Climate Denial 101

How quickly and strongly the climate responds to any given forcing is referred to as its sensitivity to that forcing. Climate sensitivities may be positive, or negative, short-term or long-term. With some forcings, the response is immediate and dramatic—like an excitable kid who can't go to sleep and has just been pricked with a sowing needle. Immediately he vaults out of bed ("OOOOOW...!") and races to the upstairs bathroom for a Power Rangers band-aid, ricocheting off the walls the whole way. In other cases, the response is more like that of the kid's listless overweight dad—stab him in the leg with an icepick and he'll slowly sit up... grumble a little... scratch his head and stare for a few minutes... ("Aw, for the love of...") and eventually drag himself out of bed and plod off in the general direction of the bathroom. Greenhouse gases emissions are more like Dad. They accumulate in the atmosphere over extended periods, gradually, but inexorably warming global climate in the process. On the other hand, increases in aerosols (e.g. smoke, or volcanic emissions) are more like the excitable kid. They do not remain suspended in the atmosphere for extended periods, but lead to temporary changes in cloud cover that often produce dramatic effects while they do.

Putting it all together

In the real world, all this is happening continuously. Short and long-term forcings impact the climate system on an ongoing basis, and it responds to each input with widely varying sensitivities. Furthermore, even during lulls in these forcings the climate system can, and often does respond by redistributing the energy it already has from one part of the system to another. Deep ocean currents continuously move their latent heat back and forth in “oscillations,” exchanging some of that heat with the atmosphere in the process (El Nino’s and the corresponding La Nina events are the best-known examples, but there are others). This leads to temporary spikes and dips in global atmospheric temperatures that have little to do with ongoing climate change in the entire system. Daddy is shuffling slowly but surely toward the bathroom, while Junior is bouncing on his shoulders, shifting his weight from side to side, screaming bloody murder, and putting dents in the ceiling every 18 inches.

Why does all this matter...? Because at least 95% of climate skeptic arguments depend on misunderstanding, or carefully misrepresenting every one of these concepts. Once we understand where this is being done and how, the errors and omissions they've so carefully hidden are out in the open, and the futility of denying anthropogenic climate change is apparent. So, without further ado, let's have a closer look at these errors and how they're being wielded by anti-climate change lobbies. In what follows I’ll be drawing from multiple skeptic sources, but for the most part I’ll concentrate on a recent Forbes editorial that manages to stumble into most of them in one fell swoop(Ferrara, 2012). The author is a lawyer for the Heartland Institute who clearly has no science background at all, much less any in climate science.

Error #1)   Skeptics do not understand system responses.

Climate deniers believe global land, sea, and atmospheric temperatures respond to being forced the way a golf ball responds to a line drive—immediately, and dramatically. They are forever equating trends in one of these components with real-time contemporary greenhouse gas emissions alone. To wit, Peter Ferrara tells us to,

"Check out the 20th century temperature record, and you will find that its up and down pattern does not follow the industrial revolution’s upward march of atmospheric carbon dioxide (CO2), which is the supposed central culprit for man caused global warming (and has been much, much higher in the past). It follows instead the up and down pattern of naturally caused climate cycles... For example, temperatures dropped steadily from the late 1940s to the late 1970s..." (Ferrara, 2012)

This is hardly surprising. We don’t expect 20th Century temperatures to follow CO2 emissions in lock-step—if they did they’d be violating the laws of physics.

Let's have another look at our climate thermal shock absorber. As we've seen, its response to CO2 emissions will lag them by a time delay that will be proportional to the ratio, in thermal terms, of its effective "mass" to the stiffness of its atmospheric "spring." The mass in this case is the latent heat storage capacity of the world's oceans, which as my daughter would say, is gi-normous. If you've ever had to warm up a hot tub or swimming pool you know that it takes an obscene amount of heat to do so, and a correspondingly high power bill. Now imagine what it would take to warm the world's oceans... Daddy is a gigantic, corn-fed sumo wrestler. On the other hand, the forcing associated with gradually building up a few hundred parts-per-million concentrations of greenhouse gases is a very soft thermal spring. Put the two together, and what you have is like towing a wagon full of bowling balls with a slinky, or heating a swimming pool with a cigarette lighter. Hell yes it's going to be a while before we see the corresponding temperature rise! On the other hand, the "naturally caused" forcings associated with solar fluctuations, atmospheric aerosols, changes in sea-ice and the like, are immediate. They're the excitable kid kicking the front and rear of the wagon along the way.

Figures 3 and 4 respectively show global mean surface temperature anomalies¹ relative to a 1961–1990 baseline with least squares trend fits for 1901–2012, 1901–1950 and 1951–2012 (Stocker, 2014 Chap. 2), and the relative strengths of various forcings contributing to these trends for most of the same period (Rohde, 2014).

