Earth Is Dimming – It’s Due to Climate Change

Earth Copernicus Sentinel-2

This image of Earth was compiled using tens of thousands of images from the Copernicus Sentinel-2 mission. Thanks to the satellite era, we are better placed to understand the complexities of our planet, particularly with respect to global change. Credit: Contains modified Copernicus Sentinel data (2019–20), processed by ESA and cloud layer from NASA

Warming oceans cause fewer bright clouds to reflect sunlight into space, admitting even more energy into earth’s climate system.

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.

Earthshine Chart

Earthshine annual mean albedo 1998–2017 expressed as watts per square meter (W/m2). The CERES annual albedo 2001–2019 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

“The albedo drop was such a surprise to us when we analyzed the last three years of data after 17 years of nearly flat albedo,” said Philip Goode, a researcher at New Jersey Institute of Technology and the lead author of the new study, referring to the earthshine data from 1998 to 2017 gathered by the Big Bear Solar Observatory in Southern California. When the latest data were added to the previous years, the dimming trend became clear.

Two things affect the net sunlight reaching the Earth: the Sun’s brightness and the planet’s reflectivity. The changes in Earth’s albedo observed by the researchers did not correlate with periodic changes in the Sun’s brightness, so that means changes in Earth’s reflectiveness are caused by something on the Earth.

Specifically, there has been a reduction of bright, reflective low-lying clouds over the eastern Pacific Ocean in the most recent years, according to satellite measurements made as part of NASA’s Clouds and the Earth’s Radiant Energy System (CERES) project.

That’s the same area, off the west coasts of North and South America, where increases in sea surface temperatures have been recorded because of the reversal of a climatic condition called the Pacific Decadal Oscillation, with likely connections to global climate change.

The dimming of the Earth can also be seen in terms of how much more solar energy is being captured by Earth’s climate system. Once this significant additional solar energy is in Earth’s atmosphere and oceans, it may contribute to global warming, as the extra sunlight is of the same magnitude as the total anthropogenic climate forcing over the last two decades.

“It’s actually quite concerning,” said Edward Schwieterman, a planetary scientist at the University of California at Riverside who was not involved in the new study. For some time, many scientists had hoped that a warmer Earth might lead to more clouds and higher albedo, which would then help to moderate warming and balance the climate system, he said. “But this shows the opposite is true.”

Reference: “Earth’s Albedo 1998–2017 as Measured From Earthshine” by P. R. Goode, E. Pallé, A. Shoumko, S. Shoumko, P. Montañes-Rodriguez and S. E. Koonin, 29 August 2021, Geophysical Research Letters.
DOI: 10.1029/2021GL094888

22 Comments on "Earth Is Dimming – It’s Due to Climate Change"

  1. The earth is “dimming” because of all the dimwitted low information types who believe this.

  2. Good science can stand all kinds of criticism. The study data, as far as I can tell, did not specify if albedo measurements were made parallel to the sun-facing side or at vertical-to-surface. Solar reflection off of the ocean surface would not be back toward the Sun. In contrast, reflections from solar panels that that face the Sun would. Unless measurements are taken from various directions and consistent between readings this will introduce uncertainty into any further calculations. Conclusions are best left to the media headliners.

    • They are measuring diffuse retroreflectance from different angles from the sunlit side of Earth. For a more detailed description of the geometry, see their linked paper.

  3. “For some time, many scientists had hoped that a warmer Earth might lead to more clouds and higher albedo, which would then help to moderate warming and balance the climate system …”

    That is the prevailing paradigm! If it isn’t happening, then it has ramifications beyond just lowered albedo. First off, albedo, which is diffuse retroreflectance, as measured by Earthshine, is a lower-bound on the total reflectivity. If clouds are actually decreasing, then more sunlight is hitting the water and being reflected specularly AWAY from the sun, not back towards it as with diffuse reflection (albedo). At about an angle of incidence of 60 degrees, the specular reflectance starts to rise steeply, reaching 100% at the terminator (90 deg). It doesn’t sound like the researchers are even aware of this, let alone took it into account to calculate a net change. They have provided a reasonable 1st-order calculation of reflectivity. However, because they haven’t addressed the 2nd-order effect of specular reflectance, we don’t know how much an increased specular reflectance compensates.

    As is all too often the case in climatology, the issues of measurement error and uncertainty aren’t given the importance they deserve. They authors remark, “The two-decade decrease in earthshine-derived albedo corresponds to an increase in radiative forcing of about 0.5 W/m^2, which is climatologically significant …” However, they don’t specify the uncertainty! In Fig. 3 they compare their results to CERES data, which they specify has an uncertainty (1 sigma?) of about 0.2 W/m^2. The shaded-gray area shown is the uncertainty (again, unspecified range in sigma) for their data, and it appears to be much larger than the CERES uncertainty. Therefore, all we can say is that their nominal annual estimates, with a decline of about 0.5 W/m^2 over two decades, has an uncertainty of at least 40% and appears to be unsymmetrical, with no explanation.

