Albedo Loss since 2001
rob...@rtulip.net
This chart shows the accelerating planetary darkening trend measured by NASA satellite data.
Source: Chart made by Robert Tulip from NASA CERES satellite data share by Professor Peter Cox of Exeter University at Climate Chat with Dan Miller 28 July 2025 time stamp 17:37 https://youtu.be/5rsIoJeveOM?t=1057
The accelerating trend line helps explain why nothing we do about carbon can make a difference to short term temperature increase. This measured albedo loss, two watts per square meter over 25 years, with an apparent tipping point of acceleration around 2014, compares to annual increase of radiative forcing due to the greenhouse effect of about 0.038 w/m2. The drivers of this acceleration show no sign of abating, meaning that without direct climate cooling action to mitigate darkening we can expect heating to continue to accelerate. Further discussion is in the attachment to my recent HPAC email on the melting of Antarctica. Excel chart is attached. I produced this by visually copying the data points in the chart shared by Professor Cox.
Regards
Robert Tulip
rob...@rtulip.net
Thanks Dan. Your work is superb and I listen to Climate Chat avidly. I don’t get why Hansen insists on using incoming rather than outgoing radiation as the denominator for albedo measurement. It does not make sense. Albedo is outgoing radiation, and as the chart below shows, that has fallen by 2% this century, not the 0.5% that Hansen derives from comparing the change to incoming radiation. The Earth as viewed from space is now 2% darker than 25 years ago, not 0.5% darker as Hansen implies. The quantum of absorbed radiation is not relevant to how bright the Earth is. Compare this to a light bulb. The brightness is how much light it gives off, not how much electricity comes in.
Regards,
Robert Tulip
From: Dan Miller <d...@rodagroup.com>
Sent: Friday, 5 September 2025 12:28 PM
To: rob...@rtulip.net
Cc: healthy-planet-action-coalition <healthy-planet-...@googlegroups.com>; Planetary Restoration <planetary-...@googlegroups.com>
Subject: Re: Albedo Loss since 2001
I had Jim Hansen on recently. He talked about this 0.5% loss of albedo over the past 25 years is indicative of a 4.5ºC ECS. I also interviewed George Tselioudis on how cloud coverage is dropping due to global warming.
Leon Simons is also covering this on BlueSky and Twitter.
Best,
Dan
2014 also corresponds to when sulfate aerosols started dropping in China and 2020 is when they dropped dramatically over the oceans. Since the effect is logarithmic, reducing aerosols over the pristine oceans has a much bigger impact than reducing aerosols over polluted China.
<image002.png>
<Albedo Loss Since 2001.xlsx>
Tom Goreau
Albedo is defined as the fraction of incoming radiation that is reflected.
That’s why Hansen uses IR as the denominator.
OR is more variable due to stratospheric dynamics (IR depends on only solar dynamics).
From:
'rob de laet' via Healthy Planet Action Coalition (HPAC) <healthy-planet-...@googlegroups.com>
Date: Friday, September 5, 2025 at 19:34
To: 'Dan Miller' <d...@rodagroup.com>, rob...@rtulip.net <rob...@rtulip.net>
Cc: 'healthy-planet-action-coalition' <healthy-planet-...@googlegroups.com>, 'Planetary Restoration' <planetary-...@googlegroups.com>
Subject: Re: [HPAC] RE: Albedo Loss since 2001
This is such crucial information to understand the recent temperature hikes in 2023 and 2024. Thank you Robert!
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rob...@rtulip.net
Thanks Tom, this definition of albedo you give is a great example of the disconnect between science and popular thinking.
Hansen speaks about the darkening of the world, describing “a substantial darkening of the planet (decreased albedo) equivalent to a CO2 increase of more than 100 ppm.” (Jan 2024)
That concept of darkening is simple intuitive language that I have been using for some time. But Hansen then reverts to albedo as a fraction of Incoming Radiation (IR). This is jargon that makes his point confusing and obscure. He speaks elsewhere about the frustration he experiences in communicating to the public, and this is a classic example of why his scientific training needs a journalistic edit for simplicity and cut-through.
Let me explain. If you get a 100 lumen light bulb and paint it so it only shines with 98 lumens, then it makes sense to say it has got 2% darker. We don’t measure its brightness against wattage (incoming electricity) except for measuring efficiency.
