My recent spat with Marc Morano taught me that deniers are becoming far more insidious. As the public in general becomes more aware of the absolute importance of peer-review, deniers are faced with a dilemma because the peer-reviewed literature overwhelmingly supports the theory that our GHG emissions are causing climate change (hence the consensus). What is a denier to do? Well people like Marc Morano, have decided that they don’t actually need peer-reviewed research that supports the conclusions they are pushing, because few people will take the time to look at the actual research, so all they need to do is claim that a paper casts doubt on climate change when in fact it does nothing of the sort, and may even explicitly support the theory of climate change.
This is exactly what Marc Morano tried to do to me, but unfortunately for him, I being aware of his reputation, took a closer look at his lists. What I found was that his lists were mostly filled with non peer-reviewed articles (op-eds, blog posts) that have absolutely no bearing to the scientific debate, and some ‘research’ (usually from conservative think tanks) masquerading as peer-review. Buried within the lists were a few actual peer-reviewed articles, but despite what Marc claimed none of them even tried to debunk climate change theory.
And this is the denier trickery. Because they know that the majority of people wont take the time to read the actual literature (and Marc purposely makes this very difficult to do) they know that their claims wont usually be challenged. And while this highlights the dishonesty of deniers it is a real problem.
This presents an interesting question though. What does it take to challenge the theory that humans are causing climate change? And equally important, what doesn’t disprove climate change?
The first question can be answered relatively easily with two words: climate sensitivity.
The main reason for concern about anthropogenic climate change is not that we can already see it (although we can). The main reason is twofold.
- Carbon dioxide and other greenhouse gases are increasing rapidly in the atmosphere due to human activity. This is a measured fact not even disputed by staunch “climate skeptics”.
- Any increase in carbon dioxide and other greenhouse gases will change the radiation balance of the Earth and increase surface temperatures. This is basic and undisputed physics that has been known for over a hundred years.
But how strong is this warming effect? That is the only fundamental doubt about anthropogenic climate change that can still be legitimately debated.
Climate sensitivity refers to the change in global average temperatures that would occur with a doubling of atmospheric GHG. The IPCC estimates that climate sensitivity is “likely to be in the range 2 to 4.5°C with a best estimate of about 3°C, and is very unlikely to be less than 1.5°C. Values substantially higher than 4.5°C cannot be excluded, but agreement of models with observations is not as good for those values.“. But of course it isn’t that simple. The IPCC’s estimate is for what is general called Charney sensitivity and it assumes the land surface, ice sheets and atmospheric composition (chemistry and aerosols) stay the same. Newer estimates of sensitivity (sometimes called ‘earth system sensitivity’) allow for those to vary and feed back on the temperature response. And while the difference between the Charney sensitivity, and the earth system sensitivity is debatable, it is a safe bet to assume that the earth system sensitivity will be higher than the Charney sensitivity. So to successfully challenge climate change one needs to make a convincing argument that the climate sensitivity (preferably the earth system sensitivity) is close to zero. Unfortunately that isn’t an easy thing to do especially since a recent peer-reviewed article in Nature found that “a climate sensitivity greater than 1.5 °C has probably been a robust feature of the Earth’s climate system over the past 420 million years, regardless of temporal scaling“.
One thing to watch out for, are deniers who purposely ignore all feedbacks, both fast (the most important of those being water vapour which is responsible for 66% to 85% of the total warming effect) and slow in order to arrive at climate sensitivity values that are unrealistically low.
The second question cannot be answered definitely, simply because we can’t know to what depths of trickery deniers will descend. But we can lay out a few example that should make it relatively painless to determine if deniers are even on the right track. The most used attack on climate change has to do with the Mann ‘hockey stick’, and the medieval warm period. Deniers love to claim that the medieval warm period was warmer that today (or that Greenland used to be green) mainly because of some possible statistical errors made by Mann when he created the ‘hockey stick’. But besides the fact that newer and better climate reconstructions have fallen within the ‘hockey stick’s’ error bars, that the NAS found that Mann’s general conclusions to be valid, that the IPCC’s conclusion that “The balance of evidence suggests that there is a discernible human influence on global climate” predates the ‘hockey stick’, and that it is very likely that the medieval warm period was a only a regional effect, completely refuting the ‘hockey stick’ and even proving that the medieval warm period was warmer (everywhere) than current temperature doesn’t in fact cast doubt on climate change. Why? Because, as I explained above it doesn’t address the issue of climate sensitivity. It is perfectly possible that natural variation caused the medieval warm period, and in fact if we go back far enough (say 55 million years) we have quite solid evidence that the earth was warmer than it is today. Natural temperature variations can be very large, but as I explained above it doesn’t in fact disprove that the current warming trend is caused by our GHG emissions.
The next favourite tactic involves the fact that Greenland has been loosing ice for at least the past hundred years. Now aside from the fact that the industrial revolution (generally accepted as the beginnings of climate change) was more than one hundred years ago, anyone who uses a regional effect, to argue for a global phenomenon, shouldn’t be taken seriously, especially if they use Greenland, because as one of the peer-reviewed papers Marc Morano sent me states “There are significant differences between the global temperature and the Greenland temperature records within the 1881–2005 period”, Which would make it an especially poor indicator of global climate.
Lately a few papers have predicted (unsurprisingly) that going forward yearly temperature variation could temporarily swamp out the relatively small warming signal. Of course what the deniers wont tell you is that these papers fully accept climate change and specifically state that over longer time scales (decades) the warming trend caused by our GHG emissions will be the dominant trend.
Another favourite method used by deniers is to ‘prove’ that climate change is false is the notion that polar bears are doing fine. But even if we accept that (and there are plenty of reasons why we shouldn’t accept that), we need to make the distinction between what causes climate change and what the effects of climate change are thought to be. The claims that polar bears are in trouble are very clearly effects of climate change, not evidence used to support climate change. The fact that polar bears are adapting to a rapidly changing arctic (and again there is reason to believe they are not) does not in anyway challenge the theory of climate change.
There are bound to be several other misguided attacks on climate change theory (see here for more), but the bottom line is that if those attacks do not attempt to convince us that climate sensitivity is near zero then they are barking up the wrong tree. What deniers are doing now is nothing but a dishonest irrational defence of their fixed beliefs. Don’t take their word that the peer-reviewed literature is filled with dissenting scientists (I thought they claimed that dissenting scientists were preventing from publishing their work… so much for constancy), look it up, read the papers look at the conclusions the authors arrive at and see if they match with the conclusions the deniers are pushing. You likely wont believe how dishonest they can be.