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Monday, August 7, 2017

Myth: John Christy Thinks There is No Evidence of the Hot Spot

This post is part of a series addressing issues related to the hot spot. The other parts of this series are listed in the "Myths about the Hot Spot" section of the "Quick Scientific Debunking" page.


The outline for this post is as follows:
  1. The Myth and Its Flaw
  2. Context and Analysis
  3. Posts Providing Further Information and Analysis
  4. References

This is the "main version" of this post, which means that this post lacks of most my references and citations. If you would like a more comprehensive version with all the references and citations, then please go to the "+References" version of this post.

References are cited as follows: "[#]", with "#" corresponding to the reference number given in the References section at the end of this post.




1.  The Myth and Its Flaw



Climate models predict that in moist tropical areas, a region of the lower atmosphere will warm more than Earth's surface. This is known as the "hot spot". The myth proposes that John Christy, a climate scientist, thinks that there is no evidence of a hot spot.

John Christy is the main proponent of this myth, those others contribute to the myth as well, including Jospeh D'Aleo, James Wallace III, and bloggers on WattsUpWithThat.

The myth's flaw: John Christy knows that there is evidence of the hot spot, since Christy made graphs presenting evidence that passed his test for the hot spot. After making these graphs, Christy changed his hot spot test, instead of admitting that the evidence passed his test. Thus Christy moved the goal-posts in order to avoid publicly stating what he already knew: scientific evidence shows the hot spot exists.



2. Context and Analysis



Earth's atmosphere contains multiple layers. The layer closest to the Earth's surface air is known as the troposphere. Climate models predict that tropospheric warming in the tropics should increase with increasing height. See "Myth: The Tropospheric Hot Spot does not Existfor more on the mechanism behind this increased warming; however, knowing this mechanism is not required for understanding the points made in this blogpost.

The aforementioned tropical warming amplification is called the tropical tropospheric hot spot by myth proponentsSo the hot spot I will discuss relates to amplification of warming as one goes from the tropical surface to higher in the tropical troposphere. This is different from the question of whether the amount or magnitude of observed tropospheric warming matches the amount of warming projected by climate models; I address the "magnitude" issue in "Myth: Santer et al. Show That Climate Models are Very Flawed". Figure 1 depicts the hot spot (amplification of warming with increasing height in the tropics) in response to warming caused by increased solar activity or in response to warming caused by increased carbon dioxide (CO2):



Figure 1: ECHAM3/LSG model (European Center/Hamburg Model 3 / Large Scale Geostrophic coupled atmosphere-ocean climate model) simulation of the atmospheric response to (a) increased solar forcing (from increased solar output) and (b) increased CO2 forcing (from increased CO2 levels). Colored areas indicate significant responses, with darker blues indicating cooling and darker reds indicating warming. The horizontal axis represents latitude, with the tropics being between roughly 30N and 30SThe vertical axis represents altitude, with decreasing atmospheric pressure as altitude increases. The tropical troposphere lies below 150hPa, while the tropical stratosphere is above 70hPa. Tropical tropospheric warming increases with height in both panels a and b, indicating that the hot spot forms in response to both solar-induced warming and CO2-induced warming. In contrast, strong tropical stratospheric cooling comes with CO2-induced warming, but not solar-induced warming. This figure is taken from a 2001 report of the United Nations Intergovernmental Panel on Climate Change (IPCC) [1, page 707].


In August 2016, Christy co-authored the first edition of a non-peer-reviewed blogpost/"report". In this "report" he presented the following test for the existence for the hot spot:

"Section IV. Tropical Hot Spot Hypothesis Testing
The proper test for the existence of the THS [tropical hot spot] in the real world is very simple. Are the slopes of the three trend lines (upper & lower troposphere and surface) all positive, statistically significant and do they have the proper top down rank order [2, page 14]?"

Let's call this test the tropical hot spot test or the THS test. The THS test makes it clear that the hot spot is about amplified tropical warming with increasing tropospheric height.

Christy never shows that the available data fails the THS test. Instead Christy claimed to subtract out warming caused by the Sun and an ocean cycle known as the El Niño-Southern Oscillation (ENSO). Christy then stated that no significant troposoheric warming remained after this subtraction. And since there was no significant tropospheric warming left, then there was no evidence of the hot spot, according to Christy's reasoning. Christy's reasoning fails for at least two reasons (I discuss these reasons more in section 3.5 of part 1 of "John Christy and the Tropical Tropospheric Hot Spot"):

