Monday, July 24, 2017

+Myth: The Sun Caused Recent Global Warming and the Tropical Stratosphere Warmed

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

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.  The Myth and Its Flaws

The tropical stratosphere, a layer of the middle atmosphere, warmed and the Sun caused most of the recent global warming. 

John Christy [1 - 4], Jospeh D'Aleo [1; 2], and James Wallace III are the main proponents of this myth [1; 2]. I will refer to these three proponents as "Christy et al." in this post.

The myth's flaws: in a non-peer-reviewed blogpost/"report", Christy et al. claim the tropical stratosphere warmed [2, pages 24 and 25], even though Christy knows the tropical stratosphere actually cooled [7, table 1 on page 1694 and figure 1 on page 1697; 31; 55]. This distortion allows Christy et al. to:
  1. conceal stratospheric cooling [2, pages 24 and 25], one of the signs of carbon-dioxide-induced (CO2-induced) global warming [18; 21; 23 - 28; 29],
  2. unfairly criticize government attempts to limit CO2 emissions [1; 2], and
  3. manufacture false evidence of long-term solar-induced warming, in the form of stratospheric warming [2, pages 24 and 25].
Christy then cited this misleading blogpost/"report" in his Congressional testimony, using the "report" as evidence that natural factors such as the Sun, but not CO2, caused recent global warming [3, page 10; 4]. Christy makes this claim, despite the fact that Christy et al. do not address well-known evidence showing that the Sun did not cause most of the recent global warming [1; 2]. So Christy misled Congress, and likely did so knowingly. In doing so, Christy obscured the fact that increased levels of greenhouse gases such as CO2, not increased solar activity, caused most of the recent global warming [25; 65 - 67; 89; 119; 145 - 181; 200; 208].

[Side-note: This myth motivated me to start blogging again; it also helped change the way I view the climate science debate, as I discuss in "John Christy and Atmospheric Temperature Trends". So if you want to blame someone for me blogging again, then blame the three proponents of this myth.] 

2. Context and Analysis

Earth's atmosphere contains multiple layers. The layer closest to the Earth's surface air is known as the troposphere. Above the troposphere is the tropopause, and above the tropopause is the stratosphere [5 - 7]. So the order of these atmospheric layers, from highest to lowest, is as follows:
  1. Stratosphere
  2. Tropopause
  3. Troposphere
Please keep this order in mind, because it will be important for understanding Christy et al.'s myth. 

Examining the stratosphere is useful because different factors produce different stratospheric temperature trends. For example:
  • Ozone reduction, due to factors such as human production of ozone-depleting chlorofluorocarbons (CFCs) [8 - 14; 195; 196; 198; 222], causes strong stratospheric cooling [15 - 23; 29; 102; 115, page 65; 195; 196; 198; 222; 223]
  • Carbon-dioxide-induced (CO2-induced) global warming results in strong stratospheric cooling [6; 18; 21; 23 - 29; 102; 115, page 176; 116, page 409; 195; 196; 198; 201, figure 4; 205, pages 101 and 102; 212, figure 16 on page 250 and page 251; 222; 223]
  • Solar-induced global warming results in mostly stratospheric warming; solar-induced warming does not account for strong stratospheric cooling [20; 24 - 26; 29 - 35; 110]

So the stratosphere allows scientists to distinguish different causes of global warming: stratospheric warming would be consistent with warming caused by increased solar output [20; 24 - 26; 29 - 35; 110], while stratospheric cooling would fit with warming caused by increased CO2 levels [6; 18; 21; 23 - 29; 102; 115, page 176; 116, page 409; 195; 196; 198; 201, figure 4; 205, pages 101 and 102; 212, figure 16 on page 250 and page 251; 222; 223]. These points are so basic that the United States National Aeronautics and Space Administration (NASA) discusses them in their laymen's level explanation of climate science [36; 37]:

"A second smoking gun is that if the sun were responsible for global warming, we would expect to see warming throughout all layers of the atmosphere, from the surface all the way up to the upper atmosphere (stratosphere). But what we actually see is warming at the surface and cooling in the stratosphere. This is consistent with the warming being caused by a build-up of heat-trapping gases near the surface of the Earth, and not by the sun getting “hotter.” [36]"

These points are also re-affirmed in a source Christy co-authored [29, pages 5 and 8]:

Figure 1: 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 [29, table 1 on page 5].

This is where Christy et al.'s myth comes in. In their non-peer-reviewed blogpost (or a "report", as Christy et al. call it), Christy et al. conclude that increased total solar irradiance (TSI) from the Sun caused most of the recent global warming [1, pages 57 and 68; 2, pages 4, 71, and 72; 3, page 10; 4]. Christy cites this "report" conclusion in his Congressional testimony [3, page 10; 4]. As Christy says in his testimony:

"Indeed, I am a co-author of a report in which we used a statistical model to reproduce, to a large degree, the atmospheric temperature trends without the need for extra greenhouse gases. In other words, it seems that Mother Nature can cause such temperature trends on her own, which should be of no surprise [4]."

In their "report," Christy et al. also claim that CO2 had no observable, significant effect on recent temperature trends [1, page 4; 2, page 4]. One could test this claim by examining stratospheric temperature to see if there is CO2-induced stratospheric cooling or solar-induced stratospheric warming. A number of scientists already performed this test.

