In Miami, sea level rise-driven flooding is already a fact of life. Photo credit: Joe Raedle/Getty Images

For years, politically and financially motivated campaigns have wrapped climate science in a cloak of doubt. Scientists, initially caught off guard, eventually responded with a relentless barrage of peer-reviewed papers producing a collection of very specific findings that together have led to irrefutable evidence of the human fingerprints on climate change. In this three-part series, we’ll look at the state of the science linking human-induced climate change to environmental, human and business impacts and whether the science has grown strong enough to be successful evidence in lawsuits holding fossil fuel producers accountable for those impacts.

By Amy Westervelt

Few people are clearer on the scientific evidence for anthropogenic climate change than those who study the warming, rising oceans. And among all of climate change’s impacts, sea level rise is the most obvious to see and quantify.

According to the latest report by the Intergovernmental Panel on Climate Change (IPCC), global sea levels have risen by about  8 inches since 1880, the start of the industrial revolution.  The report shows that rate is increasing, with projections of 2 to 7 more feet of rise this century, the higher number based on a high-emissions scenario in which the Greenland Ice Sheet melts completely by 2100.

A groundbreaking study led by Robert Kopp, associate professor in Rutgers’ Department of Earth and Planetary Sciences,  published last year in Proceedings of the National Academies of Sciences (PNAS) quantified the extent to which human behavior has impacted sea level rise.

Kopp and his colleagues found that without human-caused global warming, global sea level would have risen by less than half the observed 20th century increase and might even have fallen. “The 20th-century rise was extraordinary in the context of the last three millennia – and the rise over the last two decades has been even faster,” Kopp  said when the paper was published.

Ben Strauss, vice president for sea level rise and climate impacts at Climate Central, said research conducted over the past three years has been able to precisely pinpoint the human contribution to sea level rise by stripping  away all other potential drivers, including natural variability, sinking land, non-emissions-related human causes,  and the global cooling of the 19th century. “You need a rigorous analysis to quantify the human contribution to sea level rise, versus just quantifying total global sea rise,” he said.  

Recent research has done just that, and the results are conclusive: humans have caused the seas to rise in addition to the increases that occurred naturally. On average, globally, human causes have increased sea levels between 5 and 6 inches. The potential damage threatens coastal communities and infrastructure throughout the U.S., putting millions of people in harm’s way.

“In the period since 1980, atmospheric CO2 emissions attributable to man—and it doesn’t all stay in the atmosphere, some is deposited in oceans, forests, and so forth—but cumulative emissions from that period, 1980 to now, is equal to or greater than all previous emissions, going back to the pre-industrial age,” said Dan Cayan, a climate and atmospheric science researcher at the Scripps Institute of Oceanography at the University of California at San Diego.

“So in this relatively short period of time, we’ve almost doubled the amount of CO2 in the ecosystem.”

Cayan, who works with the state of California to determine the impacts of sea level rise and plan mitigation strategies, said both global and regional temperatures have responded accordingly. “According to most models, doubling emissions would increase temperatures in California by about 4 degrees Fahrenheit,” he said.

That might not seem like much, but it has cascading and worrisome consequences. “In California, for every degree Fahrenheit of warming, we lose about 20 percent of the spring snowpack,” Cayan said.

California will be hard hit by global climate change, as sea levels rise and coastal flooding increases. Science linking that rise to human-related CO2 emissions is now building the foundation for legal action. Lawsuits filed in July by the counties of San Mateo and Marin and the city of Imperial Beach charge some of the biggest contributors to carbon emissions – 37 fossil fuel companies – with public nuisance and negligence in an attempt to require these companies to absorb some of the costs associated with adapting to sea level rise.

Detailing the Damage

Other coastal cities may soon follow suit, pun intended. New York City has estimated its adaptation costs with respect to sea level rise at about $19.5 billion. Recent studies have attributed about $2 billion of the $12 billion in damage inflicted by superstorm Sandy in New York City alone to human contributions. That estimate was made possible in part by the research led by Kopp.

