This is a question for which I am unable to find a answer. I see a lot of claims that AGW is a scientific theory and how all scientific theories are uncertain but there is a strong possibility as claimed by IPCC, that AGW theory is probably correct in representing the cause of global warming.
Now as I understand it the claim of the AGW science can be surmised as follows-
CO2 is a greenhouse gas. CO2 occurs naturally but are also human genenerated. It is the human made CO2 that has seen a sharp hike due to industrialization, which is leading to global warming
Now we know from Karl Popper that a good test to discriminate a theory from a tautology is the test of falsifiability. Theories are always falsifiable where tautologies cannot be falsified.
As I see it, AGW theory or the AGW proposition cannot be falsified. Of course we know CO2 (which includes human made CO2) has a positive impact on temperature. As the AGW scientists point out with great delight, this is basic physics and only daft people will go against basic physics) But scientists who are sceptics are not daft people, so they are not criticising AGW theory on this ground (although majority of the AGW lobby here would like us to believe they are). They are saying 80% of the climate is affected by water vapour and clouds (there are other factors like aerosols that also may affect the temperature) and CO2 and more specifically man made CO2 influence is relatively insignificant.
From this perspective we can see that the AGW theory is unfalsifiable. If the temperature rises, the AGW scientists will claim that this empirical data validates the AGW theory, but if the temperature goes down in future, this will not falsify the theory as the AGW scientists will point to other factors (the other 80%) like cloud cover or aerosols for this decline.
So the AGW theory is unfalsifiable. So if it is unfalsifiable, is it a theory? or perhaps Popper got it all wrong.
Originally posted by What's in your mind: As I see it, AGW theory or the AGW proposition cannot be falsified. Of course we know CO2 (which includes human made CO2) has a positive impact on temperature. As the AGW scientists point out with great delight, this is basic physics and only daft people will go against basic physics) But scientists who are sceptics are not daft people, so they are not criticising AGW theory on this ground (although majority of the AGW lobby here would like us to believe they are). They are saying 80% of the climate is affected by water vapour and clouds (there are other factors like aerosols that also may affect the temperature) and CO2 and more specifically man made CO2 influence is relatively insignificant.
Just for the record, the statement "80% of the climate is affected by water vapour" sounds a little bit daft, scientifically speaking. What part of the climate is NOT affected by water vapour? (only kidding).
I guess what you mean is that almost 80% of the greenhouse effect is caused by water vapour... (and just as well, 'cos without it, we'd all freeze). That's true -- but this does NOT mean that that the role of CO2 is unimportant... or that anthropogenic CO2 emissions are insignficant.
The amount of water vapour in the atmosphere isn't substantially changing, where as CO2 concentrations have risen dramatically and continue to do so... due to human emissions. [/QUOTE]From this perspective we can see that the AGW theory is unfalsifiable. If the temperature rises, the AGW scientists will claim that this empirical data validates the AGW theory, but if the temperature goes down in future, this will not falsify the theory as the AGW scientists will point to other factors (the other 80%) like cloud cover or aerosols for this decline.[/QUOTE] Right now, AGW scientists don't think any substantial increase in negative forcing factors (like say, a huge increase in stratospheric aerosols or a major drop in total solar irradiance) is likely to happen. So, if temperatures fall, while C02 continues to rise, this prediction will be falsified.
In any case, if temperatures were to fall, it certainly wouldn't be scientifically acceptable for AGW scientists just to *speculate* that some mysterious feedback mechanism is causing the cooling and then claim that they still know what's going on... which I think is what you're suggesting they would do.
Instead, what we'd need to do is identify the cooling mechanism, figure out how it works -- then develop an updated theory, incorporating this new understanding. Then, we'd need to TEST the new theory, by factoring it into new climate models... and running a reconstruction to see if the new model predicts the hitherto unexpected drop in temperatures. Falsifiability once again, you see.
A final point: skeptical theories about climate change are falsifiable too. If temperatures continue to rise, along with C02 concentrations (as expected by AGW supporters) and there is no corresponding rise in solar activity or cosmic ray flux to provide an alternative explanation, then the hypothesis that one or both of these factors is driving the warming trend will be falsified.
