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Again.
Earth albedo changes with the type of land coverage.
You make an interesting point but without any supporting data.The point I am making is that the Earth's temperature cannot have changed by 4 C (at a minimum) without the existence of strong positive feedback effects. The changes in total incident solar radiation would have been nowhere near sufficient to have brought about such a temperature change by themselves. And there is no reason to think that the feedback effects that operated then would not operate today.
From the IPCC's calculations an increase in solar intensity of 100 W/m², would produce warming of the SurfaceOf particular importance are changes in the tilt of the Earth's axis, which affect the intensity of seasons. For example, the amount of solar influx in July at 65 degrees north latitude varies by as much as 22% (from 450 W/m² to 550 W/m²).
You make an interesting point but without any supporting data.
What were the changes in total incident solar radiation? and how do we know what those changes were?
I realize this is only Wiki, but when Wiki is wrong, people tend to correct it quickly.
https://en.wikipedia.org/wiki/Ice_age#Positive_feedback_processes
From the IPCC's calculations an increase in solar intensity of 100 W/m², would produce warming of the Surface
troposphere system of almost 30C, since we saw about a 4 to 6 degree increase, that would indicate feedbacks, negative ones.
You say, correctly,
"there is no reason to think that the feedback effects that operated then would not operate today."
There is also not reason to assume that those feedbacks can single out which warming to amplify.
Can you place a value on "tiny amount"?The section you quote is referring to the solar influx at a particular latitude, not the Earth as a whole. Celestial mechanics dictates that the total incident solar radiation, averaged over a year, cannot change by more than a tiny amount.
Can you place a value on "tiny amount"?
It is strange that you would neglect to describe the other two cycles that are part of the milankovitch-cycles. (note Plural)Take a look at this site and Figure 3 in particular:
Climate Data Information / Forcing / Milankovitch Cycles
As the text states: "The last Milankovitch cycle, which had a minimum about 50,000 years ago and a maximum about 20,000 years ago is one of the most interesting. The minimum is 340.545 W m-2 and the maximum is 340.780 W m-2 (misprint corrected), a difference of 0.07% which is an order of magnitude less that the overall range."
Also current TSI is about 1361 W m-2, or about 21 W m-2 greater than the bottom of the last ice age,The concept of the Milankovich cycles was developed in the 1930s by the Serbian mathematician Milutin Milankovitch.
They take account of three variations in the orbit of the earth around the sun.
It is strange that you would neglect to describe the other two cycles that are part of the milankovitch-cycles. (note Plural)
From you own citation.
Also current TSI is about 1361 W m-2, or about 21 W m-2 greater than the bottom of the last ice age,
Using the IPCC calculation of .3 W m-2 per degree C, we should be about 7 C warmer.
Your citation said "The minimum is 340.545 W m-2"Read the reference. The graph includes the effects of all three cycles
And who says that TSI is about 21 W m-2 greater than the bottom of the last ice age? Citation needed!
Your citation said "The minimum is 340.545 W m-2"
SORCE has plenty of tables showing the TSI at roughly 1361 W m-2,
http://lasp.colorado.edu/data/sorce...lots/images/tim_level3_tsi_24hour_640x480.png
Now, it is possible that the authors of the paper define Solar Insolation as something different than Total solar Irradiance (TSI),
which is considered at the top of the atmosphere, but still is not a lower reference number for what TSI was during the ice age.
Shell foresaw climate dangers in 1988 and understood Big Oil’s big role
Royal Dutch Shell
Very reminiscent of the [secret and hidden] tobacco company studies in the 50's-70's.
Related: 1988 Shell Confidential Report “The Greenhouse Effect”
Yep, I was not looking at the leading digit, They are discussing energy reaching the ground, but itMy citation was - I would have thought obviously - referring to the average incoming solar radiation, which is one quarter of TSI. An average incoming solar radiation of 340.545 W m-2 is therefore equivalent to a TSI of 1362.18 W m-2.
So, I ask again, what makes you think that TSI is about 21 W m-2 greater than the bottom of the last ice age?
1988 - it took Shell that long? AGW science has been around since the early 20th century.View attachment 67231926
Yep, I was not looking at the leading digit, They are discussing energy reaching the ground, but it
still does not identify the central question, how much different is the current level of energy from the sun,
vs the low of the ice ages.