Same with the Earth. Viewed from the Moon, or any external point, the Earth is now 2% darker than 25 years ago, because the planet is emitting 2% less light. Hansen calculates this darkening at due to loss of clouds (60%), aerosols (30%) loss and ice and snow (10%). (12 Feb 2025, Fig SM 15 attached). And as I have noted, since 2015 this darkening of 2 w/m2 has produced over five times the extra heat that new emissions have caused (0.36 w/m2).
Saying the Earth is only 0.5% darker because albedo is a ratio of incoming wattage makes no intuitive sense. We need a light bulb moment here, applying the simple language of brightness and darkness that Hansen uses but then confuses.
And on your final point, the annual variability of outgoing radiation (OR) is clearly shown in the initial chart, with a very pronounced 2% accelerating darkening trend.
Regards, Robert
rob...@rtulip.net
Hi Michael,
Thank you very much for these observations.
I don’t believe I, or anyone here, is trying to redefine albedo. My point is that planetary brightening and darkening are the most direct, intuitive ways to communicate the meaning of albedo change, and those concepts make most sense using past brightness as the baseline. Yes, albedo is by definition a ratio. But any ratio can be expressed in different, complementary ways.
For example, we can describe albedo loss since 2001 in two equivalent ways:
- In terms of watts: a drop from ~100 to ~98 W/m² of reflected shortwave radiation, i.e. a 2% planetary darkening.
- In terms of ratio: a fall from ~29.3% to ~28.8% of incoming radiation, i.e. about half a percent.
My sense is that the watts framing is clearer and more accessible, with the added simplicity that ~100 W/m² reflected can be treated as a practical baseline of “100% brightness.”
On your point that “albedo does not speak to absorbed radiation,” I would respectfully disagree. By definition, lower albedo means less reflection, and any energy not reflected must be absorbed. A 2% albedo loss this century is energy that has entered the Earth system as heat instead of being returned to space. Reflection and absorption are two sides of the same coin.
This change is enormous in climate terms: the absorbed heat from albedo loss since 2015 exceeds the forcing from new greenhouse gas emissions by a factor of five (~2.0 vs ~0.36 W/m²). That makes it essential to analyse reflection and absorption together, rather than treating them separately.
I strongly agree with you that all solutions must be considered. But if increasing reflection can deliver cooling more cheaply, quickly, safely and reliably than reducing emissions and GHG removal, then urgent priority should go to the most effective methods. Tragically, politics still lags far behind the physics.
Regards,
Robert Tulip
From: Michael Routh <mwr...@gmail.com>
Sent: Sunday, 7 September 2025 1:36 AM
To: Robert Tulip <rob...@rtulip.net>
Cc: Tom Goreau <gor...@globalcoral.org>; rob de laet <robd...@yahoo.com>; Dan Miller <d...@rodagroup.com>; healthy-planet-action-coalition <healthy-planet-...@googlegroups.com>; Planetary Restoration <planetary-...@googlegroups.com>; Soden, Brian J <bso...@miami.edu>
Subject: Re: [HPAC] Albedo Loss since 2001
All,
While I believe that most on this thread agree that cooling on a global basis must become a more prominent part of the climate restoration conversation, please allow me to comment here regarding the use of the word “albedo."
Let’s not spend precious time trying to simplify by re-defining long-established scientific terms, as tempting as it is. Yes, let’s translate complex concepts into something more easily digested by the broader audience…an admittedly significant challenge.
Albedo is simply defined: the ratio of reflected radiation to incoming radiation. Albedo does not speak to absorbed and re-emitted radiation. Trying to combine incoming/reflection and absorption/emission into a single concept is where one needs to be careful not to confound these contributions to earth’s energy imbalance. The net result of the two produces anomalies that we see today, but the contributions are distinct and different.
With earth’s incoming radiation assumed constant for illustration, and at the risk of oversimplifying, the combination of lower reflected light due to many factors (lower albedo), and greater absorption and/or lower re-emitted radiation due to increased atmospheric concentrations of absorbing materials (CO2, CH4, etc.), all contribute to the net energy imbalance and retained heat anomalies that earth is experiencing. Our collective work to increase albedo (reflectivity), reduce absorption (lower GHG concentrations), and increase outgoing radiation to cool the earth can take many forms and offer different scale/speed/costs, all of which are likely needed to help restore more favorable earth system conditions for humans.
But please, let’s not object to, or try to redefine, these basic definitions. Instead let’s put our energy into effectively articulating and developing our solutions in the context of how we envision attacking each of these anomalies in positive, scalable, fast, cost-effective ways.
Best regards,
Michael W. Routh, Ph.D.
.
