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Author Topic: Solar cycle  (Read 15915 times)

blumenkraft

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Re: Solar cycle
« Reply #100 on: July 13, 2020, 10:24:13 AM »
Hefaistos, your point is well received. The sun warms the earth. Heureka!
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wehappyfew

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Re: Solar cycle
« Reply #101 on: July 13, 2020, 02:31:55 PM »
Hefaistos,

Your comments do not address the errors I pointed out.

The amount of solar energy impinging upon each square meter of the Earth is ~1360 W/m^2 divided by 4, since the Earth is a sphere.

Until you acknowledge this fact, you will continue to calculate the impact of a Maunder Minimum incorrectly.

anthropocene

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Re: Solar cycle
« Reply #102 on: July 13, 2020, 02:38:28 PM »
Confirming what wehappyfew has just posted:

Hefastios;  You are confusing irradiance with forcing.

THIS IS SHOWN IN FIGURE 2 OF THE LINK WHICH YOU PROVIDED. On the left-hand side is amplitude of solar irradiance (eye-balling the graph about 1.6 watts/m^2   and on the right hand side is the forcing: 0.25 watts/m^2). Hansen et al have done the conversion for you. It says " Left scale is the energy passing through an area perpendicular to Sun-Earth line. Averaged over Earth's surface the absorbed solar energy is ~240 W/m2, so the amplitude of solar variability is a forcing of ~0.25 W/m2."

 Either you are not understanding what is presented, not reading it all or wilfully cherry-picking quotes from scientific papers to make it look like they support what you say.  (Not for the first time either).

Also Figure 3 provides the GHG forcing (approx. 3 watts/m^2). So approx 12 times the amplitude  of a (unusually large?) solar cycle.

As you say yourself - OHC and surface temperatures are almost irrelevant side-effects ( ;-) ) of what happens at the TOA interface. So why do you complicate the discussion with these points? It could be taken as an attempt at a gish-gallop.

Either accept the points made by wehappyfew (and Hansen et al) or provide evidence to refute it and support your point.
 

 

Hefaistos

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Re: Solar cycle
« Reply #103 on: July 14, 2020, 10:30:57 AM »
Hefaistos,

Your comments do not address the errors I pointed out.

The amount of solar energy impinging upon each square meter of the Earth is ~1360 W/m^2 divided by 4, since the Earth is a sphere.

Until you acknowledge this fact, you will continue to calculate the impact of a Maunder Minimum incorrectly.

Yes, of course, I was only mentioning the changes in solar irradiance. As you say, WHF, the incoming absorbed solar energy per unit surface area is S(1-a)/4
where a is albedo. On average, albedo is assumed to be around 0.3

The solar constant varies a bit over time, to get even numbers let's have it at S = 1360 W/m^2
The solar radiation at the TOA averaged over the whole surface of the earth = 340 W/m^2
The solar radiation absorbed by the earth’s climate system around 240 W/m^2 (depending on albedo).
The approximate radiation from the earth’s climate system at TOA also equals 240W/m^2 if we have energy balance (steady state). (which we don't, as the EEI is around 1 W/m^2 .

The solar 'constant' (S) varies a bit over time with the 11 year cycle, as seen in the CMIP6 forcing chart, its amplitude is about 1 W/m^2 during strong solar cycles, whereas only half of that during weak cycles.

Secondly, if we take the above figure for the Maunder minimum, it means a change in S with around -0.8 W/m^2 in S as a long term trend change.
At surface, with constant albedo it then adds about -0.14 W/m^2 in as a long term trend change in forcing.
I attach a chart with satellite measurements during 1978-1999. The absolute irradiation levels are much higher in those readings, but for some reason (why?) they have been aligned at the lower level of around 1361. (Also Hansen use the higher values)
« Last Edit: July 14, 2020, 10:39:30 AM by Hefaistos »

kassy

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Re: Solar cycle
« Reply #104 on: July 14, 2020, 03:20:23 PM »
At surface, with constant albedo

But actually we do not have a constant albedo. There is a year over year decline of ice cover in the mountains, landscape changes in Siberia, declining arctic sea ice and those changes alone will override it.

Also if you think the solar cycle helps us now that means we are in deeper trouble then we thought because of time scales.
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The Walrus

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Re: Solar cycle
« Reply #105 on: July 14, 2020, 09:10:03 PM »
At surface, with constant albedo

But actually we do not have a constant albedo. There is a year over year decline of ice cover in the mountains, landscape changes in Siberia, declining arctic sea ice and those changes alone will override it.

The decline of which you speak amounts to ~0.2% of the total surface of the Earth.  Granted the change in albedo over that portion is rather large.  How much difference does changing cloud cover constitute?  What about the decrease in forest cover from ~40% to 30% since the dawn of industrialization?  Urban areas have roughly doubled to ~3% of the surface, which their contributing albedo changes. 

Incidentally, research has shown that the albedo has been remarkably constant over time:

https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2014RG000449

Hefaistos

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Re: Solar cycle
« Reply #106 on: July 16, 2020, 10:30:11 PM »
This is a recent paper estimating TSI, albedo, and OLR

"Measurement of the Earth Radiation Budget at the Top of the Atmosphere—A Review"
by Steven Dewitte and Nicolas Clerbaux,
 Remote Sens. 2017, 9(11), 1143;

"TSI measurements with good stability have been available since 1984. They reveal a variation of the TSI in phase with the 11-year sunspot cycle, with an amplitude of the order of 1 W/m2
. The currently-ending solar cycle 24 has a low amplitude compared to the preceding ones.
The TIM TSI instruments have a different viewing geometry as compared to the classical TSI instruments, which results in a lower absolute value of the measured TSI. Reconciling the classical DIARAD/SOVIM and the new TIM/TCTE instrument, the TSI level at solar minimum is estimated to be 1362.0 +/− 0.9 W/m2
.
The ERB measurements have sufficient stability to track the temporal variability of the EEI driving climate change, but they can not measure its absolute value with sufficient accuracy. Combining the ERB measurements with independent estimates of the EEI from OHC, we obtain the most likely values of the OLR of 238.0 W/m2
and of the RSF of 101.6 W/m2—corresponding to an albedo of 29.8%
—for the period 2000–2005."

https://doi.org/10.3390/rs9111143

https://www.mdpi.com/2072-4292/9/11/1143/htm