processes that regulate the temperature. If we are trying to understand a change in the temperature of a house, surely one of the first questions we would want answered is “does the house have a thermostat?” The same is true of the climate.
Question 2: Regarding human effects on climate, what is the null hypothesis?
I will agree with Willis here – at one level, the null hypothesis is that any climate changes are natural and without human influence. This isn’t controversial in the climate science community; I think every scientist would agree with this. However, this null hypothesis is fairly narrow in scope. I think there is actually a more fundamental null hypothesis, which I’ll call null hypothesis 2 (NH2): are the factors that controlled earth’s climate in the past the same factors that control it today and will continue to do so into the future? In other words are the processes that have affected climate (i.e., the forcings – the sun, volcanic eruptions, greenhouse gases, etc.) in the past affecting climate today and will they continue to do so in the future? A basic premise of any science with an historical aspect (e.g., geology, evolution, etc.) is that the past is the key to the future.
My Comment: I assume that Dr. Meier has temporarily overlooked the fact that a null hypothesis is a statement rather than a question. Thus, his Null Hypothesis 2 (NH2) should be:
NH2: The factors that controlled earth’s climate in the past are the same factors that control it today and will continue to do so into the future
However, this formulation has some serious problems. First, a null hypothesis must be capable of being falsified. My null hypothesis (NH1) could be falsified easily, by a showing that measurements of the modern climate are outside the historical values.
Dr. Meier’s NH2, on the other hand, extends into the future … how can we possibly falsify that?
Second, to determine if the factors that controlled the climate in the past are the same factors that control it now, we must know the factors that controlled climate in the past, and we must know the factors that control climate now. But that is exactly the subject being debated – what controls the climate? We don’t know the answer to that for the present, and we know even less about it for the past. So again, his NH2 is not falsifiable.
Finally, there is a more fundamental problem with NH2. The null hypothesis has to be the logical opposite of the alternate hypothesis, so that if one is true, the other must be false. My null hypothesis NH1 is that the currently observed climate variations are the result of natural variation. The opposite of my null hypothesis is the alternate hypothesis, that currently observed climate variations are the result of human-caused GHG increases.
However, what is the opposite of NH2, which states that the factors that controlled climate in the past are those that control climate today? The opposite of that is the alternate hypothesis that the factors that controlled climate in the past are not those that control climate today.
But I have never once, in this entire decades-long debate, heard anyone make the claim that some factors that affected climate in the past have stopped affecting the climate. As a result, NH2 is a straw man. It is the null hypothesis for an alternate hypothesis that no one is propounding.
Since it is not falsifiable, and since it is a straw man null hypothesis, Dr. Meier has not proposed a valid null hypothesis. As a result, his arguments that follow from that null hypothesis are not relevant.
Question 3: What observations tend to support or reject the null hypothesis?
Let me first address NH2. We have evidence that in the past the sun affected climate. And as expected we see the current climate respond to changes in solar energy. In the past we have evidence that volcanoes affected climate. And as expected we see the climate respond to volcanic eruptions (e.g., Mt. Pinatubo). And in the past we’ve seen climate change with greenhouse gases (GHGs). And as expected we are seeing indications that the climate is being affected by changing concentrations of GHGs, primarily CO2. In fact of the major climate drivers, the one changing most substantially over recent years is the greenhouse gas concentration. So what are the indications that climate is changing in response to forcing today as it has in the past? Here are a few:
1. Increasing concentrations of CO2 and other GHGs in the atmosphere
2. Rising temperatures at and near the surface
3. Cooling temperatures in the stratosphere (An expected effect of CO2-warming, but not other forcings)
4. Rising sea levels
5. Loss of Arctic sea ice, particularly multiyear ice
6. Loss of mass from the Greenland and Antarctic ice sheets
7. Recession of most mountain glaciers around the globe
8. Poleward expansion of plant and animal species
9. Ocean acidification (a result of some of the added CO2 being absorbed by the ocean)
It is possible that latter 8 points are completely unrelated to point 1, but I think one would be hard-pressed to say that the above argues against NH2.
My Comment: Saying “it is possible that the latter 8 points are completely unrelated to point 1″ begs the question. It is possible that they are related, but that is the question at hand that we are trying to answer. If Dr. Meier thinks that they are related, he needs to establish causation, not just say it is “possible that [they] are completely unrelated”.
Whether his points argue for or against NH2 is not relevant, since NH2 is not falsifiable, and is a null hypothesis for a position no one is taking. In addition, they are presented as “indications that climate is changing in response to forcing today as it has in the past” … but it is a mix of statements about forcings, and responses to increasing warmth. So I don’t see how that applies to NH2 in any case.
Despite those problems, let me address them, one by one, starting with one without a number:
In the past we’ve seen climate change with greenhouse gases (GHGs): This cries out for a citation, but there is none. When did we see that, who showed it, what evidence is there to support it?
1. Increasing concentrations of CO2 and other GHGs in the atmosphere: Yes, GHGs are increasing. However, this says nothing either way about NH2.
2. Rising temperatures at and near the surface: Yes, temperatures generally have been rising, and they have been ever since the Little Ice Age in the mid 1600’s. But again, what does this have to do with NH2?
3. Cooling temperatures in the stratosphere (An expected effect of CO2-warming, but not other forcings): I would greatly appreciate a citation to the claim that this is an expected result of GHG forcing but not other forcings. Given our general lack of understanding of the climate, it would be a very difficult claim to establish.
For one of the reasons why it would be hard to establish, here is the actual change in the stratospheric temperatures:
Figure 1. UAH and RSS satellite measurements of stratospheric temperature. DATA SOURCES UAH, RSS
Now, how on earth (or off earth and in the stratosphere) is that an “expected effect” of increasing GHGs? Since recovering from the Pinatubo eruption stratospheric temperatures have been stable … which climate model projected that outcome? What theoretical calculations showed that flat-line response?
4. Rising sea levels: Sea levels have been rising since 1900. If GHGs were driving the rise, we would expect to see an acceleration in the rate of rise corresponding to the acceleration in the rise of GHGs. However, we have seen no such acceleration in the long-term, and we see deceleration in the short-term. Here are two long-term records. Fig.2 is from Church and White and Jevrejeva:
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