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How Scientists Got Climate Change So Wrong

How Scientists Got Climate Change So Wrong

Few thought it would arrive so quickly. Now we’re facing consequences once viewed as fringe scenarios.

Transit workers pumped water out of the South Ferry subway station in Lower Manhattan after Hurricane Sandy in 2012.
Credit…Hiroko Masuike/The New York Times

For decades, most scientists saw climate change as a distant prospect. We now know that thinking was wrong. This summer, for instance, a heat wave in Europe penetrated the Arctic, pushing temperatures into the 80s across much of the Far North and, according to the Belgian climate scientist Xavier Fettweis, melting some 40 billion tons of Greenland’s ice sheet.

Had a scientist in the early 1990s suggested that within 25 years a single heat wave would measurably raise sea levels, at an estimated two one-hundredths of an inch, bake the Arctic and produce Sahara-like temperatures in Paris and Berlin, the prediction would have been dismissed as alarmist. But many worst-case scenarios from that time are now realities.

Science is a process of discovery. It can move slowly as the pieces of a puzzle fall together and scientists refine their investigative tools. But in the case of climate, this deliberation has been accompanied by inertia born of bureaucratic caution and politics. A recent essay in Scientific American argued that scientists “tend to underestimate the severity of threats and the rapidity with which they might unfold” and said one of the reasons was “the perceived need for consensus.” This has had severe consequences, diluting what should have been a sense of urgency and vastly understating the looming costs of adaptation and dislocation as the planet continues to warm.

In 1990, the Intergovernmental Panel on Climate Change, the United Nations group of thousands of scientists representing 195 countries, said in its first report that climate change would arrive at a stately pace, that the methane-laden Arctic permafrost was not in danger of thawing, and that the Antarctic ice sheets were stable.

Illustration: Changing Estimates of Sea Level Rise by 2100

Relying on the climate change panel’s assessment, economists estimated that the economic hit would be small, providing further ammunition against an aggressive approach to reducing emissions and to building resilience to climate change.

As we now know, all of those predictions turned out to be completely wrong. Which makes you wonder whether the projected risks of further warming, dire as they are, might still be understated. How bad will things get?

So far, the costs of underestimation have been enormous. New York City’s subway system did not flood in its first 108 years, but Hurricane Sandy’s 2012 storm surge caused nearly $5 billion in water damage, much of which is still not repaired. In 2017, Hurricane Harvey gave Houston and the surrounding region a $125 billion lesson about the costs of misjudging the potential for floods.

The climate change panel seems finally to have caught up with the gravity of the climate crisis. Last year, the organization detailed the extraordinary difficulty of limiting warming to 2.7 degrees Fahrenheit (1.5 degrees Celsius), over the next 80 years, and the grim consequences that will result even if that goal is met.

More likely, a separate United Nations report concluded, we are headed for warming of at least 5.4 degrees Fahrenheit. That will come with almost unimaginable damage to economies and ecosystems. Unfortunately, this dose of reality arrives more than 30 years after human-caused climate change became a mainstream issue.


The word “upended” does not do justice to the revolution in climate science wrought by the discovery of sudden climate change. The realization that the global climate can swing between warm and cold periods in a matter of decades or even less came as a profound shock to scientists who thought those shifts took hundreds if not thousands of years.

Scientists knew major volcanic eruptions or asteroid strikes could affect climate rapidly, but such occurrences were uncommon and unpredictable. Absent such rare events, changes in climate looked steady and smooth, a consequence of slow-moving geophysical factors like the earth’s orbital cycle in combination with the tilt of the planet’s axis, or shifts in the continental plates.

Then, in the 1960s, a few scientists began to focus on an unusual event that took place after the last ice age. Scattered evidence suggested that the post-ice age warming was interrupted by a sudden cooling that began around 12,000 years ago and ended abruptly 1,300 years later. The era was named the Younger Dryas for a plant that proliferated during that cold period.

At first, some scientists questioned the rapidity and global reach of the cooling. A report from the National Academies of Science in 1975 acknowledged the Younger Dryas but concluded that it would take centuries for the climate to change in a meaningful way. But not everyone agreed. The climate scientist Wallace Broecker at Columbia had offered a theory that changes in ocean circulation could bring about sudden climate shifts like the Younger Dryas.

Then, in the early 1990s, scientists completed more precise studies of ice cores extracted from the Greenland ice sheet. Dust and oxygen isotopes encased in the cores provided a detailed climate record going back eons. It revealed that there had been 25 rapid climate change events like the Younger Dryas in the last glacial period.

