For a somewhat shorter discussion of specific issues related to the hot spot, see the "Myths about the Hot Spot" posts listed on the "Quick Scientific Debunking" page.
The outline for this post is as follows:
If you want the "tl;dr" for this post, then I suggest reading sections 1, 2, and 3.4. Alternatively, if you are familiar with John Christy's congressional testimony and you know what the "tropical tropospheric hot spot" is, then simply skip ahead to sections 2 and 3.4.
Each numbered point in section 2 corresponds with a numbered portion of section 3. So there is no need to read this entire post; instead, you can see which numbered point you find interesting in section 2, and then for further details you can skip to the corresponding numbered portion in section 3.
This is the "+References" version of this post, which means that this post contains my full list of references and citations. If you would like an abbreviated and easier to read version, then please go to the "main 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.
As I discussed in part 1, the troposphere is atmospheric layer closest to the Earth's surface air. Above the troposphere is the stratosphere, with a region between the two known as the tropopause. Above the stratosphere is the mesosphere, and above the mesosphere is the thermosphere. At Earth's surface, climate models and basic physical theory predict that warming will cause more ocean water to evaporate, especially for tropical oceans. This evaporation increases the amount of water vapor in the air, since warmer air can hold more water vapor. The water vapor then condenses with increasing atmospheric height, resulting in warming of the lower troposphere and even more warming of the upper troposphere [1; 2; 26; 27]. This is known as the tropical tropospheric hot spot. Though climate scientists have discussed this tropospheric temperature amplification since at least the 1990s [28; 29], the term "hot spot" largely originated in climate "skeptic" websites, as opposed to in mainstream scientific sources [30, page 6].
John Christy, a climate scientist, co-authored a report which argues that there is no evidence of a hot spot [3, page 4; 4, page 4]. In the first edition of his report, Christy defines the hot spot as follows [3, pages 14 and 42]:
In their report, Christy et al. argue that El Niño (also known as ENSO) and the Sun, as opposed to CO2, are responsible for most of the global warming trend observed since the 1970s [3, pages 57 and 68; 4, pages 4, 71, and 72; 6, page 10]. This may initially make sense, since even young children know that the Sun warms the Earth. Furthermore, scientists know that during the El Niño phase of ENSO, both the oceans' surface and the troposphere warm [1].
Christy cited the first edition of this report in his testimony to the US Congress [5; 6, pages 10 and 11]. The report is still not peer-reviewed, even though the report's authors have found time to make a second edition of the report. The second edition, as it stands, lacks much merit. So let's go over some of the issues with this edition.
There are a number of problems with the Christy et al's report. Competent peer review likely would have corrected these problems. So it is quite telling that Christy et al. still have not had their report peer-reviewed. Their report seems less about providing credible research to informed, skeptical scientists, and more about politically influencing uninformed, credulous politicians.
Below is a brief summary of some of the second edition's deficiencies:
(NOTE: Objections 1, 4, and 5 also applied to the report's first edition in part 1, though I have modified these objections to make them more applicable to the second edition. Objections 2, 3, and 6 are precisely the same objections presented against the first edition in part 1 of this series. Objection 7 from part 1 is not applicable to the report's second edition, so objection 7 was replaced with a different objection; this new objection applies to the second edition, but not the first edition. Objection 8 is also a new objection that applies to the second edition, but not the first edition.)
1) Christy et al. do not address much of the scientific research showing the hot spot, even though Christy et al. claim that there is no evidence of a hot spot. Christy himself presents evidence of a hot spot, thereby contradicting the conclusion of the report he co-authored. The report provides no sound argument against the existence of the hot spot, especially since Christy et al. do not directly compare the rates of upper tropospheric warming, lower tropospheric warming, and surface warming.
2) Christy et al. incorrectly state that the hot spot is claimed to be a fingerprint/signature of CO2-induced global warming. In reality, scientists know that surface warming caused by other factors (such as increased solar activity) would also result in a hot spot. Christy et al.'s proposed solar-induced and ENSO-induced ocean warming should result in a hot spot. Yet Christy et al. claim there is no hot spot. So Christy et al. position may be internally inconsistent.
3) Christy et al. discount CO2 as a cause of post-1970s global warming, even though they do not discuss data showing radiative forcing [meaning change in energy per unit area] from CO2. This forcing may be indicative of a warming effect from CO2. CO2 might also indirectly warm the atmosphere by increasing the frequency or intensity of El Niño events. If this is the case, then Christy et al. are incorrect when they claim that ENSO, not CO2, is responsible for much of the post-1970s global warming.
4) Christy et al. claim that there is no statistically valid evidence showing that CO2 significantly contributed to post-1970s temperature changes. However, Christy et al. fail to adequately address one of the fingerprints/signatures of CO2-induced global warming: stratospheric cooling. Long-term stratospheric cooling has occurred. CO2 also explains much of the observed mesospheric and thermospheric cooling. This cooling is not easily explained by Christy et al.'s proposed mechanisms of solar forcing and/or ENSO, which may be why Christy et al. conveniently evaded this cooling. Instead Christy et al. provide a graph of tropopause temperature as if this was indicative of stratospheric warming, thereby side-stepping much of the scientific evidence showing stratospheric cooling.
5) Christy et al. use a cumulative ENSO index that makes little sense in terms of atmospheric physics, undermining their report's central argument. A more plausible ENSO index undermines Christy et al.'s contention that ENSO caused most of the recent global warming. Furthermore, significant global warming remains even after volcanic activity, ENSO, and TSI are factored out, undermining the Christy et al.'s claim that most of the recent warming is attributable to volcanic activity, ENSO, and solar activity. This is consistent with Christy's own co-authored research and in contradiction to Christy et al.'s claims.
