> what would falsify the theory that humans are causing global warming and this is a bad thing.
For example,
(1) A novel physical mechanism is discovered that increases the surface temperature of the Earth without any relation to greenhouse gases. Moreover, the mechanism has such a characteristic that it was steadily increasing in the past fifty years or so, roughly matching mankind's CO2 emission by pure coincidence. (I.e., "mankind is fucked, the universe decided to kill us off" scenario.)
(2) Average global temperature starts to drop unexpectedly, and continues to drop for a decade or more (so that we can rule out yearly statistical noise), despite the increased level of CO2.
(3) A new natural source of CO2 is discovered, and it is determined that the atmospheric increase of CO2 so far was actually due to this natural source. At the same time, a new independent natural sink of CO2 is discovered, and it is also determined that all the CO2 mankind has been generating was actually consumed by this sink. Even more unexpectedly, this big CO2 producer/consumer pair, while being pretty much in lockstep until 2015, is shown to diverge starting 2015, which refutes the whole point of "Mankind is responsible for increased CO2" argument. (This actually sounds like a variation of (1), but still.)
(4) Fish stocks and marine ecosystem unexpectedly starts to rebound across the ocean, thanks to increased photosynthesis by marine microorganisms. Upon further research, this is found to be linked with increased CO2 level. (This will at least partially falsify "this is a bad thing" part.)
I know, these are tough scenarios, but falsifying established science is hard. Falsifying it in a way that disproves its original successful predictions is even harder: it almost never happens. (Even after General Relativity and Quantum Mechanics, if Newtonian mechanics had predicted a railway to be dangerously curved, it would still remain dangerous in exactly the same way.)
It's actually much easier to falsify the "this is a bad thing" part. All we have to do is wait and see if it really is a bad thing or not. The length of time to wait should be about 100 years since that's also the limits of most of the AGW predictions.
Your point (1) has a huge assumption about "kill us off". There's no sign that mankind is being killed off. We're doing just fine. The novel mechanism might be transient and the increases in CO2 might be found to reverse.
I don't know about you, but if the universe has a hidden inexplicable mechanism that started to slowly increase the temperature of the Earth fifty years ago, I would be very, very worried. Like, frog-in-a-slowly-boiling-pot worried.
Sounds like you would actually prefer that scenario to the mundane scientific consensus, where all we have to do is demolish the fossil fuel industry, cut back CO2 emission, and hopefully we could keep the number of displaced people in the order of several millions by the end of this century. Well, to each his own.
> I know, these are tough scenarios, but falsifying established science is hard.
It is also very hard to falsify the theory that invisible pink unicorns are causing global warming. It's not necessarily a good thing that a theory is hard to falsify.
For 2): there has been a 15-year global warming pause, which none of the models predicted. With your definition 2), that's actually close to a falsification of AGW.
If there wasn't, why did everyone, including leading climate scientists and the IPCC, say there was [1]?
A point I do agree on, which was also the point of my comment: a 10 or 15 year period is too short to say anything about climate. A pertinent question is then: what is a long enough period?
Ehm, no. The pop-sci reporting on that study had a very misleading title; the pop-sci report in Science was titled
"Evidence Against a Global Warming Hiatus?"
based on the scientific paper titled
"Possible artifacts of data biases in the recent global surface warming hiatus"
Also, that is a single paper, based on adjusting historical temperature data for a single data set, which then shows less of a hiatus. Compare that to the fifth IPCC report, based on a large number of data sets and a very large number of studies, which states unequivocally
“[global temperature] has shown a much smaller increasing linear trend over the past 15 years [1998-2012] than over the past 30 to 60 years.”
Look at the biased language here - "pause" implies that it's temporary. But it hasn't finished pausing yet and since our models didn't predict the pause, we don't know when or if it'll finish. It should be called a "stop".
>
Average global temperature starts to drop unexpectedly, and continues to drop for a decade or more (so that we can rule out yearly statistical noise), despite the increased level of CO2.
No, it doesn't have to drop. It just has to not rise. Which is exactly what has been happening for close to two decades now.
Furthermore, the level of CO2 has not just increased--it has increased by close to the "business as usual" scenario in the models--i.e., the worst case scenario, which the models predicted would show significant temperature rise that has not happened. In other words, the models have already been falsified.
