If you missed the first part of this long essay, it is here. I am looking at what has happened in the last ten years with respect to the central assumptions of the anthropogenic global warming (AGW) scare, about which I wrote a decade ago. You can read the original essay here. Assumptions #1 and #2 have already been dealt with.
3. Is the warming caused by our burning fossil fuels, clearing the forests and other activities?
There is no doubt that CO2 accumulations in the atmosphere are increasing, and since we are burning a lot of fossil fuels, which release CO2 when they are burned, our activities are part of the cause of that rise. But does that rise lead to global warming? Theoretically, it does: more carbon dioxide leads, at least in the laboratory, to the trapping of more heat in the atmosphere, and thus to a higher temperature. But theoretically, also, each rise of a given amount of CO2 has a logarithmic effect, such that further increases have less effect. It is conventionally assumed that CO2 levels as the Industrial Revolution began (mid 18th century) were at about 280 parts per million. In theory again, and ignoring ‘climate sensitivity’, a doubling of CO2 would produce an increase in global temperature of about 1 degree C. Now to gain that one degree increase CO2 levels would need to be at about 560 pp. They are presently (ignoring seasonal changes) at a little over 400 ppm. When I wrote the original essay CO2 was at 385 ppm. In ten years there has been a rise of a little over 15 ppm. If we assume that each decade will produce an increase of 15 ppm, then it will be about a hundred years from now when we reach the doubling. The next doubling (from 580 to 1160 ppm) would, using the same metric, occur three or four centuries later.
This simple arithmetic suggests that there is no need to worry about an increase in CO2, and indeed that would be the case were it not for ‘climate sensitivity’, a notion introduced by climate scientists to get their models to run properly (ie. show a lot of warming). The premise is that more heat retained means more clouds and more heat and therefore more rain, and so on until (in some examples) we get runaway warming, the boiling of the seas and other catastrophes. The IPCC has stuck to this view over the last twenty years and more, and offers a range of estimates for ‘climate sensitivity’ of 1.5 to 4.5 — meaning that a doubling of CO2 might lead to an increase in global temperature of 4.5 degrees C. It has maintained that range over that time, saying that it is too hard to pick up a specific number.
A lot of attention has been paid to ‘climate sensitivity’ in the past decade, and for good reason. Indeed, I’ve written about it about a dozen times (e.g. here).Without a good deal of climate sensitivity, there is no real AGW scare. The following diagram, courtesy of Jo Nova, lists the published papers on the subject, showing their estimate, and the publication date. The blue line deals with what is called ‘transient climate response’, or what will happen in the next couple of decades. The red line deals with ‘equilibrium climate response’ — what happens when everything settles down, perhaps a century from now. You will see that both lines converge towards unity, because the more recent publications present much lower estimates. Unity, of course, means that a doubling of CO2 leads to a one degree C increase in global temperature.
I should add that an equally plausible view of it all says that more heat means more clouds, which mean greater reflectivity from the greater cloud mass, which means a reduction in temperature reaching the earth, and therefore a negative feedback, akin to the work of a thermostat. Since the temperature of the earth, as measured by palaeontological proxies, suggests that for the most part temperature remains within a fairly narrow range, there is obviously something to the negative feedback hypothesis. On the face of it, human contribution to global warming seems to be slight, though real.
4. Is the global warming likely to lead to a dangerous increase in sea levels?
I have been writing about sea levels a lot in the past year or two (in fact a dozen times in six years, most recently here), and have yet to be convinced that there is anything to be worried about with respect to our country in the slow rise in sea levels that has been occurring for the past few thousand years. Tide gauges are the best indication of what is happening locally, and they present no real cause for alarm in most parts of the world, on average about 1.7 mm per annum over the last century or so. Sea-level changes can be misleading, because land can also rise and fall. But southeastern Australia is geologically stable, so the tide gauges there are decently reliable. Yes, satellite altimeters show an increase in sea level of around 3mm per annum on average, and even such an increase, if it were real and everywhere, would allow ample time for ordinary defences against the sea. But calibrating tide gauges and the satellite readings cannot yet be done without heroic assumptions. Judith Curry’s long series on sea levels at Climate etc (perhaps start with this one, which discusses satellite altimetry) is compulsory reading if you want to get into this subject. Her last essay concentrates on the US, and her conclusion is that sea-level rise is real, and that communities likely to be affected should prepare for it. But in her view CO2 is not the real problem, while land use, population movements and vertical land movement are much more important.