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<Hansen Clouds Snow Ice Aerosol Albedo Loss.png>
Robert Chris
Sent: Sunday, September 07, 2025 11:11
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Michael MacCracken
Dear Robert C--Let me offer just one nuance to consider, and that is that infrared emissions to space (outside of the CO2 bands) will depend on the layer of the atmosphere from which the infrared emissions are, on average, being emitted. This is the basis for the cirrus thinning approach to climate intervention in that if there are cirrus (can depend on cirrus thickness, etc.) at least a good share of the emission is from the very cold upper troposphere whereas if there is no (or little) cirrus, the emission to space could be coming mainly from the much lower and warmer marine stratus clouds, the water vapor that is concentrated in the lowest kilometer or two, or even the surface if there is a low amount of atmospheric water vapor.
I'd also note that in the visible, cirrus are poor reflectors of solar whereas marine stratus are good reflectors, and then solar is only an issue when the sun is up, whereas the role of clouds in the IR is going on day and night.
So, with regard to you definitive statement, clouds do matter, etc.
Best, Mike
Robert Chris
Sent: Monday, September 08, 2025 18:47
To: Robert Chris <robert...@gmail.com>; rob...@rtulip.net <rob...@rtulip.net>; 'Michael Routh' <mwr...@gmail.com>
Cc: 'Tom Goreau' <gor...@globalcoral.org>; 'rob de laet' <robd...@yahoo.com>; 'Dan Miller' <d...@rodagroup.com>; 'healthy-planet-action-coalition' <healthy-planet-...@googlegroups.com>; 'Planetary Restoration' <planetary-...@googlegroups.com>
Michael MacCracken
Hi Robert--Yes, as I said it was a nuance on your remark.
And in the subtropics where the marine stratus are disappearing, it is unlikely that there would be cirrus due to the dryness of the air. So, yes, clouds can likely be ignored.
This time, here is a URL describing IOC plans on
sulfur emissions from shipping:
https://www.imo.org/en/mediacentre/hottopics/pages/sulphur-2020.aspx
It seems we will have to recover albedo without then--or having to reverse their plans.
Best, Mike
Clive Elsworth
Hi Robert C
You prompted me to ask the question below about the threat of thickening cirrus clouds.
Once again, cooling the oceans seems to provide a strong solution, by reducing both atmospheric water vapour and soot from wildfires.
Clive
Q. Are cirrus clouds thickening, e.g. from booming air travel? What other threats might cause further global warming by increasing the warming influence of cirrus clouds?
A. Yes, the evidence strongly suggests that cirrus clouds are thickening and expanding due to air travel, and this is contributing to global warming. Furthermore, other threats like increased atmospheric moisture and soot from wildfires could further amplify this warming effect.
Let's break down the science behind this.
1. The Direct Threat: Air Travel and Contrail Cirrus
When an aircraft flies through a cold, humid layer of the atmosphere, its engines release exhaust rich in water vapor and soot particles. This exhaust instantly freezes into millions of tiny ice crystals, forming a condensation trail (contrail).
- Short-Lived Contrails: Some contrails dissipate quickly if the air is dry.
- Persistent Spreading Contrails: If the air is sufficiently humid (in Ice-Supersaturated Regions), the contrail persists and spreads outward, often for hours. It morphs from a thin line into a vast, thin layer of cirrus cloud. This human-made cloud is called Contrail Cirrus.
The Warming Influence:
Natural cirrus clouds have a dual effect:
- Cooling Effect (Albedo): They reflect a small amount of incoming solar radiation (shortwave) back to space. This cools the Earth.
- Warming Effect (Greenhouse): They are very effective at trapping outgoing heat radiation (longwave infrared) emitted by the Earth's surface. This warms the Earth.
For the thin, high-altitude cirrus clouds formed by contrails, the warming effect overwhelmingly dominates the cooling effect. They act as insulating blankets in the sky.
Is it a significant problem? Absolutely.
Pre-pandemic, the net warming effect from contrail cirrus was estimated to be even greater than the warming from the entire aviation sector's cumulative CO₂ emissions. While CO₂ lasts for centuries, contrail cirrus only lasts for hours, but we are constantly creating new ones, making their instantaneous radiative forcing very strong.
2. Other Threats That Could Increase Cirrus Warming
Beyond direct air travel, other changes in the atmosphere could alter natural cirrus clouds to make them more warming.
a) Increased Atmospheric Water Vapor
Warmer air can hold more moisture. As global temperatures rise (primarily from CO₂ and other greenhouse gases), the atmosphere becomes more humid, even at high altitudes.