> falsifying established science is hard.
Climate science is not "established science" in the way that GR or QM is. Falsifying GR or QM within their established domains of validity would be extremely hard, yes--but that's because their established domains of validity are nailed down by mountains of evidence from controlled experiments that matches the theoretical predictions to ten or more decimal places. Climate science is not even close--not even within orders of magnitude--to that kind of accuracy.
In fact, we should not expect climate science to be anywhere close to GR and QM in accuracy, because it's still a fairly new science, its domain is very complex, and it's not possible to do controlled experiments in most of the domain. We can't re-start the Earth's climate of fifty years ago with slightly different initial conditions and see how it performs.
None of this, in itself, disqualifies climate science as a science, or means that climate scientists are not doing important work. But it does mean that climate science simply cannot make the kinds of claims that GR or QM make about what is going to happen if we do or don't do particular things. The honest thing for climate scientists to do would be to admit that.
This[1] is the first Google result for "has the global warming stopped".
In addition, this is an interactive page that lets you plot yearly global temperatures up to now. Now look at this graph and please tell me if temperature did not rise in the 21st century.
Finally, this page [2] compares IPCC's 2001 prediction with observed temperatures up to 2010. Look at the graph titled "2001 Projections vs. Observations", and see how closely the prediction matches reality starting 2001. (Which is not surprising, considering that it's only 10 years.) And now ponder what would happen if this "trend" continues for another 90 years.
> Now look at this graph and please tell me if temperature did not rise in the 21st century.
These aren't "graphs", they're histograms, and it's impossible to read any trend lines off of them. So they're useless for this discussion.
> Look at the graph titled "2001 Projections vs. Observations", and see how closely the prediction matches reality starting 2001.
First of all, since the IPCC TAR was published in 2001, anything before 2001 is not a "projection", it's a "fit of model to past data". (And notice that the model does not fit all of the past data very well; before the mid-1900s in Figure 2 there is significant divergence. A model that can't retrodict the past can't be expected to predict the future.)
Second, these graphs are useless because they just give the "prediction" as a single line, with no error bars and no differentiation between the different sets of model runs that were based on different assumptions for how CO2 would rise. In other words, these graphs are spin, not science.
Real Climate is much too biased a source, and has been caught too many times in the past being disingenuous, for me to take anything they say seriously. Sorry.
Also note the graph showing the increasing mismatch between models and observations.
Of course many will object to my choice of source, just as I objected to RealClimate as a source. But the data set used is an "official" one (the RSS satellite data), though not one you hear as much about.
For example,
(1) A novel physical mechanism is discovered that increases the surface temperature of the Earth without any relation to greenhouse gases. Moreover, the mechanism has such a characteristic that it was steadily increasing in the past fifty years or so, roughly matching mankind's CO2 emission by pure coincidence. (I.e., "mankind is fucked, the universe decided to kill us off" scenario.)
(2) Average global temperature starts to drop unexpectedly, and continues to drop for a decade or more (so that we can rule out yearly statistical noise), despite the increased level of CO2.
(3) A new natural source of CO2 is discovered, and it is determined that the atmospheric increase of CO2 so far was actually due to this natural source. At the same time, a new independent natural sink of CO2 is discovered, and it is also determined that all the CO2 mankind has been generating was actually consumed by this sink. Even more unexpectedly, this big CO2 producer/consumer pair, while being pretty much in lockstep until 2015, is shown to diverge starting 2015, which refutes the whole point of "Mankind is responsible for increased CO2" argument. (This actually sounds like a variation of (1), but still.)
(4) Fish stocks and marine ecosystem unexpectedly starts to rebound across the ocean, thanks to increased photosynthesis by marine microorganisms. Upon further research, this is found to be linked with increased CO2 level. (This will at least partially falsify "this is a bad thing" part.)
I know, these are tough scenarios, but falsifying established science is hard. Falsifying it in a way that disproves its original successful predictions is even harder: it almost never happens. (Even after General Relativity and Quantum Mechanics, if Newtonian mechanics had predicted a railway to be dangerously curved, it would still remain dangerous in exactly the same way.)