Jump to content

Earth is dimming due to climate change:


beecee
 Share

Recommended Posts

https://phys.org/news/2021-09-earth-dimming-due-climate.html

Earth is dimming due to climate change

Earthshine annual mean albedo 1998–2017 expressed as watts per square meter (W/m2). The CERES annual albedo 2001–2019, also expressed in W/m2, are shown in blue. A best fit line to the CERES data (2001–2019) is shown with a blue dashed line. Average error bars for CERES measurements are of the order of 0.2 W/m2. Credit: Goode et al. (2021), Geophysical Research Letters

Warming ocean waters have caused a drop in the brightness of the Earth, according to a new study.

 

Researchers used decades of measurements of earthshine—the light reflected from Earth that illuminates the surface of the Moon—as well as satellite measurements to find that there has been a significant drop in Earth's reflectance, or albedo, over the past two decades.

The Earth is now reflecting about half a watt less light per square meter than it was 20 years ago, with most of the drop occurring in the last three years of earthshine data, according to the new study in the AGU journal Geophysical Research Letters, which publishes high-impact, short-format reports with immediate implications spanning all Earth and space sciences.

That's the equivalent of 0.5% decrease in the Earth's reflectance. Earth reflects about 30% of the sunlight that shines on it.

more at link............

 

the paper:

https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2021GL094888

Earth's Albedo 1998–2017 as Measured From Earthshine:

Abstract:

The reflectance of the Earth is a fundamental climate parameter that we measured from Big Bear Solar Observatory between 1998 and 2017 by observing the earthshine using modern photometric techniques to precisely determine daily, monthly, seasonal, yearly and decadal changes in terrestrial albedo from earthshine. We find the inter-annual fluctuations in albedo to be global, while the large variations in albedo within individual nights and seasonal wanderings tend to average out over each year. We measure a gradual, but climatologically significant urn:x-wiley:00948276:media:grl62955:grl62955-math-00010.5 urn:x-wiley:00948276:media:grl62955:grl62955-math-0002 decline in the global albedo over the two decades of data. We found no correlation between the changes in the terrestrial albedo and measures of solar activity. The inter-annual pattern of earthshine fluctuations are in good agreement with those measured by CERES (data began in 2001) even though the satellite observations are sensitive to retroflected light while earthshine is sensitive to wide-angle reflectivity. The CERES decline is about twice that of earthshine.

Plain Language Summary

The net sunlight reaching the Earth's climate system depends on the solar irradiance and the Earth's reflectance (albedo). We have observed earthshine from Big Bear Solar Observatory to measure the terrestrial albedo. For earthshine we measure the sunlight reflected from Earth to the dark part of the lunar face and back to the nighttime observer, yielding an instantaneous large-scale reflectance of the Earth. In these relative measurements, we also observe the sunlit, bright part of the lunar face. We report here reflectance data (monthly, seasonal and annual) covering two decades, 1998–2017. The albedo shows a decline corresponding to a net climate forcing of about 0.5 urn:x-wiley:00948276:media:grl62955:grl62955-math-0003. We find no correlation between measures of solar cycle variations and the albedo variations. The first precise satellite measures of terrestrial albedo came with CERES. CERES global albedo data (2001-) show a decrease in forcing that is about twice that of earthshine measurements. The evolutionary changes in albedo motivate continuing earthshine observations as a complement to absolute satellite measurements, especially since earthshine and CERES measurements are sensitive to distinctly different parts of the angular reflectivity. The recent drop in albedo is attributed to a warming of the eastern pacific, which is measured to reduce low-lying cloud cover and, thereby, the albedo.

<<<<<<<<<<<<<<<<<<<<<<<<<>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

 

I'm actually amazed how they are able to ascertain the aspect of light reflected from Earth to the Moon, from the light reflected from the Sun to the Moon. Have I missed something?

 

 

 

Link to comment
Share on other sites

Not that I can see.   I have to wonder if the albedo drop is more than just from thinning low level clouds.   Shrinking of cryosphere,  increased diesel soot on snowfields and other pale surfaces,  increased soot from wildfires, submergence of coastal lands,  etc.   This is definitely not in the category of good news.   The only countering effect I've heard about is the replacement of forests with grasslands -- grasslands have a higher albedo than forest canopies.  And that's not a good way to raise abedo, ecologically speaking. 

Link to comment
Share on other sites

11 hours ago, TheVat said:

Not that I can see.   I have to wonder if the albedo drop is more than just from thinning low level clouds.   Shrinking of cryosphere,  increased diesel soot on snowfields and other pale surfaces,  increased soot from wildfires, submergence of coastal lands,  etc.   This is definitely not in the category of good news.   The only countering effect I've heard about is the replacement of forests with grasslands -- grasslands have a higher albedo than forest canopies.  And that's not a good way to raise abedo, ecologically speaking. 

I would think loss of arctic ice would be a significant contribution, since the water reflects less well than the ice. And, of course, light not reflected is being absorbed, contributing to heating.

