Arguments
The albedo effect and global warming
What the science says...
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The long term trend from albedo is of cooling. Recent satellite measurements of albedo show little to no trend. |
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Climate Myth...
It's albedo
"Earth’s Albedo has risen in the past few years, and by doing reconstructions of the past albedo, it appears that there was a significant reduction in Earth’s albedo leading up to a lull in 1997. The most interesting thing here is that the albedo forcings, in watts/sq meter seem to be fairly large. Larger than that of all manmade greenhouse gases combined." (Anthony Watts)
At a glance
What is albedo? It is an expression of how much sunshine is reflected by a surface. The word stems from the Latin for 'whiteness'. Albedo is expressed on a scale from 0 to 1, zero being a surface that absorbs everything and 1 being a surface that reflects everything. Most everyday surfaces lie somewhere in between.
An easy way to think about albedo is the difference between wearing a white or a black shirt on a cloudless summer's day. The white shirt makes you feel more comfortable, whereas in the black one you'll cook. That difference is because paler surfaces reflect more sunshine whereas darker ones absorb a lot of it, heating you up.
Solar energy reaching the top of our atmosphere hardly varies at all. How that energy interacts with the planet, though, does vary. This is because the reflectivity of surfaces can change.
Arctic sea-ice provides an example of albedo-change. A late spring snowstorm covers the ice with a sparkly carpet of new snow. That pristine snow can reflect up to 90% of inbound sunshine. But during the summer it warms up and the new snow melts away. The remaining sea-ice has a tired, mucky look to it and can only reflect some 50% of incoming sunshine. It absorbs the rest and that absorbed energy helps the sea-ice to melt even more. If it melts totally, you are left with the dark surface of the ocean. That can only reflect around 6% of the incoming sunshine.
That example shows that albedo-change is not a forcing. That's the first big mistake in this myth. Instead it is a very good example of a climate feedback process. It is occurring in response to an external climate forcing - the increased greenhouse effect caused by our carbon emissions. Due to that forcing, the Arctic is warming quickly and snow/ice coverage shows a long-term decrease. Less reflective surfaces become uncovered, leading to more absorption of sunshine and more energy goes into the system. It's a self-reinforcing process.
If you look at satellite images of the planet, you will notice the clouds in weather-systems appear bright. Cloud-tops have a high albedo but it varies depending on the type of cloud. Wispy high clouds do not reflect as much incoming sunshine as do dense low-level cloud-decks.
Since the early 2000s we have been able to measure the amount of energy reflected back to space through sophisticated instruments aboard satellites. Recently published data (2021) indicate planetary albedo, although highly variable, is showing an overall slow decrease. The main cause is thought to be warming of parts of the Pacific Ocean leading to less coverage of those reflective low-level cloud-decks, but it's early days yet.
Albedo is an important cog in the climate gearbox. It appears to be in a long-term slow decline but varies a lot over shorter periods. That 'noise' makes it unscientific to cite shorter observation-periods. Conclusive climatological trend-statements are generally based on at least 30 years of observations, not the last half-decade.
Please use this form to provide feedback about this new "At a glance" section. Read a more technical version below or dig deeper via the tabs above!
Further details
"Clouds are very pesky for climate scientists..."
Karen M. Shell, Associate Professor, College of Earth, Ocean and Atmospheric Sciences, Oregon State University, writing about cloud feedback for RealClimate.
Earth's albedo is the fraction of shortwave solar radiation that the planet reflects back out to space. It is one of three key factors that determine Earth's climate, alongside the evolution of both solar irradiance and the greenhouse effect. Back in the 1990's, the evolution of Earth's albedo was by far the least understood of the three key factors. To address that uncertainty, it was proposed to measure Earth's albedo continuously over at least one full solar cycle. The long data series thereby obtained also helped scientists to explore potential correlations between varying solar activity and albedo change.
Thus was born the Earthshine project. It began in the Big Bear Solar Observatory (BBSO) in California in the mid-1990's. Measuring Earth's albedo was done by making observations of the illumination of the dark side of the Moon at night by light reflected off the dayside Earth. This method was pioneered in 1928 by French astronomer Andre-Louis Danjon (1890-1967).
Trial Earthshine observations were made in 1994–1995 and regular, sustained data-collection commenced in 1998. Data-collection continued until the end of 2017, representing some 1,500 nights spread over two decades.
Fig. 1: When the Moon appears as a thin crescent in the twilight skies of Earth it is often possible to see that the rest of the disc is also faintly glowing. This phenomenon is called earthshine. It is due to sunlight reflecting off the Earth and illuminating the lunar surface. After reflection from Earth the colours in the light, shown as a rainbow in this picture, are significantly changed. By observing earthshine astronomers can study the properties of light reflected from Earth as if it were an exoplanet and search for signs of life. The reflected light is also strongly polarised and studying the polarisation as well as the intensity at different colours allows for much more sensitive tests for the presence of life. Image and caption credit: ESO/L. Calçada.