As far as AGW scientists are concerned, indeed, these hypotheses have already been falsified -- since the relevant factors have not been showing any recent sign of rising dramatically. Time will tell whether or not the falsification continues.
* Free-thinking does not just mean choosing to believe whatever makes you feel good. There's no thought at all in that. *
So you are saying if the temperature falls in the near future, the CO2 theory will be falsified?
Do you think the AGW scientists themselves will agree to this statement. Of course we know there are huge uncertainties in the science of aerosol cooling as acknowledged by the IPCC itself, so for all we know aerosol CAN cool in the atmosphere in the near future. Now if aerosol cooling did not falsify the CO2 theory for the cooling period between 1940-1980, why it should do the same for any future cooling period that can be attributable to SO2?
The whole discussion is actually about the relationship between CO2 production by humans and whether it has a significant effect on the earth's climate given the climate's current balance.
There is a hypothesis that growth in anthropic CO2 currently has a significant forcing effect on climate that will lead to severe and dangerous consequences including passing certain trigger points where extra positive feedbacks will make the climate worse and average temperature rise significantly.
That is fine as a scientific hypothesis and measures can be created to quantify climate eg. Higher average temperature, rate of melting of ice, warming rate of the sea, average wind strength etc etc.
The difficulty comes in attributing changes in these quantites to a single variable because instead of their being a set of independent variables, there are a set of dependent variables. Each individually can be shown to have an effect (positive or negative) in the laboratory by experiment. But the only system big enough and complex enough to combine them is the atmosphere itself ie the thing being measured.
eg. If CO2 causes some warming (as it surely would do on its own) that increase in temperature will force more CO2 from the sea, will create more evaporation from the sea which will carry significant amounts of latent heat into the higher atmosphere and cool the sea, the water vapour will cause even more warming (as if on it's own) but also more clouds may form so cutting out the more of the sun's heat and so reducing the warming effect of the sun. Additionally when the clouds precipitate as rain the latent heat will be released at a higher point and much will escape from the earth as radiation into space.
So in this oversimplified model. CO2 creates extra temperature which creates extra cooling.
Hence the hypothesis to be tested has to combine all of these and other relevant factors into a model that can make a prediction of how the specified quantities will change.
There are 3 possible outcomes
1) The earth continues to heat with added CO2 and at some point a runaway occurs.
2) The temperature and other measures oscillate around a mean and no significant long term serious effect occurs.
3) The temperature drops significantly because the combination of feedbacks have the opposite effect and trigger a significant drop in temperature eg. Gulf stream stops, New ice age in northern hemisphere, much hotter at equator because heat can't flow away but as it's significantly hotter much more heat is lost through good old Boltzman's relationship of T raised to the power 4 so overall planet's average temperature is forced lower.
Have the current models used to predict Climate eliminated points 2 and 3 from the picture with significant confidence?
Or maybe the prediction should be that 1 & 3 are in violent oscillation?
Or aren't the models/computing sophisticated enough yet to predict any of these outcomes with measurable statistical confidence?
Thanks for the post Son of Mulder. It certainly helps. Now if you can explain this to me it will be even better- can the models show if we control CO2 emission at the margin, i,e control man made CO2 emission (imagine the AGW scientists are omnipotent and can determine the level of man made CO2 in the atmosphere), we can predict with high confidence what the future temperature will be?
Thanks for the post Son of Mulder. It certainly helps. Now if you can explain this to me it will be even better- can the models show if we control CO2 emission at the margin, i,e control man made CO2 emission (imagine the AGW scientists are omnipotent and can determine the level of man made CO2 in t
Originally posted by What's in your mind: So you are saying if the temperature falls in the near future, the CO2 theory will be falsified?
Do you think the AGW scientists themselves will agree to this statement. Of course we know there are huge uncertainties in the science of aerosol cooling as acknowledged by the IPCC itself, so for all we know aerosol CAN cool in the atmosphere in the near future. Now if aerosol cooling did not falsify the CO2 theory for the cooling period between 1940-1980, why it should do the same for any future cooling period that can be attributable to SO2?