The scientific evidence indicates that ozone depletion [6; 17 - 23; 31; 102; 195; 196; 198; 222; 223] and increased CO2 [6; 18; 21; 23 - 29; 102; 195; 196; 198; 222; 223] caused stratospheric cooling up to the mid-1990s [6; 19; 20; 23; 28; 29, pages 8, 9, 12, and 13; 31; 38 - 44; 71 - 73; 102; 195; 196; 198; 222; 223], as predicted by the scientific community during the 1960s, 1970s, and 1980s [15; 16; 45, from 26:23 to 29:54; 46 - 50]. Ozone stabilization (in response to anti-CFC international agreements such as the Montreal Protocol [8 - 14]) mitigated [17 - 22; 31; 198; 223] stratospheric cooling from the mid-1990s to the present [22; 28; 29; 31; 198; 213, figure 18; 223], though post-1997 stratospheric cooling remains in many data-sets [17 - 20; 39 - 44; 102; 113; 114; 198; 213, figure 18], especially higher in the stratosphere [17 - 20; 39 - 42; 44; 102; 113; 114; 198; 213, figure 18] where CO2-induced cooling is more pronounced [17; 18; 196; 201, figure 4; 205, pages 101 and 102]. This is in agreement with scientific predictions made in the 1970s and 1980s [15; 16; 51; 201, figure 4; 205, pages 101 and 102; 212, figure 16 on page 250 and page 251]. For instance, since at least the 1960s, scientists have known that CO2-induced stratospheric cooling increases with increasing stratospheric height [201, figure 4; 205, pages 101 and 102; 212, figure 16 on page 250 and page 251]; in 1980, this point was even acknowledged by scientists working for the fossil fuel company Exxon [202, figure 3], consistent with subsequent Exxon scientists acceptance of CO2-induced, man-made climate change [214].

Christy et al. do not mention any of this in their "report's" 1st edition. Instead they examine temperature at, and below, the upper troposphere in the tropics [1, pages 13 and 59]. Christy et al. do mention [1, page 23] a paper that shows tropical stratospheric cooling [6], but they fail to mention that the paper shows this cooling [1, page 23]. Figure 2 presents some weather-balloon-based atmospheric temperature data from said paper:

Figure 2: Tropical warming/cooling trend versus height for weather balloon measurements (from a latitude of  30°N to 30°S, unless otherwise noted)depicting stratospheric cooling and increasing tropospheric warming with increasing altitude. 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) [6]. The tropical troposphere lies below 150 hPa, while the tropical stratosphere is above 70hPa [5]. 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 [6] (see "Myth: The Tropospheric Hot Spot does not Exist" for more on what a moist adiabat is).

Figure 2 shows tropospheric warming lower in the atmosphere, at atmospheric pressures beneath 150 hPa, along with stratospheric cooling higher in the atmosphere, at pressures of 70 hPa and less [6]. Christy et al. also cite three other weather balloon analyses (RAOBCORE, RICH, and RATPAC) [1, page 23; 2, page 21] and two satellite-based analyses (UAH and RSS) [1, pages 26 - 28 and 49 - 52; 2, pages 27 - 32 and 54 - 57; 198], each of which show tropospheric warming and stratospheric cooling in the tropics [29, page 13; 31; 52, figure 9 on page 3710; 71, figure 3 on page 378; 108]. So the observations from Christy et al.'s cited sources match the atmospheric pattern one would expect for CO2-induced warming, but not solar-induced warming, as indicated in figure 1. Christy should know this, since he co-authored a 2006 report showing this pattern of tropospheric warming and stratospheric cooling in weather balloon analyses and satellite analyses [29, pages 12 and 13]. Yet Christy et al. conveniently avoid addressing this pattern, even though in a 2017 report Christy again depicts this tropospheric warming and stratospheric cooling [207, pages S16 - S19].

Christy et al. remain at pressure levels of 150 mb and greater (equivalent to a pressure of 150 hPa and greater), keeping them at or beneath the upper troposphere [1, pages 13 and 59]. This allows them to avoid the stratospheric cooling present in figure 2 above 150 hPa; thus Christy et al. evade this evidence against their solar-warming hypothesis. Figure 3 shows the highest atmospheric layer Christy et al. examine, at an atmospheric pressure of 150 mb:

Figure 3: A portion of table XXIII-1 from the 1st edition of Christy et al.'s "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 [1, page 59].

So instead of addressing stratospheric cooling, Christy et al. avoid the cooling by making sure to stay below the stratosphere in their "report's" 1st edition. This sort of evasion is common among "skeptics" of man-made, CO2-induced climate change. So Christy et al.'s evasion does not shock me. What shocks me is what they did in their "report's" 2nd edition [2]: Christy et al. make stuff up.

In their "report's" 2nd edition, they re-label 150 mb as the tropical stratosphere on at least three different occasions [2, pages 24 and 70], and thus knowingly mislead their audience. Christy et al. use their misrepresentation to make it look as if the tropical stratosphere warmed, as shown in figure 4 below:

Figure 4: This is figure VIII-3 from the 2nd edition of their "report" [2, page 25]. This (supposedly) shows tropical stratospheric data from three weather balloon data-sets [2, page 24].

Then they claim that CO2 has no observable impact on this stratospheric warming trend:

"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 [...] [1, page 24]."

Hilariously, Christy et al. fail to completely cover their tracks, since they say 150 mb is part of the tropical troposphere, not the tropical stratosphere, elsewhere in the "report's" 2nd edition [2, page 62]:

Figure 5: A portion of table XIII-1 from the 2nd edition of Christy et al.'s "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 tropospheric temperature. They call 150 mb the lower troposphere [2, page 63]; this conflicts with their "report's" 1st edition, in which they claim 150 mb is part of the tropical upper troposphere, as shown in figure 3 [1, page 59]. 150 mb should be part of the upper, not lower, troposphere since 150 mb is higher in the atmosphere 200 mb [5; 52 - 54] and figure 5 notes that 200 mb is part of the tropical upper troposphere [2, page 63]. So figure 5 contradicts atmospheric physics and an earlier figure [1, page 59] from the "report's" first edition.

They also state that their solar-induced warming model does not explain the 150 mb stratospheric temperature very well [1, pages 24 and 70]. This is ironic since the 150 mb data they refer to is tropospheric temperature, not stratospheric temperature; 150 mb (which is equivalent to 150 hPa) represents the border between the tropical lower tropopause and the tropical upper troposphere [5; 52 - 54], not the tropical stratosphere:

"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 [...] [5]."