- Threat: More available water vapor means that any ice crystals that form in the upper troposphere can grow larger, potentially leading to thicker, more widespread, and longer-lasting cirrus clouds. This would enhance their heat-trapping (warming) effect.
b) More and Better Ice Nuclei
Ice clouds need a seed—a tiny particle—for the ice to form on. These are called Ice Nucleating Particles (INPs). The type and amount of INPs can dramatically influence cirrus cloud properties.
- Soot from Wildfires and Combustion: As wildfires become more frequent and intense due to climate change, they inject massive amounts of soot (black carbon) high into the atmosphere. Aircraft engines also produce soot. Soot particles are very effective INPs. More soot can lead to:
- More Clouds: More seeds mean more ice crystals can form.
- Smaller Crystals: With a fixed amount of water vapor, more seeds lead to more, but smaller, ice crystals. Clouds with smaller crystals have a larger surface area, which generally makes them more efficient at trapping heat.
- Dust from Desertification: Land use changes and drought can increase dust storms. Mineral dust is also a very effective INP and could have a similar effect to soot.
c) Changes in Atmospheric Circulation
Climate change is altering large-scale wind patterns (e.g., the jet stream). This could change where and how frequently Ice-Supersaturated Regions—the "flight corridors" where contrails form and persist—occur. If these regions become more common, the potential for contrail cirrus formation increases.
Summary Table
Threat | Mechanism | Impact on Cirrus Clouds |
Air Travel (Contrails) | Soot and water vapor from exhaust provide nuclei and moisture for ice crystal formation in humid regions. | Creates entirely new, persistent Contrail Cirrus clouds that have a net strong warming effect. |
Increased Water Vapor | A warmer atmosphere holds more moisture, even at high altitudes. | Provides more "fuel" for existing and new cirrus clouds to form, potentially making them thicker and more widespread, enhancing their warming effect. |
More Soot (Wildfires, etc.) | Provides more effective seeds (Ice Nucleating Particles) for ice crystals to form on. | Could lead to more numerous, smaller ice crystals, creating denser cirrus clouds that are better at trapping heat. |
Conclusion and The Path Forward
The thickening of cirrus clouds, both from air travel and other climate feedbacks, is a genuine and significant amplifier of global warming. It represents a classic climate feedback loop:
- CO₂ warms the planet.
- The warmer planet has more water vapor and possibly more wildfires.
- This leads to more and thicker cirrus clouds.
- These clouds trap more heat, causing further warming (positive feedback).
What can be done?
For aviation, the solution isn't to stop flying but to innovate. Strategies include:
- Sustainable Aviation Fuels (SAFs): These can reduce soot emissions by 50-70%, dramatically reducing the ice nuclei available for contrail formation.
- Flight Path Optimization: Using weather forecasting to allow planes to slightly alter their altitude to avoid ice-supersaturated regions, preventing persistent contrails from forming in the first place. This is a very promising near-term solution.
Understanding and mitigating the impact of cirrus clouds is a crucial frontier in the effort to combat climate change.
Tom Goreau
Thanks, Clive, the threat of warming from increasing airplane condensation trails is very real!
A few years ago I was on a plane that flew over the Arctic to Guangdong in South China on route back to growing Indonesian coral reefs, the plane flew over barren Siberian tundra, the Gobi Desert, and then across the mostly densely populated part of East Central China. The atmospheric conditions were exceptionally favourable for the preservation of condensation trails: the air was supersaturated with moisture and there were no winds, so the condensation trails just stayed where they were, very slowly expanding but without drifting sideways, and each jet leaving a new sharper trail superimposed over earlier fuzzy ones.
Under these conditions the entire sky was crisscrossed with persistent condensation trails, hundreds of them in all directions, impossible to count out of an airplane window, there was more white condensation trails visible across the entire horizon than blue sky! Alas, I had no camera with me, but these are the ideal conditions for enhanced cirrus warming, and with the great increase in plane travel in China and India in recent years, we are bound to start affecting surface air temperatures from above too!
Michael MacCracken is old enough to remember when supersonic commercial jets were opposed because they could cause stratospheric clouds that would affect climate. Fortunately that threat did not develop, for economic reasons rather than technical ones, and the fact that the military did not see it as a potent weapon they had to have.
Michael MacCracken
Hi Clive--I want to suggest a bit of care on the more atmospheric water vapor argument. What more atmospheric water vapor will presumably mean is stronger convection as more energy/heat is released to power it (and more water vapor drawn in). Might it be that stronger convection will go higher and thereby wring out more of the water vapor so that air spreading out into the upper troposphere is actually drier and so might conditions become a bit less conducive to cirrus?
