Tuesday, May 8, 2018

Thoughts on Climate Change -- part 4:Yet another "saving hypothesis"

Despite a significant amount of evidence that would appear to contradict the prevailing theory of "anthropomorphic global warming" (AGW), many activists either dismiss it as "lies" or attempt to explain it away with "saving hypotheses" of the sort we've already encountered in previous posts. I'll be providing several examples of such attempts to explain away the evidence, but since I've been discussing the topic of sea level rise, let's begin with a further consideration of that issue.

I've already demonstrated that CO2 cannot possibly be held responsible for any significant degree of sea level rise at any time from the outset of the industrial revolution to the 1950's, when, as most climate scientists agree, CO2 emissions were too low to have had much of an effect. And because, from ca. 1940 through ca. 1979, we see no real sign of temperature rise, CO2 emissions could not possibly have made a difference, as temperature is by far the most significant "control knob" of sea level. What remains, therefore, is the period from ca. 1979 through the end of the 20th century, when we see global temperature, sea level, and CO2 emissions all rising simultaneously for a period of roughly 20 years. Could CO2 have affected sea level during this period? Let's take a look at the evidence:

The graph displayed above, based on research dating from 2011, shows a slow but steady rise in average sea level from 1880 to the year of publication. Note that there is no sign of any significant change in the steadily upward trend subsequent to the mid-century period of roughly 40 years (1940-1979) when temperatures were not rising. Note also that there is no sign of any acceleration of sea level rise that might reflect the sudden acceleration of temperatures seen during the last 20 years of the past century, or, indeed, any rise in temperatures during the 21st century.

Note also that the period from 1998 - 2015 saw either a decline or only a very modest upward trend in temperatures (depending on the source), a significant contrast to the rapid runup during the previous 20 years. Here is one of many graphs charting temperatures during this period, this one from UAH:

Discounting the three major El Nino events, we get an essentially level picture. Yet, as with the mid-20th-century "hiatus," sea levels have continued to rise at more or less the same pace as before.

A more recent study dating from 2016, published in the prestigious journal Nature, reports a surprising DROP in the rate of sea level rise. From the abstract:
Global mean sea level rise estimated from satellite altimetry provides a strong constraint on climate variability and change and is expected to accelerate as the rates of both ocean warming and cryospheric mass loss increase over time. In stark contrast to this expectation however, current altimeter products show the rate of sea level rise to have decreased from the first to second decades of the altimeter era. 
And here we come to yet another example of essentially the same syndrome noted here previously: the tendency among so many climate scientists to add a complicating, ad hoc "saving" hypothesis, in violation of Occam's Razor, in an effort to explain away inconvenient evidence.  As reported above, the raw evidence is clear enough. The rate of sea level rise appears to have decreased in recent years, which strongly suggests, along with all the other evidence cited above, that rapidly accelerating increases in CO2 emissions have had little or nothing to do with sea level. Is that a definitive result? No. Some other studies have supposedly claimed to find some degree of acceleration. But it's useful to consider this case, as it provides such a fascinating picture of how well meaning researchers can literally turn their results inside out in order to achieve a desired outcome.

Consider the sentence immediately following the quotation presented above: "Here, a combined analysis of altimeter data and specially designed climate model simulations shows the 1991 eruption of Mt Pinatubo to likely have masked the acceleration that would have otherwise occurred."

Seek and ye shall find. A result in line with expectations would have been uncritically accepted, with no need to look for some additional factor that might complicate, and possibly negate, the desired conclusion. But since the result was contrary to expectations, it then became necessary to cast about for some additional factor that might have "masked" the expected acceleration. And lo and behold, presto chango, the authors discover, of all things, a volcanic eruption.

Significantly, it is the speculative saving hypothesis, rather than the evidence itself, that gets enthusiastically picked up by the media, which reports a result 180 degrees out of phase with what the research actually revealed:

A sampling of headlines:

How a Volcano Hid the Acceleration of Sea Level Rise  Climate Central.

An Exploding Volcano Slowed Global Warming. Briefly.  Slate.

CLIMATE CHANGE IS ACCELERATING SEA LEVEL RISE  National Center for Atmospheric Research.
Greenhouse gases are already having an accelerating effect on sea level rise, but the impact has so far been masked by the cataclysmic 1991 eruption of Mount Pinatubo in the Philippines, according to a new study led by the National Center for Atmospheric Research (NCAR).
Volcanic eruptions can 'mask the true effects of climate change'  Wired.

Volcanic Eruption Affects Sea Level Rise  National Geographic.

Could it be true? Could the eruption of Mt. Pinatubo in 1991 have had such an effect on the vast ocean expanse that it masked what would have been a global acceleration of sea level rise? Such eruptions do in fact have a temporary cooling effect on the atmosphere, due to the thick aerosols they emit, which can block incoming solar radiation.  And the researchers have gone to considerable trouble, wielding some very impressive statistical tools, in order to demonstrate the likelihood of their hypothesis.

Which is where a dash of critical thinking becomes necessary. If we see NO sign of any significant slowdown in sea level rise in the wake of the precipitous downturn in world temperatures during the early 1940's, as revealed in the following very typical, graph,

then how can it be claimed that a single volcanic eruption, causing a far less significant dip in global temperatures over a shorter period, could have significantly altered the average water level of the entire ocean, so very vast and deep? Statistics can be teased and tortured to produce all sorts of unlikely results, but critical thinking can provide a valuable corrective. As it looks to me, the authors of this paper have produced a clearly ad hoc "saving hypothesis" in a desperate effort to undo the otherwise embarrassing results of their own research. And the media, gullible as usual, have hyped their dubious theory to the max, because they too insist on seeing only what they want to see.

And no, I am not a climate scientist nor am I a physicist. Just an independent, sometimes arrogant, gent unwilling to tolerate insults to my intelligence.

From Scientific American:
Evaluating scientific claims (or, do we have to take the scientist's word for it?):
Scientific knowledge is built on empirical data, and the details of the data . . . can vary quite a lot in different scientific disciplines, and in different areas of research within those disciplines. However, there are commonalities in the basic patterns of reasoning that scientists in all fields use to compare their theories with their data. . .

In other words, even if I can't evaluate someone else's raw data to tell you directly what it means, I can evaluate the way that data is used to support or refute claims. I can recognize logical fallacies and distinguish them from instances of valid reasoning. Moreover, this is the kind of thing that a non-scientist who is good at critical thinking (whether a journalist or a member of the public consuming a news story) could evaluate as well. -- Janet Sternweddel

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