6) Christy et al. attribute much of the recent global warming to the Sun, even though they do not discuss much of the scientific evidence against the Sun being a cause of most of the recent global warming. A more plausible use of TSI undermines Christy et al.'s contention that the Sun caused much of the recent global warming.
7) Christy et al. unjustifiably move the goalposts on what they will accept as evidence of the hot spot.
8) Christy et al. falsely insinuate that the NOAA's temperature record has been manipulated.
Let's examine each of these objections in turn.
Christy et al. likely know that 150 mb is not the tropical stratosphere, since in the first of their report they stated that 150 mb was the upper troposphere [3, pages 23, 25, and 59]:
Hilariously, they fail to completely cover their tracks, since they say 150 mb is part of the troposphere elsewhere in their "report's" 2nd edition [4, page 62]. So Christy et al. took "tropical upper troposphere" data from the first edition on their blogpost/report (figure 6), and re-labeled it as being "tropical stratospheric" data in the second edition of their blogpost/report (figure 3). This is not a one-off mistake or typo, since on at least four occasions Christy et al. refer to this as being stratospheric data [4, pages 24 and 70]. In doing so they made it look like tropical stratosphere warmed (figure 3), in line with their solar-warming hypothesis (figure 2).
Christy probably knows that his hot spot report is not actually presenting tropical stratospheric temperature, despite the report's claims to the contrary. After all, Christy likely knows that 150 mb (150 hPa) is not the tropical stratosphere, since Christy co-authored work which states that the tropical tropopause lies above 150 mb (150 hPa) at 100 mb (100 hPa):
"Figure 1 shows these temperature trends as a function of pressure (altitude) from the surface (∼1000 hPa) to the tropopause (∼100 hPa/17 km) [35, page 1696]."
The outline for this post is as follows:
- Introduction
- Summary of the Objections
- Elaboration on the Objections
- References
This is part 2 of a two part series; I highly suggest reading part 1 of this series, before reading this post.
Each numbered point in section 2 corresponds with a numbered portion of section 3. So there is no need to read this entire post; instead, you can see which numbered point you find interesting in section 2, and then for further details you can skip to the corresponding numbered portion in section 3.
This is the "+References" version of this post, which means that this post contains my full list of references and citations. If you would like an abbreviated and easier to read version, then please go to the "main 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. Introduction
John Christy, a climate scientist, co-authored a report which argues that there is no evidence of a hot spot [3, page 4; 4, page 4]. In the first edition of his report, Christy defines the hot spot as follows [3, pages 14 and 42]:
- statistically significant warming in the tropical upper troposphere, lower troposphere, and Earth's surface
- greater warming in the tropical upper troposphere vs. the lower troposphere
- greater warming in the tropical lower troposphere vs. the Earth's surface
In their report, Christy et al. argue that El Niño (also known as ENSO) and the Sun, as opposed to CO2, are responsible for most of the global warming trend observed since the 1970s [3, pages 57 and 68; 4, pages 4, 71, and 72; 6, page 10]. This may initially make sense, since even young children know that the Sun warms the Earth. Furthermore, scientists know that during the El Niño phase of ENSO, both the oceans' surface and the troposphere warm [1].
Christy cited the first edition of this report in his testimony to the US Congress [5; 6, pages 10 and 11]. The report is still not peer-reviewed, even though the report's authors have found time to make a second edition of the report. The second edition, as it stands, lacks much merit. So let's go over some of the issues with this edition.
2. Summary of the Objections
Below is a brief summary of some of the second edition's deficiencies:
(NOTE: Objections 1, 4, and 5 also applied to the report's first edition in part 1, though I have modified these objections to make them more applicable to the second edition. Objections 2, 3, and 6 are precisely the same objections presented against the first edition in part 1 of this series. Objection 7 from part 1 is not applicable to the report's second edition, so objection 7 was replaced with a different objection; this new objection applies to the second edition, but not the first edition. Objection 8 is also a new objection that applies to the second edition, but not the first edition.)
1) Christy et al. do not address much of the scientific research showing the hot spot, even though Christy et al. claim that there is no evidence of a hot spot. Christy himself presents evidence of a hot spot, thereby contradicting the conclusion of the report he co-authored. The report provides no sound argument against the existence of the hot spot, especially since Christy et al. do not directly compare the rates of upper tropospheric warming, lower tropospheric warming, and surface warming.
2) Christy et al. incorrectly state that the hot spot is claimed to be a fingerprint/signature of CO2-induced global warming. In reality, scientists know that surface warming caused by other factors (such as increased solar activity) would also result in a hot spot. Christy et al.'s proposed solar-induced and ENSO-induced ocean warming should result in a hot spot. Yet Christy et al. claim there is no hot spot. So Christy et al. position may be internally inconsistent.
3) Christy et al. discount CO2 as a cause of post-1970s global warming, even though they do not discuss data showing radiative forcing [meaning change in energy per unit area] from CO2. This forcing may be indicative of a warming effect from CO2. CO2 might also indirectly warm the atmosphere by increasing the frequency or intensity of El Niño events. If this is the case, then Christy et al. are incorrect when they claim that ENSO, not CO2, is responsible for much of the post-1970s global warming.