Good question. The difference is, we don't expect SO2 levels to increase enough to cause such a cooling effect -- not unless massive volcanic erruptions caused a huge natural increase in S02. That unlikely event aside, if emissions of both greenhouse gases and aerosols continue at predicted rates, then according to mainstream AGW theory there should be no cooling trend. Even allowing for the uncertainties about S02 acknowledged by the IPCC (which aren't as huge as you think), this just isn't expected.
So if there is such a cooling trend -- what exactly will be falsified?
I don't think it would cause many scientists to doubt basic physical facts about C02, i.e., that it absorbs infrared radiation and therefore, will have a warming influence on global temperature (as do water vapour, methane and other greenhouse gases). As you've rightly pointed out, scientifically informed AGW skeptics don't dispute these basic facts about CO2.
But mainstream AGW theory is based on a range of widely accepted calculations of the relative POWER of the various different forcing effects, both positive and negative. So far, these calculations, when used in climate models, produce results that fit the available data impressively well. But science is always provisional. If there were an unexpected cooling trend, as we've discussed, it would mean that one or more of these calculations must be wrong. This would mean that the impact of rising CO2 is less significant than currently believed -- and that negative factors and/or negative feedback mechanisms, are more important that we thought.
So yes, I'd expect AGW scientists to agree that the current theory it is empirically falsifiable in this way. If global temperatures fall, while C02 continues to rise -- then assuming there's no obvious explanation for this (like a massive volcanic erruption, as I mentioned above), the theory will have been falsified.
By the same token, if temperatures continue to rise with SO2, as AGW theory predicts -- while the various alternative candidates which some skeptics claim are driving temperature (e.g., solar activity etc.), fail to rise accordingly -- then these skeptical hypotheses will be falsified.
There is another conceivable way in which AGW theory might be falsified -- although its a bit far-fetched. Suppose we found some technology for reducing C02, and brought it right back to say, 1930s levels... but in spite of that, temperatures continued to RISe. Well, then it'd be pretty obvious, something else is driving global warming!
I hope this helps.
* Free-thinking does not just mean choosing to believe whatever makes you feel good. There's no thought at all in that. *
By the same token, if temperatures continue to rise with SO2, as AGW theory predicts -- while the various alternative candidates which some skeptics claim are driving temperature (e.g., solar activity etc.), fail to rise accordingly -- then these skeptical hypotheses will be falsified.
That particular hypothesis (solar activity) may be falsified but it still won't follow that the CO2 link is established. For example, I haven't seen any discussion of the possibility that the warming trend is predominantly a natural climatic variation - not driven by anything that has yet been identified.
Accepting that GHGs in general (including CO2) have a general warming influence, it's still quite possible that the warming trend will continue despite best effors to constrain CO2 emissions. We may expend huge resources on what may be a futile attempt to turn back the tide - resources which would have been better applied in finding ways to adapt to a warmer world and seeking ways to ameliorate adverse effects.
Now if you can explain this to me it will be even better- can the models show if we control CO2 emission at the margin, i,e control man made CO2 emission (imagine the AGW scientists are omnipotent and can determine the level of man made CO2 in the atmosphere), we can predict with high confidence what the future temperature will be?
Well if CO2 is reduced by the Omnipotent then It might get a bit cooler, the sea would disolve more CO2 from the atmosphere, become more acidic as the earth gets cooler but there would be less evaporation from the sea so less cloud, less loss of latent heat of evaporation, less blocking of the sun's heat causing warming, less water vapour causing less Global warming and well it might get cooler or it might get warmer. Who knows? What do you think?
Hey I think you got it right. It might get cooler and it might get warmer. Doing something at the margin means nothing. Now I wonder why the AGW scientists do not point to this simple fact
Hey I think you got it right. It might get cooler and it might get warmer. Doing something at the margin means nothing. Now I wonder why the AGW scientists do not point to this simple fact
There must be an authoritative peer reviewed paper somewhere explaining whether this is right or wrong, since there seems to be a lot of authoritive sounding speculation about AGW its existence and its cures everywhere I look.