Figure 3 – 20th Century Global Average Surface Temperatures

Figure 4 – 20th Century Climate Forcings and Surface Temperature Responses

The blue line in Figure 4 is the slinky towing the wagon, and the rest are the excitable kid kicking it on both ends. Comparing the two reveals that 20th Century climate change comes in three somewhat distinct chunks. Early on we see warming for which the strongest forcing was an increase in solar radiation output. Then, around 1940 or so the solar kick flattens out, and until the late 70's or so, other negative forcings like volcanic aerosols yank things back a bit. Thus, Ferrara's 1940's to 1970's cooling. Then, according to him,

"In the late 1970s, the natural cycles turned warm and temperatures rose until the late 1990s..." (Ferrara, 2012)

Nonsense! Compare those two figures again for the latter 20th Century. Prior to the 70's greenhouse gases clearly weren't a major contributor—the slinky hadn't had enough time to stretch out. But by the late 70's positive and negative natural forcings had slacked off to the point of cancelling each other out while the slinky was tightening. By the 80's or so, two centuries of post-Industrial Revolution stretching finally tightened it enough to overrun the other forcings… and surprise, surprise, the wagon picks up speed. Since then "natural cycles" have had nothing to do with it.

It's also worth noting that the same physics which makes the wagon of bowling balls take so long to respond also makes it that much harder to stop, even if we quit yanking the slinky altogether. A freight train still takes many miles to slow down, even when the engineer is standing on the brakes. Hence recent announcements that we've passed a "point of no return" with greenhouse gas emissions.

Error #2)   Skeptics confuse short-term trends with long-term ones.

Ferrara tells us that,

"In 2000, the UN’s IPCC predicted that global temperatures would rise by 1 degree Celsius by 2010... Don Easterbrook, Professor Emeritus of Geology at Western Washington University, knew the answer. He publicly predicted in 2000 that global temperatures would decline by 2010. He made that prediction because he knew the PDO had turned cold in 1999, something the political scientists at the UN’s IPCC did not know or did not think significant... Easterbrook shows that by 2010 the 2000 prediction of the IPCC was wrong by well over a degree, and the gap was widening. That’s a big miss for a forecast just 10 years away, when the same folks expect us to take seriously their predictions for 100 years in the future...." (Ferrara, 2012)

Now we're getting to the real meat and potatoes of most skeptic spin. Climate deniers are forever confusing the excitable kid’s cavorting with his sumo-wrestler dad’s slow forward march—typically based on one or more gross exaggerations of “predictions” they’ve misattributed to the Intergovernmental Panel on Climate Change (IPCC), the world’s leading climate science authority. The mere fact that Ferrara thinks "just 10 years" should be a much easier trend to determine than one for "100 years in the future" proves that he has absolutely no clue how this sort of thing even works.

Right out of the gate, he compounds his misunderstanding with outright carelessness. The skeptic he's referring to (Easterbrook, 2012) said the IPCC predicted a 1 deg. F rise by 2010, not 1 deg. C. He's misquoting a skeptic who in turn, is misrepresenting them. Naturally the IPCC said no such thing. What they’ve predicted is roughly 1.5 degs. C warming over the next 80+ years or so—a long-term average of around 0.2 deg. C per decade with progressively higher uncertainties on the short term. In 2000, their next-decade confidence interval on that 0.2 degs. C was +/- 0.24 degs. C, so there was even a chance it could go negative during that period (Colose, 2008).

No citations were provided either by either Ferrara or Easterbrook, but in this case the alleged IPCC "predictions" appear to have been taken from the work of Lord Christopher Monckton (Monckton, 2009), a British hereditary peer and policy advisor for another Astroturf front called the Science and Public Policy Institute.² The IPCC's actual predicted trends were, and continue to be clearly stated in the Working Group I Assessment Reports and the corresponding Summaries for Policy Makers (Stocker, 2014). Like most skeptics, Ferrara and Monckton were both careful not to look there. Instead, Monckton started with what he called an IPCC "forecast" of future greenhouse gas emissions. The IPCC makes no such forecasts—they provide scenarios for which a range of outcomes are generated (e.g. - if we generate this much greenhouse gas, this is what will happen). He then ran it through an equation the IPCC uses to calculate climate model steady-state temperatures (Bickmore, 2010). Climate models need be "spun up" to a stable modeled climate before being forced by various scenarios to see how they'll response. The equations used for the former have nothing whatsoever to do with the latter.

So, climate denier #1 takes an imaginary worst-case greenhouse gas scenario, plugs it into an equation he doesn’t understand, and ends up with a warming "prediction" five times the size of the actual one predicted by climate models… climate denier #2 repeats that figure uncritically… and climate denier #3 manages to almost double the original error by misquoting him in turn…