If it was shown that carbon dioxide was not a greenhouse gas that would be one way. There are lots of other assumptions that go into it that would have the same effect if they were shown to be false. However, that's not going to happen--rarely do large groups of scientists come up with an idea that can easily be shown to be false, too many people would already have thought of such things. If it were the theory of a single scientist that would be a different matter. As an example, the two-time Nobel Prize winner Linus Pauling made a blunder on his proposed structure of DNA, something that was rapidly caught once he went public.
Observations could show it to be false. For some reason, many "skeptics" think that those observations should be immediately available or the theory is not falsifiable. That's ridiculous, many times in science you just have to wait until there's enough data available--that could be 30 seconds or 300 years. Much of science is dealing with the problem of finding a relative small signal in noise that may be comparable or even larger than your signal. I have worked on experiments where this no alternative but waiting. An experiment might need to be run thousands of times before you could clearly see the signal, but nobody would say after two or three runs "Clearly, it is not falsifiable", that's rubbish. Scientists with any feel for statistics can look at the year-to-year variability in global temperature and know that an increase of less than expected over a decade or two (or even a decrease) is not going to falsify, and neither will the opposite "prove" it.
Since it can be difficult to wait so long (especially since the lifetime of a grad student is only about 6 or 7 years), the theory can be examined by computer simulations based on the physical basis of the theory. Even then you may have to run the numerical experiment many times, but at least you've got a shot of doing that. What if all the climate models showed the temperature staying the same or going down with increasing CO2, rather than going up? Wouldn't THAT be a way of falsifying it?
In a practical sense (although not strictly a scientific sense) it could be falsified by showing a conflict with accepted scientific theory, such as quantum mechanics or the laws of thermodynamics. There's a German guy that's attempted that approach, by claiming that the greenhouse effect itself violates the laws of thermodynamics. Unfortunately his "papers" are gibberish mixed with politics, and have been thoroughly debunked.
If AGW is falsifiable that would it makes it scientific (according to the philosophy of science of Karl Popper). This is one of the more practical definitions of what constitutes a science.
Falsification is a test. If I can devise an experiment to try to prove my hypothesis is wrong then it is open to enquiry. The exceptions would be a technology or a pseudo-science. The experiments that are on the corner cases, testing a theory, are typically the ones most useful in science; so looking for falsification is a positive thing, even though that may seem counter intuitive.
AGW opponents want you to say AGW is non-falsifiable because that would be a demonstration (at least from your perspective) it is a pseudo-science (or religious) belief.
What would be examples of falsification - proof there was no correlation between greenhouse gas levels and climate, proof that human activity is not increasing greenhouse gasses above naturally occurring levels. Proof that climate models are not predictive. Conflict between different sources of data used to support the theory.
It's the models which is weakest at present. Our understanding of the role of atmospheric gasses upon climate is still relatively early and models often need tweaking based on live data. It isn't until the models have been functioning for an extended period without major adjustment that they will become falsifiable through the test of corner cases. Similarly the sources of data have been questioned. Like most weather phenomena climate models where we are looking to predict change are relatively sensitive. I think there is enough here to declare AGW as scientific, but the areas where falsification is possible are those that need the most exploration to demonstrate that AGW is being taken seriously.
Falsifiable means that the theory is testable. You can pull pieces-parts out - like CO2 is a greenhouse gas - and test the parts. You can also recreate past climates and see if the theory predictions are consistent with what has been observed. The scientific theories that predict global warming are mathematical equations that are falsifiable.
In contrast, a 'theory' like intelligent design is not. It cannot predict into the future, nor be used to predict the past. The parts cannot be individually tested. It is a philosophical theory - and idea or concept. It is not falsifiable.
When statements are made that temperatures are unprecedented in the last 1000 years based on a bad temperature proxy like the Hockey Stick with the modern instrumental temperature record spliced onto. It seems clear given the availability of numerous glacial borehole measurements that indicate the LIA and MWP were very real and a global phenomena, and to ignore this and use the Mann data proxy was an intentional decision by the majority of the climate research community. Testifying to congress that the warming observed was unprecedented in the last 1000 years based upon a poorly constructed temperature proxy when a much better actual temperature measurement is available is either just bad science or intentional deception, but in no way can it be considered an honest mistake.
For AGW to be falsified, it would have to be shown that adding carbon dioxide to the atmosphere has an effect of <= 0. A more practical question would be "What does it mean for 'AGW is serious,' to be falsifiable?"
To falsify AGW, you could either show that carbon dioxide is not a greenhouse gas (passed the test =/= unfalsifiable), or you could find another explanation for the warming. And with the new explanation for the warming, show that you could get a better match to temperatures by excluding carbon dioxide than by including it.
This alternative explanation is not the Sun.
http://www.woodfortrees.org/plot/hadcrut...
To falsify "'AGW is serious," burn all of the hydrocarbons in the ground, and see whether Earth cooks or freezes.
A statement or claim being falsifiable makes it the definition of a scientific statement. And the scientific method can be employed to test it and to attempt to falsify it.
If a statement or claim cannot be falsified, then the scientific method cannot be used to test it.
By the way, I agree that claiming that AGW isn't falsifiable really doesn't help much. I would call the main AGW scientific claim to be that ECS for a doubling of CO2 is 1.5-4.5C. That really isn't a falsifiable statement but we really should narrow the range.
