The Lewis & Curry paper of 2014, where they set out to estimate Earth’s climate sensitivity to “GHGs” apparently ‘based on observations’, neatly identifies the fundamental problem with the whole “climate sensitivity” issue:
It is not a scientific proposition. It starts out as a speculation, a mere conjecture, and ends with a circular argument based on that very conjecture.
The conjecture of course being:
“More CO2 in the atmosphere can, will and does cause a net warming of the global surface of the Earth.”
This is the basic premise behind the entire AGW industry. The one thing that HAS TO be correct in order for all the other claims made to even stand a chance of being taken seriously in a proper scientific context.
But has this basic premise ever, anywhere, by anyone, been verified empirically through consistent observations from the real Earth system?
Of course not! Not even remotely so!
It is still nothing but a loose conjecture …
And yet NO ONE seems to acknowledge even in the slightest how this might pose a problem. All you get if you bring it up are shrugs of indifference and/or tuts of disapproval. ‘Go away, we’re discussing real, important issues here!’
The irony …
It is all rather fascinating. EVERYONE appears to take for granted, without a single critical thought in their mind, that this fully unsubstantiated assertion is in fact rather a long-established Truth. Warmers and lukewarmers alike. It’s like a complete blind spot to all of them. It simply isn’t seen as an issue at all. People’s eyes glaze over whenever someone tries to call their attention to it. They simply don’t understand what you’re getting at. In their world, if theoretically it should be like that, then it is like that. To them, the Truth of inescapable net CO2 warming just is, like solid bedrock (you can feel it under your feet and so you know it’s real), a piece of self-evident fact that no one apparently sees any point in even addressing, much less testing, like “Do we question gravity?”.
The problem is, gravity’s effect on its surroundings is an empirically established fact, confirmed every day through billions upon billions of casual observations. The claimed warming effect of atmospheric CO2 on the mean surface temperature of the Earth, on the other hand, has NOT been empirically verified. At all. Not even once.
A claim that more CO2 in the atmosphere will and does make the global surface of the Earth warmer on average comes without ONE SINGLE SHRED OF ACTUAL EMPIRICAL EVIDENCE! *
And still people walk around taking it as gospel truth. In all sincerity equating its validity to gravity’s pull. Which, to be frank, utterly boggles my mind …!
Most people naturally don’t know that the basic premise of the AGW proposition comes without even a single piece of empirical evidence from the real Earth system. They simply assume it does. That there are tons of evidence out there. Because that’s what they’ve been told. By the people who should know this. The “experts”. And they’ve been told so for a long time, repeatedly, incessantly. Directly and indirectly. Never actually shown any such evidence, of course. (And they don’t ask for it either …) Only insistingly assured that it does exist. Somewhere. And piles of it.
* That CO2 is a gas that absorbs (and emits) radiation at certain wavelengths within the EM spectrum is an empirical fact. And no one claims otherwise. However, the notion that putting more of it into the atmosphere will therefore automatically (by physical necessity) induce a NET warming of the surface underneath, is NOT. It simply doesn’t follow. You cannot presuppose a direct connection here … You need to test it! Verify it empirically.
CO2 being able to absorb and emit radiation at ‘normal’ temperatures and pressures makes it a “radiatively active gas”, not per se a “greenhouse gas”, because the ‘greenhouse’ term naturally implies a net warming effect as a specific consequence of its radiative properties, which is something that isn’t empirically verified in the real Earth system. There are other mechanisms at work …
So how does Nic Lewis and Judith Curry arrive at their “observationally based climate sensitivity” figures?
By assuming that all ‘global warming’ between chosen segments along a temperature graph is caused by the rise in atmospheric CO2.
So what has actually been “observed” here?
Is the claimed global temperature rise (ΔT) from the last half of the 19th century to the beginning of the 21st an “observed” one?
No! It’s an altogether made up one. The makers of the global temperature records can claim it to be whatever they want it to be. And they do …
Is the claimed increase in ‘radiative forcing’ (ΔF) from the last half of the 19th century to the beginning of the 21st an “observed” one?
Of course not. It is a calculated one. A model result. Based on certain unverified assumptions. Like the “All Else Being Equal” meme.
Here are the equations used to estimate Earth’s “climate sensitivity” to the rise in “GHGs”, based on “observations” that aren’t really:
- TCR (“transient climate response”) = F2 x CO2 (ΔT/ΔF)
- ECS (“equilibrium climate sensitivity”) = F2 x CO2 (ΔT/ΔF – ΔQ)
where ΔQ represents the change in ocean heat uptake as the total ‘forcing’ changes, basically that part of the energy imbalance allegedly created by the ‘forcing’ which doesn’t show up immediately as an increase in surface temperature, but which is rather stored as ‘ocean heat’ (OHC); one is almost tempted to call it the “missing heat” or the “warming in the pipeline” factor.
Is the change in this variable, then, something that’s been “observed” since the latter half of the 19th century?
What do you think …?
Nope. It’s models once again.
Well, anyway. Let’s just try it.
According to Lewis & Curry, the standard central estimate of F2 x CO2 (the increase in ‘radiative forcing’ from a doubling of atmospheric CO2 concentration) is +3.71 W/m2.
So, what they came up with was the following: Using “HadCRUt4” as their global temperature guide, they found a rise in the mean level of global surface temperatures (ΔT) from their chosen “base period” (1859-1882) to their chosen “final period” (1995-2011) of 0.71 Kelvin. During this same stretch of time (of around 135 years), they then speculated (‘estimated’) a global mean increase in ‘radiative forcing’ (ΔF) from the rise in “GHG” concentration in the atmosphere amounting to 1.98 W/m2, and a simultaneous increase in the heat uptake rate of the global ocean (ΔQ) equal to 0.36 W/m2.
Entering these figures into the simple equations above will then provide us with “observationally constrained estimations” of TCR and ECS, like this:
TCR = 3.71 * (0.71 / 1.98) = 1.33K
ECS = 3.71 * (0.71 / 1.98 – 0.36) = 1.63K
Lewis & Curry’s ‘best estimate’ TCR exactly matches my +1.33K, while their ‘best estimate’ ECS somehow ends up as +1.64K.
Close enough, though …
So it’s really that simple. You take two segments of the global temperature anomaly curve. You note how much the temperature has apparently gone up in between them. You assume this rise is ALL due to a concurrent rise in “GHGs” in the atmosphere. You then use a radiative transfer model to compute, based on an ‘all-else-being-equal’ approach, the increase in ‘radiative forcing’ from this increase in “GHGs”. Finally you estimate how much more heat the global ocean has managed to swallow per unit time during the assumed increase in ‘forcing’, basically by putting your finger in the air. And voilà!
As you can see, it’s nothing but assumptions all the way down. No real empirical evidence from the actual Earth system to support any of it.
And yet – in this postmodern day and age – it passes peer review and is thus called “Science!” …