4) Christy et al. claim that there is no statistically valid evidence showing that CO2 significantly contributed to post-1970s temperature changes. However, Christy et al. fail to adequately address one of the fingerprints/signatures of CO2-induced global warming: stratospheric cooling. Long-term stratospheric cooling has occurred. CO2 also explains much of the observed mesospheric and thermospheric cooling. This cooling is not easily explained by Christy et al.'s proposed mechanisms of solar forcing and/or ENSO, which may be why Christy et al. conveniently evaded this cooling. Instead Christy et al. provide a graph of tropopause temperature as if this was indicative of stratospheric warming, thereby side-stepping much of the scientific evidence showing stratospheric cooling.
5) Christy et al. use a cumulative ENSO index that makes little sense in terms of atmospheric physics, undermining their report's central argument. A more plausible ENSO index undermines Christy et al.'s contention that ENSO caused most of the recent global warming. Furthermore, significant global warming remains even after volcanic activity, ENSO, and TSI are factored out, undermining the Christy et al.'s claim that most of the recent warming is attributable to volcanic activity, ENSO, and solar activity. This is consistent with Christy's own co-authored research and in contradiction to Christy et al.'s claims.
6) Christy et al. attribute much of the recent global warming to the Sun, even though they do not discuss much of the scientific evidence against the Sun being a cause of most of the recent global warming. A more plausible use of TSI undermines Christy et al.'s contention that the Sun caused much of the recent global warming.
7) Christy et al. unjustifiably move the goalposts on what they will accept as evidence of the hot spot.
8) Christy et al. falsely insinuate that the NOAA's temperature record has been manipulated.
Let's examine each of these objections in turn.
3. Elaboration on the Objections
3.1 Avoiding evidence of the hot spot and failing to provide evidence against the hot spot's existence
As in the first edition of their report, Christy et al. do not directly compare the rates of upper tropospheric warming, lower tropospheric warming, and surface warming, in a way that would allow Christy et al. to see if the hot spot exist. Nor do Christy et al. do address much of the scientific research showing the hot spot, even though Christy et al. claim that there is no evidence of a hot spot [4, page 4], Christy's Congressional testimony presents evidence of a hot spot, and Christy's own satellite data analysis contradict other research that show a hot spot (see part 1, section 3.1 for more on this). It is quite telling that Christy et al. avoided adequately addressing any of this research that contradicted their report's conclusion.
All of the aforementioned claims also apply to the report's first edition. But matters get out-of-hand in the report's second edition; at this point, one could justifiably infer that Christy et al. are willfully misleading people. To see why, let's start by first the following graph [65] Christy sent to his fellow "skeptic" Patrick Michaels [63, pages 9 - 11; 64]:
Figure 1 is deeply flawed, as I discuss in "Myth: Santer et al. Show that Climate Models are Very Flawed" and "John Christy, Climate Models, and Long-term Tropospheric Warming". But suppose one accepts figure 1, for the sake of argument. Then the weather balloon (radiosonde) data in figure 1 shows more tropical warming in the upper troposphere at ~300hPa than in the lower troposphere, and more tropical warming in the lower troposphere than near the surface. That becomes a problem for Christy, once one places figure 1 in the timeline below:
So Christy knows there is evidence that passes his THS test, as depicted in figure 1. But instead of admitting this, Christy et al. continue to act as if there is no evidence of the hot spot [4, page 4]. And Christy passes this distortion off to Congress [5; 6, pages 10 and 11]. To borrow a quote from the "skeptic" Judith Curry [54]: I thought that there would be consequences for lying during Congressional testimony. I guess not.
All of the aforementioned claims also apply to the report's first edition. But matters get out-of-hand in the report's second edition; at this point, one could justifiably infer that Christy et al. are willfully misleading people. To see why, let's start by first the following graph [65] Christy sent to his fellow "skeptic" Patrick Michaels [63, pages 9 - 11; 64]:
 |
Figure 1: 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 [65]. |
Figure 1 is deeply flawed, as I discuss in "Myth: Santer et al. Show that Climate Models are Very Flawed" and "John Christy, Climate Models, and Long-term Tropospheric Warming". But suppose one accepts figure 1, for the sake of argument. Then the weather balloon (radiosonde) data in figure 1 shows more tropical warming in the upper troposphere at ~300hPa than in the lower troposphere, and more tropical warming in the lower troposphere than near the surface. That becomes a problem for Christy, once one places figure 1 in the timeline below:
- August 2016: Christy et al. release the first edition of their hot spot report [3]. In this report they state that the proper test for the hot spot involves looking for more tropical warming in the upper troposphere than in the lower troposphere, and looking for more tropical warming in the lower troposphere than near the surface [3, page 14]. This is the tropical hot spot test (the THS test).
- Sometime between August 2016 and February 28, 2017: Christy compiles figure 1 for Michaels [65]; this figure includes weather balloon data that passes the THS test. So Christy's own graph shows the hot spot and presents data that passes Christy et al.'s THS test. Michaels cites figure 1 in his Congressional testimony of February 28, 2017 [65].
- March 29, 2017: Christy cites the report's first edition in his Congressional testimony [5; 6, pages 10 and 11]; in this report Christy et al. claim that there is no hot spot and no evidence passing the THS test [3, pages 4].
- On or before April 2017: Christy et al. change their position and claim that passing the THS test is not sufficient for showing the hot spot [4, page 14]; I discuss this more in section 3.7. This change/evasion provides Christy et al. the cover they need to claim that there is no evidence of the hot spot [4].
- April 2017: Christy et al. release their report's second edition, in which they claim there is no evidence of the hot spot and include their evasion re-interpretations of their THS test [4, pages 4 and 14].
So Christy knows there is evidence that passes his THS test, as depicted in figure 1. But instead of admitting this, Christy et al. continue to act as if there is no evidence of the hot spot [4, page 4]. And Christy passes this distortion off to Congress [5; 6, pages 10 and 11]. To borrow a quote from the "skeptic" Judith Curry [54]: I thought that there would be consequences for lying during Congressional testimony. I guess not.
