THE REAL CLIMATE CRISIS IS NOT GLOBAL WARMING BUT GLOBAL COOLING. 

On October 27, 2019, the climate blog WUWT published a guest article with the title “The Real Climate Crisis Is Not Global Warming, It Is Cooling, And It May Have Already Started“. The article is a critical evaluation of AGW theory and the climate movement.  The full text of the article is available online [LINK] . In it the authors present their case against catastrophic AGW saying that CAGW is a failed hypothesis and scientific fraud with no credible evidence to support its outrageous claims, and that it is a politically motivated alarmist movement that takes advantage of the gullibility of the masses to fear based activism. The authors claim that they have “ample evidence that the CAGW hypothesis has been falsified”. 

THIS POST IS CRITICAL REVIEW OF SOME OF THE CLAIMS MADE IN THIS ARTICLE 

CLAIM#1: “Global warming has slowed since the mid-1990s”. RESPONSE: This is an interesting point and generally accepted. It is easily verified for example by comparing the first half and the second half trends in UAH global mean temperatures 1979-2018 shown below. The blue line shows the trends in the first half of the sample period for each calendar month labeled 1 to 12. The 13th point is the average trend for the 12 calendar months. The corresponding data for the 2nd half appear in red. The comparison shows warming in both halves but with the warming in the 2nd half 1999-2018 slower than in the first half 1979-1998. We conclude from the chart below that the rate of global warming has slowed. However, a comparison of warming rates in two consecutive 20-year periods of convenience has no implication for or against the theory of AGW. For example, this comparison in itself does not imply that this is the beginning of the end of AGW or that the slowing will continue until the warming is over. As shown in a related post on “trend profiles” [LINK] , long term warming trends are the net result of decadal and multi-decadal cycles of warming at very different rates such that slowing or rising of decadal warming rates have no interpretation in terms of the overall long term temperature trend.

CLAIM#2: “Temperatures were much higher during the Medieval Warm Period. RESPONSE: The paleo data clearly show a very warm period ≈800 to ≈1400 AD and it very well might have been warmer than today. However, this issue has become contentious and this acrimonious debate survives because of large uncertainties in the paleo data. The literature shows a general agreement of large uncertainties in the data such that the selection of the type of proxy data (eg tree ring, sediment, borehole, or climate model) and the geographical location where data were gathered strongly influences findings. It is uncertain whether it was global or localized in Europe and if so whether it was all of Europe or just Northern Europe. It is also uncertain as to exactly when the MWP occurred and for how long it lasted. Most of all it is uncertain as to exactly how warm it got specifically with respect to the current 20th century warming of “the industrial economy since pre-industrial times”. Uncertainty of course creates controversy and given the the large stake for the climate science argument for human cause that the current warming is “unprecedented in the last two millennia” , the MWP issue has generated a great deal of acrimonious debate. This controversy is partisan and sustained by the so called “Texas Sharpshooter” fallacy because uncertainty allows different researchers to pay more attention to the portion of the uncertainty band that supports their hypothesis. Thus it is not clear that “Temperatures were much higher during the Medieval Warm Period”. A literature review of this issue is presented in a related post [LINK] and a general overview of the violent and chaotic cycles of warming and cooling at centennial and millennial time scales seen in the Holocene is presented in yet another related post [lLINK] that sets the context for Holocene climate variability.  The current warming does not appear anomalous in that context. Also the issue is not how strong the warming is but whether it is explained by fossil fuel emissions. The intensity of warming is not a human cause determinant. Strong warming does not prove human cause and weak warming does not prove absence of human cause. The MWP is a nonsensical issue in the AGW debate.

CLAIM#3: The hottest USA surface temperature records occurred in the 1930’s, before fossil fuel combustion accelerated circa 1940.  RESPONSE: The AGW issue is about long term trends in global mean surface temperature. Regional warming events have no direct interpretation in that context.

CLAIM#4: Fossil fuel combustion accelerated strongly at the start of World War II, and global temperatures COOLED significantly from 1940 to 1977. This cooling event disproves the causal link between fossil fuel emissions and warming. RESPONSE: It is true that there was an explosive growth in emissions in the post war economic boom. The observed cooling at a time of rising emissions is a high profile issue and generally recognized as an anomaly in AGW. However, the issue is more complex in light of the Schneider 1971 argument about aerosols discussed in a related post on this site [LINK] . Stephen Schneider, (may he rest in peace) had argued that both the war itself and the explosive post war economic growth on both sides of the Atlantic that involved a sharp increase in industrialization and coal burning with no environmental constraints, caused a spike in stratospheric aerosols that explained the net cooling even in the presence of AGW warming. In the late 1960s and early 1970s environmental legislation and control of industrial pollution virtually removed the supply of aerosols – particularly that of sulfate aerosols that are known to have a very strong cooling effect. The temporary cooling and the resumption of warming was thus explained. Therefore, the 1970s cooling anomaly case against AGW is not complete without a response to the Schneider aerosol argument.