Strauss and his team have taken that research and run with it, analyzing the frequency of nuisance floods, defined as flooding that closes coastal area roads, overwhelms storm drains, and compromises infrastructure. Strauss calculated  that from 1950 through 2014, 5,809  of the 8,726 nuisance flood days— two-thirds of them— would not have taken place without human-caused global sea level rise. Even using a low estimate, more than 3,500 of the flood days would not have taken place.

“Intuitively, you could say that every coastal flood should be more damaging if it starts at a higher sea level, and most attribution science focuses on the question of whether a damaging event was made more likely by climate change,” Strauss said. “But working with sea level and coastal floods you can sidestep that question entirely. You can basically say we don’t care how or why the storm happened, in fact you can even assume climate change had no role in the strength or length of the storm, and still say it did more damage because it started at a higher sea level.”

Strauss said three out of four coastal floods over the last decade in the U.S. were tipped over the balance by human-caused climate change. “They would not have exceeded the National Weather Service’s definition of a flood if you removed that human-caused sea level rise,” he said.

Strauss and his team are now working to refine work they began in 2014, quantifying the cost of the damage inflicted by human-induced sea-level rise during superstorm Sandy. By focussing on New York City, the team initially attributed about $2 billion of the $12 billion in damages to human-related sea level rise. “That was before the Kopp et al paper came out,” Strauss said. “Now we’re working with real numbers, and we’re expanding to include the tri-state area.”

Those numbers run counter to the arguments used by fossil fuel companies for decades to justify continuing and unlimited fossil fuel burning: that climate change is not driven by human activity, and even if it was, its impacts won’t be significant and won’t be felt until far in the future.

Data and Deception

That campaign to obscure the realities of climate change has come into increasing focus in recent years.

“There is growing awareness and documentation that major fossil fuel companies knew of the impacts of their products back in the 1980s and that they invested millions of dollars and time in order to sow confusion and avoid regulation,” said Peter Frumhoff, director of science and policy at the Union of Concerned Scientists.

Much of that documentation has come to light in the cases brought against ExxonMobil by the attorneys general of New York and Massachusetts. A timeline included in the exhibits filed as part of the California cases reveals the impact of this deception. It shows mounting scientific evidence, and transparency, around the human drivers of climate change in the 1970s and 1980s, building to the summer of 1988 when several bills targeting greenhouse gas emissions were proposed (half by Republicans). The trends shift in the early 1990s, as fossil fuel industry trade groups like the Information Council for the Environment (ICE), formed by the coal industry, and the American Petroleum Institute, begin to fund national climate change denial campaigns. In the intervening years, scientists have worked to compile data that is hard, if not impossible, to politicize or deny.  

In addition to the work Kopp and Strauss have done to pinpoint how humans have impacted sea level rise, Frumhoff and his colleagues have worked to link human-induced climate change to natural disasters and their resulting deaths. Frumhoff also points to the work of Richard Heady, which quantified the contribution of a relatively small group of companies – what Heady calls the “carbon majors” – to climate change. “Heady’s work reveals the remarkable fact that two thirds of industrial emissions are attributable to a small number of companies,” Frumhoff said.

The amount of evidence mixed with the documented deception has many drawing parallels to the  tobacco cases in the 1980s and 1990s.

“One thing I’ve been struck by is that in the early days of cases being brought against tobacco, juries and judges initially ruled for industry,” Frumhoff said. “They focused on smoking as a personal choice, and so forth. Over time that changed and by the 1980s cases were beginning to be adjudicated differently and hold companies liable. But the science didn’t change, it stayed the same. What changed was the evidence – some through legal discovery – that companies were engaging in obfuscation, and it was clear that they knew what they were doing and were deliberate in their behavior.”

Frumhoff sees a similar pattern now, with even more powerful new science strengthening the argument.

“There are changes in climate science that are germane,” he said. “The fact that we have this list of a few companies that are primary contributors to climate change coming out at the same time that we have this evidence of deception from companies on climate science … it would be ironic if it weren’t also catastrophic.”