3.2 Misidentifying a fingerprint/signature of CO2-induced global warming
As in the first edition of their report, Christy et al. state that the hot spot is claimed to be a fingerprint or signature of global warming caused by greenhouse gases [4, pages 4 and 12]. However, this is not an accurate representation of the claims made by the mainstream scientific community. Many scientists know that surface warming caused by other factors (such as increased solar activity) would also result in a hot spot (see part 1, section 3.2 for more on this).
3.3 Disregarding evidence of CO2's effect on radiative forcing, temperature, and (possibly) ENSO
As in the first edition of their report, Christy et al. discount CO2 as a cause of post-1970s global warming [4, pages 4, 7, and 71], even though they do not discuss data showing radiative forcing from CO2 within specific infrared wavelengths [8; 9; 31, from 9:13 to 10:28]. This forcing may be indicative of a warming effect from CO2 and is one fingerprint of warming caused by CO2. Christy et al. also do not discuss evidence showing that forcing from anthropogenic CO2 contribute substantially to Earth's energy balance (the amount of energy the Earth takes up vs. the amount of energy the Earth releases) [32].
3.4 Obfuscating stratospheric cooling, a fingerprint/signature of CO2-induced global warming
Christy et al. note that, based on their data analysis, there is no statistically valid evidence showing that CO2 impacted long-term, post-1970s temperature trends [4, page 71]. As in the first edition of their report, Christy et al. ignore mesospheric and thermospheric cooling, which are both signatures of CO2-induced global warming (see part 1, section 3.4 for more on this). However, unlike in the first edition, Christy et al. indirectly touch on one of the fingerprints/signatures of CO2-induced global warming: stratospheric cooling [4, pages 24 - 26, 70]. There has been stratospheric cooling, with much of this cooling attributable to CO2. Long-term stratospheric cooling is not easily explained by volcanic activity [13; 19; 20; 23], solar activity, and ENSO, which may be why Christy et al. conveniently overlooked this cooling in the first edition of their report. If Christy et al.'s solar warming hypothesis is correct, then the stratosphere should have warmed, as acknowledged by a source Christy co-authored [28, pages 5 and 8] (see part 1, section 3.4 for more on this). A table from that source is shown below [28, page 5]:
 |
Figure 2: Summary of factors influencing global climate, and the predicted effects of these factors. The top two rows are the primary non-anthropogenic/natural forcing factors, while the other rows summarize the main anthropogenic factors. Some of the listed effects last only a few years (ex: volcanic warming of the stratosphere), while other effects last longer (ex: the effects of well-mixed greenhouse gases last for decades to centuries). Note that CO2-induced global warming would cool the stratosphere, while solar-induced warming would warm the stratosphere [28, table 1 on page 5]. |
Christy et al. note that their model does not perform very well when it comes to explaining stratospheric temperature [4, pages 24 and 70]. Yet, strangely, Christy et al. do not show a graph of tropical stratospheric cooling, despite published evidence of tropical stratospheric cooling [1; 7; 12 - 15; 33; 52; 53] (including evidence from one of the sources [7] Christy et al. cited [4, page 21]). They also do not present satellite analyses of tropical stratospheric temperature, even though such analyses are available [1; 13; 14; 33] and Christy et al. find time to discuss satellite analyses of tropospheric temperature [4, pages 27 - 32]. Christy was presumably the one who chose not to include these analyses [4, page 11]. But instead of showing a cooling tropical stratosphere, Christy et al. make it seem as if the tropical stratosphere warmed [4, pages 24 to 25]. To do this, they present "Tropical Stratospheric" data at a pressure of 150 mb or 150 hPa [4]:
"For comparison to the rest of the results presented in this report, Tropical Stratospheric 150 mb Balloon Data is shown next in Figure VIII-3. Interestingly, the 1977 shift is still evident. But not surprisingly, the overall model explanatory power is lower [...]. Nevertheless, no impact of CO2 is evident [...] [4, page 24]."
But this 150 hPa pressure level likely represents the lower tropical tropopause or the upper troposphere, instead of the tropical stratosphere that lies above the upper tropopause [10; 11; 50; 51]:
"We present an overview of observations in the [tropical tropopause layer] [...]. We present a synthesis definition with a bottom at 150 hPa [...] and a top at 70 hPa [...] [10]."
This is confirmed in a number of sources [10; 11; 50; 51], including in research showing the hot spot [4, page 21; 50]. Even one of the sources cited by Christy et al. [4, page 21] states that 150 hPa is around the tropical tropopause region that is associated with a transition from tropospheric warming to stratospheric cooling [7]. This source also shows clear tropical stratospheric cooling, as depicted in the following two figures [7]:
"For comparison to the rest of the results presented in this report, Tropical Stratospheric 150 mb Balloon Data is shown next in Figure VIII-3. Interestingly, the 1977 shift is still evident. But not surprisingly, the overall model explanatory power is lower [...]. Nevertheless, no impact of CO2 is evident [...] [4, page 24]."
 |
Figure 3: This is figure VIII-3 from the second edition of the hot spot report [4, page 25]. This (supposedly) shows tropical stratospheric data from three weather balloon data-sets [4, page 25]. |
But this 150 hPa pressure level likely represents the lower tropical tropopause or the upper troposphere, instead of the tropical stratosphere that lies above the upper tropopause [10; 11; 50; 51]:
"We present an overview of observations in the [tropical tropopause layer] [...]. We present a synthesis definition with a bottom at 150 hPa [...] and a top at 70 hPa [...] [10]."
