The inspiration for this post was reading Assessing ExxonMobil’s global warming projections, published just this month in the academic journal Science. Here’s the introductory paragraph:

“For decades, some members of the fossil fuel industry tried to convince the public that a causative link between fossil fuel use and climate warming could not be made because the models used to project warming were too uncertain. Supran et al. show that one of those fossil fuel companies, ExxonMobil, had their own internal models that projected warming trajectories consistent with those forecast by the independent academic and government models. What they understood about climate models thus contradicted what they led the public to believe.” - Assessing ExxonMobil’s global warming projections. Supran, G., S. Rahmstorf, & N. Orestes/Science (2023)*

The authors make their case by contrasting climate models developed by ExxonMobil’s own scientists with the company’s public statements, mostly made by CEOs. Their basic argument is that since ExxonMobil scientists created these model-based climate projections, the scientists must have also believed climate change as modeled was actually happening, and so the company leadership must have known climate change was real, but they lied to the public anyway. More excerpts from the paper:

“In 2000, ExxonMobil Corp CEO Lee Raymond wrote that “[W]e do not now have a sufficient scientific understanding of climate change to make reasonable predictions and/or justify drastic measures...the science of climate change is uncertain….” 

“In 2013, his successor, Rex Tillerson, called climate models “not competent”. In 2015, he stated: “We do not really know what the climate effects of 600 ppm versus 450 ppm will be because the models simply are not that good”. The company’s own modeling contradicts such statements… [such as] Exxon’s 1982 projection…” **

“In 2013, ExxonMobil Corp CEO Rex Tillerson said: “[T]he facts remain there are uncertainties around the climate…what the principal drivers of climate change are… [T]here are other elements of the climate system that may obviate this one single variable [of burning fossil fuels]…And so that’s that uncertainty issue…”

Note that the authors are claiming ExxonMobil has known about climate change for decades, by which I’m assuming they mean at least back to the 1980s. For example, they quote an internal memo from 1988 to “emphasize the uncertainty in scientific conclusions regarding the potential enhanced greenhouse effect”.

One of my first thoughts in reading this paper was why aren’t we hearing from the ExxonMobil scientists themselves? They could shed some light on how they were thinking when they were developing their climate models. For instance, did they consider these models an exploratory exercise based on a range of assumptions and hypotheticals, a serious attempt to predict climate changes in the 21st century, or what? And did they produce other climate charts that were left out of the Supran et al paper, perhaps charts that did not support the authors’ argument?

I also questioned the apparent assumption that a company would only consider what their own scientists said when educating themselves on an issue. What was being said in the world beyond ExxonMobil personnel? In other words, what about some historical context?

Historical Context

I’ll start with a few excerpts from the 1996 report by the Intergovernmental Panel on Climate Change (IPCC):

“The limited available evidence from proxy climate indicators suggests that the 20th century global mean temperature is at least as warm as any other century since at least 1400 A D. “

“Most of these [recent] studies have detected a significant change and show that the observed warming trend is unlikely to be entirely natural in origin.” 

“Our ability to quantify the human influence on global climate is currently limited because the expected signal is still emerging from the noise of natural variability, and because there are uncertainties in key factors. These include the magnitude and patterns of long term natural variability and the time-evolving pattern of forcing by, and response to, changes in concentrations of greenhouse gases and aerosols, and land surface changes. Nevertheless, the balance of evidence suggests that there is a discernible human influence on global climate.”

The 1996 IPCC report was its second on climate change. The first IPCC report came out in 1990. Here’s a 1998 description from JW Anderson of Resources for the Future, an environmental non-profit:

“…in 1990 the first IPCC reports appeared, demonstrating a broad consensus among scientists in the field that the possibility of global warming at least had to be taken seriously. If warming had not yet started, the IPCC said, continuing increases in concentrations of greenhouse gases would certainly lead to it sooner or later... In its general outline and tone, the IPCC report gives great prominence to the uncertainties and gaps in the present scientific understanding of the climate. As it notes, politicians will have to make decisions on climate policy without waiting for conclusive scientific evidence on the key questions.”