Take a look at this site and Figure 3 in particular:
Climate Data Information / Forcing / Milankovitch Cycles
As the text states: "The last Milankovitch cycle, which had a minimum about 50,000 years ago and a maximum about 20,000 years ago is one of the most interesting. The minimum is 340.545 W m-2 and the maximum is 340.780 W m-2 (misprint corrected), a difference of 0.07% which is an order of magnitude less that the overall range."
My post #56 addressed exactly that question. Here it is again:
In terms of TSI, the figures are 1362.18 W m-2 and 1363.12 W m-2, a difference of 0.94 W m-2. As I said, tiny. Yet somehow this tiny change in overall incident solar radiation triggered a change in global temperature of at least 4 C. This can only have happened if strong positive feedbacks are present in the Earth's climate system.
and if the TSI is 4 times the insolation, that places the TSI changes at <10 Wm−2.Note that the mean annual global insolation changes caused by the eccentricity are very small (<2.5 Wm−2)
The fact that the knowledge that burning fossil fuels could raise temperatures was entered into the public domain
as early as 1912, says that the oil companies could not have been hiding anything.
Everyone knew, and so everyone who used fossil fuels is complicit.
The reality is that the forcing warming from CO2 is relatively weak, and we will run out of cheap fossil fuels
before it becomes an issue.
The only thing that makes CO2 scary, is the predicted amplified feedbacks, which may not exists
at the level to warrant any alarm.
Other research show the variance was greater,
https://pdfs.semanticscholar.org/71cf/2b17dd2107786268fabe01dbf1fa60cc090e.pdf
Beer says,
and if the TSI is 4 times the insolation, that places the TSI changes at <10 Wm−2.
There are many other factors as well, like the actual spectra of the sun.
Personally, I think the fact that we have at least 3 known cycles, (and likely several unknown),
that we get periods of constructive and destructive interference between the cycles, that ether push us into, or out of
the ice ages.
The current science places the forcing warming from CO2 at between 1 and 1.1 C."Weak" is a relative term. According to the models, which have proven to be very accurate, our atmosphere can already hold more than 2% moisture in tropical areas, due to the added heat. In another decade, this will be 4%. That may not sound like much, but consider a 24-hour storm, and add another 1/2 hour. That could be the difference between a neighborhood flooding or not. And it's going to get worse before it gets better. I inputted another thread about wildfires, which is probably a more serious impact.
Complacency is our biggest enemy.
If the change in solar insolation (energy reaching the surface) was about 2.5 Wm-2, then the change in TSINo, the sources are in full agreement. While the mean annual global insolation changes caused by the eccentricity are generally very small (<2.5 Wm−2), the change in mean annual global insolation from the last ice age to the present, which is what we were discussing, was particularly small (0.235 Wm−2). Yet it still triggered the warming that resulted in the current interglacial period. How could that happen if there are no large positive feedbacks?
If the change in TSI were 10 Wm-2, then the forcing would be about 3C, just by itself.My citation was - I would have thought obviously - referring to the average incoming solar radiation, which is one quarter of TSI.
If the change in solar insolation (energy reaching the surface) was about 2.5 Wm-2, then the change in TSI
would have been about 10 Wm-2
Based on what you said,
If the change in TSI were 10 Wm-2, then the forcing would be about 3C, just by itself.
We may still need some positive feedback, but it does not have to be large.
Well at least on published paper says the change is solar insolation was as much as 2.5 W-m2But the change in solar insolation resulting from Milankovich effects between the last ice age and now wasn't 2.5 Wm-2, it was 0.235 Wm−2.
It would nice if you would actually read what I write!
You yourself said that insolation number is 1/4th of the TSI number.Note that the mean annual global insolation changes caused by the eccentricity are very small(<2.5 Wm−2)
Well at least on published paper says the change is solar insolation was as much as 2.5 W-m2
https://pdfs.semanticscholar.org/71cf/2b17dd2107786268fabe01dbf1fa60cc090e.pdf
You yourself said that insolation number is 1/4th of the TSI number.
The IPCC says that each Wm-2 increase in energy imbalance would force a .3 C increase
in the surface troposphere system.
The energy imbalance can be caused by more coming in, just as well as less leaving.
Yes, the solar insolation due to changes in the Earth's orbital eccentricity can vary by as much as 2.5 W-m2. However, the difference between the last ice age and now is just 0.235 Wm−2. Look at the graph in the reference you posted. See how small the change is from the last ice age to now.
Ice doesn't melt spontaneously; it melts because the Earth warms. So that's one positive feedback effect that still operates, albeit less strongly, today. Perhaps you can think of more.
Ice doesn't melt spontaneously
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