This is confirmed in a number of sources [10; 11; 50; 51], including in research showing the hot spot [4, page 21; 50]. Even one of the sources cited by Christy et al. [4, page 21] states that 150 hPa is around the tropical tropopause region that is associated with a transition from tropospheric warming to stratospheric cooling [7]. This source also shows clear tropical stratospheric cooling, as depicted in the following two figures [7]:
Figure 4: Tropical temperature trend versus height for weather balloon measurements. Pressure decreases from the Earth's surface (near the bottom of the y-axis) to the troposphere to the stratosphere (near the top of the y-axis). The green line extends to the beginning of satellite era of atmospheric temperature measurements (1979), while the purple line extends to before the satellite era. The inset legend for circles, diamonds, etc. indicates different temperature trends given different data analysis choices. The blue line roughly indicates the warming pattern expected for a moist adiabat [7]. Figure 5: Temperature in the lower stratosphere at 50 hPa, relative to a baseline [7]. |
Christy et al. likely know that 150 mb is not the tropical stratosphere, since in the first of their report they stated that 150 mb was the upper troposphere [3, pages 23, 25, and 59]:
 |
Figure 6: A portion of table XXIII-1 from the first edition of Christy et al.'s hot spot report. In this portion of the table, Christy et al. use weather balloon data from 150 mb, weather balloon data from 200 mb, and mid-troposphere temperature (TMT) satellite data as indicative of tropical upper tropospheric temperature. The numbers on the right indicate the "r bar squared" values for these data-sets [3, page 59]. |
Hilariously, they fail to completely cover their tracks, since they say 150 mb is part of the troposphere elsewhere in their "report's" 2nd edition [4, page 62]. So Christy et al. took "tropical upper troposphere" data from the first edition on their blogpost/report (figure 6), and re-labeled it as being "tropical stratospheric" data in the second edition of their blogpost/report (figure 3). This is not a one-off mistake or typo, since on at least four occasions Christy et al. refer to this as being stratospheric data [4, pages 24 and 70]. In doing so they made it look like tropical stratosphere warmed (figure 3), in line with their solar-warming hypothesis (figure 2).
Christy probably knows that his hot spot report is not actually presenting tropical stratospheric temperature, despite the report's claims to the contrary. After all, Christy likely knows that 150 mb (150 hPa) is not the tropical stratosphere, since Christy co-authored work which states that the tropical tropopause lies above 150 mb (150 hPa) at 100 mb (100 hPa):
"Figure 1 shows these temperature trends as a function of pressure (altitude) from the surface (∼1000 hPa) to the tropopause (∼100 hPa/17 km) [35, page 1696]."
And in this same paper, Christy also shows tropical cooling at 150 hPa and 100 hPa (150 mb and 100 mb, respectively) [35, table 1 on page 1694 and figure 1 on page 1697]; thus Christy knows that the tropical atmosphere cooled at 150 mb and 100 mb. Christy's UAH satellite data analysis also shows stratospheric cooling [1, figure 3 on page 378; 28, pages 8, 9, 12, and 13; 61; 62], including cooling of the tropical stratosphere [1, figure 3 on page 378; 28, page 13; 61]. Yet in figure 3 above, Christy et al. make it look as if the tropical stratosphere warmed [4, page 25]. So Christy et al.'s "report"/blogpost presents misinformation that Christy likely knows is false, misinformation that conveniently supports Christy et al.'s solar warming hypothesis and conveniently removes one of the hall-marks of CO2-induced global warming. At this point, one might be forgiven for thinking that Christy is simply lying in his "report"/blogpost.
When other studies examined tropical stratospheric temperature, these studies showed tropical stratospheric cooling [1; 7; 12 - 15; 28, page 13; 33; 52; 53; 61], confirming one of the fingerprints of CO2-induced global warming. This contradicts the fictitious warming trend Christy et al. present for the tropical stratosphere in figure 3 [4, pages 24 to 25]. Therefore, Christy et al. likely misled Congress (unintentionally or intentionally) with respect to stratospheric cooling, since Christy et al. presented tropopause / upper troposphere data as if this data were indicative of a warming stratosphere. To borrow a quote from the climate scientist Chris Colose:
"Many of the “errors” speakers or writers make are so elementary, that if they are actually honest mistakes, any relevant degree in climate that they received should be taken away [34]."
Or to borrow another quote from the "skeptic" Judith Curry [54]: I thought that there would be consequences for lying during Congressional testimony. I guess not.
(The denialist Anthony Watts deserves special mention here. On his climate science blog, Watts approvingly posted an article championing the first and second editions of Christy et al.'s hot spot report [59; 59]. This despite the fact that Christy et al.'s falsely claims that the tropical stratosphere warmed. Yet Watts also wrote an article [60] on research showing tropical stratospheric cooling [12]. Apparently, Watts missed how this research conflicted with the Christy et al. Watts may have committed this oversight, because Watts was too busy misusing this research to justify his erroneous stance on the hotspot, as I discussed in section 3.1 of part 1. This falls in line with Watts' habit of evading, and not changing his mind in response to, evidence that shows he is wrong (for further examples of Watts' tendency, see section 3.1 of part 1, section 3.2 of "John Christy, Climate Models, and Long-term Tropospheric Warming", and section 3.5 of part 1 of "Christopher Monckton and Projecting Future Global Warming"). Such a tendency is a classic sign of a denialism, in contrast to scientific skeptics who change their mind in response to evidence [55; 56; 57, page 96; 66].)
