I touched on Steven Koonin's book Unsettled three years ago here.  It remains an import read for anyone really interested in climate change as opposed to just the media spin on it.  The book delves into detail on the metrics, the models and the variability of things we read about as "settled science".  Koonin has a piece in the WSJ this week that notes:

There is a disconnect between public perceptions of climate change and climate science—and between past government reports and the science itself. Energy Secretary Chris Wright understands this. It’s why he commissioned an independent assessment by a team of five senior scientists, including me, to provide clearer insights into what’s known and not about the changing climate.

He then nets it out saying Among the report’s key findings:

• Elevated carbon-dioxide levels enhance plant growth, contributing to global greening and increased agricultural productivity.

• Complex climate models provide limited guidance on the climate’s response to rising carbon-dioxide levels. Overly sensitive models, often using extreme scenarios, have exaggerated future warming projections and consequences.

• Data aggregated over the continental U.S. show no significant long-term trends in most extreme weather events. Claims of more frequent or intense hurricanes, tornadoes, floods and dryness in America aren’t supported by historical records.

• While global sea levels have risen about 8 inches since 1900, aggregate U.S. tide-gauge data don’t show the long-term acceleration expected from a warming globe.

• Natural climate variability, data limitations and model deficiencies complicate efforts to attribute specific climate changes or extreme events to human CO2 emissions.

• The use of the words “existential,” “crisis” and “emergency” to describe the projected effects of human-caused warming on the U.S. economy finds scant support in the data.

• Overly aggressive policies aimed at reducing emissions could do more harm than good by hiking the cost of energy and degrading its reliability. Even the most ambitious reductions in U.S. emissions would have little direct effect on global emissions and an even smaller effect on climate trends.

We've become immune to throw away lines in lightweight mainstream media articles (looking at you SF Comicle) that toss in "climate change" when talking about anything from insurance rates to hurricanes to endangered salamanders.  The seven bullet points above suggest that is at least as dangerous and the changes happening to the climate.

After introducing Steven Koonin's new book here in Part 1, let's start the overview of it with some of the key definitions one needs to understand to even begin getting a grip on The Science.  Starting back in college stats class:

Every measurement of the physical world has an associated uncertainty interval (usually denoted by the Greek letter sigma: σ).  We can't say what the measurement's true value is precisely, only that it is likely to be within a range specified by σ.  Thus we might say the global mean surface temperature in 2016 was 14.85^o C with a σ of o.o7^o C.  That is there is a two-thirds chance that the true value is between 14.78 and 14.92^o C.  The measured annual increase of 0.04^o C between 2015 (14.81 +/- 0.07^o C) and 2016 is insignificant since it is smaller than the uncertainties–about half as large.  The media might well still scream "Temperatures Continue to Rise, either out of ignorance or to capture readers' attention.

Next, "weather" does not equal "climate".  A location's climate is the average of its weather over decades.  The UN's World Meteorological Organization defines climate as a thirty-year average, although some climate researchers will sometimes discuss averages over a period as short as ten years.  So changes in the weather from one year to the another do not constitute changes in the climate.

Alas, it isn't easy to measure the surface temperature over the whole earth, particularly when you are looking for changes of a fraction of a degree over decades.  You have to worry  about variations in the thermometers themselves, how they're housed, and exactly where they're located.  And even if a station hasn't been move over the years, urbanization around a site is a concern, since buildings, roads, and concentrated human activity make cities a few degrees warmer than their rural surroundings.

The global temperature anomaly is the deviation of the average daily temperature from its expected value, averaged over each day of the year and over the whole globe.  The rate of rise was twice as large as our 0.09^o C/decade long-term average during the forty years from 1980 to 2020 (0.02^o C) while it was negative during the forty years from 1910 to 1940 (-0.05^o C/decade).

That is just a little warm-up to the types of details, Koonin adds to the discussion.  The bit about measurement uncertainty is something I have known for years, but he really crystalizes it with the numbers.  As he looks at the models that are the source of the forecasts, we have to keep the uncertainty intervals in mind.