The sea level rises for two principal reasons. As the oceans get warmer their volume increases, and melting land ice from glaciers, Greenland and Antarctica plays a part too. The difficulty is that anyone developing a ‘budget’ for sea levels is faced with the need to make other heroic assumptions. Some glaciers are retreating and others are advancing (there are about a quarter of a million of them) while Greenland and Antarctica are difficult field sites. Sea ice is irrelevant.
Sea level does not seem an immediate problem for much of Australia. And there is some evidence that the oceans are cooling.
5. The use of computer modeling to predict future climates
Ten years ago claims were made that improved computer power and improved modeling would solve all the problems of prediction. We don’t hear such claims so often now, and in fact, while there have been some advances, the fundamental problems remain. There are three of them. The first is that wherever we live we really need to know about our own particular climate, our own precipitation, our own floods, droughts and fires. But that is hard to do, because the global circulation models can’t easily be broken down into regional models (though attempts do exist). The second is that the chaotic element in weather and climate has not been dealt with. The third is that even the IPCC admits that our knowledge of clouds and their consequences is ‘low’. It is perhaps for these reasons that IPCC ‘projections’ of global temperature increases in AR4 and AR5 proved to be much too warm.
6. The reluctance to admit uncertainty
It should be clear now that everything we think we know about climate is surrounded by uncertainty. Some of that uncertainty is acknowledged (rarely), but on the whole those who push the AGW scare hardly ever refer to error bars, sampling error, measurement errors, empty cells, and so on. That was true in 2008. Sadly, it remains true today.
7. So, finally, what should we do about it all?
Our present Government is trying to do the impossible: somehow organise electricity supply so that it is cheap and reliable, while remaining ‘true’ to the Renewable Energy Target (RET). It simply cannot be done. Coal has become demonised, though it is the core of our electricity system. While we have a putatively ‘conservative’ government, its leading members, including the Prime Minister, are quite unwilling to educate the Australian community about the realities of ‘climate change’. Perhaps they don’t even understand them. There seems to be no real threat from ‘climate change’ to anyone in our country. There hasn’t been any evidence of harm since the late 1980s, when James Hansen told the world that doom was coming. In fact, quite the contrary. Agricultural productivity has benefited from the extra carbon dioxide available, while the planet, according to satellite imagery, is noticeably greener than it was. Extra CO2 allows plants greater vigour without the need for extra water. Supposed links from examples of ‘extreme weather’ to ‘climate change’ have no foundation in evidence, and are bogus.
Carbon taxes are not much talked about any more, but the RET is the kind of government commitment that has the effect of a tax, on everyone and on every productive enterprise. It is, quite simply, a kind of madness. It doesn’t matter what Australia does. A week’s activity in China will obviate any reduction in greenhouse gas emissions that Australia makes. If we were true to these CAGW beliefs we would not sell coal at all to anyone. That wouldn’t stop Chinese emissions: China would simply buy the coal it needed from elsewhere, but it would at least show that someone actually took it all seriously. What we have, at the government level, is out-and-out hypocrisy.
That we continue to export coal, while retaining an RET, is fatuous. Its only rationale is the fear of losing votes. And there’s the rub. The Labor Party has announced that if elected it will be even sillier, if that is possible, than the Coalition. To repeat: on the evidence, ‘global warming’ is not harmful to people, the planet or to eco-systems now, and for an extraordinarily long time, if then. ‘Climate change’ is not, on the face of it, due to human activity, at least to any noticeable degree. The two terms make up a semi-religious belief, as one can see by reading any Greens material on the issue.
That we have endured it for so long is almost incredible. Worse, I don’t see any sign of a quick back-track.
LATER: Frequent commentator David (and others from time to time) find it hard to understand about the rise and rise of CO2 over the last half-century, along with the rise and then relative stasis of ‘average global temperature’ Though I have provided this diagram before, perhaps it’s time to show it again:
Yes, there has been a rise since 2016 (and then a more recent fall). It’s not too difficult to understand, and just a casual glance might make a reader wonder about the imagined CO2 control knob.