So even in the second edition of their report, Christy et al. avoided directly addressing stratospheric cooling, one of the main fingerprints of CO2-induced global warming. And stratospheric cooling still debunks Christy et al.'s claims that there is no evidence of CO2 significantly impacting recent temperature trends [4, page 71].
When other studies examined tropical stratospheric temperature, these studies showed tropical stratospheric cooling [1; 7; 12 - 15; 28, page 13; 33; 52; 53; 61], confirming one of the fingerprints of CO2-induced global warming. This contradicts the fictitious warming trend Christy et al. present for the tropical stratosphere in figure 3 [4, pages 24 to 25]. Therefore, Christy et al. likely misled Congress (unintentionally or intentionally) with respect to stratospheric cooling, since Christy et al. presented tropopause / upper troposphere data as if this data were indicative of a warming stratosphere. To borrow a quote from the climate scientist Chris Colose:
"Many of the “errors” speakers or writers make are so elementary, that if they are actually honest mistakes, any relevant degree in climate that they received should be taken away [34]."
Or to borrow another quote from the "skeptic" Judith Curry [54]: I thought that there would be consequences for lying during Congressional testimony. I guess not.
(The denialist Anthony Watts deserves special mention here. On his climate science blog, Watts approvingly posted an article championing the first and second editions of Christy et al.'s hot spot report [59; 59]. This despite the fact that Christy et al.'s falsely claims that the tropical stratosphere warmed. Yet Watts also wrote an article [60] on research showing tropical stratospheric cooling [12]. Apparently, Watts missed how this research conflicted with the Christy et al. Watts may have committed this oversight, because Watts was too busy misusing this research to justify his erroneous stance on the hotspot, as I discussed in section 3.1 of part 1. This falls in line with Watts' habit of evading, and not changing his mind in response to, evidence that shows he is wrong (for further examples of Watts' tendency, see section 3.1 of part 1, section 3.2 of "John Christy, Climate Models, and Long-term Tropospheric Warming", and section 3.5 of part 1 of "Christopher Monckton and Projecting Future Global Warming"). Such a tendency is a classic sign of a denialism, in contrast to scientific skeptics who change their mind in response to evidence [55; 56; 57, page 96; 66].)
So even in the second edition of their report, Christy et al. avoided directly addressing stratospheric cooling, one of the main fingerprints of CO2-induced global warming. And stratospheric cooling still debunks Christy et al.'s claims that there is no evidence of CO2 significantly impacting recent temperature trends [4, page 71].
3.5 Using implausible physical indices
Christy et al. claim that volcanic activity, ENSO, and the Sun account for most of the post-1970s global warming [4, pages 4, 71, and 72; 6, page 10]. To do this, Christy et al. use a cumulative multivariate ENSO index and cumulative total solar irradiance (cumulative MEI and cumulative TSI, respectively) to subtract out most of the atmospheric warming, resulting in no tropospheric hot spot and not much CO2-induced warming [4; pages 16 - 19, 71, and 72]. In making these claims, Christy et al. use physically implausible indices for ENSO and TSI, undermining their report's central argument. Furthermore, when one uses a physically plausible, non-cumulative ENSO index and volcanic index, ENSO and volcanic activity do not account for most the recent global warming. This is consistent with Christy's cited [6, page 10], co-authored research [49] and in contradiction to Christy et al.'s claims. Thus Christy et al. do not provide a compelling physical basis for thinking that ENSO caused most of the long-term global warming (see part 1, section 3.5 for more on these points).
In addition to their cumulative ENSO index and cumulative TSI, Christy et al. also correct for volcanic activity [4, page 18]. Yet significant global warming remains even after volcanic activity, ENSO, and TSI are factored out [16 - 20]. This undermines Christy et al.'s claim that post-1970s warming is predominately due to volcanic activity, ENSO, and solar activity [4; pages 16 - 19].
3.6 Disregarding evidence that the Sun did not cause most of the recent global warming
As in the first edition of their report, Christy et al. attribute much of the post-1970s global warming to the Sun [4, pages 4, 71, and 72; 6, page 10], even though they do not discuss much of the scientific evidence against the Sun being a cause of most of the recent global warming (see part 1, section 3.6 for more on this).
Between the first and second edition of their report, Christy et al. increased the burden of proof that must be met for them that a hot spot exists. To see this, let's look at all of section IV of the report's first edition:
"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 [3, page 14]?"
That is all of section IV, and it includes the THS test discussed in section 3.1.
Now let's look at all of section IV of the report's second edition, with an emphasis on the portions that were added in the time between the first edition and the second edition:
"The proper test for the existence of the THS in the real world seem [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] [4, page 14]?"
That is all of section IV from the second edition.
So between the first and second edition, Christy et al. move from saying that their test is simple, to claiming that their test seems simple. They then claim that their test provides necessary, but not sufficient, conditions for identifying the hot spot. Yet Christy et al. do not say what would be sufficient conditions for identifying the hot spot. They do 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 a tropical tropospheric hot spot. Instead Christy et al. simply modify their testing criteria the moment it seems that some of their data may meet their testing criteria (as I discussed in section 3.1). 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 [24; 25]:
"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 [24]."
So it is quite telling that Christy et al. resort to moving the goalposts.
3.7 Unjustifiably pushing back the goalposts
Between the first and second edition of their report, Christy et al. increased the burden of proof that must be met for them that a hot spot exists. To see this, let's look at all of section IV of the report's first edition:
"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 [3, page 14]?"
That is all of section IV, and it includes the THS test discussed in section 3.1.
Now let's look at all of section IV of the report's second edition, with an emphasis on the portions that were added in the time between the first edition and the second edition:
"The proper test for the existence of the THS in the real world seem [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] [4, page 14]?"