Link to comment
Share on other sites

Yep.  That's why I listed shrinking of cryosphere first.  Arctic ice does cover a lot of ocean most of the year.  Max extent is historically around 6 million square miles.   The minimum,  iirc,  is recorded around September 1, and that figure has been dropping.  

Link to comment
Share on other sites

1 hour ago, TheVat said:

Yep.  That's why I listed shrinking of cryosphere first.   

Not sure why, but my brain completely skipped over that bit when I was reading.

Link to comment
Share on other sites

  • 1 month later...

iirc James Lovelock in the 90's suggested dimming is delaying the real effects of climate change and mitigating  loss of albedo on the ground. When we clean up the air the real problem starts.

Edited by StringJunky
Link to comment
Share on other sites

On 10/1/2021 at 12:12 AM, TheVat said:

grasslands have a higher albedo than forest canopies.  And that's not a good way to raise abedo, ecologically speaking. 

Sorry Vat, didn't see you'd already mentioned soot. Forests might produce more cloud cover than grasslands though, so that might cancel out the higher albedo

On 9/30/2021 at 11:24 PM, beecee said:

I'm actually amazed how they are able to ascertain the aspect of light reflected from Earth to the Moon, from the light reflected from the Sun to the Moon. Have I missed something?

I think you just measure the brightness of the dark bit of the moon. That is lit up purely by the light from the Earth. ( maybe a tiny bit of starlight thrown in too)

Link to comment
Share on other sites

Excuse me for injecting some science here, but the Earth re-radiates in the infrared range ( black body radiation of 20o C )
The same infrared range that is absorbed by water vapor molecules and CO2 molecules in the atmosphere and re-radiated back towards the Earth. That is how greenhouse gases work; to trap re-radiated planetary heat back on itself.

Unless we are measuring the infrared illumination of the Moon by the Earth, those numbers may ( or may not ) be meaningless, in relation to atmospheric CO2 levels. 
It may be just a result of changing surface cover, such as melting ice, vegetation covering, city sprawl, etc.
All these may  indirectly result from CO2 levels, and directly from climate change.

Link to comment
Share on other sites

7 minutes ago, MigL said:

Excuse me for injecting some science here, but the Earth re-radiates in the infrared range ( black body radiation of 20o C )
The same infrared range that is absorbed by water vapor molecules and CO2 molecules in the atmosphere and re-radiated back towards the Earth. That is how greenhouse gases work; to trap re-radiated planetary heat back on itself.

Unless we are measuring the infrared illumination of the Moon by the Earth, those numbers may ( or may not ) be meaningless, in relation to atmospheric CO2 levels. 
It may be just a result of changing surface cover, such as melting ice, vegetation covering, city sprawl, etc.
All these may  indirectly result from CO2 levels, and directly from climate change.

So, you are saying the re-radiated photons preferentially travel towards Earth? If photon scattering is random, half will head away and half towards the ground. By my  estimation that is a 50% reduction in absorption by the ground, roughly.

Link to comment
Share on other sites

Not quite.
Earth receives radiation from the Sun centered on the visible wavelength ( roughly 4000o C ).
This provides heating of the Earth.

The Earth then re-radiates this heat, but at a much lower mean temperature, approx. 20o C ( infrared/microwave wavelength ).
The atmospheric molecules of CO2 ( and others ) vibrate and bend at this characteristic wavelength.
It is then re-emitted by the CO2/greenhouse gas, and up to 50 % can head back to the Earth.

What greenhhouse gases do, is obstruct the planet's ability to radiate heat away

Link to comment
Share on other sites

8 hours ago, MigL said:

Excuse me for injecting some science here, but the Earth re-radiates in the infrared range ( black body radiation of 20o C )

That's not really relevant to the thread though. The albedo that they measure is due to reflected light, not re-radiated.

Link to comment
Share on other sites

And the phrase "excuse me for injecting some science, " should come from someone well acquainted with three distinct aspects of radiative forcing.  Absorption, reflection, and longwave re-radiation.  From wiki... 

Radiative forcing on Earth is meaningfully evaluated at the tropopause and at the top of the stratosphere. It is quantified in units of watts per square meter, and often summarized as an average over the total surface area of the globe. Radiative forcing varies with solar insolation, surface albedo, and the atmospheric concentrations of radiatively active gases - commonly known as greenhouse gases - and aerosols.

 

Almost all of the energy that affects Earth's climate is received as radiant energy from the Sun. The planet and its atmosphere absorb and reflect some of the energy, while long-wave energy is radiated back into space. The balance between absorbed and radiated energy determines the average global temperature. Because the atmosphere absorbs some of the re-radiated long-wave energy, the planet is warmer than it would be in the absence of the atmosphere: see greenhouse effect.

The radiation balance is altered by such factors as the intensity of solar energy, reflectivity of clouds or gases,  absorption by various greenhouse gases or surfaces   and heat emission by various materials. Any such alteration is a radiative forcing, and changes the balance. This happens continuously as sunlight hits the surface, clouds and aerosols form, the concentrations of atmospheric gases vary and seasons alter the groundcover. 