    It is always good to remember, “Correlation is not proof of causation!”

    • “If it isn’t happening, then it has ramifications beyond just lowered albedo.” Indeed it does. The “climate emergency” depends on it.
      But, what may have been overlooked in this reflectance study is the fact that because of our added CO2 and a small increase in global temperature, the Earth (as seen from NASA satellites) has been getting greener. This must have had to affect the albedo since 1998. (An interesting choice of a starting point. Right after a record El-Nino in 1997).

  4. Here is to hoping that we go extinct before we colonize the universe. Only drawback is that we are going to take a lot of innocent species with us.

  5. These “conclusions” and prognostications are a clear case of the TAIL WAGGING THE DOG. “Earth is DIMMING: It’s Due to Climate Change”; is like saying: What Goes DOWN must come UP, reversing CAUSE and EFFECT, and begs the question: Which Came First, the CHICKEN or THE EGG. Go FIGGER. Justin Case suggests: The Earth has been “drying out” for (at least) three decades. As a result, particulates in the atmosphere have increased, which EFFECTS (as a CAUSE) albedo; which, in-turn, is feeding and accelerating climate change, largely due to changes in the Sun, enhanced by increases in CO² saturation from a variety of CAUSES, including those generated by Human Industry and expanded burning of fossil fuels (among others). By definition, GLOBAL ANYTHING is cyclic-to-polycyclic, in a CONTINUUM; accelerated/decelerated within (and without) this CONTINUUM. In this context, Gross WEATHER MODIFICATION is a major player. Christ on the cross: FORGIVE THEM FATHER, FOR THEY KNOW-NOT WHAT THEY DO. This is “One-eye Blind” SCIENCE: FLAT, MONOCULAR Science.
    The Chinese School of LOGICIANS offered this PARADOX: The ARROW, once launched from the bow, is NEITHER in-flight nor at-rest; in the sense that the ARROW is constantly halving the distance to the target. Do the MATH: it is an INFINITE PROCESS of subdivision, which ultimately yields UNREAL NUMBERS (appropriate to this analogy), which “crack-on” to INFINITY. So much for LOGIC. I would suggest, however, if one’s HEART is the intended TARGET (The MATHS aside), that one Get TF OUT OF THE WAY! Lest TIME itself run out for ONE (and All).


  6. We’re all dead. Get over it!

  7. I remember when everything was blamed on cyclamates and freon….. oh well…Now it is AOC’s farting cows…..

  8. Didn’t know scitech enabled comments. Haven’t seen them on other stories. Something to click?

  9. This is brought to you by the same people that said the earth is flat and DDT will not hurt you and don’t forget 9 out of 10 doctors smoke cigarettes because they are safe.

  10. It was the Greeks that figured the earth was a globe about the same time as geometry was developed about three thousand years back. Cigarettes were bad by all measures and there are those who will say anything at all for money.

    Words I try to remember…everyone else is as smart as me and many are smarter. Ideas that are silly remain silly regardless of volume.

    The premise of Earth dimming is directly related to energy absorbed. It takes a lot of energy to light the planet and just the fact of being able to measure the change at all means it is significant.

    • “… just the fact of being able to measure the change at all means it is significant.”

      Not necessarily! What is really important is why is it “dimming,” and how much. The authors didn’t consider other possible influences such as the NASA-documented ‘greening’ from increased vegetation and possible increases in dust from droughts. Their measurements leave a lot to be desired. It looks like their measurements may have an uncertainty of about 50%. If you interviewed for a job, and the interviewer quoted you a nominal salary with the caveat that it might be 50% higher or lower, would you be quick to accept an offer? I wouldn’t! I’d ask for something firmer.

  11. I’m sure chem trails have nothing to do with it.

  12. Sourdough Alaska | October 2, 2021 at 2:33 pm | Reply

    Scientific BS funded with taxpayer $$$,$$$,$$$,$$$
    Question: during ice ages when the Earth was covered with clouds refectling more sun light… did the oceans get warmer?

    • Yes. There are cyclical oscillations in the planet’s orbital parameters called Milankovitch Cycles that were found to correlate with ice age patterns. The most notable was eccentricity which brought the earth closer to the sun for a while. Ocean conveyors restarted, pushed warm water to the poles and kicked off melting. Right now we are moving to a more circular orbit.

      That was figured out long before people started worrying about climate change.

  13. Well even if the climate doesn’t collapse we will still have no place to swim cuz everythings f*king polluted.

  14. This is a little counter-intuitive. I would think that the warmer ocean is more conducive to evaporation and more cloud forming as a result.

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