That is all of section IV from the second edition.
So between the first and second edition, Christy et al. move from saying that their test is simple, to claiming that their test seems simple. They then claim that their test provides necessary, but not sufficient, conditions for identifying the hot spot. Yet Christy et al. do not say what would be sufficient conditions for identifying the hot spot. They do 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 a tropical tropospheric hot spot. Instead Christy et al. simply modify their testing criteria the moment it seems that some of their data may meet their testing criteria (as I discussed in section 3.1). 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 [24; 25]:
"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 [24]."
So it is quite telling that Christy et al. resort to moving the goalposts.
3.8 Baseless accusations of data manipulation
Christy et al. up the ante from calling scientists "alarmist" in the first edition of their report (see part 1, section 3.7 for more on this), to accusing scientists of data manipulation in the second edition of their report. Christy et al. claim that the National Oceanic and Atmospheric Administration (NOAA) ocean temperature data has been manipulated, since the NOAA data still shows warming even after Christy et al. correct for ENSO, TSI, and volcanic effects [4, pages 43 and 58]. Thus Christy et al. engage in transparently self-serving reasoning, where they accuse scientists of data manipulation simply because the scientists generated results that conflicts with Christy et al.'s pre-conceived notions.
In making these claims, Christy et al. advocate a debunked conspiracy theory. This conspiracy theory posits that the NOAA intentionally introduced spurious warming into their Extended Reconstructed Sea Surface Temperature (ERSST) record when updating this record from ERSSTv3b to ERSSTv4 [36 - 38; 43; 44; 69]. This conspiracy theory fails. Scientists provided sound justifications for the ERSSTv4 updates [40; 41]. Furthermore, ERSSTv4 does not display signs of dubious manipulation. Instead, in comparison to ERSSTv3b, ERSSTv4 better matches ocean temperature data from other sources such as buoys, floats, and satellites [39, figures 1 and S2; 42]. For example, see figures 7 and 8 below [39]:
Of course, Christy et al. and other committed conspiracy theorists might object that scientists also manipulate the data from those other sources (or the scientists analyzing those sources are biased), so it's no surprise that those sources have results matching NOAA's ERSSTv4. This objection suffers from some of the flaws I discuss in section 3.1 of "John Christy, Climate Models, and Long-term Tropospheric Warming". But if Christy et al. wish to resort to this objection, then Christy et al. bear the burden of proof, since they need to support their charge of data manipulation. Christy et al. have yet to meet this burden. So they retract their insinuation that the NOAA's data was manipulated. This applies especially to Christy's co-author D'Aleo, who regularly smears the NOAA [67; 68; 72], and to Christy himself, since he also peddles paranoid conspiracy theories about the scientific community [70; 71].
In making these claims, Christy et al. advocate a debunked conspiracy theory. This conspiracy theory posits that the NOAA intentionally introduced spurious warming into their Extended Reconstructed Sea Surface Temperature (ERSST) record when updating this record from ERSSTv3b to ERSSTv4 [36 - 38; 43; 44; 69]. This conspiracy theory fails. Scientists provided sound justifications for the ERSSTv4 updates [40; 41]. Furthermore, ERSSTv4 does not display signs of dubious manipulation. Instead, in comparison to ERSSTv3b, ERSSTv4 better matches ocean temperature data from other sources such as buoys, floats, and satellites [39, figures 1 and S2; 42]. For example, see figures 7 and 8 below [39]:
 |
Figure 7: Comparison of ocean temperature records from 1997 to 2015 for different sources, relative to a 1997-2001 baseline. The sources are buoys, the NOAA's Extended Reconstructed Sea Surface Temperature (ERSST) record for both ERSSTv3b and ERSSTv4, and the European Space Agency Climate Change Initiative (CCI) [39, figure 1]. |
 |
Figure 8: Comparison of ocean temperature records from 1997 to 2015 for different sources. NOAA's Extended Reconstructed Sea Surface Temperature (ERSST) record for ERSSTv3b and ERSSTv4 are compared to ocean heat measurements from Argo floats. Argo(H2008) [45], Argo(APDRC) [46; 47], and Argo(RG2000) [48] represent three different near-surface temperature data-sets derived from the Argo data. ERSSTv4 data is presented relative to a 1997-2001 baseline, while the other data sources are aligned to the 2005-2007 baseline for ERSSTv4 [39, figure S2]. |
Of course, Christy et al. and other committed conspiracy theorists might object that scientists also manipulate the data from those other sources (or the scientists analyzing those sources are biased), so it's no surprise that those sources have results matching NOAA's ERSSTv4. This objection suffers from some of the flaws I discuss in section 3.1 of "John Christy, Climate Models, and Long-term Tropospheric Warming". But if Christy et al. wish to resort to this objection, then Christy et al. bear the burden of proof, since they need to support their charge of data manipulation. Christy et al. have yet to meet this burden. So they retract their insinuation that the NOAA's data was manipulated. This applies especially to Christy's co-author D'Aleo, who regularly smears the NOAA [67; 68; 72], and to Christy himself, since he also peddles paranoid conspiracy theories about the scientific community [70; 71].
