Ruminations on the science in Katharine Hayhoe’s 'Saving Us: A climate scientist’s case for hope and healing in a divided world'

In Saving Us: A Climate Scientist’s Case for Hope and Healing in a Divided World (One Signal Publishers, 2021), Professor Katherine Hayhoe, a climatologist and a Christian, classifies people by their beliefs about global warming: the Alarmed, the Concerned, the Cautious, the Disengaged, the Doubtful, and the Dismissive (whom she explicitly says aren’t worth arguing with — a nifty way to relieve herself and other alarmists of the need to face their arguments).^[1]

Clearly, she is “Alarmed.” I am a hybrid between the “Cautious” and the “Doubtful,”— I still need to be convinced that human-induced climate change is serious and urgent — let alone an existential threat.

My purpose is not to review the book. Rather I shall focus on Chapter 4, The Facts are the Facts, where, in a mere eight pages, she discusses the science of climate change, defending her alarmist beliefs and dismissing all arguments to the contrary. Three pages in, she has a section entitled “The Explanation is Simple” — this despite the fact that the climate system is inherently complex, probably the most complex system on the planet except life itself. It is an intricate dance played by astronomical influences, the atmosphere, the biosphere, the cryosphere (ice), the hydrosphere (water), the lithosphere (land), and the oceans. Whenever someone argues that “the science is simple” regarding climate change, you are likely to be swindled.

To begin this section, Hayhoe asserts: “The Earth’s climate is complex … understanding what we humans are doing to it isn’t”— as if adding another component to an already complex system somehow makes it simpler, not more complex. She then resorts to the inappropriate analogy, “the Earth’s atmosphere is like a blanket.” A blanket warms, in large part, by reducing convection (inhibiting the rise of warm air) whereas the atmosphere serves to enhance convection. As meteorologist Alistair Fraser wrote, “to claim that the atmosphere acts like a blanket, is to admit that you don’t know how either one of them operates.”^[2] Hayhoe then establishes four “zombie arguments” to eliminate as culprits of warming.

The term “zombie” is used because, she asserts, the processes to which they appeal have been often and completely debunked as agents of warming, but the arguments return from the dead, as it were, to provide fodder for the Dismissives. These arguments point to the Sun, Volcanoes, and Orbital and Natural Variability. She establishes them as zombies to be slain, leaving only anthropogenic increases in greenhouse gas concentrations as the culprit. To me, they are, as she presents them, more like strawmen, caricatures that fail to accurately portray any semblance of reality.

Strawman #1 — The Sun. Hayhoe argues that “since the 1970s, satellite radiometer data show that the Sun’s energy has been decreasing.” In fact, total solar irradiance between 1970 and 2000 increased substantially, with a grand solar maximum occurring between 2000 and 2002.^[3]  The decrease in solar activity since 2002 corresponds to the hiatus in warming of 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, she misses the important point that the last 30 years have seen a dearth of volcanic activity.^[4]  In the satellite record, the eruptions of El Chichon (1982) and Mt. Pinatubo (1991) caused profound decreases in global air temperature in the years following them. The absence of equal or greater eruptions since then is what those who appeal to volcanoes present as a possible explanation of some of the ensuing warming. Other major eruptions occurred in the late 1800s and early-to-mid 1900s, but it is the lack of major volcanic eruptions, not their occurrence, that is a real potential culprit of warming.

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

Strawman #4 — Natural Cycles. Hayhoe asserts, “Natural cycles can’t create heat out of nothing … they warm one part of the planet while simultaneously cooling another.” But then she admits that El Niño and La Niña events (ENSO, or the El Niño/La Niña Southern Oscillation) — warming of the central Pacific Ocean — can slightly raise/lower global temperatures, respectively. Hayhoe dismisses the impact of ENSO, arguing that since the planet is warming, the impact of ENSO must be trivial. In the satellite record, however, ENSO events play a significant role in changing global air temperatures.3 Moreover, she ignores longer-term variability — such as the Atlantic Multidecadal Oscillation (AMO) — a natural fluctuation that lasts from 50 to 70 years. The AMO switched from strongly negative to strongly positive between 1970 and 2010.

Having eliminated the four strawmen, Hayhoe proclaims that “Humans are responsible” and launches into a standard “the situation is dire” diatribe, replete with the trite admonition, “We humans are conducting a truly unprecedented experiment with the only home we have.” In her view, only five suspects exist — and since the other four have alibis, carbon dioxide must be guilty.

But whether Hayhoe is aware of them or not, there are other possible culprits. The surface air temperature record is rife with problems owing to changes in instrumentation, changes in station location, and temporal and spatial inconsistencies. Observations are largely made in lower elevations, in middle latitudes, along the coasts, and in or near built-up areas with their “urban heat island effect” (which could explain as much as half the apparently global warming over land from 1980–2002^[5] and beyond). They are almost completely lacking over the oceans, in high altitudes and latitudes, and in sparsely populated locations. Consequently, the appearance of global warming over the relevant period is likely significantly exaggerated, and the possibility that it is entirely an artifact of these problems cannot be ruled out.

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

Whatever the cause(s), this warming is not the dire situation that Hayhoe paints.

As John Adams said, “Facts are stubborn things; and whatever may be our wishes, our inclinations, or the dictates of our passion, they cannot alter the state of facts and evidence.”

[1] Leiserowitz, A., E. Maibach, C. Roser-Renouf, and N. Smith (2011). Global Warming’s Six Americas, May 2011. Yale University and George Mason University, New Haven, CT: Yale Project on Climate Change Communication. 57pp.

[2] https://personal.ems.psu.edu/~fraser/BadMeteorology.html

[3] Scafetta, N., R. C. Willson, J. N. Lee, and D. L. Wu, 2019: Modeling quiet solar luminosity variability from TSI satellite measurements and proxy models during 1980-2018. Remote Sensing, 11, 27.

[4] Christy, J.R., and R.T. McNider (2017). Satellite bulk tropospheric temperatures as a metric for climate sensitivity. Asia-Pacific Journal of Atmospheric Science, 53, 511-518.

[5] McKitrick, Ross R., and Patrick J. Michaels (2007). “Quantifying 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 https://www.nsstc.uah.edu/data/msu/v6.0/tlt/uahncdc_lt_6.0.txt.