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Internal company documents uncovered by a Dutch news organization show that the oil giant Shell had a deep understanding, dating at least to the 1980s, of the science and risks of global warming caused by fossil fuel emissions.

They show that as the company pondered its responsibility to act, Shell's scientists urged it to heed the early warnings, even if, as they said, it might take until the 2000s for the mounting evidence to prove greenhouse gases in the atmosphere were causing unnatural climate change.

"With the very long time scales involved, it would be tempting for society to wait until then before doing anything," company researchers wrote in a 1988 report based on studies completed in 1986. "The potential implications for the world are, however, so large that policy options need to be considered much earlier. And the energy industry needs to consider how it should play its part."

Otherwise, a team of Shell experts said, "it could be too late to take effective countermeasures to reduce the effects or even to stabilize the situation."

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For the next decade—as the emerging science was becoming increasingly robust, and as international efforts to curb heat-trapping emissions gained steam and calls for action grew more urgent—the company persisted in emphasizing the lingering uncertainties of climate science and the costs of ambitious policies, the documents show.

Shell's own "review of the scientific uncertainty and the evolution of energy systems indicates that policies to curb greenhouse gases beyond 'no regrets' measures could be premature, divert economic resources from more pressing needs and further distort markets," a February 1995 management brief advised.

The documents were unearthed by the journalist Jelmer Mommers of De Correspondent, whose investigative article was published on Thursday in Dutch. Many of the documents, along with explanatory notes, were released on the Climate Files website, where researcher and climate advocate Kert Davies maintains extensive archives. To get their work before a broader audience, they shared embargoed copies of the documents.

What Shell Knew & What It Means for Lawsuits

Just like researchers at other oil and gas companies, notably Exxon, Shell's scientists and managers understood, before the general public, that uncontrolled greenhouse gas emissions could eventually put its core businesses at risk—and alter ecosystems and put much of the world's population in peril.

The accretion of evidence complicates the industry's position as Big Oil defends itself in a broadening array of climate-related litigation.

On Wednesday, Dutch environmentalists said they plan to sue Royal Dutch Shell to force it to cut its oil and gas investments and production. Donald Pols, director of Friends of the Earth Netherlands/Milieudefensie, said the company "should take its responsibility to stop wrecking the climate."

Responding to the litigation, Shell said that it has long embraced climate change science and strongly supports the Paris climate agreement aimed at limiting global warming to 2 degrees Celsius or less. But it said that meeting that target is a complex social challenge, that energy is important to the global quality of life, and that the issues should not be tackled in court. Rather, it called for sound government policy and a cultural shift toward green energy.

Shell is already a defendant in other court cases.

The key legal question in much of the litigation is whether the companies understood risks of global warming well enough, and early enough, to be held accountable for damages that are already occurring and are likely to grow.

'Major Social, Economic, Political Consequences'

The Shell documents released so far don't address in significant detail questions of liability or whether Shell was properly disclosing risks to shareholders.

Litigators are sure to note a brief, but telling, remark in the 1988 document: The fossil fuels Shell consumed and sold at the time "account for the production of 4 percent of the CO2 emitted worldwide from combustion." Two tables broke the data down.

"In the light of the possible effects of an increase in greenhouse gases, it is important to examine the likely political responses to expressions of environmental concern," Shell's report said.

The emerging problem "could have major social, economic and political consequences," it said—a powerful enough upheaval to be "the greatest in human history."

By then, Shell had to be acutely aware of the growing political repercussions of its contribution to the climate problem. After all, the 1988 document was circulated just as NASA scientist James Hansen testified in Congress that global warming had already arrived and had to be dealt with urgently.

Shell's What-If Scenario: East Coast Hurricanes

Over the decades, Shell spent considerable effort generating what-if scenarios to help it grope its way forward.

In one, a 1998 planning document carrying the acronym TINA (for "there is no alternative"), the company even imagined events in the year 2010 after violent and damaging storms wreaked havoc on the East Coast of the U.S.