4. References
- "Comparing tropospheric warming in climate models and satellite data"
- https://www.skepticalscience.com/tropospheric-hot-spot-advanced.htm
- "On the Existence of a “Tropical Hot Spot" & The Validity of EPA’s CO2 Endangerment Finding"
- "On the Existence of a “Tropical Hot Spot” & The Validity of EPA’s CO2 Endangerment Finding, Abridged Research Report, Second Edition"
- http://climatefeedback.org/scientists-reactions-us-house-science-committee-hearing-climate-science/
- "U.S. House Committee on Science, Space & Technology, 29 Mar 2017, Testimony of John R. Christy"
- "Atmospheric changes through 2012 as shown by iteratively homogenized radiosonde temperature and wind data (IUKv2)"
- "Observational determination of surface radiative forcing by CO2 from 2000 to 2010"
- "Increases in greenhouse forcing inferred from the outgoing longwave radiation spectra of the Earth in 1970 and 1997"
- "Tropical Tropopause Layer" [doi:10.1029/2008RG000267]
- "Insights into Tropical Tropopause Layer processes using global models"
- "Evidence for an earlier greenhouse cooling effect in the stratosphere before 1980 over the Northern Hemisphere"
- "Stratospheric temperature trends over 1979–2015 derived from combined SSU, MLS, and SABER satellite observations"
- "Regional and seasonal stratospheric temperature trends in the last decade (2002–2014) from AMSU observations"
- "The JRA-55 reanalysis: Representation of atmospheric circulation and climate variability"
- "Deducing multidecadal anthropogenic global warming trends using multiple regression analysis"
- "Global temperature evolution 1979–2010"
- "Volcanic contribution to decadal changes in tropospheric temperature"
- "Identifying human influences on atmospheric temperature"
- "Human and natural influences on the changing thermal structure of the atmosphere"
- "Prominent signers of "An evangelical declaration on global warming""
- "An evangelical declaration on global warming"
- "Attributing the forced components of observed stratospheric temperature variability to external drivers"
- "HIV denial in the internet era"
- "Irreducible incoherence – a look into the conceptual toolbox of a pseudoscience"
- "Elevation-dependent warming in mountain regions of the world"
- https://ourchangingclimate.wordpress.com/2013/08/19/tropospheric-hot-spot/
- "Executive Summary: Temperature trends in the lower atmosphere - Understanding and reconciling differences"
- "Tropospheric temperature trends: history of an ongoing controversy"
- "Extended Summary of the Climate Dialogue on the (missing) tropical hot spot"
- Ray Pierrehumbert's 2012 video: "Tyndall Lecture: GC43I. Successful Predictions - 2012 AGU Fall Meeting"
- "Anthropogenic and natural warming inferred from changes in Earth’s energy balance"
- "Use of SSU/MSU satellite observations to validate upper atmospheric temperature trends in CMIP5 simulations"
- https://chriscolose.wordpress.com/2008/12/20/will-the-real-skeptics-please-stand-up/
- "A comparison of tropical temperature trends with model predictions"
- potholer54's video: "NOAA vs Mail on Sunday -- FACT CHECK"
- "How a culture clash at NOAA led to a flap over a high-profile warming pause study"
- "Politicians shouldn't troll through scientists' e-mails"
- "Assessing recent warming using instrumentally homogeneous sea surface temperature records"
- "Possible artifacts of data biases in the recent global surface warming hiatus"
- "Extended Reconstructed Sea Surface Temperature Version 4 (ERSST.v4). Part I: Upgrades and intercomparisons"
- https://twitter.com/hausfath/status/834069858270670849/photo/1
- "As the planet warms, doubters launch a new attack on a famous climate change study"
- "How an interoffice spat erupted into a climate-change furor"
- "Validation of Aquarius sea surface salinity with in situ measurements from Argo floats and moored buoys"
- "A monthly mean dataset of global oceanic temperature and salinity derived from Argo float observations"
- "Improved description of global mixed-layer depth using Argo profiling floats"
- "The 2004–2008 mean and annual cycle of temperature, salinity, and steric height in the global ocean from the Argo program"
- "Satellite greenhouse signal"
- "New estimates of tropical mean temperature trend profiles from zonal mean historical radiosonde and pilot balloon wind shear observations"
- "Revisiting the controversial issue of tropical tropospheric temperature trends"
- "Westward shift of western North Pacific tropical cyclogenesis"
- "Influence of tropical tropopause layer cooling on Atlantic hurricane activity"
- https://judithcurry.com/2017/03/31/deniers-lies-and-politics/
- "How the growth of denialism undermines public health"
- "Sceptics and deniers of climate change not to be confused"
- "Debating global warming in media discussion forums: Strategies enacted by “persistent deniers” and implications for schooling"
- https://wattsupwiththat.com/2016/09/22/study-tropical-hotspot-fingerprint-of-global-warming-doesnt-exist-in-the-real-world-data/
- https://wattsupwiththat.com/2017/04/02/why-john-christies-missing-hotspot-matters/
- https://wattsupwiththat.com/2014/08/04/what-stratospheric-hotspot/
- "Stratospheric temperature changes during the satellite era"
- "UAH version 6 global satellite temperature products: Methodology and results"
- "Climate Denial 101: A User’s Guide to the arguments of global warming skeptics"
- https://skepticalscience.com/patrick-michaels-history-getting-climate-wrong.html
- "At what cost? Examining the social cost of carbon"
- http://www.csicop.org/news/show/deniers_are_not_skeptics
- "Surface temperature records: Policy-driven deception?"
- "On the validity of NOAA, NASA and Hadley CRU global average surface temperature data & the validity of EPA’s CO2 endangerment finding"
- http://www.snopes.com/2017/02/08/noaa-scientists-climate-change-data/
- "Open letter to the climate science community: Response to "A Climatology Conspiracy?""
- https://www.americanthinker.com/articles/2009/12/a_climatology_conspiracy.html
- https://tamino.wordpress.com/2010/03/05/message-to-anthony-watts/
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