Even the paper cited by Christy et al. [1, page 23; 2, page 21] states that 150 hPa is around the tropical tropopause region that is associated with a transition from tropospheric warming to stratospheric cooling [6]. This transition is shown in figure 2 above, which comes from said paper [6]. This paper also shows strong, tropical stratospheric cooling [6], as shown in figure 2 and figure 6 below:

Figure 6: Temperature in the lower stratosphere at 50 hPa, relative to a baseline [6].

The strong, tropical stratospheric cooling displayed in figures 6 and 2 contrasts with Christy et al.'s made-up stratospheric warming shown in figure 4; Christy et al. misrepresent tropospheric warming as being stratospheric warming [2, pages 24 and 70]. This is ironic since for years Christy (falsely) claimed that the tropical troposphere had not warmed [45, from 36:31 to 37:10; 103 - 105; 106, pages 5 and 6; 197], yet Christy now attempts to exploit the tropospheric warming that he long denied.

Other research also shows tropical stratospheric cooling [20; 28; 29, page 13; 31; 38; 39; 43; 71 - 73; 113; 114; 198], providing further evidence against Christy et al.'s claim of tropical stratospheric warming [1, pages 24 and 25]. Christy et al.'s solar-induced warming model likely could not explain this stratospheric cooling, since solar-induced warming does not account for strong, long-term stratospheric cooling [20; 24 - 26; 29 - 35; 110]. Christy knows this since he co-authored a document explaining this point [29, pages 5 and 8], as I discussed with respect to figure 1. Yet despite this knowledge, Christy chooses not to include stratospheric temperature data from above 150 mb [1, page 11; 2, page 11]. It is as if Christy is willfully ignoring evidence against his solar-induced warming model.

Christy not only ignores evidence from other researchers, but Christy also ignores his own published research. For example, Christy co-authored a paper which states that 100 mb (100 hPa) lies within the tropical tropopause:

"Figure 1 shows these temperature trends as a function of pressure (altitude) from the surface (~1000 hPa) to the tropopause (~100 hPa/17 km) [7, page 1696]."

Since the tropopause is beneath the stratosphere [5 - 7], then this means that any pressure level beneath 100 mb must be beneath the tropical stratosphere and thus must not be part of the tropical stratosphere. Since 150 mb is beneath 100 mb (see figure 2 above) [5 - 7], then 150 mb is not part of the tropical stratosphere. Thus Christy's co-authored paper [7, page 1696] implies that 150 mb is not part of the tropical stratosphere, contrary to the 2nd edition of Christy et al.'s "report" [2, pages 24 and 70].

Christy's published research also shows tropical cooling at 150 mb and 100 mb [7, table 1 on page 1694 and figure 1 on page 1697]. So Christy is clearly aware of data on cooling above 150 mb, but he chooses not to include this data [1, page 11; 2, page 11]. Furthermore, Christy co-runs the University of Alabama in Huntsville (UAH) satellite data analysis [55], and this UAH analysis shows stratospheric cooling [29, pages 8, 9, 12, and 13; 31; 55; 71, figure 3 on page 378], including cooling in the tropics [29, page 13; 31; 71, figure 3 on page 378].

Figure 7 shows depicts this UAH cooling trend, along with satellite-based cooling trends from Remote Sensing Systems (RSS) and the National Oceanic and Atmospheric Administration Center for Satellite Applications and Research (NOAA/STAR):

Figure 7: (A),(B) 1979 - 2016 near-global (A) and tropical (B) lower stratospheric cooling trends predicted by climate models and observed in satellite data analyses. Trends are presented as an average of all the trend values for a given trend length. (C),(D) Ratio between the near-global (C) and tropical (D) stratospheric cooling trend predicted by the climate models vs. the stratospheric cooling trend observed in the satellite data analyses [71, figure 3 on page 378].

Yet remarkably, in Christy et al.'s "reports" Christy chooses [1, page 11; 2, page 11] not to mention his UAH stratospheric temperature analysis [1, pages 13 and 59; 2, pages 13 and 62], even though he chooses [1, page 11; 2, page 11] to mention his UAH tropospheric temperature analysis [1, pages 26 - 28, 49 - 52, and 63 - 65; 2, pages 27 - 32, 54 - 57, and 64 - 68]. UAH's stratospheric cooling data would have argued against Christy's solar-induced warming hypothesis [20; 24 - 26; 29 - 35; 110], which may be why Christy decided [1, page 11; 2, page 11] not to mention his UAH analysis.

So given this evidence against Christy et al.'s solar-induced warming hypothesis, how do Christy et al. attempt to support their hypothesis? To do this, Christy et al. claim to subtract out warming caused by the Sun and an ocean cycle known as the El Niño-Southern Oscillation (ENSO). Christy et al. then state that no significant tropospheric and surface warming remained after this subtraction [1, pages 16, 18, 67 and 68]. Thus recent global warming was likely caused by the Sun and ENSO.

Christy et al.'s aforementioned reasoning fails, since Christy et al. use flawed, cumulative indices to correct for solar-induced and ENSO-induced warming [1, page 18]. 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 et al.'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 [4]: a warmer Earth would radiate more energy into space, instead of all the energy just accumulating [74 - 76]. Scientists can observe this increased radiation during a warm El Niño [77 - 79]; the radiation increase occurs largely because El Niño increases cloud cover and these clouds then reflect the solar radiation Earth would otherwise absorb [77; 80]. This cloud-based mechanism compensates [77; 79] for less emission of radiation by clouds during El Niño [81; 82]. So increased radiation during warm El Niño events debunks the implausible physics implied by Christy et al.'s cumulative indices.