The evidence in those ice cores would prove pivotal in turning the conventional wisdom. As the science historian Spencer Weart put it: “How abrupt was the discovery of abrupt climate change? Many climate experts would put their finger on one moment: the day they read the 1993 report of the analysis of Greenland ice cores. Before that, almost nobody confidently believed that the climate could change massively within a decade or two; after the report, almost nobody felt sure that it could not.”

In 2002, the National Academies acknowledged the reality of rapid climate change in a report, “Abrupt Climate Change: Inevitable Surprises,” which described the new consensus as a “paradigm shift.” This was a reversal of its 1975 report.

“Large, abrupt climate changes have affected hemispheric to global regions repeatedly, as shown by numerous paleoclimate records,” the report said, and added that “changes of up to 16 degrees Celsius and a factor of 2 in precipitation have occurred in some places in periods as short as decades to years.”

The National Academies report added that the implications of such potential rapid changes had not yet been considered by policymakers and economists. And even today, 17 years later, a substantial portion of the American public remains unaware or unconvinced it is happening.

Photo: Melt water poured into a fjord in western Greenland this summer when a heat wave that smashed records in Europe moved over the island.
Credit…
Caspar Haarl’v/Associated Press

Were the ice sheets of Greenland and Antarctica to melt, sea levels would rise by an estimated 225 feet worldwide. Few expect that to happen anytime soon. But those ice sheets now look a lot more fragile than they did to the climate change panel in 1995, when it said that little change was expected over the next hundred years.

In the years since, data has shown that both Greenland and Antarctica have been shedding ice far more rapidly than anticipated. Ice shelves, which are floating extensions of land ice, hold back glaciers from sliding into the sea and eventually melting. In the early 2000s, ice shelves began disintegrating in several parts of Antarctica, and scientists realized that process could greatly accelerate the demise of the vastly larger ice sheets themselves. And some major glaciers are dumping ice directly into the ocean.

By 2014, a number of scientists had concluded that an irreversible collapse of the West Antarctic ice sheet had already begun, and computer modeling in 2016 indicated that its disintegration in concert with other melting could raise sea levels up to six feet by 2100, about twice the increase described as a possible worst-case scenario just three years earlier. At that pace, some of the world’s great coastal cities, including New York, London and Hong Kong, would become inundated.

Then this year, a review of 40 years of satellite images suggested that the East Antarctic ice sheet, which was thought to be relatively stable, may also be shedding vast amounts of ice.

Illustration: Changing Estimates of Sea Level Rise by 2100

Photo: Credit…Richard Coleman/Agence France-Presse — Getty Images

As the seas rise, they are also warming at a pace unanticipated as recently as five years ago. This is very bad news. For one thing, a warmer ocean means more powerful storms, and die-offs of marine life, but it also suggests that the planet is more sensitive to increased carbon dioxide emissions than previously thought.

The melting of permafrost has also defied expectations. This is ground that has remained frozen for at least two consecutive years and covers around a quarter of the exposed land mass of the Northern Hemisphere. As recently as 1995, it was thought to be stable. But by 2005, the National Center for Atmospheric Research estimated that up to 90 percent of the Northern Hemisphere’s topmost layer of permafrost could thaw by 2100, releasing vast amounts of carbon dioxide and methane into the atmosphere.

For all of the missed predictions, changes in the weather are confirming earlier expectations that a warming globe would be accompanied by an increase in the frequency and severity of extreme weather. And there are new findings unforeseen by early studies, such as the extremely rapid intensification of storms, as on Sept. 1, when Hurricane Dorian’s sustained winds intensified from 150 to 185 miles per hour in just nine hours, and last year when Hurricane Michael grew from tropical depression to major hurricane in just two days.

If the Trump administration has its way, even the revised worst-case scenarios may turn out to be too rosy. In late August, the administration announced a plan to roll back regulations intended to limit methane emissions resulting from oil and gas exploration, despite opposition from some of the largest companies subject to those regulations. More recently, its actions approached the surreal as the Justice Department opened an antitrust investigation into those auto companies that have agreed in principle to abide by higher gas mileage standards required by California. The administration also formally revoked a waiver allowing California to set stricter limits on tailpipe emissions than the federal government.

Even if scientists end up having lowballed their latest assessments of the consequences of the greenhouse gases we continue to emit into the atmosphere, their predictions are dire enough. But the Trump administration has made its posture toward climate change abundantly clear: Bring it on!

