Yes, the statements in the OP are all essentially correct.
Quartz, I appreciate that you’re “on the fence” to use your words, and not arguing denialism, but I have to criticize what I would regard as some pretty basic misinformation nevertheless.
Direct comparisons with the state of climate hundreds of millions of years ago when the planet’s geology and ecosystem were radically different, involving climate transitions that took millions of years to manifest, are really quite irrelevant to an understanding of present changes spanning a mere few hundred years or less. Specifically, the CO2 range between glaciation and inter-glacials has followed a regular and well-bounded pattern for more than 1.2 million years, from a low of 180 ppm to a high of 280 to 300 ppm at the peak of inter-glacials. To suddenly break out of this pattern with artificially elevated CO2 at 400 ppm represents an entirely new climate era unprecedented in human history. What the climate was doing 400 million years ago is absolutely irrelevant in that context. For instance, though I’m pretty sure you’re wrong about any glaciation at all during the Devonian, even if there was, it can confidently be said that there’s no way we can enter a glacial cycle in the contemporary geological era with CO2 at 400 ppm and rising, so that fact wouldn’t be relevant anyway. We can only enter an era of increasing warming, barring unrelated events like a major volcanic eruption, which would only slow it down temporarily.
You are also wrong about “the Earth has seen these temperatures before, but you have to go a long way back in human terms, but not geologically”. When was this? If you’re thinking of the Medieval Warm Period, the effects were largely regional and not globally synchronous, and even in areas where they were most prevalent they weren’t consistently warmer than today. The MWP represents an entirely different phenomenon, related to internal variability and not externally forced changes to the global energy budget.
The first part is right – there are many sources of natural climate variability, and virtually all of them operate on geologic timescales. The last part is wrong. No sustained natural forcings have been identified that are relevant to the period of post-industrial warming in the sense that they could operate at the magnitude and speed of present GHG emissions to either offer an alternative explanation to the bleeding obvious – the well-quantified magnitude of CO2 forcing, or to potentially mitigate or reverse it. Natural variations in terms of ocean and atmosphere circulation changes can produce regional effects and even enhance or mitigate global temperature changes, but only over a short time. In the longer term, no matter how much one appeals to complexity and chaos, the net change to the earth’s total energy budget is always going to dominate.
See above. Arguing that the absolute increase is “very small” is just as specious as arguing that CO2 is “just a trace gas”. What matters is the huge relative change to the very delicate climate balance. Does this look like something that should be described as “very small”?
Wrong. Wrong according to the IPCC, wrong according to the National Academy of Sciences, wrong according to the national science academies of all first-world nations, wrong according to the prevailing published science. Just wrong. At least, wrong unless you like to define a minimum 95% certainty that human activity is the primary cause of global warming as being “far from certain”. :rolleyes:
What would be correct is to say that the influence of natural variability – both positive and negative – in the post-industrial era hasn’t been precisely quantified, but it’s been assessed well enough to know with a very high level of confidence that it’s small enough to be overwhelmed by anthropogenic CO2. The standard denialist trick is to take the first part of that statement, obfuscate and exaggerate it, and produce the false assertion that you stated.
As pointed out by myself and others in the several in-depth discussions about this in GD, bad science deserves to be criticized, and those who are so singled out are guilty of provably bad science, mostly either publishing in second-rate or off-subject journals or, more commonly, simply relegating themselves to Internet blogs. One of my favorite events in recent years in one of these, Judith Curry’s blog, is when she appealed to her throng of mostly unscientific and sometimes marginally illiterate followers to come up with reasons – any reasons – why climate science was wrong about AGW. She proposed to review and prioritize the reasons proposed by these scientifically illiterate pinheads for why a century of climate research was all wrong, and then post the list. This is the kind of “science” that goes on in blogs, and Curry is one of the better ones! WUWT is another one, run by a self-proclaimed “meteorologist” who is actually a former TV weatherman who dropped out of college, and is notable for the fact that almost nothing ever posted in it is correct.
The rote argument that science must be prepared to be challenged is now a tired old red herring, because of course it always is, but in the published scientific domain of climate science, there is no longer a debate about AGW because there isn’t any serious evidence to support the contrarian view, but overwhelming evidence in support of AGW. Denialism has now become exclusively the domain of cranks, supported by a well-funded campaign from the usual vested interests.
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