Given this defect in Christy et al.'s cumulative indices, scientists rarely (if ever) use Christy et al.'s indices. In fact, I know of no peer-reviewed scientific paper that uses Christy et al.'s cumulative indices. Scientists instead use non-cumulative indices to account for solar-induced and ENSO-induced warming. Even Christy's [1, page 18; 3, page 10] sources apply non-cumulative solar [83; 84] and ENSO indices [85; 86; 87, page 231], as does Christy in his peer-reviewed work [84; 206]. These non-cumulative indices are compatible with Earth radiating more energy as Earth warms, in contrast to Christy et al.'s cumulative indices. Christy may not even believe his claims regarding the cumulative ENSO index, since in subsequent research he used a non-cumulative ENSO index to argue that sea surface warming had a negligible effect on post-1979 tropospheric warming [206, pages 512 and 517]. Similarly, Christy may not believe his claims regarding his cumulative TSI index, since in the same subsequent research Christy wrote: 

"The amplitude of the 11-year [solar] cycle has diminished since the peak in 2000 and, in our residual time series, there is indeed a slight slowdown in the rise after 1998. One may arbitrarily select an accumulation period of TSI [emphasis added], so that a peak occurs near 1998 so the TSI coincides with (explains) variations in [lower tropospheric temperature] (e.g., a 22-year TSI trailing average peaks in 2000, though other averaging periods do not), but this would compromise the independence between the predictors and predictand [emphasis added] [the predictor is the factor used to predict the predictand] [206, page 514]."

In this same paper, Christy also admitted that CO2 caused significant tropospheric warming [206]; thus Christy contradicts his claim of no evidence that CO2 had no observable, significant effect on recent temperature trends [1, page 4; 2, page 4]. So Christy's published research contradicts his cumlative-index-based, blog article claims.

Strangely, Christy et al. seem to use a non-cumulative CO2 index for their work [2, page 8], as pointed out by Brandon R. Gates [107]. By using a non-cumulative CO2 index [2, page 8], Christy et al. avoid passing down all of CO2's impact from year to subsequent year. In contrast, Christy et al. use cumulative solar and ENSO indices, allowing them to pass all of the solar and ENSO impacts from year to subsequent year. This double-standard makes it easier for Christy et al. to (incorrectly) argue that the Sun and ENSO caused recent warming [1, pages 57 and 68; 2, pages 4, 71, and 72; 3, page 10; 4], while CO2 did not [1, page 4; 2, page 4].

In fact, Christy et al. cite [1, page 18; 2, page 18] a 1993 paper for their cumulative solar index, even though this 1993 paper uses a non-cumulative solar index [83]. This 1993 paper also notes that solar irradiance and Northern hemisphere temperature diverged in recent decades ("recent decades" before 1993) in a way consistent with CO2-induced warming [83, figure 10 on page 18,904]. This suggestion from 1993 does not fit well Christy et al.'s claim that the Sun, not CO2, is responsible for much of the post-1970s global warming trend [1, pages 16, 18, 57, 67 and 68; 2, pages 4 and 68; 3, page 10].

And since 1993, things have only gotten worse for Christy et al.'s solar-warming hypothesis. To see why, let's contrast Christy et al.'s cumulative total solar irradiance (TSI) index with a non-cumulative TSI index:

Figure 8: Cumulative TSI and cumulative ENSO index used by Christy et al. [1, page 18].

Figure 9: Non-cumulative TSI from the NOAA's Climate Data Record (CDR), based on satellite observations. The peaks and troughs represent the 11 year solar cycle. Data sources are SORCE TIM (Solar Radiation and Climate Experiment, with Total Irradiance Monitor), ACRIM (Active Cavity Radiometer Irradiance Monitor) and PMOD (Physikalisch-Meteorologisches Observatorium Davos) [109].

Figure 9 shows an 11-year cycle in solar output. Once one takes this cycle into account, there is not a post-1979 increase in TSI. Yet Christy et al. transform this lack of an increase into a cumulative TSI increase [1, page 18], as shown in figure 8. They perform this transformation using the faulty method Christy critiqued above: arbitrarily selecting an accumulation period, thus compromising the relationship between TSI (the predictor) and temperature trends (the predictands) [206, page 514]. Christy et al. then use this manufactured TSI increase (from their defective cumulative TSI index) to argue that the Sun caused much of the recent global warming [1, pages 16, 18, 57, 67 and 68; 2, pages 4 and 68; 3, page 10].

When scientists use non-cumulative indices to correct for solar-induced warming [30; 60 - 62; 208] and ENSO-induced warming [30; 60 - 62; 88 - 91; 208], most of the post-1950s tropospheric and surface warming remained [30; 60 - 62; 88 - 91; 208], contrary to the claims Christy et al. made in their blogpost/"report" [1, pages 16, 18, 67 and 68;  2, pages 4 and 68]. Thus these non-cumulative indices provide another line of evidence against Christy et al.'s solar-induced warming model.

So let's summarize some of the relevant lines of evidence against Christy et al.'s solar-induced warming hypothesis and/or evidence in favor of the CO2-induced warming hypothesis:
  1. Significant global warming remains even after correcting for TSI [30; 60 - 62; 208].
  2. The relationship between solar output and global warming fails a number of statistical tests and model-based tests [63 - 70].
  3. Solar output has not correlated well with recent global warming [56 - 59].
  4. The stratosphere cooled [6; 19; 20; 23; 28; 29, pages 8, 9, 12, and 13; 31; 38 - 44; 71 - 73; 102; 198; 213, figure 18], in accordance with CO2-induced global warming [6; 18; 21; 23 - 29; 102; 115, page 176; 116, page 409; 195; 196; 198; 201, figure 4; 205, pages 101 and 102; 212, figure 16 on page 250 and page 251; 222] but not solar-induced warming [20; 24 - 26; 29 - 35; 110]. The tropopause also rose [215 - 217; 219; 221], consistent with stratospheric cooling caused by ozone depletion and increased CO2 [46; 215; 218; 220].
  5. Observed cooling of the mesosphere and thermosphere, atmospheric layers above the stratosphere, fits with CO2-induced global warming [92 - 99; 204; 222; 223].
  6. The regional pattern of warming and precipitation matches what one would expect from CO2-induced warming, instead of warming caused by other factors such as increasing levels of solar-radiation-absorbing aerosols and increasing solar output [35; 203; 224; 225; 226, page 946].
  7. CO2 absorbs energy in particular wavelengths and emits energy in particular wavelengths [45, from 9:13 to 10:28; 117; 118; 199], shifting Earth's energy balance (the amount of energy the Earth takes up vs. the amount of energy the Earth releases) [119 - 122]. Climate sensitivity states how much warming results from CO2's effect on Earth's energy balance[123; 124]. Scientists estimate climate sensitivity in a number of ways [123; 125 - 144], such as examining how much warming occurred with CO2 increases in the distant past [125 - 128]. Scientists can then use these climate sensitivity estimates to determine how much of the recent global warming was caused by the increased CO2 (I discuss this more in "Christopher Monckton and Projecting Future Global Warming, Part 1").

