I noticed there’s a post at Curry’s in which Frank Bosse uses my method (and my program) to adjust global temperature data for things we know cause it to fluctuate. By removing fluctuations of known origin (or at least, our best estimate of them), we hope to sharpen our view of the changes that are happening for other reasons.
As a starting point, Bosse takes the global temperature estimate of Cowtan & Way. The known factors allowed for are ENSO (the El Niño Southern Oscillation), atmospheric aerosols from volcanic eruptions, and variation in the output of the sun.
El Niño is an oscillation of the ocean/atmosphere system. Every few years or so (it’s quite unpredictable really) it exposes more warm ocean water to the atmosphere, which transfers heat from sea to air. Since the air is where we live, and where our weather happens, we see an increase in global temperature. But it’s only temporary, and it doesn’t increase Earth’s total energy, it just moves some of it to where we notice its effect on the weather. Its opposite phase, la Niña, tends to cool off the globe temporarily.
Volcanic eruptions, especially large ones, can throw massive amounts of junk into the air. If the eruption is explosive to boot, that stuff can get thrown high up there (way up in the stratosphere even) where it can take years to finally settle out of the air. And some of that junk is sulfur compounds.
Atmospheric chemical processes make those sulfur compounds into sulfate aerosols, tiny particles, which tend to be reflective, giving the atmosphere a bright haze. It’s subtle, but measurable, and the bright hazy atmosphere scatters incoming sunlight in all directions, some of it right back to space. Less gets through to reach the ground and warm our world. This does change Earth’s total energy, reducing the power we get from the sun. That tends to cool the planet off.
The sun is, ultimately, the source of the energy that powers our weather and our lives. And it literally keeps the planet warm. If the sun gets hotter the Earth does too, and vice versa. The energy output of the sun is very reliable, but it does fluctuate a little, fluctuations which are sure to affect global temperature.
Running my program to estimate the influence of those factors and remove them, to generate adjusted data which (we hope) show us what else is happening to global temperature, I got this (including data through the incomplete year 2018):
The most obvious effect that the strong peaks from the 1998 and 2016 el Niño events aren’t in the adjusted data. Other events, like the drop in 1993 from the Mt. Pinatubo volcano, are also gone.
Let’s look at just the adjusted data:
Some things are obvious. Talk of a “pause” or “hiatus” starting in 1998 or any other time, is just ridiculous. These data suggest two different episodes, with the trend rate changing in 1978 (from changepoint analysis). We can estimate the trend thus:
Another thing to note is that whether using raw or adjusted data, the hottest four years are the last four years (presuming 2018 will come out in the top 4, pretty much a sure thing). Interesting that using the adjusted data, the hottest year of all wasn’t 2016, it was 2017.
Frank Bosse got a different result from using my program:
Notice that the 1998 el Niño peak is still there strongly, as is the 2016 peak. A clue to why his is so different, might be when he says:
For the C&W dataset I downloaded annual averages for 1950…2016. Thereafter the data was passed the “Tamino- filter” (shown in fig.1 and 2 of the cited post) for eliminating the influences of ENSO, volcano and variations in the solar forcing.
The program can’t run on annual averages. It absolutely requires monthly averages. What I’ve done above is adjust the monthly data, and only then compute annual averages for plotting purposes. Even if he used monthly data, something still went horribly wrong because he got the wrong result. Any conclusions based on it are also wrong.
Frank Bosse has a lot to say. I’m not impressed with any of it, in fact, getting the wrong adjusted values for the Cowtan & Way data seems to me just the start of his problems.
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