In 2005, a new automated telescope was installed in a small, dedicated dome at the BBSO. The two telescopes, new and old, were then run together from September 2006 through to January 2007, for calibration purposes. Observations made with the more accurate automated telescope were then made through to the end of 2017.
Since the early 2000s, scientists have also been measuring planetary albedo with a series of satellite-based sensors known as Clouds and the Earth’s Radiant Energy System, or CERES. These instruments employ scanning radiometers in order to measure both the shortwave solar energy reflected by the planet - albedo in other words – and the longwave thermal energy emitted by it. The overall aim is to monitor Earth's ongoing energy imbalance caused by our copious greenhouse gas emissions.
The Earthshine project and the CERES satellite-based measurements (2001-present day) both record great variation in albedo. That is as might be expected, because cloudiness is such an important albedo-controlling factor and varies so much. However, a slightly decreasing trend was detected (fig. 1, Goode et al. 2021).
Figure 2: Earthshine annual mean albedo anomalies 1998–2017 expressed as reflected flux in Wm. The error bars are shown as a shaded grey area and the dashed black line shows a linear fit to the Earthshine annual reflected energy flux anomalies. The CERES annual albedo anomalies 2001–2019, also expressed in Wm, are shown in blue. A linear fit 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 Wm/2. From Goode et al. 2021.
The data cover two solar maxima, in 2002 and 2014, plus a solar minimum in 2009. Recorded variations in albedo show no correlation with the 11-year solar cycle, the cosmic ray flux or any other solar activity indices. Therefore, the data do not support any argument for detectable effects of solar activity on the Earth's albedo over the past two decades.
In comparison with the CERES data, both show a downturn in recent years, even though they cover slightly different parts of the Earth (Goode et al. 2021 and references therein). To put some numbers on things, in the earthshine data the albedo has decreased by about 0.5 Wm, while for CERES data, 2001–2017, the decrease is about 1.5 Wm. CERES data shows the sharp downturn to have begun in 2015.
The explanation put forward for the difference in albedo decrease between Earthshine and CERES has been further investigated and calibration-drift, a known issue with satellites, has been discounted. Instead, a recent and appreciable increase in sea surface temperatures off the west coasts of North and South America has been cited. The increase has led to reduced overlying low level cloud-deck cover. That would certainly cause significant albedo-decrease. The sea surface warming is attributed to a flip in the Pacific Decadal Oscillation (PDO), beginning in 2014 and peaking during the 2015–2017 period. It began to decline before the end of the decade.
However, a lot of this is very new, as pointed out by Gavin Schmidt at Realclimate in 2022. The role played by, for example, aerosols is not quantified in any great detail yet. But qualitatively, these developments demonstrate how impacts to the long-wave radiation combined with cloud feedbacks can lead to big shifts in short-wave reflectivity. Needless to say, this complex area is the firm focus of much ongoing investigation and will be for the foreseeable future.
Last updated on 3 March 2024 by John Mason. View Archives
I think in general this site does a fantastic job, and fully support it. Though I struggled with this article a little bit, I also thought it was informative, and for the issue of cloud cover albedo, linked to it here.
But, though I know this is an old post (though I don't think that makes it or comments in it have any less value) I have a question on this article as well. It reads "Overall, the Earth's albedo has a cooling effect."
Has a cooling affect relative to what? Doesn't the earth have to have some level of albedo? So the albedo can't cool or heat, but only cool or heat relative to a higher or lower albedo??
I also wonder, since the myth is supplied by Anthony Watts, who seems to have gotten a lot of fairly central stuff incorrect, if the end of that statement supplied at the outset "the albedo forcings.. seem to be ...larger than that of all manmade greenhouse gases combined."
Again, doesn't this have to be relative to some baseline, such as a marked and precise change in albedo over a specific time period? It's also unclear from the myth quote whether he is talking about the allleged "decrease in albedo" over some set of years prior to '97 (followed by a "lull," which presumable means no change from the prior year?) or the alleged increase in albedo after '97. And is the statement of total affect even accurate? And again, relative to what (not Watt) specifically?
Ned, comment 7 above: Helpful comment. It also says "So, a change in the earth's albedo can increase or decrease the amount of energy that is absorbed, without necessarily increasing or decreasing the amount of energy that is emitted."
I want to make sure I understand this correctly, as I'm also unclear on this as well. A higher albedo will reflect more radiation away from the surface, which has not affected the amount of energy the surface is emitting, but is affecting the energy absorbed by increasing (in the case of a higher albedo) the amount simply reflected away (like a white shirt) and thus decreasing the amount not reflected, but simply absorbed. Making high (versus low) albedo huge, because much of it then goes back into space, instead of heating the surface it hit, and then adding to overall thermal emittance from that warmed surface. I botch anything major there?
