Ruminations on science in Katharine Hayhoe’s book Saving Us

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In Save Us: A Climate Scientist’s Case for Hope and Healing in a Divided World (One Signal Publishers, 2021) Professor Katherine Hayhoe, climate scientist and Christian, categorizes people according to their beliefs about global warming: the alarmed, the worried, the cautious, the disengaged, the doubtful and the dismissive (which she explicitly says aren’t worth discussing – a clever way to relieve themselves and other alarmists of having to face up to their arguments).[1]

Clearly, she is “alarmed”. I’m a hybrid between the “Cautious” and the “Doubtful”, – I have yet to be convinced that human-induced climate change is serious and urgent – not to mention an existential threat.

My purpose is not to criticize the book. I’ll focus on Chapter 4 instead. Facts are facts where, in just eight pages, she discusses the science of climate change, defending her fearmongering beliefs and rejecting all arguments to the contrary. Three pages later she has a section titled “The explanation is simple” – this despite the fact that the climate system is inherently complex, probably the most complex system on the planet except for life itself. It is a complex dance played by astronomical influences, the atmosphere, the biosphere, the cryosphere (ice), the hydrosphere (water), the lithosphere (land) and the oceans. Every time someone says “the science is simple” regarding climate change, you are likely to be scammed.

To begin this section, Hayhoe states, “The Earth’s climate is complex… understanding what we humans do to it is not” – as if adding another component to an already complex made it simpler, not more complex. She then resorts to the inappropriate analogy, “Earth’s atmosphere is like a blanket.” A blanket heats up, in large part, by reducing convection (inhibiting the rise of warm air) while the atmosphere serves to enhance convection. As meteorologist Alistair Fraser wrote, “to say that the atmosphere acts as a blanket is to admit that you don’t know how either works.”[2] Hayhoe then establishes four “zombie arguments” to be eliminated as the culprits of global warming.

The term “zombie” is used because, she claims, the processes they appeal to have been often and completely debunked as warming agents, but the arguments come back from the dead, so to speak, to provide fodder to the Dismissives. These arguments point to the Sun, volcanoes, and orbital and natural variability. It establishes them as zombies to be killed, leaving only anthropogenic increases in greenhouse gas concentrations as the culprit. To me, they are, as she portrays them, more like straw men, caricatures that fail to accurately depict a semblance of reality.

Strawman #1 — The Sun. Hayhoe argues that “since the 1970s, data from satellite radiometers show that the Sun’s energy is decreasing”. In fact, total solar irradiance between 1970 and 2000 increased dramatically, with a large solar maximum occurring between 2000 and 2002.[3] The decrease in solar activity since 2002 corresponds to the hiatus in warming air temperature over the same period.

Strawman #2 — Volcanoes. Here, Hayhoe correctly notes that volcanoes cool the Earth due to aerosol emissions more than they warm it by emitting carbon dioxide. However, it misses the important point that the last 30 years have seen a dearth of volcanic activity.[4] In satellite records, the eruptions of El Chichon (1982) and Mount Pinatubo (1991) caused deep drops in global air temperature in the years that followed. The absence of equal or greater eruptions since then is what those who appeal to volcanoes present as a possible explanation for some of the ensuing warming. Other major eruptions occurred in the late 1800s and early to mid-1900s, but it is the absence of major volcanic eruptions, not their occurrence, that is a real potential culprit for warming.

Strawman #3 — Orbital cycles. This potential culprit is a red herring, because changes in the variation of Earth’s orbit around the Sun occur on time scales of thousands of years. Few scientists argue that orbital cycles affect climate on shorter time scales. Admittedly, the argument is weak at best, but it is not the one that the “Cautious” and the “Doubtful” usually offer.

Strawman #4 — Natural cycles. Hayhoe says, “Natural cycles cannot create heat out of thin air…they warm one part of the planet while cooling another. But then she admits that El Niño and La Niña (ENSO, or the El Niño/La Niña Southern Oscillation) events – the warming of the central Pacific Ocean – may raise/lower global temperatures slightly, respectively. Hayhoe dismisses ENSO’s impact, arguing that since the planet is warming, ENSO’s impact must be insignificant. In satellite records, however, ENSO events play an important role in the evolution of global air temperatures.3 Moreover, it ignores longer-term variability – such as the Atlantic Multidecadal Oscillation (AMO) – a natural fluctuation that lasts 50-70 years. The AMO went from strongly negative to strongly positive between 1970 and 2010.

After eliminating the four straw men, Hayhoe proclaims that “humans are responsible” and launches into a standard “the situation is dire” rant, replete with the banal disclaimer: “We humans are conducting a truly free experiment. previous with the only house we have. According to her, only five suspects exist – and since the other four have alibis, Carbon Dioxide must be guilty.

But whether Hayhoe is aware of it or not, there are other possible culprits. Recording surface air temperature is fraught with problems due to changes in instrumentation, changes in station locations, and temporal and spatial inconsistencies. Observations are largely made at lower altitudes, at mid-latitudes, along coasts and in or near built-up areas with their “urban heat island effect” (which could explain up to half of the apparently global warming on land from 1980 to 2002[5] and beyond). They are almost totally lacking over oceans, at high altitudes and latitudes, and in sparsely populated places. Therefore, the occurrence of global warming during the relevant time period is likely greatly exaggerated, and the possibility that it is entirely an artifact of these issues cannot be ruled out.

The satellite record is much more spatially complete and escapes these problems, but only goes back about 40 years. Yet this shows that – after accounting for volcanoes and ENSO – the unexplained warming is only about 0.14°C per decade – much less, as shown in the graph below by the Dr. Roy W. Spencer of the University of Alabama-Huntsville, that the rate commonly alleged, for example, by the United Nations Intergovernmental Panel on Climate Change and simulated by the computer climate models he uses.[6]

Whatever the cause or causes, this warming is not the disastrous situation described by Hayhoe.

As John Adams said, “Facts are stubborn things; and whatever our desires, our inclinations or the precepts of our passion, they cannot alter the state of the facts and the proofs.

[1] Leiserowitz, A., E. Maibach, C. Roser-Renouf and N. Smith (2011). The six Americas of global warming, May 2011. Yale University and George Mason University, New Haven, CT: Yale Climate Change Communication Project. 57pp. [2] [3] Scafetta, N., RC Willson, JN Lee and DL Wu, 2019: Modeling silent solar luminosity variability from TSI satellite measurements and proxy models during the period 1980-2018. remote sensing, 11, 27. [4] Christy, JR and RT McNider (2017). Bulk satellite tropospheric temperatures as a measure of climate sensitivity. Asia-Pacific Journal of Atmospheric Sciences, 53, 511-518. [5] McKitrick, Ross R. and Patrick J. Michaels (2007). “Quantification of the influence of anthropogenic surface processes and inhomogeneities on gridded global climate data.” Journal of Geophysical Research: Atmospheres, 112 D24. [6] Christy and McNider; UAH Satellite Global Temperature Database, online at

David R. Legates is a professor of climatology at the University of Delaware, a Senior Fellow of The Cornwall Alliance for Creative Stewardshipand a director of Scientific and environmental policy project.

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