Link to comment
Share on other sites

What I said ...

11 hours ago, MigL said:

Earth receives radiation from the Sun centered on the visible wavelength ( roughly 4000o C ).
This provides heating of the Earth.
The Earth then re-radiates this heat, but at a much lower mean temperature, approx. 20o C ( infrared/microwave wavelength ).
The atmospheric molecules of CO2 ( and others ) vibrate and bend at this characteristic wavelength.
It is then re-emitted by the CO2/greenhouse gas, and up to 50 % can head back to the Earth.
What greenhhouse gases do, is obstruct the planet's ability to radiate heat away

And what your link says ...

 

31 minutes ago, TheVat said:

Almost all of the energy that affects Earth's climate is received as radiant energy from the Sun. The planet and its atmosphere absorb and reflect some of the energy, while long-wave energy is radiated back into space. The balance between absorbed and radiated energy determines the average global temperature. Because the atmosphere absorbs some of the re-radiated long-wave energy, the planet is warmer than it would be in the absence of the atmosphere: see greenhouse effect.

The only difference is that I provided the mean wavelength of the energy arriving and leaving the Earth.
Or do you need me to explain in simpler words ...

 

4 hours ago, mistermack said:

That's not really relevant to the thread though. The albedo that they measure is due to reflected light, not re-radiated.

And what I previously said ...

13 hours ago, MigL said:

Unless we are measuring the infrared illumination of the Moon by the Earth, those numbers may ( or may not ) be meaningless, in relation to atmospheric CO2 levels. 
It may be just a result of changing surface cover, such as melting ice, vegetation covering, city sprawl, etc.
All these may  indirectly result from CO2 levels, and directly from climate change.

There seems to be a pandemic of reading miscomprehension affecting Forum members.
Have you guys been vaccinated against that ?

Edited by MigL
Link to comment
Share on other sites

The thread topic is how albedo levels impact warming,  and not on the CO2 aspect of it.  So it is not about greenhouse gases and infrared re-radiation but rather about visible light being reflected and never heating surface in the first place.   I could be wrong but I think the perception was you were bringing in an infrared herring.   If not,  then sorry to waste time on this. 

 

Link to comment
Share on other sites

10 minutes ago, TheVat said:

rather about visible light being reflected and never heating surface in the first place

I believe I addressed that.
Sorry I wasn't more clear.
I did not mean it to be an infrared herring 😄 .

Link to comment
Share on other sites

59 minutes ago, MigL said:

I did not mean it to be an infrared herring 😄 .

Something fishy about that, but it's best we skate over it. 

They must have to apply some mathematics to the brightness levels of the Moon, because the Earth won't always be fully lit, as seen from the Moon. 

Link to comment
Share on other sites

15 minutes ago, mistermack said:

Something fishy about that, but it's best we skate over it. 

They must have to apply some mathematics to the brightness levels of the Moon, because the Earth won't always be fully lit, as seen from the Moon. 

It's a load of codswallop.

Link to comment
Share on other sites

5 hours ago, StringJunky said:

LOL

Wait,  MigL repeats my infrared herring joke (made in the post previous to his)  and he gets the plus ones for it??   Do not quite follow the pecking order here,  but it's not my cup of tea.   

Link to comment
Share on other sites

1 minute ago, TheVat said:

Wait,  MigL repeats my infrared herring joke (made in the post previous to his)  and he gets the plus ones for it??   Do not quite follow the pecking order here,  but it's not my cup of tea.   

There you go. lol

Link to comment
Share on other sites

There is a claim that the ‘Earth is dimming’ In an article by the American Geophysical Union, cited in the OP.

I found it interesting for a couple of reasons. The term ‘dimming’ is a little confusing, because other authors use the term to describe the degree to which our atmosphere  allows the penetration of solar energy to the Earth’s surface.

In this research cited in the OP, the atmosphere of the Earth could be said to be brightening because there is less reflected solar radiation reaching the moon. This suggests that more energy is penetrating to the surface of the Earth.

The authors claimed that the decrease in the amount of solar energy being reflected is of the order of 0.5 Wm-2.

The second point of interest to me is that the finding appears to complement the findings of Wild (2009; https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2008JD011470) [A1] in the peer-reviewed Journal of Geophysical Research titled Global dimming and brightening: A review. The paper seems to sum up most of the work to that date.

If you look at Figure 9 of that article, you will see that our atmosphere is ‘brightening’ during that period when the American Geophysical Union claimed that less solar energy is being reflected to the moon from Earth.

Does anyone else see that complementation?

 


 [A1]

brightening of atmosphere.jpg

Link to comment
Share on other sites

11 hours ago, TheVat said:

Wait,  MigL repeats my infrared herring joke (made in the post previous to his)  and he gets the plus ones for it??   Do not quite follow the pecking order here,  but it's not my cup of tea.   

Best you put the kettle on then.

A fine kettle of fish.jpg

Edited by mistermack
Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share

×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.