It’s already here. And it is going to get worse. A lot worse.

The flooded roadway into the Brooklyn Battery Tunnel in Manhattan after Hurricane Sandy.

Credit…Andrew Burton/Getty Images

Eugene Linden, who writes about the human relationship with the natural world, is the author of, most recently, “Deep Past,” a novel.

The Times is committed to publishing a diversity of letters to the editor. We’d like to hear what you think about this or any of our articles. Here are some tips. And here’s our email: letters@nytimes.com.

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Source: New York Times

By:  Eugene Linden
Mr. Linden has written widely about climate change.
Nov. 8, 2019

LINK: https://www.nytimes.com/2019/11/08/opinion/sunday/science-climate-change.html?auth=login-email&fbclid=IwAR12CQLLF8964V10317laAcqPHHMcFtvmepXHpWgFA8cbyQgVZSekxp5IIY&login=email&smid=nytcore-ios-shar

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Science Isn’t Always Perfect—But We Should Still Trust It

Science montage.

Science montage.
Ian Murray—Getty Images/Ikon Images
IDEAS
Oreskes is the author of Why Trust Science? She is a Professor in the History of Science at Harvard University and also the co-author of Discerning Experts: The Practices of Scientific Assessment for Environmental Policy

From vaccinations to climate change, we make decisions every day that implicate us in scientific claims. Are genetically modified crops safe to eat? Do childhood vaccinations cause autism? Is climate change an emergency? In recent years, many of these issues have become politically polarized, with people rejecting scientific evidence that misaligns with their political preferences. When Greta Thunberg, the youthful climate activist, testified in Congress last month, submitting as her testimony the IPCC 1.5° report, she was asked by one member why should we trust the science. She replied, incredulously, “because it’s science!”

For several decades, there has been an extensive and organized campaign intended to generate distrust in science, funded by regulated industries and libertarian think-tanks whose interests and ideologies are threatened by the findings of modern science. In response, scientists have tended to stress the success of science. After all, scientists have been right about most things, from the structure of the universe (the Earth does revolve around the sun, rather than the other way around) to the relativity of time and space (relativistic corrections are needed to make global positioning systems work).

That answer isn’t wrong, but for many people it’s not persuasive. After all, just because scientists more than 400 years ago were right about the structure of the solar system doesn’t prove that a different group of scientists are right about a different issue today.

An alternative answer to the question—Why trust science?—is that scientists use “the scientific method.” If you’ve got a high school science textbook lying around the house, you’ll probably find that answer in it. But this answer is wrong. But what is typically asserted to be the scientific method—develop a hypothesis, then design an experiment to test it—isn’t what scientists actually do. Historians of science have shown that scientists use many different methods, and these methods have change with time. Science is dynamic: new methods get invented, old ones get abandoned, and any particular juncture scientists can be found doing many different things. And that’s a good thing, because the so-called scientific method doesn’t work. False theories can yield true results, so even if an experiment works, it doesn’t prove that the theory it was designed to test it is true. There also might be many different theories that could yield that same experimental result. Conversely, if the experiment fails, it doesn’t prove the theory is wrong; it could be that the experiment was badly designed or there was a fault in one of the instruments.

If there is no identifiable scientific method, then what is the warrant for trust in science? How can we justify using scientific knowledge—as Greta Thunberg and many others insist that we must—in making difficult personal and public decisions?

The answer is not the methods by which scientists generate claims, but the methods by which those claims are evaluated. The common element in modern science, regardless of the specific field or the particular methods being used, is the critical scrutiny of claims. It’s this process—of tough, sustained scrutiny—that works to ensure that faulty claims are rejected and that accepted claims are likely to be right.

A scientific claim is never accepted as true until it has gone through a lengthy process of examination by fellow scientists. This process begins informally, as scientists discuss their data and preliminary conclusions with their colleagues, their post-docs and their graduate students. Then the claim is shopped around at specialist conferences and workshops. This may result in the scientist collecting additional data or revising the preliminary interpretation; sometimes it leads to more radical revision, like redesigning the data collection program or scrapping the study altogether if it begins to look like a lost cause. If things are looking solid, then the scientist writes up the results. At this stage, there’s often another round of feedback, as the preliminary write-up is sent to colleagues for comment.

