Climate denialists are fond of arguments regarding the falsifying of hypotheses. There are two main thrusts they use here, (ironically enough mutually exclusive thrusts**). The first is that global warming is an “unfalsifiable” theory and therefore not a true scientific construct. I don’t recall any good example essays making this point to link to (maybe someone can post a link in the comments?), but I believe the idea comes mostly from the all too common conflation of the actual science and the mainstream reporting of the science. They say that the IPCC claims that extreme warmth and extreme cold, floods and droughts, more storms and fewer storms, and shrinking ice and growing ice are all the result of anthropogenic global warming and therefore no matter what happens, the theory is confirmed.
Of course, this is not true and illustrates a variety of misconceptions.
Extreme warmth is certainly on the agenda, but I don’t believe extreme cold is. This canard is most likely derived from the very unlikely hypothetical collapse of the Gulf Stream current which brings much milder winters to northwestern Europe than they would otherwise have. Aside from sensational newspaper articles, no one talks about this as coming to pass in the foreseeable short term (2100ish) future.
Both floods and droughts are predicted, but this is not the contradiction denialists would have us believe. On the one hand, less frequent but more intense rainfall can mean cycles of floods and droughts in the same regions, and on the other hand regional responses to global warming vary. Here is an IPCC summary paragraph:
The response of the hydrological cycle is controlled in part by fundamental consequences of warmer temperatures and the increase in water vapour in the atmosphere (Chapter 3). Water is transported horizontally by the atmosphere from regions of moisture divergence (particularly in the subtropics) to regions of convergence. Even if the circulation does not change, these transports will increase due to the increase in water vapour. The consequences of this increased moisture transport can be seen in the global response of precipitation, described in Chapter 10, where, on average, precipitation increases in the inter-tropical convergence zones, decreases in the subtropics, and increases in subpolar and polar regions. Over North America and Europe, the pattern of subpolar moistening and subtropical drying dominates the 21st-century projections.
The “more storms and fewer storms” bit could come from the still controversial projections of tropical cyclone behaviour. I say controversial, but when it comes to projections, the best word would be uncertain. The controversy is really around the existence of an already observable effect on storms, I don’t think there is much of a scientific case for warming oceans resulting in less severe storms. The actual projection at the moment is for stronger tropical cyclones, but also fewer tropical cyclones. Clearly this is a distinction designed to confuse the already sorry state of science journalism around global warming issues.
Ice sheet and glacier response to a warming climate is another area where real life just is not as simple as we might like and yes actually, ice sheets and glaciers can grow in response to a warming climate. This is simply because the the formula for growing land ice is snow accumulation minus ice loss and warmer temperatures in a cold climate can result in more snowfall. As in the case of the interior of the Greenland Ice Sheet, the increased snowfall outpaces the melting and ablation so the interior of Greenland is gaining mass (even as it loses mass overall due to dramatically increased melting and faster calving at the edges.) Another datapoint that is spun on its head is the marginally growing sea ice in the antarctic. The fact is that modeling does not lead us to expect any significant changes in antarctic sea ice for a while yet. So ~2% growth over the last few decades does not contradict climate change theory, but nor does it confirm it and I challenge readers to find a credible source making any such claim.
The second “falsification” angle taken by the denalists is that real world observations have contradicted AGW theories, pour me a glass of heavy crude, it is a hoax, check and mate!
Sorry, they are wrong again. The global cooling meme has been debunked over and over and over again, nothing new to say there. The next favorite meme is the “missing hotspot.” The reason this does not mean what they say it means is that such a pronounced region of warming in the tropical troposphere is a prediction of warming driven by many means, including the favorite solar driven warming, and its possible absence does not let CO2 off the hook by any means. This also begs the question of whether it is not in fact there, but we haven’t detected it yet, though it seems hard for some reason for denialists to question this particular subset of the temperature data. At best, it reveals a problem in the details of atmosperic circulation, but as we all live at the surface where warming proceeds as forewarned, one has to wonder how significant it is that the upper troposphere remains enigmatic.
But what I really wanted to highlight with this post is how this emphasis on falsification simply vanishes when it comes to the sceptical blog scientists’ claims that come and go and come yet again. Anthony Watts devotes tremendous time and energy to the (reasonable) hypothesis that the very complicated and extensive adjustments CRU makes to raw temperature station data may have introduced a bias in the global trend. He highlights cherry pick after cherry pick of stations where the adjusted data diverges dramatically upward from the raw data, the clear implication being that warming is an artifact, if not an out and out fraud.
Here is an hypothesis dead easy to falsify, just take a fair sample of the stations (not one cherry at a time) and compare the raw to the adjusted data. Why hasn’t he done that? (That’s a rhetorical question). Never mind, others have and lo and behold, the adjustments do very little to the overall trend except to reduce uncertainties. Another great way to check out this (reasonable) hypothesis is look at the average direction and magnitude of all the adjustments. Watts picks on the stations he can find with upwards adjustments, but what do we find if we look at them all? Here is your answer, almost exactly equal amounts of upwards adjustments as downwards adjustments. Seems very consistent with honest and diligent scientists trying to remove errors and equipment biases and very inconsistent with a false warming trend introduced through conspiracy or incompetence.
In a very similar vein, Tamino has taken to task another of Watts’
deceptions theories. You see, sometime around 1990 the number of stations included in the GHCN database was dramatically reduced. Watts has noted that the majority of stations that were dropped were in high altitude and high latitude locations which tend to be colder. Now, incredibly, it is taken as a given that this must cause a warming bias in the temperature trend because, well, if you take away cold you get warm, right? Um, no, actually. We are talking about trends here, not absolute temperature, so it hardly matters if a location is colder or warmer, it only matters if it has changed. And actually, high latitudes are predicted to and have been observed to warm faster than mid and low latitudes, so if anything we could expect dropping more high latitude stations would reduce the trend. But yet again that is only if the scientists doing the analysis are idiots and don’t weight the data according to the density of stations in any given grid area.
Anyway, tamino took the time to compare trends of dropped stations with those kept and, wait for it, found no difference. One can hardly imagine a more compelling falsification of that particular canard.
Where are the champions of Karl Popper now?
** Skeptical Science has an editable web page devoted to pairing upcontradictory denialist claims. I encourage all with interest and time to go add in their favorite example of contrarian cognitive dissonance.