Global warming and falsifiability.

I’m not interested in debating whether global warming is real or not (I know for certain that temperatures are rising), but how can the theory that humans are causing global warming be falsified? We don’t have another “control” Earth without the presence of humans, for instance, so how is it possible to even test the theory? Scientists may point out that global temperatures have increased rapidly since the industrial revolution, and this in itself is indirect evidence that we are the cause, but is this really good science, seeing as it’s impossible to know exactly what would have happened without the presence of humans?

Climatologists, meteorologists et al, is there any hard evidence that humans are to blame for rising temperatures?

We don’t, of course, know exactly what would happen without humans. However, there have been periods of rapid warming in the past. In these cases, paleoclimatologists have usually been able to identify a cause. These causes appear to be absent in the present case, or at least don’t explain the present extent of warming, leaving humans holding the bag. We’re standing around with a smoking gun and the usual suspects are nowhere to be seen.

The case is largely circumstantial. However, I think many people have been hung on the basis of worse evidence.

What are the other causes of global warming. I remember hearing about a study about a year ago that there was a larger global warm-up in the high middle ages @ 1200 AD. What “usual suspects” are missing now?

Natural causes of warming periods can include the activity of the sun, the wobble of Earth’s orbit (Milankovich cycles), vulcanism, and changes in albedo… there are probably others, but I can’t claim to know them all.

I’m not sure about the period in the 1200s of which you speak, so I can’t comment on that.

It’s also not necessary that the “usual suspects” be missing, just that their mode of action be inconsistent with observed composition of the atmosphere, position of the Earth relative to the sun & all that kind of stuff.

Try this :-
http://news.bbc.co.uk/1/hi/sci/tech/4636115.stm

It is evidence of a medievla warm period bewteen 800AD and 1300AD as well as the little ice age between 1400 and 1850.

The site has links to other evidence that global warming is occuring and that humans are to blame.

One other thing. I think the OP is confusing whether or not something can be falsified with the fact that in science nothing can be “proven” with absolute certainty. If a hypothesis can’t in principle be subjected to a test that would prove it wrong, then it isn’t science. But hypotheses can never be absolutely proven to be correct; they can only be demonstrated to be consistent with the evidence. If hypotheses have repeatedly been subjected to strong testing and not been falsified, then they are accepted. This does not mean no doubt whatever can remain about whether they are correct.

Anthropogenic global warming could be falsified if:

  1. Humans were not producing carbon dioxide at a rate capable for accounting for its accumulation in the atmosphere.

  2. Carbon dioxide did not act as a greenhouse gas and cause global warming.

  3. Volcanic eruptions over the past couple centuries had introduced much more carbon dioxide into atmosphere than humans had.

And so on.

The hypothesis that humans are responsible for global warming has been tested repeatedly, and has not been falsified. Most competing hypotheses have also been tested, and have been falsified. That is why a large majority of climate scientists today believe that humans have been responsible for the global warming we see today.

You say that paleoclimatologists can usually find a cause. Are the cases of warming in which they cannot find a cause due to them being too far back in history or are they true mysteries?

Sorry, I pressed reply too quickly.

But surely this smacks of scientists approaching the evidence with a preconceived idea of what is the cause? For example, if I were to investigate a certain phenomenon and approach the evidence with a list of three possible causes, two known to produce certain effects consistent with the evidence gathered and a third oddball one like “elves did it”, after discounting the first two possible causes, it wouldn’t be reasonable to assume that the third is necessarily true, would it?

I should note that I’m playing Devil’s Advocate a bit, here.

I am not aware of documented instances of global warming in the past which might be regarded as “true mysteries” in the sense that the usual causes can be ruled out.

“Elves did it,” or anything similar, would not be a scientific hypothesis (since it would not be falsifiable) and thus would not even be on the table. A scientific hypothesis must be in accord with a known mechanism in order to be accepted.

