Wednesday, 6 May 2020

Somebody please make it stop!!

Exhibit A, from the BBC:

There are natural fluctuations in the climate but scientists say temperatures are now rising faster than at many other times.

This is linked to the greenhouse effect, which describes how the Earth's atmosphere traps some of the Sun's energy. Solar energy radiating back to space from the Earth's surface is absorbed by greenhouse gases and re-emitted in all directions.

This heats both the lower atmosphere and the surface of the planet. Without this effect, the Earth would be about 30C colder and hostile to life.

1. As ever, they say "the Earth would be about 30C colder" instead of "the Earth's surface would be about 30C colder".

2. The Earth's atmosphere is, on average, about 30C cooler than the Earth's surface. They always gloss over that bit. The lowest part (where it touches the surface) is 30C warmer than average and the highest part is 30C cooler than the average.

3. The Barometric Formula explains that there has to be a temperature gradient going up ('adiabatic lapse rate' in Newspeak).

4. After we'd done out Physics O Level, the teacher said, let's stretch our mental legs a bit, and did some clever workings to show that if you know atmospheric pressure and density of air at sea level, you can extrapolate upwards to see where the top of the troposphere is, which contains 99% of the atmosphere (it gets a bit mad further up). I can't remember how he did it, but it all stacked up. To cut a long story short, pressure falls at a fairly constant rate, so it's not difficult to estimate pressure at a given height if you know pressure at sea level and that it's effectively zero 11 km up. And temperature also falls at a fairly constant rate. That's two of the variables you need for the formula without breaking a sweat. Expected temperature then just pops out of the formula, and is surprisingly close to observed results.

5. If the facts fitted the BBC's "really simple guide", then not only would the surface be 30C warmer, the top of Mt Everest would also be warmer - but it's not, it's a lot colder. They hedge their bets and fudge it with this claim: "This heats both the lower atmosphere and the surface of the planet." Are they trying to say that the top of Mt Everest would be warmer if there were no CO2?

6. To use a crude analogy, a perfectly efficient fridge doesn't change the average temperature of your kitchen. It causes the inside to be colder and warms up the rest of the kitchen to balance. The atmosphere does the same sort of thing. It can't change its own average temperature (how?), that's dictated by the Sun, but it cools the top half and warms the bottom half in equal and opposite measure.
Exhibit B, from Wikipedia:

The temperature of the troposphere generally decreases as altitude increases. The rate at which the temperature decreases, -dT/dz, is called the environmental lapse rate (ELR). The ELR is nothing more than the difference in temperature between the surface and the tropopause divided by the height. The ELR assumes that the air is perfectly still, i.e. that there is no mixing of the layers of air from vertical convection, nor winds that would create turbulence and hence mixing of the layers of air.

The table below gives an ELR of 6.5C/km. You can measure this directly or work it out by plugging height and pressure into the formula. Rather infuriatingly, they give a variant of the formula in the section above, but don't draw any conclusions from it.

The reason for this temperature difference is that the ground absorbs most of the sun's energy, which then heats the lower levels of the atmosphere with which it is in contact. Meanwhile, the radiation of heat at the top of the atmosphere results in the cooling of that part of the atmosphere.

Sure, direct sunlight heats up the ground and that must warm the air directly above it. So the equilibrium is disturbed and tries to re-establish itself. But that is moving the goal posts. How much of the earth's surface is getting direct sunlight at any one point in time? It can't be more than half (day-night) and in the day time, maybe there's direct sunlight half the time (clouds). So overall, one-quarter? And two-thirds of the Earth's surface is water, which warms (and cools) much more slowly that the land.

Nonetheless, the temperature gradient is much the same by day or by night, when it could be argued that the surface cools the air above it. It is the same above the oceans (fairly constant surface temperature, day or night); it is the same above land (warms faster by day; cools faster by night); it is the same whether it's sunny or cloudy.
We know all this stuff, or can easily find out. Why do they keep trotting out explanations that contradict each other and are completely at odds with known facts and basic physics?

(As ever, for sure, we also know that CO2 blocks/reflects infra red at a few frequencies, but that is a very marginal effect, no more than one degree here or there. There is twenty times as much C02 in the Martian atmosphere, but it is still bloody cold because it is further from the Sun, obviously, but also because the Martian atmosphere is only one-hundredth as thick as Earth's. The fact that it is 95% CO2 is largely irrelevant).


Bayard said...

"There are natural fluctuations in the climate but scientists say temperatures are now rising faster than at many other times."

Yes the times when temperatures were falling, all "many" of them. A completely meaningless statement.

Re Mars, it was reported early on in the Global Warming/Climate Change extraordinary popular delusion, that the polar ice caps on Mars were getting smaller, i.e. Mars was getting warmer. However since then, NASA has become a subscriber to the EPD and therefore this sort of thing can't be mentioned in polite society any more.

Mark Wadsworth said...

B, that first claim is highly subjective so I didn't bother questioning it. The sceptics have done their own cherry picking and found plenty of examples where they were rising faster than now. Either way, proves nothing.

The second claim is also hotly disputed on both sides.