I think the main use of "AGW isn't falsifiable" doesn't really apply to scientific hypothesis or method like I mentioned in my first para but to observations, all of which seem to support AGW. So when the pause in surface temperatures is explained away or the polar vortex is linked to melting Arctic ice we tend to say "everything is caused by AGW" which is equivalent to "AGW cannot be falsified". So that term is not used in the proper sense but I think the intent is fairly clear.
AGW hypothesis is: humans caused .8C warming of the last 250 years by increasing the amount of CO2 (and other carbon compounds) in the atmosphere from 280 to 400 ppm. The temperature will necessarily increase its acceleration as carbon increases, primarily in the middle troposphere, and will increase 6 degrees with a doubling of CO2 (when it reaches 540 ppm). Ocean waters will, as a result of higher levels of CO2, drop in pH. Global temperatures will increase (both high and low temperatures will be higher), causing climates to change. Generally, deserts will increase in size. Ice caps and glaciers will melt.
All of these things have been proven, and are unable to be falsified because that's the way it is. plllbbt
Jeff M gave a very reasonable example of what the scientific falsification of the AGWT would look like. I had earlier reduced this to being in order to falsify the AGWT you would need to find the error(s) in the Laws of Physics, Chemistry and Thermodynamics that would render the AGWT as invalid since the AGWT is fully formed from the laws of science. The observations made will also have to support the theory.
I see that Ottawa Mike and Matthew speak of the "scientific method" and I wish for either or both of them to explain just what the scientific method is.
The mainstream science on anthropogenic climate change is based on thousands of studies over the past century, which in turn are based on a massive array of empirical data and a well-developed body of theoretical models, nearly all producing consistent results. The standard science is falsifiable, but proving it false would require (a) overturning much if not most of that scientific theory and evidence, and (b) a MORE plausible and consistent explanation (other than AGW) for the portion of observation and theory not thereby overturned.
AGW is not falsifiable, because even though you can do lab experiments on certain parts of the theory, like the absorption of heat by CO2, it doesn't in anyway prove anything because it is how the atmosphere works as a whole that counts, the only way you can test it is to find another earth like our world and inject CO2 into it's atmosphere, or wait a couple of hundreds years and see what happens to our planet.
Certain Parties here keep claiming that AGW "isn't falsifiable".
I would like them to defend their case, by (at a minimum) explaining what they think something being falsifiable means. And I'd like the realists reading this to explain how AGW *is* falsifiable, perhaps by listing some things that, if they occurred, would suggest that AGW was in some way substantially incorrect.
See Russell's tea pot.
Either show us the missing heat, or stop claiming it arrived as predicted but has been mysteriously transported to the bottom of the ocean or perhaps to the inside of Russell's tea pot where no thermometer can ever record it.
Co2 levels continue to steady rise unabated. Where is the extra heat all this additional Co2 is supposedly retaining?
Global Warming's exact location was located only by figuring it out from outside our ozone, so that only iced areas on earth would and did melt starting in 1977. The cause of Global Warming was an ALIEN Organism from another galaxy 23 years from earth. My Global Teams from all walks of life ran my experiments to find a way to destroy it, but were fired upon and I ordered them out of there. Results of the exact location was observed in areas of Glaciers that freshwater on top of saltwater and Glaciers stopped melting and froze almost immediately. I had all my Teams start my first Global Warming Solution by extracting sand off the ocean floors 20 miles out and around each of their continents, so the melting Glacier's freshwater on top of the saltwater would'nt take to much dry land on all of earth's land masses, (infact their still doing this for me (Global Command-civilian) since 2008.) In 2011 I figured out a solution called Triple output and gave it to a Nation to feed their people 4 times better and after they implemented it in 2012. Global Warming ceased to exist, confirmed by our satelite reports 11/28/2012. Global Command
Falsification in any science can occur. This is what makes science science. The ways AGW can be falsified is through such things as showing CO2 is not a greenhouse gas, that the addition of CO2 into the atmosphere is not causing more energy retention at those frequencies involved, that the CO2 emitted from burning fossil fuels are not actually being emitted into the atmosphere, and so on. Every one of these aspects has been looked at and studied. Most of their argument center around one or more of these things, depending on the season.
If something is claimed that has a possibility of being true scientists will have to put devices in orbit or measure them on the ground in order to find if that possibility is true. This is what scientists do, they try and find out about the world around us. They do not base their opinions of things on some blog that they read or a biased news source.
Tomcat: Are you ignoring the error bars on Mann's hockey stick? It appears as if you are. Look at the image again.
http://yale1962.org/speakout/Photos/Hock...
Certainly with our present knowledge and technology, AGW isn't falsifiable meaning it isn't capable of being tested. For example, we don't know what the range of sensitivity is for the CO2 added. That pretends a greater knowledge than we possess. We can say that it appears to have a range from here to here assuming ...... (and it is a long list of assumptions).
Note: I wonder just what part of my answer the useful idiots who gave thumbs down disagree with. I realize when someone believes something like it is a religion, they tend to strike out at those who threaten their religion. They are among the useful idiots that Lenin talked about IMO
AGW is non-falsifiable If it were falsifiable, then at least one of these moronic people who disagree could prove it wrong. BUT they can't
Global warming fails scientific method.