The aforementioned points, along with other lines of evidence, show that increases in greenhouse gases such as CO2 (not increased solar activity) caused most of the post-1950s and post-1970s global warming [25; 65 - 67; 89; 119; 145 - 181; 200; 208]. The figure below illustrates this for point 1:

Figure 10: Relative global temperature from 1979 - 2010 for three surface temperature records (GISS, NCDC and CRU) and two lower tropospheric temperature records (RSS and UAH), after correction for TSI, volcanic effects, and ENSO [61].

Christy et al. should be aware of the six aforementioned points since a they are well-known; NASA even discusses these issues when educating non-experts about climate science [36; 37]. For instance, NASA explains points 4 and 5 as follows:

"But several lines of evidence show that current global warming cannot be explained by changes in energy from the sun: 
If the warming were caused by a more active sun, then scientists would expect to see warmer temperatures in all layers of the atmosphere. Instead, they have observed a cooling in the upper atmosphere, and a warming at the surface and in the lower parts of the atmosphere. That's because greenhouse gases are trapping heat in the lower atmosphere [37]."

And the United States National Oceanic and Atmospheric Administration (NOAA) has noted as much as well [100; 101]. Yet Christy et al. conveniently side-step the aforementioned points, even though these points argue against their solar warming hypothesis. In fact, Christy et al. insinuate that the NOAA is engaged in deceptive data manipulation with regard to global warming [2, pages 43 and 58] (Christy's co-author D'Aleo regularly smears the NOAA in this way [111; 112]); I discuss Christy et al.'s debunked NOAA conspiracy theory in section 3.8 of part 2 of "John Christy and the Tropical Tropospheric Hot Spot".
So who is more likely to be deceptive: the NOAA and NASA who seek to educate non-experts on climate science, or Christy et al. who willfully conceal relevant evidence from non-experts?

In conclusion, Christy et al. non-peer-reviewed blogposts/"reports" [1; 2]:
  • exclude data relevant to testing their solar-induced warming hypothesis
  • distort evidence in a way that suits their preferred conclusion
  • rely on a litany of misrepresentations
  • offer claims inconsistent with other claims made in the "reports"
  • conflict with Christy's published research
They do this on behalf of ICECAP, an organization that uses Christy et al.'s blogposts/"reports" to attack the United States Environmental Protection Agency's attempts to regulate CO2 emissions [182]. Christy's co-authored these blogposts [1; 2] with ICECAP's founder Joseph D'Aleo [211]. D'Aleo uses his religious and political ideology to discount the negative effects of CO2-induced, man-made climate change [209, signer #7; 210], as does Christy's UAH colleague Roy Spencer [209, signer #35; 210]. This may provide further context as to why ICECAP incorporates D'Aleo and Christy's blogposts/"reports" into their political attacks on EPA regulation of CO2 emissions [182].

It is unfortunate that Christy peddled these shoddy blogposts/"reports" to Congress in 2017 [3, page 10; 4]:

"Indeed, I am a co-author of a report in which we used a statistical model to reproduce, to a large degree, the atmospheric temperature trends without the need for extra greenhouse gases. In other words, it seems that Mother Nature can cause such temperature trends on her own, which should be of no surprise [4]."

This greatly differs from testimony Christy gave in a 2007 court case. As stated in court documents from that case:

"Plaintiffs’ own expert, Dr. Christy, agrees with the IPCC’s [Intergovernmental Panel of Climate Change] assessment that in the light of new evidence and taking into account remaining uncertainties, most of the observed warming over the last fifty years is likely to have been due to the increase in GHG [greenhouse gas] concentrations. [...]. Christy agrees that the increase in carbon dioxide is real and primarily due to the burning of fossil fuels, which changes the radiated balance of the atmosphere and has an impact on the planet’s surface temperature toward a warming rate [183]." 

Yet in his aforementioned 2017 Congressional testimony, Christy says that atmospheric temperature trends can largely be explained "without the need for extra greenhouse gases [4]." So from 2007 to 2017, Christy's public acceptance of strong greenhouse-gas-induced warming went away, even though more evidence of greenhouse-gas-induced warming accumulated over this same time-period [25; 65 - 67; 89; 119; 145 - 147; 152 - 155; 157 - 164; 167; 169 - 181]. The IPCC went in the opposite direction as Christy in response to the evidence: the IPCC moved from saying in 2007 that it was likely (>66% chance [193, page 3]) that greenhouse gas increases caused most of the warming [192, page 665], to saying in 2013 that it was very likely (>90% chance [193, page 3]) that greenhouse gas increases caused most of the warming and that it it was extremely likely (>95% chance [193, page 3]) that human activities caused most of the warming [194, page 869].

So in response to new evidence, the IPCC expressed increased confidence in the evidence-based claims, while Christy expressed reduced confidence to the point that he no longer accepted the evidence-based claims. Make of that what you will, especially in light of the following oft-repeated points [184 - 188; 189, page 96; 190; 191]:

"It is, however, important not to confuse denialism with genuine scepticism, which is essential for scientific progress. Sceptics are willing to change their minds when confronted with new evidence; deniers are not [184]."

"A skeptic will question claims, then embrace the evidence. A denier will question claims, then reject the evidence [191]."

