Thanks for that post ktonine.
For example, no, PV = nRT does not tell you how geopotential height responds to surface temperature!
I'm sorry but, what? This makes no sense to me, probably due to my ignorance in the topic. Let me review, can someone please point where I'm wrong?
From Wikipedia:
PV = nRT
P is the pressure of the gas,
V is the volume of the gas,
n is the amount of substance of gas (also known as number of moles),
R is the ideal, or universal, gas constant
T is the absolute temperature of the gas.
If n and R remain constant T increases near the surface, then P or V (or both) must increase near the surface. If V increases near the surface wouldn't that result in changes in V higher up in the atmosphere? I imagine it would happen with a decreasing gradient but 200hPa seems low enough to be eventually affected.
It may be that the ideal gas law is a simplification that the models used in this experiment do not use for practical reasons, but the physics seem clear to me. You change the temperature, you change the geopotential heights. The changes should have at least some influence all the way out to the stratosphere, but as it increases the impact of the changes decrease approaching 0.
An honest assessment of the literature (see IPCC for example) would say that the jury remains out on that.
I Imagine he refers to this :
https://www.ipcc.ch/publications_and_data/ar4/wg1/en/ch3s3-5-2.htmlTo claim it is not natural variability you would have to show that the way that the spatial pattern of convection tropics has evolved in the last 30+ years is not natural variability.
Define natural variability. If he means free of human influence then he is the one who must prove that humans did not have a significant effect on the climate. Over the last 10,000 year we stopped the natural variability of the planet the slow cool down to the next ice age. Until the 1800's we prevented the planet from cooling as much as it would have without humans. After the 1800, we started actually warming the planet, contrary to what Milankovitch cycles indicate.
We didn't just warmed the planet, we changed a significant fraction of the surface of the planet making some places colder other warmer with their respective atmospheric changes. By razing forest we changed precipitation patterns and cloud formations that changed atmospheric patterns. We create aerosols that change the local temperatures to such magnitude that it has a visible effect on global temperatures.These and many more low altitude changes have small but real impacts in higher altitude currents. They must. How can they possibly not? Sure they are almost impossible to measure as they get lost in the noise but the changes must be there due to the most basic laws of physics.
To the extent that the decadal tropical changes ARE a forced response, then our estimate for the natural variability is an upper bound,
I would love to see the lower bound. My bet it is on 0% bound for natural variability, but it could very well be 30-40% lower bound due to random variability extrinsic to the arctic. Random variability !=Natural variability.