Climate Model Errors = 20 W m-2
CO2 Climate Forcing = 0.2 W m-2
Scott Pruitt, the new head of the U.S. Environmental Protection Agency, has recently been characterized as a climate science “denialist” by world news organizations. A UK Guardian headline, for example, has claimed that “EPA head Scott Pruitt denies that carbon dioxide causes global warming“.
The “denialist” characterization stems from an interview with CNBC’s Joe Kernen in which Pruitt was asked whether he believes that CO2 has been proven to be the climate’s “control knob”. Pruitt replied that “we don’t know that yet” and that “there’s tremendous disagreement about the degree of impact.” But he also said, no, he doesn’t think CO2 is a primary contributor to climate change. Apparently that is all it takes to unleash the climate “denialist” name-calling.
Scott Pruit: “No. I think that measuring with precision human activity on the climate is something very challenging to do, and there’s tremendous disagreement about the degree of impact. So no, I would not agree that it’s a primary contributor to the global warming that we see. But we don’t know that yet. … We need to continue the debate and continue the review and the analysis.”
In a Washington Post analysis of Pruitt’s comments entitled “EPA Chief’s Climate Change Denial Easily Refuted…”, the host’s reply to Pruitt’s last statement about the need to continue debating the degree of human impact was included:
“That’s the whole point of science. You keep asking questions.”
Responding to this rather fundamental point, Washington Post political journalist Philip Bump seemingly agreed with the need to keep questioning and debating the science (since that is indeed the “whole point of science”). But then he immediately contradicted himself.
“Well, sure. But the point of science is also to accept the answers to those questions once determined. And in the scientific community, the answer to the question of the link between greenhouse gases and warming has been determined.”
So apparently because it “has been determined” that CO2 causes warming or cooling when increased or decreased, therefore we should not question the degree to which the climate models accurately record the effect of increasing or decreasing CO2, or how much warming or cooling is caused by CO2 fluctuations relative to other climate-forcing factors.
And why should we refrain from asking questions about the relative influence of CO2 forcing on the climate? Because those questions have not been determined…or answered. Not even close. After all, the uncertainty and error margins associated with modeling the radiative energy changes in the Earth system are 10 to 100 times greater than the entirety of the forcing attributed to CO2 changes.
1. CO2 Radiative Forcing Effect Just 0.2 W m-2 For 2000-2010
As the Intergovernmental Panel on Climate Change (IPCC) has indicated, “global climate is determined by the radiation balance of the planet.” If the balance in the radiative energy budget (incoming vs. outgoing energy) tips positive (as expressed in Watts per square meter, or W m-2), warming occurs. If it dips negative, cooling occurs. The IPCC presumes that positive energy balances have been ongoing for decades, driven almost exclusively by the increase in anthropogenic CO2 emissions.
According to climate models, the total climate forcing effect of the roughly 120 parts per million (ppm) increase in atmospheric CO2 during the ~165 years since 1750 is 1.8 W m-2.
As assessed in a 2015 paper published in the journal Nature, the CO2 concentration increased by 22 ppm during the first 10 years of the 21st century. The radiative forcing (warming) effect of this 22 ppm CO2 increase was modeled to be 0.2 W m-2. So of the 1.8 W m-2 of total radiative forcing since 1750, 0.2 W m-2 was added during the first decade of this century.
2. The Radiative Energy Imbalance For 2000-’10 Was 0.6 W m-2
In a 2012 Nature Geoscience paper entitled “An update on Earth’s energy balance in light of the latest global observations” by Stephens et al. (2012), the radiative energy imbalance for the 2000-2010 decade was determined to be positive, as expected. Interestingly, though, the positive energy balance of 0.6 W m-2 was 3 times larger than the forcing value (0.2 W m-2) attributed to the CO2 increase during the same period.
“The current revised depiction of the global annual mean energy balance for the decade 2000–2010 is provided … For the decade considered [2000-2010], the average imbalance is 0.6 Wm–2 when these TOA fluxes are constrained to the best estimate ocean heat content (OHC) observations since 2005.”
3. 67% (0.4 W m-2) Of The 2000-’10 Energy Increase Not From CO2
If the imbalance in the energy budget was 0.6 W m-2 during 2000-2010, and the modeled CO2 radiative forcing estimate was 0.2 W m-2 during the same period, that means that there was a positive forcing of 0.4 W m-2 that was not due to the increase in CO2 concentration. What this indicates is that the IPCC’s conclusion that all or nearly all of recent global warming is due to the increase in anthropogenic CO2 emissions is not supported by the surface energy imbalance estimates. Two-thirds of climate forcing must be due to some unknown mechanism or mechanisms that the IPCC has somehow failed to identify in etiological analyses. And if only 33% of recent climate forcing is anthropogenic, and 67% cannot be accounted for, where does the certainty that humans are driving climate change come from?
