Few Questions

[jenb]

In the attached graph, which I think is from NASA but I don’t for sure, how is temperature of past centuries and thousands of years ago determined? When I studied environmental physics 20 years ago, I was taught that CO2 content of Antarctic ice core samples was correlated directly to temperature.  Was a different method used here?

Can someone please direct me to some peer reviewed info on atmospheric effects?  I’m specifically trying to find information on how much of the infra red radiation from the sun is prevented from reaching the earth’s crust and inner atmosphere by refraction or similar. I want to know if increase in atmospheric CO2 could yield any decrease in IR radiation that heats the inner atmosphere and crust, and if the potential issue has been studied.

Thanks in advance.

Edited January 29, 2020 by jenb

[swansont]

26 minutes ago, jenb said:

 

Can someone please direct me to some peer reviewed info on atmospheric lensing?  I’m specifically trying to find information on how much of the infra red radiation from the sun is prevented from reaching the earth’s crust and inner atmosphere by the lensing effect. I want to know if increase in atmospheric CO2 could yield any decrease in IR radiation that heats the inner atmosphere and crust, and if the potential issue has been studied.

Is this an issue? Any lensing sends light toward the earth, not away from it (for a higher index, light bends towards the normal), so it's a converging lens. And any increase in CO2 is going to have a minuscule effect on the index of refraction. At STP it's 1.0003, so it's small to begin with.

[jenb]

Well I recall a greenhouse effect diagram that shows most of the IR light being bent almost entirely away from the earth, and showing the Ir radiation from the earth being trapped by atmospheric greenhouse gasses.  The upshot was that the increase in greenhouse gasses increases the temperature because it doesn’t reduce much or any incoming heat, it just reduces outgoing heat.

Edited January 29, 2020 by jenb

[Strange]

50 minutes ago, jenb said:

In the attached graph, which I think is from NASA but I don’t for sure, how is temperature of past centuries and thousands of years ago determined? When I studied environmental physics 20 years ago, I was taught that CO2 content of Antarctic ice core samples was correlated directly to temperature.  Was a different method used here?

The temperature is determined by measuring the ratios of hydrogen and oxygen isotopes in the water. A good explanation here: https://www.scientificamerican.com/article/how-are-past-temperatures/

9 minutes ago, jenb said:

Well I recall a greenhouse effect diagram that shows most of the IR light being bent almost entirely away from the earth, and showing the Ir radiation from the earth being trapped by atmospheric greenhouse gasses.  The upshot was that the increase in greenhouse gasses increases the temperature because it doesn’t reduce much or any incoming heat, it just reduces outgoing heat.

Without seeing the diagram, I can't be sure but it sounds more like it was showing reflection not refraction. (But I don't think CO2 reflects light significantly either.)

[swansont]

1 hour ago, jenb said:

Well I recall a greenhouse effect diagram that shows most of the IR light being bent almost entirely away from the earth, and showing the Ir radiation from the earth being trapped by atmospheric greenhouse gasses.  The upshot was that the increase in greenhouse gasses increases the temperature because it doesn’t reduce much or any incoming heat, it just reduces outgoing heat.

It would be nice if you could find a link to that.

Sometimes the diagrams are schematic in nature, and not meant to be taken literally. e.g. it might represent reflection, or absorption that is reradiated outward. Can't tell without looking at it

 

like this one (the lines do not represent the actual path of the light)

https://marine.rutgers.edu/cool/education/class/yuri/erb.html

[Ken Fabian]

On 1/29/2020 at 11:31 PM, jenb said:

how much of the infra red radiation from the sun is prevented from reaching the earth’s crust and inner atmosphere

Not sure my attempted explanation will be better than all the other explanations out there but I think that many of the attempts to keep it simple result in passing over important aspects...

IR coming in can be reflected back to space or absorbed by the atmosphere, with about half of that absorbed to be re-radiated up and half down and none of that is changed much by changing greenhouse gas concentrations. Swansont's linked schematic is quite good. If it showed before and after changed CO2 it would be that "Radiated to space from clouds and atmosphere" figure that changes the most.

It is only when high in the troposphere and into the stratosphere that long IR will make it directly back to space. It can get there by the radiating up and being absorbed and re-emitted - about half going up and half down each time and of what makes it that high (and stays up their long enough) about half of that will radiate to space. But it is bulk air movement - wind and convection - that moves most of the atmospheric heat that gets to the top of the atmosphere.

Swansont's linked diagram -

 

 

 

[jenb]

Thanks.  Based on your help, and with a bit of research, I think I just misremembered it, and possibly misunderstood it originally.  With my research, I found a couple of helpful pages.  This one says that 49% of the radiation emitted by the sun is lower frequency than visible light, and Another source says that 55% of the solar radiation arriving at the earth’s surface is this type of energy.

http://www.ces.fau.edu/nasa/module-2/radiation-sun.php

And the attached diagram (available at the link below) shows that CO2 absorbs more of such radiation than is emitted from the surface of the earth.  With the huge increase in atmospheric CO2 over past decades, shouldn’t we have observed a change in the percentage of lower than visible frequency light arriving at the earth’s surface?  If this diagram is correct, then wouldn’t increased atmospheric CO2 result in so much less energy arriving at the earth’s surface during the day that it should at least partially offset the increase in trapped radiation from the earths surface at night? Do the doom and gloom predictions take that into account?

http://www.ces.fau.edu/nasa/module-2/how-greenhouse-effect-works.php

 

 

[Ken Fabian]

40 minutes ago, jenb said:

wouldn’t increased atmospheric CO2 result in so much less energy arriving at the earth’s surface during the day that it should at least partially offset the increase in trapped radiation from the earths surface at night?

What incoming IR that can reach the surface directly will be mostly short or "near" IR, which is less absorbed by greenhouse gases than long IR. A lot of the re-radiation from sun warmed earth back upwards is long IR. Any short IR that is absorbed along with long IR (which is more strongly effected and doesn't penetrate all the way through, going up or coming down) is absorbed in the atmosphere and will be retained within the climate system, not lost. Bulk air movement will carry it around and mix it.

So, no it isn't going to offset the warming from raised CO2.

Edited January 30, 2020 by Ken Fabian

[swansont]

1 hour ago, jenb said:

 With the huge increase in atmospheric CO2 over past decades, shouldn’t we have observed a change in the percentage of lower than visible frequency light arriving at the earth’s surface?  If this diagram is correct, then wouldn’t increased atmospheric CO2 result in so much less energy arriving at the earth’s surface during the day that it should at least partially offset the increase in trapped radiation from the earths surface at night? Do the doom and gloom predictions take that into account?

The overall effect is only about 0.1% of the solar radiation, so you aren’t going to see a huge shift