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A new study from the Proceedings of the National Academy of Sciences (PNAS) says by 2100 melting ice sheets will create up to 7.5 feet of sea-level rise (SLR), inundating many coastal communities.

The alarming prognosis is being touted by the media as further proof of catastrophic climate change. For example, a story on NBC’s website states, “A provocative new study suggests that as Earth’s climate continues to warm and the planet’s ice sheets continue to melt, seas could inundate coastal cities around the world, submerging vast swaths of land and displacing almost 200 million people by the end of the century.”

Gosh, that really does sound dire! However, a close look at the study shows it’s not based on any science at all, but rather a poll of scientists’ opinion. Yes, it’s an opinion piece, and a collective one, too. It’s not based on scientific data.

In the study, titled “Ice Sheet Contributions to Future Sea-Level Rise from Structured Expert Judgment,” the authors use a process called “structured expert judgement.” “Expert judgment” denotes a wide variety of techniques, ranging from a single undocumented opinion to preference surveys.

In other words, the authors of the study managed to get a bunch of “experts” together, asked them what they thought about sea-level rise in the next 80 years due to ice melt, ranked their opinions, and based on the ranking score, wrote a paper that says “sea level rise is going to be worse than we thought.”

This type of “climate science” has about as much validity as the famous catchphrase “four out of five dentists recommend our brand-new toothpaste!”

The paper itself, perhaps trying to justify its own existence, touts how bad climate models are at predicting future of sea-level rise.

Of course, what they won’t tell you —at least, not in a clear way — is that expert opinions often don’t always pan out. In a publication by J.Scott Armstrong of the University of Pennsylvania, titled “The Seer-Sucker Theory: The Value of Experts in Forecasting,” Armstrong suggests a collection of experts forming opinions (who often co-author papers together) leads to a confirmation bias, when evidence contrary to the expert opinion is often ignored.

According to Armstrong, “The advice to seek disconfirming evidence is not new — it is the principle behind ‘objective’ scientific experiments. Unfortunately, it is not often used even by scientists, and training does not seem to help. In a study using Wason’s 2-4-6 problem, Mahoney and DeMonbreun found that the aversion to disconfirming evidence is just as prevalent among physical scientists as it is among psychologists.”

For those who prefer hard data over “expert opinion,” a Heartland Institute Policy Study by geophysicist Dennis E. Hedke titled “Data versus Hype: How Ten Cities Show Sea-level Rise Is a False Crisis” examines the actual sea-level data from 10 coastal cities around the world and concludes “sea-level rise is a false crisis.”

Unfortunately, “sea-level rise is a false crisis” is not as likely to drive traffic to left-leaning websites with headlines such as “Rising sea levels could swamp major cities and displace almost 200 million people, scientists say.”

Anthony Watts is a 40-year veteran on on-air radio and television meteorology, and operates the most-viewed website on climate in the world, wattsupwiththat.com. He is a senior fellow of the Heartland Institute for environment and climate.

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