Friday, October 09, 2015

Ted Cruz's global warming diatribe based on a fallacy

The right wing and climate denying sections of the popular press and the blogosphere have been positively salivating recently over a video showing denier-in-chief and potential Republican nominee Senator Ted Cruz grilling Sierra Club president Aaron Mair on climate change. The exchange occurs as part of the testimony to the Senate Judiciary Subcommittee on Oversight, Agency Action, Federal Rights and Federal Courts, which Cruz happens to chair, a mouthful of legalese usually shortened to "the global warming hearings".
Mair, considering his position, does a terrible job of standing his ground, and Cruz is clearly by far the better politician, using his years as a lawyer to great effect. The video is excruciating to watch, and while some have castigated Cruz for bullying, he does so in an apparently respectful and reasonable way.
But are Cruz's claims actually factually correct?
Unfortunately not. Cruz's main contention is the so-called "Pause", with a capital "P". This is  the idea that, in Senator Cruz's own words from the interview, "The satellite data over the last 18 years demonstrate no significant warming whatsoever". It is a sacred tenet in the climate denial belief system, and an attempt to use science to make their case. The claim has been refuted many times, though, despite Cruz's slick presentation of it as irrefutable science. One of the best and simplest explanations of the phenomenon I have found comes, surprisingly enough, from an article in the straight-laced but undeniably reputable Washington Post, which is essential reading on the subject. It turns out that the "Pause" claim can be refuted on many fronts.
For one thing, it relies on just one specific source of data, satellite temperature readings in the lower troposphere, mainly based on reports by Carl Mears of Remote Sensing Systems. But satellite data do not actually measure temperature and temperature changes directly; rather, they measure "radiance" from the sun, which is then converted using a mathematical model into a measure of temperature. Unfortunately, this model has repeatedly been shown, even with a couple of tweaks over the years, to systematically underestimate atmospheric temperatures.
So, when Senator Cruz, and many other climate change deniers, claim that satellite data is the best and most reliable data we have on climate change, they are being disingenuous at best, and deliberately obfuscatory and self-serving at worst. Mears himself cautions that satellite data is notoriously unreliable, and that we should pay at least as much, if not more, attention to the ground-based temperature data of the NOAA and NASA, which show much stronger warming trends. Both NASA and NOAA, using different methodology, show 2014 as the warmest year on record, followed by 2010, then 2005 and possibly 2013, and only then 1998. In more long-range terms, the World Meteorological Organization's data show that the 2000s were indeed globally warmer than the 1990s, which were in turn warmer than the 1980s.
Furthermore, it should be noted, even the satellite data that Senator Cruz is using do not show "zero warming", as he claims, just a slight slowing down of the rate of the increase. Carl Mears again: "Does this slow-down in the warming mean that the idea of anthropogenic global warming is no longer valid? The short answer is 'no'."
Cruz also selectively picks data beginning in 1998, an unreliable and exceptional year due to the very strong ENSO (El Niño - Southern Oscillation) in that year. It is Mears again who points out: "When one starts their analysis on an extraordinarily warm year, the resulting trend is below the true long term trend". Both the El Niño and the opposite La Niña effects have been stronger in recent decades than historically (partly due to, guess what?, global warming), making temperature data much more variable than heretofore.
So, Aaron Mair was quite correct to say that: "97 percent of the scientists concur and agree that there is global warming, and anthropogenic impact with regards to global warming". But his feckless and embarrassing performance under pressure has unfortunately just given the denial camp another stick to beat the climate change activists with.
As for Ted Cruz? Full marks for political opportunism and aggressive interrogation, but very few marks for science, I'm afraid. It certainly takes a lot of gall to say, with a straight face, as Senator Cruz does in this interview, "The problem with that statistic that gets cited a lot is that it’s based on one bogus study", when in fact it is he that is the one guilty of just that.

Courtesy of The Guardian: With just a month and a half left in 2015, it’s clear that this year will be by far the hottest on record, easily beating the previous record (which was set just last year). So, the temporary slowdown in the speed of warming of global surface temperatures (which was mainly due to the prevailing La Niña conditions from 1999 to 2012) has ended, as each of the past four years has been hotter than the one before.
If we look at the temperature trends just for El Niño years, for La Niña years, and for neutral years, each has a trend of 0.15–0.17°C global surface warming per decade since the 1960s (see the graph in the same Guardian article). Note that the years during the mythical “pause” fall right along the long-term trend lines for each category.

It seems that Senator Cruz can no longer even rely on the one climate metric which even vaguely supported his case, as the Mears figures at Remote Sensing Systems have recently been updated for "diurnal drift", which makes them slightly more reliable. And, guess what, they also now show significant warming throughout the so-called "Pause" period.
The figures are still in need of some other model adjustments, which would have the effect of bringing them even more in line with surface and ocean temperature warming trends, but even this minor adjustment effectively puts paid to Cruz's claims. Don't expect any shamefaced admissions and humble apologies any time soon, though.

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