A Fresh Reading Of Exxon’s Predictions Of Global Warming And Climate Change From 40 Years Ago.

Originally published on Forbes.com on January 17, 2023

Exxon predicted global warming and got this right. They also said climate changes are less predictable, and that is right too, despite criticism that they cast doubt on climate science.

An Exxon study done in 1982 focused on global warming by increasing greenhouse gas (GHG) emissions. Remarkably, thirty-seven years ago Exxon accurately predicted that by 2019, the earth would hit a carbon dioxide concentration of 415 ppm and a temperature increase of almost 1°C (Figure 1).

Under questioning by Rep. Alexandria Ocasio-Cortez (D-NY), former Exxon scientists disclosed this prediction in a Congressional committee hearing in late 2019. In the ultimate irony, the biggest US oil and gas company predicted four decades ago almost the exact global warming situation that we had in 2019 and that we have today.

But Exxon apparently did nothing about it, except to shelve the study. As reported by Inside Climate News, scientist Martin Hoffert described his distress at the company’s newspaper ads in the 1990s contradicting the science on fossil fuel emissions’ link to global warming: “What they did was wrong. They deliberately created doubt when their internal research confirmed how serious a threat it was.”

In 2019 the company was taken to court over this, by the state of Massachusetts. It appears the court is ongoing.

Exxon's prediction
Figure 1. One proprietary model of Exxon from 1982. Exxon predicted (1) GHG concentration on the left, (2) effect this has on temperature on the right. Source: G. Supran et al, Science.

Predictions by Exxon 1982 – 2003.

A new report, just out, shows predictions from Exxon in 1982. They first predicted the concentration of the main GHG, carbon dioxide, CO2, in the atmosphere.

The second prediction by Exxon was for global temperature (Figure 1). A more sophisticated model predicted curve 12 in Figure 2 (the upper dark curve) which was done in 2003.

Figure 2. Modeling by Exxon plus third party sources.  Source: G. Supran et al, Science.
Figure 2. Modeling by Exxon plus third-party sources. Source: G. Supran et al, Science.

In Figure 2, the actual measured temperature is the red line. In the late 1970s until 2003, modeling predictions by Exxon are shown by gray or black lines. Dashed lines are projections that came from third-party sources. Solid lines have grayness increasing by dates when modeling was done — from light gray (1977) to dark gray (2003 – top black curve labeled 12). We can assume the latter is the latest and best prediction by Exxon modelers.

These were serious, sophisticated studies of global warming predictions that Exxon was happy to publish in peer-reviewed journals between 1983 and 1984: Journal of the Atmospheric Sciences and an American Geophysical Union monograph.

The temperature predictions out to 2020 in both models, 1982 and 2003, are very well matched by actual temperature measurements shown by red lines. This is quite remarkable – predictions were made in one case 40 years ago, and in the second case 20 years ago.

Exxon knew the CO2 levels were increasing over time and must have known and presumably modeled, the major contribution to this from the burning of fossil fuels including their own production of oil and gas. Fossil fuels today contribute 73% of all global greenhouse gas (GHG) emissions.

A 2015 report by Inside Climate News found that Exxon scientists predicted overall warming with such low uncertainty that it was clear the burning of fossil fuel was warming the planet.

Exxon climate scientist Dr Martin Hoffert (a consultant) said, “We were excellent scientists,” when during a congressional hearing in 2019 he was shown a graph (Figure 1) that Exxon scientists made in 1982 — which predicted the rate of global warming for the next 40 years with stunning accuracy. 

It is clear that Exxon got it right 20-40 years ago (Figures 1 and 2). But in later years Exxon in public would cast doubt on the science of climate change.

Uncertainties in predicting climate change.

But these predictions were about global warming, not climate change. Prediction of the effects of climate change is another big step and is fraught with uncertainties. Let’s look at these uncertainties.

Most of Exxon’s work in the 1970s and 1980s focused on predicting global warming. But they did acknowledge the potential effects this might have on climate. In 1980, the head of theoretical sciences at Exxon, Roger Cohen, wrote, “There is unanimous agreement in the scientific community that a temperature increase of this magnitude [Figure 1] would bring about significant changes in the earth’s climate, including rainfall distribution and alterations in the biosphere.”

Later, Exxon acknowledged the uncertainties surrounding many aspects of climate science, especially in the area of forecasting the consequences of global warming.

“Let’s agree there’s a lot we really don’t know about how climate will change in the 21st century and beyond,” Exxon’s CEO Lee Raymond said in his speech before the World Petroleum Congress in Beijing in October 1997.

What is the difference between global warming and climate change?

Scientists point to a major drought in the southwest USA over the past 30 years, including the emptying of Colorado basin dams and the wildfires in California. But just in the past few weeks, since Christmas 2022, California has been engulfed by torrential rains and massive flooding.