3. Posts Providing Further Information and Analysis

4. References

  1. "On the Existence of a “Tropical Hot Spot" & The Validity of EPA’s CO2 Endangerment Finding"
  2. "On the Existence of a “Tropical Hot Spot” & The Validity of EPA’s CO2 Endangerment Finding, Abridged Research Report, Second Edition"
  3. "U.S. House Committee on Science, Space & Technology, 29 Mar 2017, Testimony of John R. Christy"
  5. "Tropical Tropopause Layer" [doi:10.1029/2008RG000267]
  6. "Atmospheric changes through 2012 as shown by iteratively homogenized radiosonde temperature and wind data (IUKv2)"
  7. "A comparison of tropical temperature trends with model predictions"
  8. "The ozone story: A model for addressing climate change?"
  9. "Depletion of the ozone layer in the 21st Century"
  10. "The Antarctic ozone hole: An update"
  11. "Antarctic ozone loss in 1979–2010: First sign of ozone recovery"
  12. "Quantifying the ozone and ultraviolet benefits already achieved by the Montreal Protocol"
  13. "Evidence for the effectiveness of the Montreal Protocol to protect the ozone layer"
  14. "Emergence of healing in the Antarctic ozone layer"
  15. "Ozone depletion, greenhouse gases, and climate change"
  16. "Trace gas trends and their potential role in climate change"
  17. "A hiatus in the stratosphere?"
  18. "Isolating the roles of different forcing agents in global stratospheric temperature changes using model integrations with incrementally added single forcings"
  19. "Stratospheric temperature climate data record from merged SSU and AMSU-A observations"
  20. "Stratospheric temperature trends over 1979–2015 derived from combined SSU, MLS, and SABER satellite observations"
  21. "Stratospheric ozone change and related climate impacts over 1850–2100 as modelled by the ACCMIP ensemble"
  22. "The impact of ozone-depleting substances on tropical upwelling, as revealed by the absence of lower-stratospheric cooling since the late 1990s"
  23. "Models versus radiosondes in the free atmosphere: A new detection and attribution analysis of temperature"
  24. "Attributing the forced components of observed stratospheric temperature variability to external drivers"
  25. "Identifying human influences on atmospheric temperature"
  26. "Human and natural influences on the changing thermal structure of the atmosphere"
  27. "Towards a physical understanding of stratospheric cooling under global warming through a process-based decomposition method"
  28. "Use of SSU/MSU satellite observations to validate upper atmospheric temperature trends in CMIP5 simulations"
  29. "Executive Summary: Temperature trends in the lower atmosphere - Understanding and reconciling differences"
  30. "Spectrally dependent CLARREO infrared spectrometer calibration requirement for climate change detection"
  31. "Stratospheric temperature changes during the satellite era"
  32. "On the detection of the solar signal in the tropical stratosphere"
  33. "Observed tropospheric temperature response to 11-yr solar cycle and what it reveals about mechanisms"
  34. "Robustness of dynamical feedbacks from radiative forcing: 2% solar versus 2× CO2 experiments in an idealized GCM"
  35. "Comment on “Climate Science and the Uncertainty Monster” by J. A. Curry and P. J. Webster"
  36. "Is the Sun causing global warming?"
  38. "Evidence for an earlier greenhouse cooling effect in the stratosphere before 1980 over the Northern Hemisphere"
  39. "Regional and seasonal stratospheric temperature trends in the last decade (2002–2014) from AMSU observations"
  40. "A method for merging nadir-sounding climate records, with an application to the global-mean stratospheric temperature data sets from SSU and AMSU"
  41. "Linear trends and closures of 10-yr observations of AIRS stratospheric channels"
  42. "The stratospheric changes inferred from 10 years of AIRS and AMSU-A radiances"
  43. "The JRA-55 reanalysis: Representation of atmospheric circulation and climate variability"
  44. "The JRA-55 reanalysis: General specifications and basic characteristics"
  45. Ray Pierrehumbert's 2012 video: "Tyndall Lecture: GC43I. Successful Predictions - 2012 AGU Fall Meeting"
  46. "Tropopause height and zonal wind response to global warming in the IPCC scenario integrations"
  47. "The greenhouse theory of climate change: A test by an inadvertent global experiment"
  48. "Global climate changes as forecast by Goddard Institute for Space Studies three-dimensional model"
  49. "Long-term temperature trends in the stratosphere: Possible influence of anthropogenic gases"
  50. "Major greenhouse cooling (yes, cooling): The upper atmosphere response to increased CO2"
  51. "Sensitivity of surface-temperature and atmospheric-temperature to perturbations in stratospheric concentration of ozone and nitrogen-dioxide"
  52. "New estimates of tropical mean temperature trend profiles from zonal mean historical radiosonde and pilot balloon wind shear observations"
  53. "Revisiting the controversial issue of tropical tropospheric temperature trends"
  54. "Insights into Tropical Tropopause Layer processes using global models"
  55. "UAH version 6 global satellite temperature products: Methodology and results"
  56. "The impact of the revised sunspot record on solar irradiance reconstructions"
  57. "Cosmic rays, solar activity and the climate"
  58. "Unusual activity of the Sun during recent decades compared to the previous 11,000 years"
  59. "Recent oppositely directed trends in solar climate forcings and the global mean surface air temperature"
  60. "Deducing multidecadal anthropogenic global warming trends using multiple regression analysis"
  61. "Global temperature evolution 1979–2010"
  62. "Natural variability, radiative forcing and climate response in the recent hiatus reconciled"
  63. "Can solar variability explain global warming since 1970?
  64. "Solar variability and global warming: a statistical comparison since 1850"
  65. "Solar trends and global warming"
  66. "Small influence of solar variability on climate over the past millennium"
  67. "Evidence of recent causal decoupling between solar radiation and global temperature"
  68. "Statistical assessments of anthropogenic and natural global climate forcing. An update"
  69. "Causes of the global warming observed since the 19th century"
  70. "Quantifying the role of solar radiative forcing over the 20th century"
  71. "Comparing tropospheric warming in climate models and satellite data"
  72. "Westward shift of western North Pacific tropical cyclogenesis"
  73. "Influence of tropical tropopause layer cooling on Atlantic hurricane activity"