CLAIM#5: Christy & McNider (2017) and Lewis & Curry (2018) have shown that the maximum possible value of Equilibrium Climate Sensitivity is ECS=1 but climate scientists have presented AGW theory and its catastrophic consequences based on sensitivity values of 3<ECS<5, much higher than ECS=1. Therefore AGW is false and simply a fear mongering device because no dangerous runaway warming is possible at ECS≤1.  RESPONSE: The low values of ECS reported here are not anything new as a review of the ECS literature that goes back to Manabe and Wetherald 1964 shows. The extant literature shows ECS values over a large range that includes ECS≤1.  In related posts on this site are cited a large number of works that report ECS values of ECS<1 to ECS>10   [LINK] [LINK] [LINK] [LINK] . A specific issue in the literature is found in Andronova 2000 where she reports ECS = [2.0-5.0] with the note that more than half of that figure can be explained by solar variability. That leaves her with residual CO2 sensitivity ECS=[0.94-2.35]. This finding weakens the role of human cause in AGW but in the context of a body of research that has failed to identify the value of ECS. The real ECS issue may therefore be not what its value is but whether such a parameter exists. Please see: [LINK] [LINK] [LINK] [LINK]

CLAIM#6: Global temperature is certainly NOT primarily driven by increasing atmospheric CO2, because CO2 changes LAG global temperature changes in time, both in the ice core proxy record and also in the modern data record. The Vostok ice core record shows a lag of CO2 after temperature of ~~800 years.  RESPONSE: That CO2 lags temperature by 800 years in the ice core record is often cited as an argument against AGW. If this lag serves as evidence that the causation is in reverse – that warming causes CO2 – then a causation mechanism at a time scale of 800 years must be presented. Without that detail, the 800 year lag in the proxy record has no interpretation in terms of AGW.

CLAIM#7: “despite continuing increases in atmospheric CO2, no significant global warming occurred in the last decade, as confirmed by both Surface Temperature and satellite measurements in the Lower Troposphere. RESPONSE: The chart on the left shows UAH August temperatures for the lower troposphere 1979-2019. A sustained warming trend is seen across the sample period. The chart on the right shows decadal trends for the same data in a moving 10-year window. The comparison of the two charts shows that even during a long term sustained warming trend, decadal trends can vary a great deal with decades of cooling and decades showing no trend intermixed with decades showing warming trends. In this context, long term temperature trends should be understood as a portfolio of decadal trends such that no single decadal trend in isolation contains useful information about the long term trend of which it is a part. {the charts for the other calendar months may be found in a related post [LINK] . Therefore, that “despite continuing increases in atmospheric CO2, no significant global warming occurred in the last decade” is not useful information in the context of AGW.

CLAIM #8: The velocity of changes of atmospheric CO2 [dCO2/dt] varies contemporaneously with changes in global temperature. Therefore the integral of dCO2/dt, changes in atmospheric CO2, lag changes in global atmospheric temperature by ~9 months. The very close relationship of dCO2/dt (red) vs global temperature (blue) is clearly apparent. Major volcanoes (some VEI5 and most VEI6 events) disrupt the relationship. Integrating the dCO2/dt data gives changes in CO2, which lag changes in temperature by ~9 months. The 12-month delta in CO2 is used to allow for the “seasonal sawtooth” in the Keeling Curve. Therefore, changes in atmospheric CO2 does not cause warming but rather, warming causes changes in atmospheric CO2. And that proves that AGW is a flawed theory and therefore a falsehood.  RESPONSE: The issue raised here, that changes in atmospheric CO2 are responsive to surface temperature, is an interesting one because higher temperatures increase the equilibrium partial pressure of carbon dioxide in the oceans as well as on wetlands. Therefore the amount of CO2 added to the atmosphere by the carbon cycle from these sources in any year would depend on the temperature of these sources. And in fact, correlation analysis does show that relationship as seen in the two charts below where annual change in atmospheric CO2 for each calendar month is compared with surface temperature using correlation analysis. The first chart uses the HADCRUT4 global surface temperature as suggested by the authors of CLAIM#8. The second chart uses the HADSST3 global sea surface temperature series. The numbers from 1 to 12 along the bottom of each chart identifies the calendar month. The calendar months are analysed separately because their behavior in deltaCO2, temperature, and the relationship between the two vary significantly among the calendar months. Here we see that, as claimed by the authors of CLAIM#8, there is indeed a correlation and the correlations do survive into the detrended series for 5 of 12 calendar months in the case of global surface temperature and for 11 of 12 calendar months for global sea surface temperature. In this case the authors have made an interesting point about the temperature dependence of year to year changes in atmospheric CO2 that has an interpretation in terms of carbon cycle dynamics. However, the further interpretation of this finding in terms of AGW, that it disproves the heat trapping effect of atmospheric CO2 has no basis. That surface temperature changes carbon cycle dynamics is not inconsistent with the GHG effect of CO2. It is also noted that the claim by the authors that there is no GHG effect of CO2 is inconsistent with their earlier claim that the GHG effect of CO2 is governed by a climate sensitivity of ECS=1.

CLAIM#9: Predictions of Imminent Global Cooling, Starting Anytime Soon. Allan MacRae also published on September 1, 2002, based on a conversation with Dr. Tim Patterson, the prediction that global cooling, which happened from ~1940 to 1977, would recommence by 2020-2030: RESPONSE: This claim is part of an obsession with the solar cycle by grand-solar-minimum enthusiasts, armed with the works of Zharkova, that “we are entering a cooling phase” that will prove AGW wrong. Yet, this claim has no support in global mean temperature data as shown in a related post [LINK] although it is true that the works of Zharkova and others do imply a relationship between the solar cycle and surface temperature [LINK] .