Some people have blamed both extremes on global warming. Climate scientists say global warming causes more weather extremes, which is a clever way of saying all extremes can be blamed on global warming.

Figure 3. Top trace is for all hurricanes 1980 - 2022. Bottom trace is for major hurricanes. Source: Ryan Maue.
Figure 3. Top trace is for all hurricanes 1980 – 2022. Bottom trace is for major hurricanes. Source: Ryan Maue.

But this is not true. Catastrophes caused by the “killer quad” of droughts, wildfires, super-rainstorms, and hurricanes are regarded as having major effects on human lives, famines, migration, and the stability of governments.

But there is no long-term worsening of these extreme weather events on a worldwide basis (Figure 3). Not more hurricanes now, not more wildfires than 30, 40, or 50 years ago. This is supported by continuous data from the past decades.

The last 40-50 years is a period when global temperature rise has been consistent and very strong, rising 0.8-1.0 degrees C. If the world were sensitive to 0.2C or even 1.0C global warming, it should show up in long-term data trends. But it doesn’t. (see also Ref 1).

But there do exist other worldwide effects associated with global warming. These include Arctic ice melting, glaciers retreating, sea levels rising, coral bleaching, and biodiversity habitats changing. These have been serious, but so far have not induced famines, floods, mass migrations, or government collapse on a worldwide basis. Local effects, yes, but catastrophes, no.

Where does this leave Exxon?

There is a distinction between global warming and climate change. Global warming is proven, and scientists can model it fairly well. And it’s agreed that it has a human cause – largely due to the burning of fossil fuels.

But predicting climate change is a different animal, rife with uncertainties with respect to catastrophes caused by droughts, wildfires, super-rainstorms, and hurricanes.

This may be where Exxon was coming from. Yes, the company was successful in predicting global warming. But that’s not the same thing as predicting climate change.  There is a disconnect between the two.

Until models can explain why there has been no worsening of the “killer quad” extreme weather events over the last 40-50 years, Exxon is safe in saying that climate change, and its effect on humanity, are far too uncertain to be predicted by models. 

As one example of Exxon’s more recent statement of this position, chief executive Rex Tillerson said in 2013, “The facts remain there are uncertainties around the climate… what the principal drivers of climate change are.” 

As an example of the confusion between global warming and climate change, a recent report said the following about Exxon:                 

“New academic research shows that oil giant Exxon’s own climate projections, dating back decades, consistently predicted how burning fossil fuels would cause global warming. The finding lends statistical rigor to the understanding that Exxon executives knew climate change was real, but publicly cast doubt on the science anyway.” 

The first sentence is accurate. The second sentence replaces global warming with climate change, and muddies the water. The second sentence could have been, “Exxon executives knew global warming was real, but publicly cast doubt on predictions of extreme weather events caused by global warming.” 

Recent climate solutions by ExxonMobil.

Despite their statements that uncertainties make it very difficult to predict climate changes, Exxon has set a course to limit their GHG emissions. If emissions from burning their oil and gas by parties who buy their products are included, ExxonMobil’s contribution to global emissions is massive because they are the biggest oil major in the US, and one of the biggest in the world.

ExxonMobil is reducing methane emissions with a goal of net-zero Scope 1 and 2 greenhouse emissions in their Permian Basin unconventional operations by 2030.

ExxonMobil has a dozen or more active Carbon Capture and Storage (CCS) projects, mostly in the US. Based on this experience, they are investing $3 billion in a new carbon company, and have proposed a $100 billion joint enterprise to capture and pump CO2 underground in the Gulf of Mexico.

ExxonMobil seems to be saying, by their actions, that climate changes may become serious, and that they are embarking on these actions to reduce or bury GHG emissions, just in case.  But not serious enough for Exxon to begin to switch from production of oil and gas to production of wind and solar or other renewable energies.


The predictions made 20-40 years ago by Exxon of greenhouse gases and global warming was remarkably accurate. They got this right. And they agreed that it had a human cause – largely due to the burning of fossil fuels.

But predicting climate change is a different animal. Weather extremes such as the “killer quad” of droughts, wildfires, super-rainstorms, and hurricanes can wreak havoc in the form of famines, flooding, migration, and government instability. But these most severe effects of climate change show no worsening over the last 40-50 years, on a global basis.

The global data seem to be saying that these weather extremes are not sensitive to small temperature rises of less than 1 degree C– because they are not sensitive to larger rises of 0.8 – 1.0 degrees C that have taken place over the past 40-50 years.

Until climate change predictions can explain this, Exxon is right in saying that climate change, and its effects on humanity, are too uncertain to be predictable.

The distinction between global warming and climate change may be where Exxon was coming from. This could be important as ExxonMobil face legal actions in several court cases that have been brought against them for suppressing the dangers of global warming.


  1. Gregory Wrightstone, Inconvenient Facts, Silver Crown Productions, 2017.
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