Four Revolutions in the Earth Sciences

By Bryan Walker 28/01/2015


James Lawrence Powell is a former geology professor, college president and museum director. He is currently the executive director of the US National Physical Science Consortium. He is also an excellent communicator of science for the general reader. I reviewed two of his climate change-related books back in 2011 here and here. His latest book, Four Revolutions in the Earth Sciences: From Heresy to Truth, is wider in its scope, and places climate science alongside three other major scientific understandings which emerged in the course of the 20th century, profoundly affecting our knowledge of the planet.

Powell the geologist was familiar with the fact that great geological discoveries of the 20th century had had to struggle for decades to gain acceptance by the community of geologists. It was no easy ride for the propositions that the planet is billions of years old, that continents and sea floors move, and that meteorites crash into the earth. The opposition and the controversy his book narrates were often intense before the theories gained wide acceptance.

Powell had researched modern climate science, but was less familiar with its past history. He discovered that its early proponents had also suffered initial rejection of their theories and it was many decades before the correctness of their discoveries was acknowledged.

We are used to hearing of the fundamental contribution of Arrhenius to our understanding of the effect of atmospheric carbon dioxide on temperature. In the late 19th century he showed that atmospheric carbon dioxide alone, had its amount doubled or halved, would have caused temperature mutations of several degrees. But readers may be less aware that, following initial welcome for the theory, scientists “piled on to reject it”. It was another fifty years before scientists began to investigate greenhouse warming seriously and a further fifty before an international panel of scientists would corroborate Arrhenius’s finding.

 “A century is a long time to wait to affirm a scientific theory, especially one with the dire consequences of global warming.”

Arrhenius did not foresee those dire consequences, assuming, perhaps understandably from a Swedish perspective, that a warmer world would be more pleasant to live in. But by the late 20th century Nasa scientist James Hansen was in no doubt as to the malign consequences of warming for human society. The work of Hansen and his group dominates the latter pages of this section of Powell’s book. Hansen is respected not only for being one of the most productive modern climate scientists but also for being courageous and outspoken in his desire to warn, in every possible forum, of the dangers of global warming.

When Powell wrote his earlier books on climate change a distinguished medical friend challenged him as to why he accepted the theory. To his reply that virtually all publishing scientists accepted anthropogenic global warming his contrarian-inclined friend rejoined that scientists have been wrong before. Powell’s subsequent research into the history of 20th century climate science enabled him to see that the “scientists have been wrong before” route had already been traversed in the years immediately following Arrhenius.  For fifty years the “magisters of meteorology” favoured a debunking of Arrhenius which didn’t stand the course of time. They were wrong. As more scientists examined the data and published their findings the fundamentals became irresistible and the modern consensus emerged. This time it is right. Anthropogenic global warming has taken its place among the known facts of our planet.

The capacity of science to self-correct is in Powell’s eyes its cardinal virtue. In his book we see that process repeated four times over in the scientific revolutions he describes. What moved scientists to first reject for so long the four theories only to have later generations come to regard them as virtually self-evident? Looking back over the record it is plain, says Powell, that scientists accepted the theories when the data demanded that they do so. “To call themselves scientists they had no choice.”

But reaching this point is not necessarily straightforward. Powell comments that where science is concerned we cannot trust our common sense. In all four revolutions covered in book the discoveries are counter-intuitive.  Being able to make them is ”a triumph of human intellect, a testament to our ability to observe effects and reason back to causes”.

“I am not a scientist” is the latest mantra of denial in the US Congress, as if that statement somehow justifies a refusal to act to restrain greenhouse gas emissions or even to understand what is at stake. It’s a disgraceful evasion of intellectual and moral responsibility. One doesn’t need to be a scientist to understand the thrust of the scientific theories explained in this book, as any general reader of the book can attest.

The discovery of anthropogenic climate change may represent a triumph of human intellect, but that doesn’t put it out of reach of average human understanding. No patient reader of Powell’s book could come away confused about the scientific understandings it details, least of all  about how well established is the science of climate change. American scientists have played a prominent part in climate science. It’s hard to understand why any self-respecting American politician should continue to profess ignorance.