  74. "Global monthly precipitation estimates from satellite-observed outgoing longwave radiation"
  75. "An observationally based energy balance for the Earth since 1950"
  76. "An analysis of the dependence of clear-sky top-of-atmosphere outgoing longwave radiation on atmospheric temperature and water vapor"
  77. "ENSO-driven energy budget perturbations in observations and CMIP models"
  78. "Advances in understanding top-of-atmosphere radiation variability from satellite observations"
  79. "Observed changes in top-of-the-atmosphere radiation and upper-ocean heating consistent within uncertainty"
  80. "The ENSO effects on tropical clouds and top-of-atmosphere cloud radiative effects in CMIP5 models"
  82. "Does vertical temperature gradient of the atmosphere matter for El Niño development?"
  83. "A discussion of plausible solar irradiance variations, 1700-1992"
  84. "Satellite greenhouse signal"
  85. (accessed June 12, 2017)
  86. "El Niño/Southern Oscillation behaviour since 1871 as diagnosed in an extended multivariate ENSO index (MEI.ext)"
  87. "The role of ENSO in global ocean temperature changes during 1955-2011 simulated with a 1D climate model"
  88. "Volcanic contribution to decadal changes in tropospheric temperature"
  89. "Clarifying the roles of greenhouse gases and ENSO in recent global warming through their prediction performance"
  90. "Equilibrium climate sensitivity in light of observations over the warming hiatus"
  91. Foster et al.: "Comment on “Influence of the Southern Oscillation on tropospheric temperature” by J. D. McLean,C. R. de Freitas, and R. M. Carter"
  92. "A model estimate of cooling in the mesosphere and lower thermosphere due to the CO2 increase over the last 3–4 decades"
  93. "Evidence of CO2-induced progressive cooling of the middle atmosphere derived from radio observations"
  94. "Ozone and temperature decadal trends in the stratosphere, mesosphere and lower thermosphere, based on measurements from SABER on TIMED"
  95. "Why CO2 cools the middle atmosphere-a consolidating model perspective"
  96. "Effect of trends of middle atmosphere gases on the mesosphere and thermosphere"
  97. "How will changes in carbon dioxide and methane modify the mean structure of the mesosphere and thermosphere?"
  98. "Temperature trends in the midlatitude summer mesosphere"
  99. "Role of carbon dioxide in cooling planetary thermospheres"
  102. "Postmillennium changes in stratospheric temperature consistently resolved by GPS radio occultation and AMSU observations"
  103. "The reproducibility of observational estimates of surface and atmospheric temperature change"
  104. "The effect of diurnal correction on satellite-derived lower tropospheric temperature"
  105. "Tropospheric temperature trends: history of an ongoing controversy"
  106. "Review of the consensus and asymmetric quality of research on human-induced climate change"
  108. "Radiosonde Atmospheric Temperature Products for Assessing Climate (RATPAC): A new data set of large-area anomaly time series"
  109. "A solar irradiance climate data record"
  110. "On the aliasing of the solar cycle in the lower-stratospheric tropical temperature"
  111. "Surface temperature records: Policy-driven deception?"
  112. "On the validity of NOAA, NASA and Hadley CRU global average surface temperature data & the validity of EPA’s CO2 endangerment finding"
  113. "Atmospheric temperature change detection with GPS radio occultation 1995 to 2008"
  114. "Atmospheric climate change detection by radio occultation data using a fingerprinting method"
  115. "Principles of planetary climate"
  116. "Global physical climatology"
  117. "Observational determination of surface radiative forcing by CO2 from 2000 to 2010"
  118. "Increases in greenhouse forcing inferred from the outgoing longwave radiation spectra of the Earth in 1970 and 1997"
  119. "Anthropogenic and natural warming inferred from changes in Earth’s energy balance"
  120. "Insights into Earth’s energy imbalance from multiple sources"
  121. "Reconciling estimates of ocean heating and Earth’s radiation budget"
  122. "Observed and simulated full-depth ocean heat-content changes for 1970–2005"
  123. "The equilibrium sensitivity of the Earth’s temperature to radiation changes"
  124. "Feedbacks, climate sensitivity and the limits of linear models"
  125. "Climate sensitivity in the geologic past"
  126. "Deep time evidence for climate sensitivity increase with warming"
  127. "Can the Last Glacial Maximum constrain climate sensitivity?"
  128. "Climate sensitivity estimated from temperature reconstructions of the Last Glacial Maximum"
  129. "Recent developments in Bayesian estimation of climate sensitivity"
  130. "Inference of climate sensitivity from analysis of Earth's energy budget"
  131. "Variation in climate sensitivity and feedback parameters during the historical period"
  132. "Observational constraints on mixed-phase clouds imply higher climate sensitivity"
  133. "The implications for climate sensitivity of AR5 forcing and heat uptake estimates"
  134. "Reconciled climate response estimates from climate models and the energy budget of Earth"
  135. "Implications for climate sensitivity from the response to individual forcings"
  136. "Implications of potentially lower climate sensitivity on climate projections and policy"
  137. "Disentangling greenhouse warming and aerosol cooling to reveal Earth’s climate sensitivity"
  138. "Inhomogeneous forcing and transient climate sensitivity"
  139. "On a minimal model for estimating climate sensitivity"
  140. "Corrigendum to "On a minimal model for estimating climate sensitivity" [Ecol. Model. 297 (2015), 20-25]"
  141. "Projection and prediction: Climate sensitivity on the rise"
  142. "Spread in model climate sensitivity traced to atmospheric convective mixing"
  143. "Long-term cloud change imprinted in seasonal cloud variation: More evidence of high climate sensitivity"
  144. "Nonlinear climate sensitivity and its implications for future greenhouse warming"
  145. "On the causal structure between CO2 and global temperature"
  146. "Assessing the observed impact of anthropogenic climate change"
  147. "Detection and attribution of climate change: a regional perspective"
  148. "Combinations of natural and anthropogenic forcings in twentieth-century climate"
  149. "A multimodel update on the detection and attribution of global surface warming"
  150. "The detection and attribution of climate change using an ensemble of opportunity"
  151. "Estimation of natural and anthropogenic contributions to twentieth century temperature change"
  152. "Attribution of observed historical near-surface temperature variations to anthropogenic and natural causes using CMIP5 simulations"
