May 16, 2017 | David F. Coppedge

Doubts About Climate Consensus

Several papers make it hard to believe that humans are to blame for climate change, or that scientists even know what is going on.

The political hot potato of climate change—held to dogmatically by Big Science but questioned by others—only relates to creation and evolution in terms of the politics of consensus in science. Insights into the thinking of scientists on one can illuminate thinking on the other, because both incur charges of “Denier!” to those who dare to question the consensus. Yet how solid is the consensus on human-caused climate change? Consider some recent news:

Angkor Wat’s Collapse From Climate Change Has Lessons for Today (National Geographic). “The powerful civilization was hammered into oblivion by drought and floods, underscoring the connections between climate and people,” this article says. Yet the extensive civilization at Angkor Wat, Cambodia, collapsed long before humans were pumping carbon dioxide into the air, implying that the “connection” is one-way: climate causes people to move. Similar climate collapses are believed to explain the abandonment of many Indian dwellings in the southwestern United States. So how can National Geographic say that today’s civilizations are at fault?

“The medieval Khmer were confronted with a period of climatic instability that they had no experience of, and which fully changed the rules of the game that they had been playing for hundreds of years,” said Penny.

“A similar scale of challenge is now confronting contemporary communities, as the climate begins to change.”

This has led to large uncertainties in modelled estimates of terrestrial carbon storage and carbon cycle–climate feedbacks.

Biogeochemistry: Large rise in carbon uptake by land plants (Nature). A team came up with a new proxy for estimating global production of plant life due to warming, an important measure because it involves a feedback loop. Author Dan Yakir is glad, because such measurements can only be taken indirectly. “The potential growth in terrestrial gross primary production (GPP) as a result of increasing atmospheric carbon dioxide concentrations remains poorly understood,” the Editors say. “This has led to large uncertainties in modelled estimates of terrestrial carbon storage and carbon cycle–climate feedbacks.” How, then, can important measures with such large uncertainties provide any confidence about temperature predictions for the future? And what does this new method imply about the accuracy of previous measures? Those formed the basis for international treaties, like the Paris Climate Accords.

Tectonic controls on the long-term carbon isotope mass balance (PNAS). A statement on the Significance of this paper should give one pause. How confident are climate scientists about their numbers?

The carbon isotope record has played a major role in reconstructing the oxygen and carbon dioxide content of the ancient atmosphere. However, known oxygenation events are not always reflected in the isotopic record of marine carbonate rocks, while conventional interpretations imply that less organic matter is buried when erosion rates are high, which is hard to explain. Here we show that both issues can be resolved if limestone weathering makes up a proportionately greater fraction of the global carbon cycle at high erosion rates. We argue that the link between carbon isotopes and oxygenation is more tenuous than commonly assumed, and propose a case-by-case reexamination of earth’s oxygenation history.

Increased scrutiny of climate-change models should be welcomed (Nature). The Editors of Nature are not waffling on climate change, but they agree that members of the consensus should welcome criticism. A case in point is the so-called climate ‘hiatus’ that caused a bit of “hysteria” when it was announced (see another Nature paper about how a team found a way to ‘reconcile’ the conflicting data within the consensus). The Editors offer this advice from that episode:

In the end, the hiatus controversy led to reinvigorated explorations of many mossy crevasses of climate science. This is not a bad thing, and might not have happened without the public (and political) firestorm. The next time something looks odd in climate science — as it surely will — researchers should once again denounce the inevitable and risible attacks for what they are, while welcoming the opportunity to question their own assumptions, sharpen data sets and revisit collective understanding of the underlying processes.

Climate skeptics will undoubtedly claim that Nature‘s pompous suggestions here have not been followed, because anyone who asks questions gets shouted down as a science denier.

Is it possible for thousands of scientists to be wrong? Absolutely. We don’t take a position on their rightness or wrongness about climate change, but we need to remember that scientists are only fallible people. They are subject to the same foibles as the rest of us: peer pressure, groupthink, the need for money. For a complex subject like climate, there are way too many variables to keep track of. Our contention is that it is not even philosophically possible to interpret climate change trends and predictions without bias – certainly not to the precision the consensus dumps on the public with finger-wagging authority. How much less an even more complex subject as evolution! The ones who should be dubbed ‘anti-science’ are those who make science a god instead of a tool.

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