Unsettled?: What Climate Science Tells Us, What it Doesn 't, and Why it Matters.

• Author: Yohe, Gary

Unsettled?: What Climate Science Tells Us, What it Doesn 't, and Why it Matters, by Steven Koonin (Benbella Books,1 Dallas Texas, 2021). 240 pages, ISBN: 9781950665792 (hard cover).

The major theme of this new book on climate change is conveyed by the question mark in the title. More broadly, in his own words, Dr. Koonin's (2021) lead is:

'The earth has warmed during the past century, partly because of natural phenomena and partly in response to growing human influences. These human influences (most importantly the accumulation of [CO.sub.2] from burning fossil fuels) exert a physically small effect on the complex climate system. Unfortunately, our limited observations and understanding are insufficient to usefully quantify either how the climate system will respond to human influences or how it varies naturally. However, even as human influences have increased almost fivefold since 1950 and the globe has warmed modestly, most severe weather phenomena remain within past variability. Projections of future climate and weather events rely on models demonstrably unfit for the purpose.' (pg 24)

So who is this author and is the science about the Earth's climate still unsettled? Steven Koonin is a former undersecretary for science in the Department of Energy during the Obama administration. He was, in 2012, appointed to the Board of Governors of Lawrence Livermore and Los Alamos National Laboratories; he still serves in that capacity. He was considered for an advisory post to the Environmental Protection Agency during the early days of the Trump administration. Thus, he is well credentialed; so his opinions get broad national coverage.

The dominant adjective in the book is 'unsettled,' which Webster (2021) indicates is: 'not decided or determined' or 'not resolved or worked out'. Both definitions indicate uncertainty. However, even if the science is still uncertain, it does not mean that human decision-makers are not sufficiently skilled to accommodate and adapt to current levels of uncertainty. Dr. Koonin assumes that they are not, but that is not true. Scientific findings that include individual assessments of confidence (likelihood) and published with traceable accountings of impacts (consequences) are what they need. For those skilled decision-makers, the science is sufficiently settled; as a corollary, Dr. Koonin's unqualified assessments are useless because even with uncertainties, they know 'why it matters '.

How is that? Scientists of all variety, even physicists, know that their science is dynamic. So do honest opinion makers and decision-makers and ordinary citizens. Decision-makers around the world have adopted a risk management approach to their climate decisions since IPCC (2007) and beyond (See, as well, NCA4 (2017). In a risk management approach properly qualified scientific findings must be expressed in terms of risk, which is fundamentally the product of the likelihood and consequence across possible futures.

To be very specific, IPCC (2007) asserted with very high confidence that 'Responding to climate change involves an iterative risk management process that includes both mitigation and adaptation and takes into account climate change damages, co-benefits, sustainability equity, and attitudes toward risk. ' As soon as that sentence was accepted, the countries of the world had agreed on the fundamental premise of their future negotiations under the United Nations Framework Convention on Climate Change--investment in either mitigation or adaptation depends critically upon efficiently processing information about the ranges of observed and projected consequences of climate change as well as their relative likelihoods. And so, they wanted to be informed about both by the IPCC.

This is not a foreign concept to most of us. We buy insurance. Not because we need protection from average outcomes in the middle of the road. Rather we need protection from more extreme events that haunt the shoulders or the outer lanes. We pay annual premia to be compensated if the house burns down or other valuables are stolen or destroyed. In a normal year with no destruction, we get nothing in return except peace of mind.

(1.) The structure of the book

To support his 'unsettled' conclusion, Dr. Koonin provides 13 chapters with their own separate themes. They are divided into two Parts:

Part 1. The Science

Importantly, this part begins in Chapter 1 with coverage of uncertainty that includes complementary evaluations of a wide range of assessments. It includes two highlighted sections about how the climate community deals with uncertainty. One is entitled 'Understanding uncertainties' (pp 18-20) and the other speaks 'About assessment reports' (pp 21-22). The uncertainty guidance and language documents prepared by the Intergovernmental Panel on Climate Change (IPCC) are both favorably and accurately portrayed in this chapter.

Following this discussion of uncertainty, Chapter 2 devotes its attention to earth's temperature rising with a balanced explanation of both natural and human influences. Chapter 3 speaks to the link between greenhouse gas emissions (GHGs), particularly [CO.sub.2], and temperature.

Chapter 4 turns to computer models of the climate system. He opines that those models 'give results that differ significantly not only from each other but also from observations (that is, they're right in a few ways but wrong in many others)'. Evidence says otherwise, if the appropriate modifiers are included in the claim. Take, for example the generic 'The climate is warming and humans are to blame'. It is an unmodified statement of two fundamental scientific findings. The first part of this statement evolved from IPCC (1995): human influences have had a 'discernable influence on the global climate.' That conclusion evolved to the point where noted climate expert Kevin Trenberth...