Just wondering.
Mike MacCracken
Clive Elsworth
Hi Mike
> Might it be that stronger convection will go higher and thereby wring out more of the water vapor..
I’m not qualified to answer that. This time (FWIW) I asked Grok:
Q. As global temperatures rise is there any reason why upper tropospheric air might become drier, leading to thinner cirrus clouds?
A. Yes, there is a proposed reason based on the "iris hypothesis," first put forward by climate scientist Richard Lindzen and colleagues in 2001. According to this idea, as global temperatures rise—particularly sea surface temperatures in the tropics—deep convective storms become more efficient at precipitating out moisture. This means more water vapor condenses and falls as rain lower in the atmosphere rather than being transported (or "detrained") upward into the upper troposphere as ice crystals or vapor. The result would be less moisture available in the upper troposphere, making it drier and thereby reducing the formation, extent, or thickness of high-altitude cirrus clouds, which are composed of ice crystals and form in that region. Thinner or fewer cirrus clouds would allow more outgoing longwave (infrared) radiation to escape to space, potentially acting as a negative feedback to limit further warming.
However, this hypothesis remains controversial and has not been widely supported by subsequent research. Numerous observational and modeling studies have found little to no evidence for a significant "iris effect," with some suggesting that any changes in cirrus clouds might instead produce a weak positive feedback that amplifies warming, or that the effect is overestimated or absent altogether. For instance, analyses of satellite data have shown inconsistencies with the predicted reduction in cloud cover, and the overall body of evidence points toward the upper troposphere generally becoming moister—not drier—with global warming, due to increased evaporation and atmospheric capacity for water vapor in a warmer climate.
Clive
P.S. It listed 34 references! Here are the first five:
How Atmospheric Water Vapor Amplifies Earth's Greenhouse Effect
Global warming at near-constant tropospheric relative humidity is ...
Response of upper tropospheric water vapor to global warming and ...
Water vapor in the upper atmosphere amplifies global warming
Upper-tropospheric moistening in response to anthropogenic warming
Michael MacCracken
Hi Clive--the really controversial aspect of the Lindzen hypothesis had to do with changes in cloud cover and, as I recall, the notion that there was no way for ocean surface temperature to exceed something like 30 C. I don't recall if there was questioning of the upper troposphere getting drier. References do seem to indicate tendency is for upper tropospheric moistening. There is, however, a real challenge for models in simulating the vertical moisture loading given that its mixing ratio changes by something like 4 orders of magnitude as one goes up through the troposphere, so a real challenge for the numerical representation of the changes
Mike
Tom Goreau
Lindzen claimed that the ocean surface could never get warmer than 30C because higher temperatures would induce a strong negative cloud cooling feedback.
He concluded there was no need to worry about global warming from GHG increases, because they would correct themselves.
In fact we are seeing ocean surface temperatures get well above this, with no signs of self-control cooling……
It’s just another fairy story from a simple minded model extrapolated beyond its limits, and in fact no one took his suggestion seriously apart from oil companies and right-wingnuts.
Jan Umsonst
Resolving the 21st century temperature trends of the upper troposphere–lower stratosphere with satellite observations
To view this discussion visit https://groups.google.com/d/msgid/healthy-planet-action-coalition/2f9b4738-8614-4896-984e-1a0de7b699c0%40comcast.net.
Dan Miller
Dan Miller
Robin Collins
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Jan Umsonst
Hi all,
just checked the newest paper on tropospheric water vapor - El Ninos increase it La Ninas decrease it with a mean increasing trend that diminishes poleward.
The graphs are from this study:
"Response of upper tropospheric water vapor to global warming and ENSO"; https://www.nature.com/articles/s41598-024-56639-5#Fig8
And here the NOAA table of precititable water - what is interesting that the signal since 2023/24 El Nino is not really receding - somewhat but not too much: https://psl.noaa.gov/cgi-bin/data/timeseries/timeseries.pl?ntype=1&var=Precipitable%20Water&level=2000&lat1=90&lat2=-90&lon1=0&lon2=360&iseas=0&mon1=0&mon2=0&iarea=1&typeout=1&Submit=Create%20Timeseries
All the best
Jan
-- Jan Umsonst Wallauer Str. 6D, 30326 Frankfurt am Main Tele: 0176 41114523 E-Mail: j.o.u...@gmail.com Performing Vitality: https://performingvitality.wordpress.com/
rob de laet
Robert Chris
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