Without a doubt, climate change is one of the hottest topics at this moment. In the debate, two opposing sides – not necessarily evenly distributed – can be distinguished. On the one side we have the climate scientists, who hold the view that (i) a global warming is taking place and that (ii) human actions are the cause of it. On the other side we have the climate skeptics, who doubt that global warming is taking place and/or that human actions are the cause of global warming (if any).
Without taking sides, it is simply observable that the climate scientists claim that their views are based on science. However, to apply the term ‘science’ in this context, it is not enough to come up with a curve that fits the data: the view must be falsifiable – the notion of falsifiability is what distinguishes science from non-science. Of course a curve is falsifiable, but if new data do not fit the present curve one can always come up with a new curve that does fit the data. So, what I'm interested in is a criterion of falsifiability for the underlying hard core, that is, the aforementioned premises (i) and (ii): precisely what observations would falsify the idea that a global warming is taking place and that human actions are the cause of it?
Of course, the climate scientists’ views are falsified if a new ice age begins tomorrow. But among all possible observations that would falsify the climate scientists views, there has to be an infimum with the mildest possible observable conditions. So, the climate scientists are hereby challenged to come up with the mildest criterion of falsifiability.
Keith,
could you elaborate a little on your answer?
Which aerosols do you mean - aerosols of what? - and how would the observation of these aerosols refute the premises of human-caused global warming?
I am working on the measured total aerosol optical depth as it varies month by month across the year as well as inter-annual variability.
I have just started working on CMIP6 data and It appears that the aerosol levels in the model atmospheres are reduced significantly from the measured data. The journal atmospheric physics and chemistry has preprints of some of my papers. The paper on ENSO the IOD and drought in south eastern Australia explains why aerosols are extremely important and the supplement shows the eight continental scale aerosol plumes which now occur annually. My website https://keithpotts.net/ has details of the plumes.
Keith,
I've had a look at your material.
Correct me if I'm wrong, but as I understood it you make two suggestions:
I've a question then.
The aerosol density is inferred from satellite data, but how can the satellite discern between aerosols produced by natural sources and aerosols produced by humans? In other words: how can you infer from the satellite data which part of the observed aerosols is produced by humans?
Marcoen,
To identify the sources requires research - for example the aerosol plume over south east Asia comprises: volcanic tephra (data Smithsonian Global Volcanism Program), biomass burning (peer reviewed literature) and gas flares (industry knowledge) whilst the South American aerosol plume is only biomass burning from the clearing of the Amazon rain forest (scientific literature).
Keith,
Thanks for your reply - fair enough.
Let's assume you are right concerning the correlation between aerosol density and global warming; do you think that it is a possibility that the global aerosol density distribution could change - by a decrease in aerosol production from natural and human sources - to the extent that global warming could come to a halt (or even reverse)?
Sorry for the delay in replying.
Yes aerosols could be reduced BUT the effects of these plumes have to be recognised first or no one will be interested.
However the CMIP6 data shows a reduction in aerosols from the middle of this century - who knows why? Possibly to increase the global temperature in 2100 as the "climate industry" believes aerosols cool the world.
I happy to discuss off line and will be in Amsterdam/London later this year if that works for you
I am not a climate scientist, or even really a general fan of the science they do. I remember the issue of water vapor, they lead with their "intuition" well beyond their actual data, and it seems to be that way on a lot of issues. Too many parameters, they could fit any data. Your note that it is unfalsifiable is probably a good one.
However, the premise that "falsifiability is what makes science" is a bit too much Popper for me to let it pass without a note. Real scientists aren't really trying to falsify any hypotheses either (every paper a confirmation of this or that initial lark, and every grant proposal just writing in future tense things already worked up in notebooks).
As a Kuhnian scientist, I mostly see people working hard to recreate their received knowledge, regardless of discipline. People go to college, and then graduate school and postdocs etc, because they value the information they have learned, and they generally use it being correct and useful as a starting point for inquiry. This is not bad, but it makes people more and more committed to ideas the longer they have worked at understanding them.
This is quite different from falsifiability. There is loads of evidence general relativity fails outside the galaxy, and on average it would seem the failure far outweights its success. Additionally, it is not entirely reconcilable with quantum field theory... so a standard model that admits GR is both unfalsifiable (or at least currently calling those falsifications "dark energy" and "dark matter" that result from its inclusion) and possibly incoherent (having it both ways about negative mass antimatter for example).
The suggestion of Kuhn is that, because general relativity involves lots of very hard math (the paradigm), that the people who have learned it are unlikely to be able to toss it aside, even when overwhelming evidence is presented, until such a situation leads to a huge breakdown or a crucial experiment. For the general relativists, this will probably be when antimatter falls up instead of down.
So for the Kuhnian philosopher of science, the question is not about falsifiability, but about a crucial experiment: what results would lead those who follow the paradigm to change their minds?
Seems like there are a number of results that we would / could get here that would meet that condition: if the CO2 kept climbing and yet global surface temperatures didnt increase, if humans adequately sequestered their CO2 output and stopped the gasses climbing that would change some of the extrapolations, if solar became much cheaper than gas energy, say because of a war... all sorts of things that could change the paradigm in climate science, because its brand of unfalsifiability is extremely data driven... to the Kuhnian, it doesn't really matter.
Best,
Evans
Started to look at CMIP6 data from the HadGem3, CESM2 and CSIRO climate models which also show that aerosols are the main cause of climate change!!
Hi Evans,
I did not have a particular framework of falsificationism in mind with my question on the falsifiability of the climate scientists' views.
Of course Popper's idea of instant rationalism, by which a theory is instantly rejected upon falsification, has been superseded by Kuhn's idea of scientific revolutions, where one paradigm is superseded by another one after a prolonged crisis period.
But then Kuhn's framework has been superseded by Lakatos' idea of research programs, where one research program is superseded by another one on rationalistic grounds, but only after a prolonged battle of research programs.
I myself view the scientific landscape in terms of research programs, but regardless whether one sees the climate scientists' views (i) and (ii) - see the original question for the formulation - as a Popperian theory, as a Kuhnian paradigm, or as the hard core of a Lakatosian research program, in one way or the other these views have to be falsifiable to be viewed as 'scientific'.
I'm not a climate scientist, but I'm interested in what observations we would have to make in order for the climate scientists' theory to be falsfied c.q. for the climate scientists' paradigm to end up in a crisis c.q. for the climate scientists' research program to become degenerative.
Keith has suggested an answer; what else is there?
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