NEW: In @ScienceMagazine today, our latest peer-reviewed research shows Exxon scientists predicted global warming with shocking skill & accuracy between 1977 & 2003, contradicting the company's decades of climate denial. THREAD.
📰No pay wall for 2 weeks: bit.ly/ExxonKnew2poin…
2/n: This is the first ever systematic assessment of an oil and gas company's climate projections. It's published by me, climate scientist @rahmstorf (@PIK_Climate), and historian of science @NaomiOreskes.
3/n: We began by collecting every available global warming prediction reported by Exxon scientists in internal memos & peer-reviewed papers. This yielded 16 temperature projections from 1977-2003 in 12 graphs, shown here with subsequent *observed* temp changes overlaid in red.
4/n: For example, this is a graph from a "proprietary" 1982 Exxon memo showing “an estimate of the average global temp increase” from 1960-2080 due to future fossil fuel burning. Overlaid are:
Blue = Observed CO2
Red = Observed temp change
Immediately, the overlap is striking.
5/n: Next, we digitized all 16 global warming projections reported by Exxon scientists, and plotted them on one graph:
Gray = Exxon's predictions
Red = Observed temperature change
This, in a single image, is what #ExxonKnew.
6/n: Our analysis also allows us, for the first time, to put a number on what #ExxonKnew: that burning coal, oil, and gas was going to heat the planet by 0.20° ± 0.04°C every decade.
And they were right on the money...
7/n: Using established IPCC statistical techniques to test the performance of Exxon’s temperature predictions in comparison to historical observations, we find that most of Exxon’s global warming forecasts were accurate (63-83%, depending on the metric used).
8/n: Exxon's global warming projections were also CONSISTENT with, and AT LEAST AS SKILLFUL as, those of independent academic and government models. Here are the stats...
9/n: CONSISTENT:
Exxon’s average projected warming (0.20° ± 0.04°C per decade) was, within uncertainty, the SAME as that of independent models (0.19° ± 0.03°C per decade).
10/n: SKILLFUL:
Global warming projections modeled by Exxon scientists had an average ‘skill score’ of 72 ± 6%, with the highest scoring 99%.
For comparison, NASA scientist Dr. James Hansen’s predictions presented to US Congress in 1988 had skill scores of 38 to 66%.
11/n: (⬆️ When we account for differences between forecast and observed atmospheric CO2 levels, the ‘skill score’ of projections modeled by Exxon scientists was 75 ± 5%, with seven projections scoring 85%+. Hansen’s 1988 projections had corresponding skill scores of 28 to 81%.)
12/n: We also show that Exxon scientists:
1⃣ Correctly rejected the prospect of a coming ice age.
2⃣ Accurately predicted when human-caused global warming would first be detectable.
3⃣ Reasonably estimated the ‘carbon budget’ for holding warming below 2°C.
13/n: In public, however, ExxonMobil contradicted each of these conclusions.
Here's ExxonMobil repeatedly exaggerating the uncertainties of climate science and modelling.
14/n: ExxonMobil has also often denigrated climate models.
In 1999, CEO Lee Raymond said future climate “projections are based on completely unproven climate models, or, more often, sheer speculation.”
In 2013, CEO Rex Tillerson called climate models "not competent."
15/n: And here's Mobil and ExxonMobil cultivating the myth that in the 1970s, there was a scientific consensus that the planet was going to cool down rather than heat up.
16/n: In sum, our study is #ExxonKnew2point0. It puts a number on, and paints a picture of, what #ExxonKnew, which is that burning fossil fuels would heat the planet by 0.20° ± 0.04°C per decade.
A picture tells a thousand words, and this one sums up how Exxon knew and misled.
17/n: We now have airtight, statistically rigorous evidence that Exxon accurately predicted global warming years before it turned around and publicly attacked climate science and scientists.
In that sense, this graph doesn't just communicate a crisis, it confirms complicity.
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