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 14.85o C with a σ of o.o7o C. That is there is a two-thirds chance that the true value is between 14.78 and 14.92o C. The measured annual increase of 0.04o C between 2015 (14.81 +/- 0.07o 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 0.09o C/decade long-term average during the forty years from 1980 to 2020 (0.02o C) while it was negative during the forty years from 1910 to 1940 (-0.05o 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.
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