  153. "Attributing observed SST trends and subcontinental land warming to anthropogenic forcing during 1979–2005"
  154. "Sensitivity of the attribution of near surface temperature warming to the choice of observational dataset"
  155. "A probabilistic quantification of the anthropogenic component of twentieth century global warming"
  156. "Quantifying anthropogenic influence on recent near-surface temperature change"
  157. "Evidence for external forcing on 20th-century climate from combined ocean-atmosphere warming patterns"
  158. "Observed 21st century temperatures further constrain likely rates of future warming"
  159. "CMIP5 historical simulations (1850–2012) with GISS ModelE2"
  160. "Climate variability and change since 850 C.E.: An ensemble approach with the Community Earth System Model (CESM)"
  161. "Uncertainties in the attribution of greenhouse gas warming and implications for climate prediction"
  162. "Application of regularised optimal fingerprinting to attribution. Part II: application to global near-surface temperature"
  163. "A fractal climate response function can simulate global average temperature trends of the modern era and the past millennium"
  164. "Evaluating global climate responses to different forcings using simple indices"
  165. "Causes of twentieth-century temperature change near the Earth’s surface"
  166. "Causes of climate change over the past 1000 years"
  167. "How natural and anthropogenic influences alter global and regional surface temperatures: 1889 to 2006"
  168. "Detecting climate signals in the surface temperature record"
  169. "Detecting the influence of fossil fuel and bio-fuel black carbon aerosols on near surface temperature changes"
  170. "Drivers of decadal hiatus periods in the 20th and 21st centuries"
  171. "Statistically derived contributions of diverse human influences to twentieth-century temperature changes"
  172. "Testing the robustness of the anthropogenic climate change detection statements using different empirical models"
  173. "A new statistical approach to climate change detection and attribution"
  174. "A contribution to attribution of recent global warming by out-of-sample Granger causality analysis"
  175. "Testing for linear Granger causality from natural/anthropogenic forcings to global temperature anomalies"
  176. "Anthropogenic and natural causes of climate change"
  177. "Improved constraints on 21st-century warming derived using 160 years of temperature observations"
  178. "Climate of the past millennium: combining proxy data and model simulations"
  179. "The role of Atlantic Multi-decadal Oscillation in the global mean temperature variability"
  180. "The Atlantic Multidecadal Oscillation as a dominant factor of oceanic influence on climate"
  181. "Return periods of global climate fluctuations and the pause"
  183. "United States District Court for Vermont, Case No. 2:05-cv-302"
  184. "How the growth of denialism undermines public health"
  185. "The ethics of belief, cognition, and climate change pseudoskepticism: Implications for public discourse"
  186. "Sceptics and deniers of climate change not to be confused"
  187. "HIV denial in the Internet era"
  189. "Debating global warming in media discussion forums: Strategies enacted by “persistent deniers” and implications for schooling"
  190. "Science denial and the science classroom"
  192. "Climate change 2007: The physical science basis; Chapter 9: Understanding and attributing climate change"
  193. "Guidance note for lead authors of the IPCC Fifth Assessment Report on consistent treatment of uncertainties"
  194. "Climate change 2013: The physical science basis; Chapter 10: Detection and attribution of climate change: from global to regional"
  195. "Anthropogenic and natural influences in the evolution of lower stratospheric cooling"
  196. "Relative contribution of greenhouse gases and ozone-depleting substances to temperature trends in the stratosphere: A chemistry–climate model study"
  197. "Effects of orbital decay on satellite-derived lower-tropospheric temperature trends"
  198. "Troposphere-stratosphere temperature trends derived from satellite data compared with ensemble simulations from WACCM"
  199. "The spectral signature of recent climate change"
  200. "Scaling fluctuation analysis and statistical hypothesis testing of anthropogenic warming"
  201. "The effects of doubling the CO2 concentration on the climate of a general circulation model"
  202. "Exxon Research and Engineering Company's technological forecast CO2 greenhouse effect"
  203. "Dependence of the land-sea contrast in surface climate response on the nature of the forcing"
  204. "Global change in the upper atmosphere"
  205. "On the distribution of climate change resulting from an increase in CO2 content of the atmosphere"
  206. "Satellite bulk tropospheric temperatures as a metric for climate sensitivity"
  207. "State of the climate in 2016"
  208. "Lower tropospheric temperatures 1978-2016: The role played by anthropogenic global warming"
  209. "Prominent signers of "An evangelical declaration on global warming""
  210. "An evangelical declaration on global warming"
  212. "Thermal equilibrium of the atmosphere with a given distribution of relative humidity"
  213. "Climatology and interannual variability of dynamic variables in multiple reanalyses evaluated by the SPARC Reanalysis Intercomparison Project (S-RIP)"
  214. "Assessing ExxonMobil's climate change communications (1977–2014)"
  215. "Contributions of anthropogenic and natural forcing to recent tropopause height changes"
  216. "Response to Comment on "Contributions of anthropogenic and natural forcing to recent tropopause height changes""
  217. "Variability and trends in the global tropopause estimated from radiosonde data"
  218. "Scaling behaviour of the global tropopause"
  219. "A global blended tropopause based on ERA data. Part II: Trends and tropical broadening"
  220. "Impact of changes in climate and halocarbons on recent lower stratosphere ozone and temperature trends"
  221. "Trends in the global tropopause thickness revealed by radiosondes"
  222. "Whole atmosphere simulation of anthropogenic climate change"
  223. "Progress in observations and simulations of global change in the upper atmosphere"
  224. "Divergent global precipitation changes induced by natural versus anthropogenic forcing"
  225. "Observed heavy precipitation increase confirms theory and early models"
  226. "Characteristics of temperature change in China over the last 2000 years and spatial patterns of dryness/wetness during cold and warm periods"