  • Christy used cumulative indices to correct for solar-induced and ENSO-induced warming. These indices are "cumulative" because the indices assume that the Earth accumulates energy from solar-induced and ENSO-induced warming, such that a warmer Earth does not radiate more energy. For example, Christy's cumulative ENSO index assumes that when Earth's troposphere warms during an El Niño year, the energy in the troposphere simply accumulates and is passed on to the next year. But this conclusion violates basic physics, as the climate scientist Timothy Osborn points out: a warmer Earth would radiate more energy into space, instead of all the energy just accumulating. Scientists can observe this increased radiation during a warm El Niño; the radiation increase occurs largely because El Niño increases cloud cover and these clouds then reflect the solar radiation Earth would otherwise absorb. This cloud-based mechanism compensates for less emission of radiation by clouds during El Niño. Given the defects in Christy's cumulative indices, scientists rarely (if ever) use Christy's indices. In fact, I know of no peer-reviewed scientific paper that uses Christy's cumulative indices. Scientists instead use non-cumulative indices to account for solar-induced and ENSO-induced warming. Even Christy's sources applied non-cumulative solar and ENSO indices, as did Christy in his peer-reviewed work. These non-cumulative indices are compatible with Earth radiating more energy as Earth warms. When scientists used these non-cumulative indices to correct for ENSO-induced and solar-induced warming, most of the post-1950s tropospheric and surface warming remained, contrary to the claims Christy made in his blogpost/"report". And even a representative of the organization Friends of Science, claims that Christy did not appropriately correct for ENSO, despite the fact that Friends of Science deny that the hot spot exists.
  • The hot spot may be there before one subtracts out solar-induced and ENSO-induced warming. So it would be non sequitur to infer that the hot spot does not exist, based on Christy's correction for warming caused by the Sun and ENSO.

So the hot spot could still exist even if one assumes (for the sake of argument) that Christy's solar and ENSO corrections are correct. But even if one claims that there is no hot spot after solar and ENSO corrections, that still leaves the question of whether Christy thought the hot spot exists. And it is this question that is the subject of the myth. The myth fails if: 1) Christy claimed that there was no evidence of the hot spot and, 2) Christy knew the hot spot existed. The first edition of Christy's blogpost/"report" met condition 1. Let's move on to condition 2.

After completing the first edition of his "report", Christy further examined data relevant to the hot spot. This process culminated in Christy compiling the figure below between August 2016 and February 28, 2017 for Patrick Michaels' Congressional testimony:


Figure 2: Comparison of the observed tropical warming trend (from latitudes of 20N to 20S) to model-based projections of the warming trend. The horizontal axis shows the rate of warming. The vertical axis shows altitude, with atmospheric pressure decreasing with increasing altitude. The red lines indicate the range of warming projected from models used by the United Nations Intergovernmental Panel on Climate Change (IPCC). The observed warming trend comes from weather balloon data (RICH, RAOBCORE, RATPAC A, and UNSW), satellite data (UAHv6.0, RSSv4.0, NOAAv4.0, and UW), and temperature re-analyses (ERA-I, MERRA2, and JRA-55). The "TMT" inset near the top shows observed mid-tropospheric warming trend from each data source, in comparison to the model projections of this trend [3].

  • Christy failed to acknowledge that the weather balloon (radiosonde) analyses were likely spuriously cool.
  • Christy exaggerated the difference between the models and the satellite data.
  • Michaels and Christy claimed that the model-to-data difference is predominately due to a flaw in the models, when this is not the case.

But suppose one takes Christy's figure at face value, for the sake of argument. Then figure 2's model-to-data comparison would not help Christy's case for at least two reasons. First, Christy's "report" argued against using climate models to evaluate the existence of the hot spot in real world observations:

"Section III. Research Design
Unlike some research in this area, this research does not attempt to evaluate the existence of the THS [tropical hot spot] in the real world by using the climate models. This would constitute a well-known error in mathematics and econometrics [...] [2, page 14]."

Second, the divergence between the models and the data would not change the warming pattern present in figure 2's data. The weather-balloon-based warming pattern is one of greater tropical warming with increasing tropospheric height, with a warming maximum in the tropical upper troposphere at ~300 hPa. This overall pattern is consistent with published weather balloon analyses. So the weather balloon data in figure 2 passes the THS test; Christy's February 28, 2017 figure therefore shows evidence of the hot spot. This means that by February 28, 2017 Christy knew there was evidence showing the hot spot.

In his March 2017 written Congressional testimony, Christy again showed evidence that passes the THS test, with greater tropical warming with increasing tropospheric height. This is shown in figure 3 below from Christy's testimony:


Figure 3: Comparison of tropical warming trend to model-based projections of the warming trend. The red and blue lines indicate projected warming from models used by the United Nations Intergovernmental Panel on Climate Change (IPCC); the effects of extra greenhouse gases (GHGs, such as CO2) are included in the red line projections, but not in the blue line projections. The gray lines indicate the observed warming trends [4]. 