There must be an authoritative peer reviewed paper somewhere explaining whether this is right or wrong, since there seems to be a lot of authoritive sounding speculation about AGW its existence and its cures everywhere I look.
Yes, you would expect that won't you? But going by the strange silence from the AGW lobby here it seems no one has got around asking this question yet
I am really surprised by the continuing silence of the AGW lobby on the issue of the peer reviewed science that claims that global temperature can be stabilized/ controlled by controlling CO2 at the margin. I hope they come up with something as it is unbelievable that the whole AGW enterprise is not based on any science.
In the meantime, we can read the abstract of this paper, which claims sulphar aerosols will have significant effect on future temperature which goes quite contrary to the claims made here by the AGW lobby that sulphar aerosols will not have any significant effect in future climate change. Happy reading
On Modification of Global Warming by Sulfate Aerosols
. F. B. Mitchell and T. C. Johns
Hadley Centre for Climate Prediction and Research, Meteorological Office, Bracknell, Berkshire, United Kingdom
Volume 10, Issue 2 (February 1997)
ABSTRACT
There is increasing evidence that the response of climate to increasing greenhouse gases may be modified by accompanying increases in sulfate aerosols. In this study, the patterns of response in the surface climatology of a coupled ocean–atmosphere general circulation model forced by increases in carbon dioxide alone is compared with those obtained by increasing carbon dioxide and aerosol forcing. The simulations are run from early industrial times using the estimated historical forcing and continued to the end of the twenty-first century assuming a nonintervention emissions scenario for greenhouse gases and aerosols. The comparison is made for the period 2030–2050 when the aerosol forcing is a maximum. In winter, the cooling due to aerosols merely tends to reduce the response to carbon dioxide, whereas in summer, it weakens the monsoon circulations and reverses some of the changes in the hydrological cycle on increasing carbon dioxide. This response is in some respects similar to that found in simulations with changed orbital parameters, as between today and the middle Holocene. The hydrological response in the palaeosimulations is supported by palaeoclimatic reconstructions. The results of changes in aerosol concentrations of the magnitude projected in the scenarios would have a major effect on regional climate, especially over Europe and Southeast Asia.
There is increasing evidence that the response of climate to increasing greenhouse gases may be modified by accompanying increases in sulfate aerosols
Wot, like before the clean air acts?
And if CO2 reduction at the margin is ineffective?
What other economic, realistically feasible, safe technologies are there that could be employed (emphasis on economic, realistically feasible, safe), without having to eliminate oil & coal, and still enabling rapid economic growth for the rest of the 2nd/3rd world.
I'll start with nuclear fission as an energy source and atmospheric aerosol or orbiting veil of some sort of reflective dust if needed. Safe if managed properly.
As the man said bring me solutions not problems, by which he means safe solutions.
Originally posted by What's in your mind: I am really surprised by the continuing silence of the AGW lobby on the issue of the peer reviewed science that claims that global temperature can be stabilized/ controlled by controlling CO2 at the margin. I hope they come up with something as it is unbelievable that the whole AGW enterprise is not based on any science.
In the meantime, we can read the abstract of this paper, which claims sulphar aerosols will have significant effect on future temperature which goes quite contrary to the claims made here by the AGW lobby that sulphar aerosols will not have any significant effect in future climate change. Happy reading
On Modification of Global Warming by Sulfate Aerosols
. F. B. Mitchell and T. C. Johns
Hadley Centre for Climate Prediction and Research, Meteorological Office, Bracknell, Berkshire, United Kingdom
Well, I'm not part of the “AGW lobby”, and since I'm only fooling with this website in odd hours of a ski vacation, which ends tomorrow, other rational people will have to take up the cudgels, but I’ll do this one, because it was just so funny.
The article was slightly mis-cited: it’s John F.B. Mitchell or JFB Mitchell. For reasons that will become apparent later, this particular choice of article & authors was … hysterically funny, and is quite revealing of “What’s In Your Mind “(WIYM)’s level of competence and knowledge.
