Sea level rise is such a huge problem, and is so undeniable, that climate deniers have gone loony trying to blame it on anything and everyting but global warming. It’s not working; the recent idiocy from congressman Mo Brooks trying to blame sea level rise on rocks and dirt filling the oceans didn’t increase doubt about human cause like he hoped, rather it raised extreme doubt about his competence. He, and his idea, quickly became a laughingstock. Others have been ridiculed for similarly ridiculout ideas. Now Roy Spencer has joined the crowd with something almost as dumb as rocks.
His “thesis” is that sea level rise before 1950 had to be all natural. His thesis is wrong. He further supposes that since 1950 it has continued to rise at the pre-1950 rate for entirely natural reasons. His further supposition is wrong. Only by using such blatantly false suppositions can he conclude that the human contribution to sea level rise is only 0.3 inches per decade (that’s 0.76 mm/yr). His conclusion is wrong.
Let’s consider his (and others’) first premise, that everything before 1950 had nothing to do with human activity but was all natural. Typically he says “sea level has been rising naturally, for at least 100 years before humans could be blamed.”
Here’s the CO2 concentration since 1958 according to data from the Mauna Loa atmospheric observatory, and before that from the Law Dome ice core:
The value in 1950 was just about 312 ppm, the pre-industrial level about 278 ppm. That means that in 1950 it was already 34 ppm higher than pre-industrial. Since it’s presently about 409 ppm, 26% of the rise due to human activity was already there. Earth to Roy Spencer: 26% is not nothing. It’s not even negligible.
What about mankind’s influence on global temperature up to 1950? Climate models can estimate how Earth’s temperature has changed over time due to many factors, some natural, some not. They are often run with only the natural forcings, leaving out the human contribution, enabling us to compare how it would have changed without mankind’s interference to how it changed with human influence. I averaged global temperature (yearly averages) for all model runs using only natural influences, and for all model runs including all forcings (natural + anthropogenic), then computed temperature anomaly using a baseline from 1880 to 1900, and got this:
Clearly the natural-only behavior is not the same “before 1950.” But Roy Spencer wants us to believe that pre-1950 the human influence is nothing. Here’s the estimated difference which is due to human influence:
Human activity — not natural forces — caused about 0.15°C warming from 1900 to 1950 alone. That’s not nothing, it’s not even negligible. But in addition, there’s good reason to believe Earth had already warmed by about 0.2°C from 1750 to 1900 due to human activity — not natural forces. That makes around 0.35°C warming by 1950 from human influence alone. Earth to Roy Spencer: that’s not nothing. It’s not even negligible.
Roy Spencer’s premise — that the human influence can be neglected before 1950 — is one of the most common techniques of climate deniers in general. In my opinion, it’s not just mistaken, not just ludicrous, it’s sometimes dishonest, because some people, like Roy Spencer — really ought to know better.
Perhaps Spencer’s most hilariously ridiculous comment is when he cautions that “…it is dangerous to extrapolate any short term trends far into the future.” Yet that is exactly what he did. He took the sea level trend up to 1950, called it “entirely natural” (when it isn’t), then extrapolated it to the present (nearly 70 years). Question for Roy Spencer: when you said your caution against extrapolation, were you paying attention?
The main reason that sea level rise is getting so much attention from climate deniers is that it’s such a major and undeniable problem. They can no longer deny that it’s happening (except for a few fringe nut-cases). Hence they’re scraping below the bottom of the barrel to find any excuse to blame it on anything but the real reason: man-made global warming. Roy Spencer: when you retire, I suggest you buy yourself a lovely beachfront home. May I suggest Miami Beach?
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