Lola said...

It's the BBC. It's not interested in facts. It's interested in power and the dissemination of its own world view. So what do you expect?

Dinero said...

The barometric formula, is not an explanation for warmer temperature at surface level. The term lapse rate means just that , higher temperature at lower altitude, and that is one of the variables to be put into the formula, not a product of the formula. And so the Formula is not an explanation, it is a formula for getting the temperature for individual heights from the lapse rate and standard temperature that the user of the formula puts in themselves. The lapse rate is partly a product of the composition of the atmosphere. And so the barometric formula already has the effect of the thermal characteristics of the constituent gases such as CO2 in it, does it not.

Mark Wadsworth said...

L, it winds me up no end. It actually raises my heart rate, and not in a good way.

All these people come up with contradictory and increasingly implausible explanations. If they came up with one single explanation which sort of stacked up in isolation and stuck to it doggedly, then I'd accept it quite happily. But it's all paper thin. It's like arguing with Home-Owner-Ists, they keep contradicting themselves and you can never pin them down because in the next breath they say the opposite.

Mark Wadsworth said...

Din, we've done this.

you're wrong and it is.

You can plug in variables you know and the other one pops out. The lapse rate is not an inherent property of the atmosphere, it depends on gravity. I saw a great video on YouTube where somebody sent up a weather balloon and took readings of pressure, temperature, height on the way up. He then plugged these into the formula and worked backwards to get gravity. You'd be insane if you think that pressure influences gravity.

Dinero said...

Put another way, if the atmosphere did not contain any infra red absorbers/emitters there would be no temperature gradient and lapse rate and no Barometric formula for temperature. The barometric formula is a product of the thermal characteristics of the constituents of the atmosphere.

Mark Wadsworth said...

Din, that is clearly nonsense.

The formula is based in Ideal Gas Laws and the actual constituent gases are irrelevant, only the molecular weight matters. The Gas Giants are mainly hydrogen, and they have their own lapse rate (different obviously, as H is very light).

You could mix H2O and CO2 in the right proportions to get the same density as average density as 4 x N2 and 1 x O2, and the lapse rate would be the same.

Dinero said...

OK but still you can not derive the lapse rate from the Barometric formula independently from temperature , because the one of the variable is Tb and the lapse rate is already integral to the other variables h, hb, P and Pb. The difference in the P terms is temperature dependant, and so the measured P terms allready contain temperature difference as a nested variable and combined with the h terms , the lapse rate.i.e the p terms are affected by the thermal characteristics of the constituents of the atmosphere.

Mark Wadsworth said...

Din, you can!

You can easily work out height and pressure.

Plug 'em in for various height/pressure.

The balancing figure is temperature.

Subtract results for 3km and 4 km and that's your lapse rate.

In maths, and in an equilibrium situation like this, there are no "dependent" or "independent" variables. They are interlinked. If I tell you what it costs me to fill a tank and the tank size, you can work out price/litre. Or I could tell you price/litre and tank size, you can work out the total cost. Etc.

"the p terms are affected by the thermal characteristics of the constituents of the atmosphere"

Exactly not! That is the whole point! One of the key inputs is molecular weight of air, 29g/cubic metre. That's a known figure. Apart from that, you don't need to know anything about the constituent gases!!

Bayard said...

"The second claim is also hotly disputed on both sides."

I'm not surprised, it's highly inconvenient to the Warmenists, but, unfortunately for them, the data was released before anyone was really interested in everyone singing from the same hymnsheet on GW/CC.

Bayard said...

"B, that first claim is highly subjective so I didn't bother questioning it."

It's not a claim. It would be if it said "There are natural fluctuations in the climate but scientists say temperatures are now rising faster than at any other time." but it doesn't, it says "many other times". Now "many other times" includes all those times that the temperature on Earth was falling, in the run-up to an Ice Age, say, so the statement is completely meaningless. It is true for all cases that the temperature is rising, however slowly.

Dinero said...
This comment has been removed by the author.
Dinero said...

Mark "Subtract results for 3km and 4 km and that's your lapse rate."
well that is it exactly what you are confusing, those figures are measured not derived, and so the lapse rate is recorded not derived. And so therfore the equation is a trivial formula for equating measured inputs it is not a physics explanation.

Mark Wadsworth said...

B, you are right, the opening statement is grammatically poor and logically meaningless. Pure spin.

D, of course the variables are measured! They're in units. Gravity has to be measured, mole weight of gas has to be measured, Joules, R etc have to be defined.

"the equation is a trivial formula for equating measured inputs it is not a physics explanation"

Whatever. The point is, if you know all variables but one, you can work out the missing one.

Dinero said...

To use it to calculate surface temperature you would have to put in the pressure at two heights. As pressure is temperature dependant, that is where the constituent gases and their thermal characteristics come into the equation. Different greenhouse gasses will cause different pressures in the Barometric formula, and a different surface temperature.

Mark Wadsworth said...

Din, first sentence, delete words "their thermal characteristics" and replace with "molecular mass"; second sentence, delete word "greenhouse" and we're peachy.