Let’s evaluate this article, like I would do for any other: - Hadley Centre is one of the key centers for climate modeling in the world. [Good start]
- The Journal of Climate is a top-rank journal (American Meteorological Society). [Good]
- The authors have massive relevant publication records. [Good] I could find this via Google Scholar … but in this case, I already knew the answer, because I recognized one of the names offhand … and laughed.
- From the abstract [and I laughed there also], I knew what it was about, but since the article is freely-accessible, I read it also, and would encourage people with technical backgrounds to read it as well, to make sure I’m not misrepresenting it: http://ams.allenpress.com/perlserv/?request=get-documen...AOMOGWB%3E2.0.CO%3B2
I briefly summarize it as: - It uses computer models for quantifying the effects of AGW, whose existence is not doubted by the authors.
-It says that the cooling effects of sulfate aerosols will lessen the warming, locally, in some areas, in particular, SouthEast US, Eastern Europe, and Eastern China (see Figure 1). This effect, of course is believed to have contributed strongly to the cooling of 1940-1970, which ended as Clean Air Acts became more effective, to lessen acid rain. This is quite familiar to climate scientists. I don’t understand where WIYM gets the idea that people ignore sulfates. The IPCC certainly doesn’t: http://www.grida.no/climate/ipcc_tar/wg1/172.htm#5226]
They note that to actually get the modeled lessening of warming: “this would lead to severe problems with acid rain.”
And they conclude:
“The implication of our findings is that some of the changes in hydrology predicted to occur with increases in greenhouse gases may be less extreme in the short- and medium-term future (several decades). This situation may not prevail in the longer term—sulfate concentrations will be maintained only as long as sulfur emissions continue, whereas CO2 has a lifetime of a century or so, ensuring that concentrations will remain high for many decades to come.”
They’re saying that if we accept really, really bad acid rain, maybe we can temporarily slow AGW down for a few geographic areas, for a few decades.
SUMMARY: - far from being sceptical of AGW, this paper does detailed modeling of the amounts to be expected, and it models scenarios to account for sulfate aerosols. -it has nothing to do with quantifying natural-vs-anthropogenic warming or the effects of reducing the growth rates in anthropogenic CO2. If you had wanted papers about that, the same people have co-authored papers like:
Estimation of natural and anthropogenic contributions to twentieth century temperature change JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 107, NO. D16, 4306, doi:10.1029/2000JD000028, 2002 http://www.agu.org/pubs/crossref/2002.../2000JD000028.shtml I used to be an AGU member, but not lately, so I didn’t bother to spend $9 to see the article, but the abstract is enough.
And
The effect of stabilizing atmospheric carbon dioxide concentrations on global and regional climate change Geophysical Research Letters, Volume 27, Issue 18, p. 2977-2980. Here’s a URL for an abstract: http://adsabs.harvard.edu/abs/2000GeoRL..27.2977M
But neither of those would give any comfort whatsoever to a denialist. ===== Now, why was I so amused, that WIYM picked this particular article?
First, it is obvious that the abstract is not an AGW-sceptic article.
Second, if one wants to pick an article to show AGW scepticism, it might be nice to read the article. WIYM either didn’t bother, or couldn’t understand the article or the abstract.
Third, it is truly hysterical to cite Tim (TC) Johns and John FB Mitchell as AGW sceptics. Even the mention of Hadley Centre should make someone think twice. Of all the people in the world to pick… :-)
Professor John F B Mitchell OBE FRS is Chief Scientist at the UK Met, where he took charge in 1978 of the Climate Change group (which became the Hadley Centre). His specialty is the study of the climactic effects of increases in greenhouse gases and related pollutants. HE HAS BEEN A LEAD AUTHOR IN THE LAST 3 IPCC WORKING GROUP I REPORTS!!
Mitchell has thus been a strong supporter and modeler of AGW for decades and a key IPCC person.
This is all just too funny.
Presumably the thoughtful reader will use this to assess WIYM’s competence and knowledge in this topic, and remember this for any further WIYM postings. Related discussions are in other threads, and somebody might choose to augment them by pointing at this post, but vacation is over, so I'm done. Good luck there in the UK.