Figure 3 involves the same mistakes I noted for figure 2. But more importantly, Christy presented figure 3 in his written March 2017 testimony, after Christy knew there was evidence of the hot spot. Yet Christy did not acknowledge the hot spot present in figure 3 nor the hot spot in his previous figure 2. Instead, on the pages following figure 3, Christy mentioned the first edition of his blogpost/"report" in which he says there was no evidence of the hot spot. So in his Congressional testimony, Christy brazenly cited a blogpost that contradicted his own testimony and what he knew to be true. Weird. But what happened next was even more bizarre.

At this point, you might think that a honest scientist like Christy would admit that there was evidence that passed his THS test, and thus he would admit that there was evidence showing the hot spot. Maybe Christy would do this on April 2017 in the second edition of his non-peer-reviewed, hot spot blogpost/"report"? If you think this, then you have too much confidence in John Christy, as I once did. In his "report's" second edition Christy still claimed there was no evidence of the hot spot, even though he knew the evidence existed. To get away with this, Christy changed the THS test. This becomes more clear when one compares section IV of the "report's" 2016 first edition with section IV of the "report's" 2017 second edition. 

From the August 2016 first edition:

"Section IV. Tropical Hot Spot Hypothesis Testing
The proper test for the existence of the THS in the real world is very simple. Are the slopes of the three trend lines (upper & lower troposphere and surface) all positive, statistically significant and do they have the proper top down rank order [2, page 14]?"

From the April 2017 second edition, with bolding for the portions different from the August 2016 first edition:

"Section IV. Tropical Hot Spot Hypothesis Testing
The proper test for the existence of the THS in the real world seem [sic] [emphasis added] very simple. Are the slopes of the three trend lines (upper & lower troposphere and surface) all positive, statistically significant and do they have the proper top down rank order? Note that this is a necessary, but not sufficient, condition for THS theory validation. In fact, currently some tropical tropospheric temperature data sets do have statistically significant upward sloping trend slopes [emphasis added] [5, page 14]?"

So between the first and second edition, Christy moved from saying that his test is simple, to claiming that his test seems simple. He then claimed that the THS test provided necessary, but not sufficient, conditions for identifying the hot spot. Yet Christy did not say what would be sufficient conditions for identifying the hot spot. He did not explain why an increasing tropical warming trend from the surface to the lower troposphere to the upper troposphere, would not be sufficient for showing the tropical hot spot. Instead Christy simply modified his testing criteria when he realized that the data might pass his THS test.

This sort of post hoc, ad hoc modification is known as moving the goalposts. Pseudoscientists and denialists of various stripes often move the goalposts in order to avoid accepting evidence that is inconvenient for their position. For example, many creationists move the goalposts in order to evade accepting evidence of evolution. Similarly so for AIDS denialists who move the goalposts in order to dodge evidence that HIV causes AIDS:

"Pushing Back the Goalpost
[...]
Of all the characteristics of deniers, repeatedly nudging back the goalpost—or the threshold of evidence required for acceptance of a theory—is often the most telling. The strategy behind goalpost-moving is simple: always demand more evidence than can currently be provided. If the evidence is then provided at a later date, simply change the demand to require even more evidence, or refuse to accept the kind of evidence that is being offered [6]."

[Some AIDS denialists compare themselves to "skeptics" of anthropogenic global warming (AGW). Furthermore, AIDS denialists sometimes publish in the same disreputable venues as AGW "skeptics". So I am no longer shocked to see an AGW "skeptic" like Christy employing the same discredited tactics as AIDS denialists.]

So it is quite telling that Christy resorted to moving the goalposts in order to avoid acknowledging evidence of the hot spot. Christy is aware that the hot spot exists, but he denies that there is evidence of the hot spot and he relies on pseudoscientific tactics in order to defend his denial. Yet people, including Christy himself, keep appealing to Christy's claim that there is no evidence of the hot spot. In fact, Christy makes his blogposts/"reports" on behalf of ICECAP, an organization that uses Christy's hot spot claims to attack the US Environmental Protection Agency's attempts to regulate CO2 emissions. What a farce.




3. Posts Providing Further Information and Analysis





4. References


  1. "Climate change 2001: The scientific basis; Chapter 12: Detection of climate change and attribution of causes"
  2. "On the Existence of a “Tropical Hot Spot" & The Validity of EPA’s CO2 Endangerment Finding"
  3. "At what cost? Examining the social cost of carbon"
  4. "U.S. House Committee on Science, Space & Technology, 29 Mar 2017, Testimony of John R. Christy"
  5. "On the Existence of a “Tropical Hot Spot” & The Validity of EPA’s CO2 Endangerment Finding, Abridged Research Report, Second Edition"
  6. "HIV denial in the internet era"