As for those politicians, they weren’t doing much in the climate policymaking department. Again from Mr. Anderson:

“Far from talking about increased energy prices, the [Clinton] administration was saying that under its plans they would stay low or perhaps even fall. Lower prices generally mean higher consumption and higher CO 2 emissions. The administration did not deal with this contradiction but merely deferred it, with much else, to the future.”

President Clinton eventually signed the the Kyoto Protocol to the UN Framework Convention on Climate Change, but he never submitted it to the Senate for ratification. That’s because the Senate had already made it crystal clear that the vote would not go well: just two years before the Senate has passed a resolution 95-0 telling Mr. Clinton not to sign any treaty that committed the US to cut emissions without also requiring undeveloped countries to do so.

America’s unions also came out against the Kyoto Protocol. This from the AFL-CIO :

“Numerous economic analyses, including studies conducted by the Clinton Administration, have concluded that unilateral action to reduce greenhouse gas emissions to 1990 levels can have serious adverse economic consequences for workers. The Clinton Administration released a study in July 1997 to the House Commerce Committee that showed stabilization at 1990 levels by 2010, in the absence of any action by developing countries, would cost 900,000 jobs by 2005. Other studies have concluded that such policies could result in the loss of over 1.5 million jobs by 2005… The AFL-CIO Executive Council therefore calls upon the President to refrain from signing the proposed Kyoto Protocol to the U.N. Framework Convention on Climate Change.”

Basically, a sense of certainty and urgency about climate change didn’t become widespread in this country until the 21st century. And as the early IPCC reports show, that includes the scientific community. So I’m going to give ExxonMobil a pass for whatever they said or did about climate change in the 1980s and 1990s. Sure, some climate models from the 80s and 90s were troubling, but models are research tools not forms of evidence. Evidence may eventually validate models, but that takes time.

As for the ExxonMobil statements, yes, the CEOs before 2006 often brought up uncertainties regarding climate change. But for Rex Tillerson, who became CEO in 2006, it wasn’t to justify inaction but to stress the need to proceed with care, mindful of tradeoffs and the possibility of unintended consequences. Tillerson viewed “global warming and climate change as a serious risk” (his words) and actually expressed tentative support for a carbon tax. This from his  2013 interview with Charlie Rose:

Charlie Rose: When you look at gas, a carbon tax, you are in favor?

Rex Tillerson: …my view is, a carbon tax is much more straightforward [than cap and trade]. It's much simpler to administer and it does not leave itself open to as much gaming of the system as a trading platform does.

So, what’s my point here? That the fight against climate change does not justify misrepresenting the historical/scientific record, or quoting perceived adversaries out of context. Enlightenment values trump short-term political gains. The search for truth benefits from a diversity of opinions.

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* The citation provided by Science listed “Supran, G., S. Rahmstorf, et al.” as the authors, even though the “et al” was comprised of just one person (Naomi Orestes). Also, although this excerpt was presented as part of the paper (as the introductory paragraph titled “Insider Knowledge”), it refers to the authors as “they” and is attributed to an “HJS”. No full-name attribution for this paragraph was provided in the online version of the paper. WTF not?!

** Tillerson appears to be using the word “competence” in a technical sense, as a way to evaluate the performance of models. Competence is an engineering and machine learning concept. See, e.g., An Online Competence-Based Concept Drift Detection Algorithm, Lie et al (2016). https://doi.org/10.1007/978-3-319-50127-7_36

References:

Climate Change 1995: The Science of Climate Change. Edited by J.T. Houghton, L.G. Meira Filho, B.A. Callander, N. Harris, A. Kattenberg and K. Maskell  Intergovernmental Panel on Climate Change 1996. https://www.ipcc.ch/site/assets/uploads/2018/02/ipcc_sar_wg_I_full_report.pdf 

R. Tillerson on “Charlie Rose” (7 March 2013). Charlie Rose PBS (2013); https://perma.cc/ERS4-RCEY 

Supran, G., S. Rahmstorf, and N. Orestes. (2023). Assessing ExxonMobil’s global warming projections. Science 379(6628): 8 DOI: 10.1126/science.abk0063 

The Negotiating Record Up to 1996:The Kyoto Protocol on Climate Change by J.W. Anderson/ Resources for the Future January 1998 https://media.rff.org/documents/RFF-RPT-kyotoprot.pdf