"Although it is not clear whether the storms are caused by climate change, people are not willing to take further chances," the document speculates. "After all, two successive IPCC reports since 1995 have reinforced the human connection to climate change."

"Following the storms, a coalition of environmental NGO's brings a class-action sit against the U.S. government and fossil-fuel companies on the grounds of neglecting what scientists (including their own) have been saying for years: that something must be done," the scenario states.

How Shell's Thinking on Climate Changed

Shell's documents of the era, like papers from Exxon at the time that were published in 2015 by InsideClimate News, are full of passages about the uncertainties that surrounded the emerging science. A nuanced reading suggests that Shell, then as now, gave more attention to the need for global action on climate, and did so earlier, than Exxon.

To this day, the company opens the door a bit wider to a more responsive approach to the climate crisis. But its current thinking continues to generate debate over whether its vision is ambitious enough.

The Dutch archives trace the evolution of the company's thinking over years of considerable climate policy turmoil.

For example, Shell participated in the work of the Global Climate Coalition, founded in 1989 to fight the Kyoto Protocol, only to leave it 10 years later over irreconcilable differences over the protocol's emissions targets, which Shell embraced.

All the while, concentrations of carbon dioxide moved inexorably upward. Children born since that time have never lived through a year in which the world's climate was cooler than the previous average.

One passage from 1988, even though written in a dry corporate style, reads now like an evocation of this perspective across the generations.

"The changes in climate, being considered here, are at an unaccustomed distance in time for future planning, even beyond the lifetime of most of the present decision makers but not beyond intimate (family) association," it said.

In other words, it said you might not see the results of your decisions, but your children and grandchildren might.

In the Mid-1990s, Straddling the Line

In a 1995 "management brief" on climate change that stressed its "major business implications for the fossil fuel industry," Shell conceded the "general consensus" of its human causes while making a nod to what it called "well-grounded scepticism." It said "a definitive, unequivocal position on the science of global warming ... quite simply is beyond current capabilities."

Still, it suggested that "over the next decades, renewable forms of energy can gradually become competitive," and it projected that "CO2 emissions could peak at about 10 gigatonnes of carbon (GtC) a year before the middle of the next century and decline." (The figure Shell predicted for the eventual emissions peak is equivalent to 36.4 gigatonnes of carbon dioxide equivalent (GtCO2e). Global emissions from energy and cement reached 32.5 GtCO2 last year.)

The next year, as the Intergovernmental Panel on Climate Change was publishing its second major assessment of climate science, Shell found itself in a delicate balancing act between accepting the scientific consensus and arguing that there was still too much uncertainty to dictate aggressive action.

"Although climate change is a long term issue, today's responses do not have to be long term," Shell argued. "'Irreversible' actions need to be avoided."

'An Evolutionary, Not a Revolutionary Process'

In hindsight, it's possible to say that this ambivalence would prove costly.

And the litigation over who should pay these costs will hinge on how jurists today read this kind of document from the past—along with any more evidence yet to emerge from these lawsuits.

It's not so much that any one document contains a smoking gun. It's rather that the steady accumulation of documents, which is bound to continue, will build up the weight of the evidence.

In that way, the legal question resembles the scientific question Shell addressed in a 1995 document called "Is Climate Change Occurring Already?"

"Detection of a human induced change in the earth's climate will be an evolutionary and not a revolutionary process," it said. "It is likely that a slow accumulation of evidence, rather than a 'smoking gun,' will indicate man-made emissions as the cause of some part of the observed climate change."

Editor's note: This story has been changed to convert Shell's 1995 forecast of eventual peak greenhouse gas emissions from gigatonnes of carbon (GtC) to gigatonnes of carbon dioxide equivalent (GtCO2e), a standard conversion, for purposes of comparison to the International Energy Agency's current data.