4. Energy Change Uncertainty 10-100 Times Larger Than CO2 Forcing
Speaking of certainty — or, more appropriately, uncertainty — in climate forcing or energy imbalance values, Stephens and colleagues emphasize the requisite uncertainty in the estimates of the energy imbalance for 2000-2010: an enormous ±17 W m-2.
A 17 W m-2 uncertainty range in the energy balance estimate (0.6 W m-2) means that the actual energy balance could be anywhere from -16.4 W m-2 to +17.6 W m-2. This range of uncertainty effectively renders the 0.2 W m-2 CO2 forcing estimate meaningless, as the uncertainty in the volume of energy change during 2000-2010 is 85 times greater than the forcing attributed to CO2 for the same period.
“This small imbalance [0.6 W m-2] is over two orders of magnitude [100 times] smaller than the individual components that define it and smaller than the error of each individual flux.”
“The net energy balance is the sum of individual fluxes. The current uncertainty in this net surface energy balance is large, and amounts to approximately 17 Wm–2. This uncertainty is an order of magnitude [10 times] larger than the changes to the net surface fluxes associated with increasing greenhouse gases in the atmosphere.”
“The quoted value of the sensible heat flux is a combination of the land and ocean sensible heat fluxes with a simple weighting based on land/ocean surface area. The flux value of 24 Wm–2 is also larger than previously assumed and remains highly uncertain, as exemplified by the range of 14–34 Wm–2 that results from different land flux estimates. No definitive measure of the uncertainty of this flux exists and the uncertainty range given merely reflects a judgement on where the value most likely lies.”
Even the IPCC acknowledges that the uncertainty in heat flux estimates reaches up to 20 W m-2, and that this uncertainty dwarfs the less than 2 W m-2 of total radiative forcing attributed to anthropogenic CO2 emissions during the last few centuries.
“Unfortunately, the total surface heat and water fluxes are not well observed. Normally, they are inferred from observations of other fields, such as surface temperature and winds. Consequently, the uncertainty in the observational estimate is large – of the order of tens of watts per square metre [20 W m-2] for the heat flux, even in the zonal mean.”
“The overall uncertainty of the annually averaged global ocean mean for each term is expected to be in the range 10 to 20%. In the case of the latent heat flux term, this corresponds to an uncertainty of up to 20 W m–2. In comparison, changes in global mean values of individual heat flux components expected as a result of anthropogenic climate change since 1900 are at the level of <2 W m–2 (Pierce et al., 2006).”
“It turns out that uncertainties in the energetic responses of Earth climate systems are more than 10 times larger than the entire energetic effect of increased CO2.”
5. IPCC Hides Uncertainty, Errors In Radiative Energy Change
Advocates of the position that CO2 is the climate’s “control knob” would like to divert attention away from the uncertainties and errors in climate modeling, of course. Likewise, the IPCC has notoriously buried data that might cast doubt on the “consensus” position (which states that most climate changes have been driven by anthropogenic CO2 emissions since the mid-20th century).
To find the uncertainty and error ranges in the climate model estimates of radiative forcing, one must deliberately set out to locate the esoteric “Supplemental Material” documents from each report. The IPCC would not dare publish estimates of massive climate modeling errors and uncertainty in locations where they are most likely to be viewed.
“One must go into Chapter 8 and especially Ch 8 Supplementary Material in the recently released IPCC AR4 to find GCM [General Circulation Model] errors graphically displayed in W m-2. Such forthright displays [of error/uncertainty, as shown in the graphs below] do not appear in the SPM [Summary for Policy Makers] or in the Technical Summary; i.e., where public bodies are more likely to see them.“
Supplementary Material from Chapter 8, IPCC AR4
“Figure S8.5 shows that GCM errors in ‘mean shortwave radiation reflected to space’ range across 25 W m-2.”
“The errors in outgoing longwave radiation, Figure S8.7, are similarly large [~20 W m-2]…”
6. ‘From Where Comes The Certainty Of A Large CO2 Impact On Climate?’
So if the models are so hopelessly riddled with errors and uncertainty that an anthropogenic radiative forcing signal cannot be distinguished from noise, or if the total magnitude of the warming attributed to humans is one-tenth to one-hundredth of the error or uncertainty ranges, why are those who dare question the degree to which humans affect the Earth’s climate branded as “deniers” of science?
Exactly what is the truth that climate “deniers” are actually denying?