A more scientific hypothesis might be that a star passed nearby in the distant past and caused an episode of global warming. However, unless some test of that hypothesis can be devised, it would remain more in the category of an ad hoc explanation - which scientists dislike - than a true scientific hypothesis.

The problem with a thread like this is that we’re discussing things qualitatively. It’s true that there are many things that can raise the temperature of the earth - CO2 from human activity, solar activity, volcanic activity, etc. But the temperature rise from each effect can be calculated quantitatively, based on known data (amount of oil and coal burnt, measurements of solar activity, etc). If one of them fits the data much better than others, then it’s a very strong argument in favor of that theory.

If currently accepted model is incorrect, you can prove that by: (1) showing why this model does not fit data (i.e. why the previous studies showing a good fit were wrong), and (2) showing that another model does fit the observed data. One or the other would cast strong doubt on the current theory, but it takes both to shoot it down.

Global warming is just a theory. It’s not a proven fact. Scientists have some fancy computer models and such, but I think it’s safe to say that they don’t undestand the complex workings of our climate to say for certain (otherwise we’d get more accurate weather predictions). For most of its life, earth was much warmer than it is now. What we call global warming could be a return to a more normal climate as far as the earth is concerned, or it could be a slight variation like those that have occurred many times in the past.

However, if you look at the temperature of the earth over the time period that we’ve kept track of temperature, it goes up rather suspiciously hand in hand with the amount of crap that we are throwing up into the atmosphere.

The OP is correct though. It’s just a theory at this point. It’s pretty likely to be true, but it’s far from proven. I don’t think it can be proven or disproven until we understand how the earth works a little bit better. It’s a lot like smoking and lung cancer. We’re pretty sure that we see cause and effect, but it’s hard to prove it in court because we don’t understand the mechanisms involved. As far as the OP is concerned though, simply understanding how the earth works and what is actually causing the warming, and being able to accurately predict temperature swings and all sorts of other stuff (which is what scientists are trying to do) would probably be enough to sufficiently prove or disprove humans as the root cause. I don’t see how a “control” earth would be necessary.

I got into an argument with a co-worker one day at lunch by saying that global warming isn’t necessarily a bad thing. If it gets hot and moist much of the earth will be a tropical paradise, like it was during the times of the dinosaurs. It’s only if it gets hot and dry that things could get bad. Then you could have things like skyrocketing food prices, food shortages and mass starvation, and all sorts of bad things.

Maybe this should say global warming is an observation, and the idea that it is anthropogenic is a theory? I’m pretty sure our numbers on temperature are reliable, regardless of how little we understand climate as a whole.

True that it might not necessarily be a bad thing for humans in general, but given that our population and infrastructure are positioned to do well in the current climate (think agricultural breadbaskets, use of rivers for transport and avoidance of building on current flood plains), changes to the climate are more likely to cause disruption than to just be hunky-dory.

Climate change is incredibly more likely to be a bad thing for natural ecosystems, which appear to have much shorter times to respond to changes than they did in the past, and are additionally pressured and constricted by human activities. I’m not saying the Earth will turn into a wasteland; new ecosystems will take their place, but we might lose a lot of things we’d rather keep around, like coral reefs.

To be technical, both the proposition that the global climate has been becoming significantly warmer, and the idea that global warming is anthropogenic, are both hypotheses, that is, propositions subject to being tested against the evidence. Within the last decade sufficient evidence has accumulated that most climate scientists accept both hypotheses as being confirmed, but of course they can never be proven absolutely in scientific terms.

From here:

The idea that global warming is anthropogenic does not have the kind of breadth needed considered a “theory” in the scientific sense. To scientists, the term theory only applies to such broad concepts as evolution, plate tectonics, general relativity, quantum mechanics and so on, not to narrower subjects.

Ah, I see.

So “string theory” is neither scientific, nor a theory.

Cool.

String Theory is certainly scientific, since for confirmation it depends on testing falsifiable hypotheses. Since it has not been fully confirmed, I suppose it would not yet satisfy all the criteria listed, though it is still referred to as a theory because of its potential breadth of explanatory power.