Until this point, scientific feedback is typically fairly friendly. But the next step is different: once the paper seems ready, it is submitted to a scientific journal, where things get a whole lot tougher. Editors deliberately send scientific papers to people who are not friends or colleagues of the authors, and the job of the reviewer is to find errors or other inadequacies in the paper. We call this process “peer-review” because the reviewers are scientific peers—experts in the same field—but they act in the role of a superior who has both the right and the obligation to find fault. Reviewers can be pretty harsh, so scientists need to be thick-skinned and accept criticism without taking it personally. (Editors sometimes weigh in too, and often their contributions are not all that nice, either.) It is only after the reviewers and the editor are satisfied that recognizable errors and inadequacies have been fixed that the paper is accepted for publication and enters into the body of “science.” Even then, the story is not over, because if serious errors are detected after publication, journals may issue errata or even retractions.

Why do scientists put up with this difficult and sometimes nasty process? Many don’t; a lot of people drop out along the way and move into other professions. But those who persist can see how it improves the quality of their work. The philosopher Helen Longino has called this process of critical scrutiny transformative interrogation: interrogation, because it’s tough, and transformative because over time our understanding of the natural world is transformed.

A key aspect of scientific judgment is that it is not done individually; it is done collectively. It’s a cliché that two heads are better than one: in modern science, no claim gets accepted until it has been vetted by dozens, if not hundreds of heads. In areas that have been contested, like climate science and vaccine safety, it’s thousands. This is why we are generally justified in not worrying too much if a single individual scientist, even a very famous one, dissents from the consensus. There are many reasons why an individual might dissent: he might be disappointed that his own theory didn’t work out, bear a personal grudge, or have an ideological ax to grind. She might be stuck on a detail that just doesn’t change the big picture, or enjoy the attention she gets for promoting a contrarian view. Or he might be an industry shill. The odds that the lone dissenter is right, and everyone else is wrong, are not zero, but so long as there has been adequate opportunity for the full vetting of his and everyone else’s claims they are probably in most cases close to zero. This is why diversity in science is important: the more people looking at a claim from different angles, the more likely they are to identify errors and blind-spots. It’s also why we should have a healthy skepticism towards brand-new claims: it takes years or sometimes decades for this process to unfold.

In a way science is like a trial, in which both sides get to ask tough questions in hope that the truth becomes clear, and it is the jury that makes that call. But there are several differences between science and the law. One is that the jury are not common citizens, but experts who have the specialized training required to evaluate technical claims. Technical expertise is highly specific, which is why geologists are not called on to judge vaccine safety. (Indeed, it should be a red flag when we see scientists pontificating on subjects outside their expertise.) This highlights a second difference: in science, there is no presiding judge. The judges are all the other members of the expert community; we accept something as true when the expert community comes to a consensus that it is true. A third difference is that in science there is double jeopardy (or even triple or quadruple…); there is always the possibility of re-opening the case on the basis of new evidence.

Does this process ever go wrong? Of course. Scientists are human. But if we look carefully at historical cases where science went awry, typically there was no consensus. Eugenics is a case in point. The novelist Michael Crichton argued because the scientific consensus on eugenics turned out to be mistaken, we should not trust the consensus on climate change. But his premise was faulty (as well as his logic): there wasn’t a consensus on eugenics. Many scientists objected, in particular socialist geneticists who flagged the obvious class bias in eugenic theory and practice.

Some people argue that we should not trust science, because scientists are “always changing their minds.” While examples of truly settled science being overturned are actually rather rare—far fewer than is sometimes claimed—they do exist. But the beauty of this scientific process is that it explains what might otherwise appear paradoxical: that science produces both novelty and stability. New observations, ideas, interpretations, and attempts to reconcile competing claims introduce novelty; transformative interrogation leads to collective decisions and the stability of a good deal of scientific knowledge. Scientists do sometimes change their minds in the face of new evidence, but this is to their credit: it is a strength of science, not a weakness, that scientists continue to learn and to be open to new ways of thinking about old problems. The fact that we may learn new things in the future does not mean that we should throw away what hard-earned knowledge we have now.

Modern society relies on trust in experts, be they dentists, plumbers, car mechanics, or professors. If trust were to come to a halt, society would come to a halt, too. Like all people, scientists make mistakes, but they have knowledge and skills that make them useful to the rest of us. They can do things that we can’t. And just as we wouldn’t go to a plumber to fix our teeth or a dentist to fix our car, we shouldn’t go to actresses or politicians, much less industries with a vested interest or ideologically-driven think-tanks, for answers to scientific questions. If we need scientific information, we should go to the scientists who have dedicated their lives to learning about the matters at stake. On scientific matters, we should trust science.

Contact us at editors@time.com.

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