…And yet, highly credentialed scientists, including Nobel Prize–winning physicist Ivar Giaever, reject what is often called the “climate consensus.” Giaever resigned from the American Physical Society in protest of the group’s statement that evidence of global warming was “incontrovertible” and that governments needed to move immediately to curb greenhouse-gas emissions. Sixteen distinguished scientists signed a 2012 Wall Street Journal article, in which they argued that taking drastic action to “decarbonize” the world’s economy—an effort that would have major effects on economic growth and quality of life, especially in the developing world—was not justified by observable scientific evidence. And, like Giaever, they objected to the notion of a climate consensus—and to the unscientific shutting down of inquiry and the marginalization of dissenters as “heretics.”…
Another dissenter, the American atmospheric physicist Murry Salby, has produced a serious analysis that undermines key assumptions underpinning the AGW worldview. His work and its reception illustrate just how unsettled climate science remains—and how determined AGW proponents are to enforce consensus on one of the great questions of our age.
In April 2013, concluding a European tour to present his research, Salby arrived at Charles de Gaulle Airport in Paris for a flight back to Australia, where he was a professor of climate science at Macquarie University. He discovered, to his dismay, that the university had canceled the return leg of his nonrefundable ticket. With Salby stranded, Macquarie then undertook misconduct proceedings against him that swiftly culminated in his dismissal. The university claimed that it did not sack Salby for his climate views but rather because he failed to “fulfill his academic obligations, including the obligation to teach” and because he violated “University policies in relation to travel and use of University resources.”
Salby and his supporters find it hard to believe the school’s claims. Salby’s detractors point to reports of his investigation by the National Science Foundation (NSF) for alleged ethical improprieties, claims surrounding which surfaced on an anti-climate-skeptic blog, along with court papers relating to his divorce. Salby has indeed been embroiled in conflicts with the NSF—the organization debarred him from receiving research grants for three years, even though, teaching in Australia, he wasn’t eligible, anyway—and with the University of Colorado, where he taught previously and was involved in a decade-long dispute with another academic. At one point, the NSF investigated the disappearance of $100,000 in Salby’s research funds, which, in the wake of the investigation, was returned to Salby’s group. However, all these matters have involved bureaucratic rights and wrongs. They have no bearing on his science, just as Antoine Lavoisier’s being a tax farmer had no bearing on his demolition of the phlogiston theory of combustion. And Salby had earned high marks as a scientist. He originally trained as an aerospace engineer before switching to atmospheric physics and building a distinguished career. He taught at Georgia Tech, Princeton, Hebrew, and Stockholm Universities before coming to the University of Colorado, and he was involved as a reviewer in the IPCC’s first two assessment reports.
Starting in the late 1990s, Salby began a project to analyze changes in atmospheric ozone. His research found evidence of systematic recovery in ozone, validating the science behind the 1987 Montreal Protocol, which introduced specific steps for curtailing ozone-depleting gases. Preparing to write a graduate-level textbook, Physics of the Atmosphere and Climate, later published by Cambridge University Press and praised by one reviewer as “unequalled in breadth, depth and lucidity,” Salby then undertook a methodical examination of AGW. What he found left him “absolutely surprised.”
Most discussion on the science of AGW revolves around the climatic effects of increased levels of carbon dioxide in the atmosphere. How it got there in the first place—the assumption being that increased carbon dioxide arises overwhelmingly from human activities—is often taken for granted. Yet Salby believed that he had uncovered clear evidence that this was not the case, as his trip to Europe was designed to expose.
The IPCC estimates that, since the Industrial Revolution, humans have released 365 billion tons of carbon from burning fossil fuels. Annual emissions, including those from deforestation and cement production, are less than 9 billion tons. Yet natural carbon cycles involve annual exchanges of carbon between the atmosphere, the land, and the oceans many times greater than emissions from human activities. The IPCC estimates that 118.7 billion tons of carbon per year is emitted from land and 78.4 billion tons from oceans. Thus, the human contribution of 9 billion tons annually accounts for less than 5 percent of the total gross emissions. The AGW hypothesis, as well as all the climate-change policies that depend on it, assumes that the human 5 percent drives the overall change in the amount of CO2 in the atmosphere—and that the other 95 percent, comprising natural emissions, is counterbalanced by absorption of CO2 from the atmosphere by natural processes. Summing it up, the IPCC declared in its fourth assessment report, in 2007: “The increase in atmospheric CO2 is known to be caused by human activities.”
Salby contends that the IPCC’s claim isn’t supported by observations. Scientists’ understanding of the complex climate dynamics is undeveloped, not least because the ocean’s heat capacity is a thousand times greater than that of the atmosphere and relevant physical observations of the oceans are so sparse. Until this is remedied, the science cannot be settled. In Salby’s view, the evidence actually suggests that the causality underlying AGW should be reversed. Rather than increased levels of CO2 in the atmosphere triggering global temperatures to rise, rising global temperatures come first—and account for the great majority of changes in net emissions of CO2, with changes in soil-moisture conditions explaining most of the rest. Furthermore, these two factors also explain changes in net methane emission, the second-most important “human” greenhouse gas. As for what causes global temperatures to rise, Salby says that one of the most important factors influencing temperature is heat exchange between the atmosphere and the ocean.
Why is the IPCC so certain that the 5 percent human contribution is responsible for annual increases in carbon dioxide levels? Without examining other possible hypotheses, the IPCC argues that the proportion of heavy to light carbon atoms in the atmosphere has “changed in a way that can be attributed to addition of fossil fuel carbon”—with light carbon on the rise. Fossil fuels, of course, were formed from plants and animals that lived hundreds of millions of years ago; the IPCC reasons that, since plants tend to absorb more light carbon than heavy carbon, CO2 emissions from burning fossil fuels reduce the share of heavy carbon in the atmosphere. But Salby points to much larger natural processes, such as emissions from decaying vegetation, that also reduce the proportion of heavy carbon. Temperature heavily influences the rate of microbial activity inherent in these natural processes, and Salby notes that the share of heavy carbon emissions falls whenever temperatures are warm. Once again, temperature appears more likely to be the cause, rather than the effect, of observed atmospheric changes.
Further, Salby presents satellite observations showing that the highest levels of CO2 are present not over industrialized regions but over relatively uninhabited and nonindustrialized areas, such as the Amazon. And if human emissions were behind rising levels of CO2 in the atmosphere, he argues, then the change in CO2 each year should track the carbon dioxide released that year from burning fossil fuels—with natural emissions of CO2 being canceled out by reabsorption from land sinks and oceans. But the change of CO2 each year doesn’t track the annual emission of CO2 from burning fossil fuels, as shown in Figure 1, which charts annual emissions of CO2, where an annual increase of one part per million is approximately equivalent to an annual growth rate of 0.25 percent.
While there was a 30 percent increase in CO2 fossil-fuel emissions from 1972 to 1993, there was no systematic increase in net annual CO2 emission—that is, natural plus human emissions, less reabsorption in carbon sinks. These data, Salby observes, are inconsistent with the IPCC’s claim to certainty about human causation of rising CO2 levels in the atmosphere…
Genuine scientific inquiry is degraded when science becomes politicized. The standards that have prevailed since the Scientific Revolution conflict with the advocacy needs of politics, and AGW would be finished as the basis of a political program if confidence in its scientific consensus were undermined. Its advocates’ evasion of rigorous falsifiability tests points to AGW’s current weakness as a science. As an academic critic of the science on which AGW rests, Murry Salby may have been silenced for now. The observed behavior of nature, from which he draws his analysis, cannot be dismissed so readily.