(Maybe this is going too far afield, and also showing whatI need to learn about the changing wavelengths, but if it is simply reflected and the wavelengths stay the same, then it won't be much impeded by atsmopheric gg gas absorption and re radiation - but, if it is not reflected, but aborbed (say into warmer water) not only does it heat the surface (or water) but when some of that energy is released as heat, in longer thermal radiation form, more of it is then trapped, and re radiated in all directions, by the gg gases in the atmosphere, then otherwise would have been had it been bounced back originally in its original shorter wavelength (and thus not, or less? gg gas absorbable) and less goes back out into space, yet again. ?? )
There is alot more happening with the earth then just some global warming that is the least of the worries i carry around in my head, if we are trying to reflect the suns radiation and solar energy then why are we absorbing it with solar panels more then ever in the last 10 years Solar Panels might be a very bad thing if they are worried about how much we are reflecting MAN worry more about how much we are absobing YOU THINK :)
[PS] Please read the comments policy. no all-caps.
Note your point is discussed here though I havent checked the figures.
JimmyJames @64, yes I do. Better than that, I quantify.
In 2012, global primary energy supply was 71,013 terawatt hours, or 2.56 x 10^20 Joules. Total insolation after albedo was 153218.46 x 10^20 Joules, so total primary energy supply was just 0.0017% of the energy the Earth recieves from the Sun. Put another way, at 5% efficiency, we would need to cover just 0.033% of the Earth with solar cells to completely power our civilization. With a maximum albedo loss of 1, that represents a change in albedo of just 0.033% - ie, completely negligible.
To put that figure in context, that is significantly less than the area currently covered by roads.
Of course, if it should ever be a problem, we could just cover a compensating area with a high albedo surface (like concrete, or sand) to prevent any net change in albedo.
My apologies. @65, I failed to account for the roundness of the Earth, so that total insolation should be divided by 4, and the percentage terms multiplied by 4. That still requires only 0.132% of the Earth's surface to be covered in solar cells to entirely supply human energy needs at 5% efficiency, and a 0.132% change in albedo. That represents a maximum forcing of 0.45 W/m^2 easily compensated by other means as noted in my final paragraph.
blaisct:
From here: It is generally a waste of time to do your own calculations. The albedo of urban areas cannot have changed more that 50%. The area of urban areas is less than 1% of the Earth's surface. A 50% change in albedo in such a small area cannot have such a large effect.
For starters you need to devide incoming solar radiation by 4 and not 2 to account for day/night and the curvature of the Earth.
Vacant land converted into farmland has significant (possibly greater) changes in abedo than urban areas and is a much greater part of the Earth's surface. The melting of Arctic ice causes a greater change in albedo than the rural/urban change does. We see that reflected in the Arctic increasing in temperature faster than the rest of the Earth. If urban areas caused 30% of the warming they would all be extremely hot during the day. This is not observed. If your calculations were correct than albedo changes would account for all of global warming and that is not what is observed.
If you look in the just released IPCC report you will undoubtedly find a chapter on albedo change. See what the scientists say. An old saying among grad students is "An hour in the library will save you a week in the lab". See what you can find in the IPCC report and come back here to inform us.
Also in response to blaisct's comment #66 posted over on the Urban Heat Island discussion.
Blaisct:
You continue to make poor choices in the numbers and calculations that you are doing. Going over your latest effort by number:
1. You continue to select an albedo for urban areas that is too low for anthropogenic surfaces, and you have failed to cite a reference for your value. In my comment # 64 on the Urban Heat Island discussion, I gave a reference to several artificial surface materials, all with albedo values that exceed the the value you have chosen. "Urban" areas are a mix of things like grass, roads, houses, etc. You would need to calculate how much of the surface is covered by each type, and work out an albedo for an "urban" area that way. If that is what you have done, you need to show your detailed calcuations on how you arrive at the 0.08 value.
2. There are no assumptions in the 0.31 albedo value for the earth as a whole. That is based on satellite measurements, and includes reflection from the surface, clouds, clear atmosphere, etc. Note that the only part of the surface reflection that reaches space is the part that makes it back out through the atmosphere and cloud cover. To calculate this in a model (which is what you are trying to do), you need to account for spatial variations (and daily/seasonal cycles) of solar input, surface albedo, cloud cover, and atmospheric conditions.
3 to 14. You continue to make unreasonable assumptions about the area that is undergoing a surface change, and how it relates to population. There is no reason to think that they are related through a simple proportion.
15 to 20. You continue to make errors in converting solar output (1367 W/m^2 measured perpendicular to the sun's rays) to an areal average over the surface of the earth. As MIchael Sweet points out, there is a factor of 4 involved, not a factor of 2. I also mentioned this in my earlier comment. If you do not understand why this is the case, then it is difficult to see how you can expect to do any useful calculations. You also need to consider seasonal variations in solar radiation distribution and seasonal albedo.
21. Converting radiative forcing to global temperature change involves looking at the top-of-atmosphere changes (what is seen from space), not surface changes alone. To properly incorporate surface changes into a calcuation, you need to use a much more complicated model of climate response to surface albedo changes.
22. You still get a wildy incorrect answer, due to bad data input and bad assumptions.
I have not bothered to follow the link to the Mark Healey document you mention. If that is the source you are getting your incorrect ideas from, then it is not worth bothering. The result you quote (that albedo changes can account for all the obsvered temperature rise) is completely inconsistent with the science.
Over at RealClimate, they have recent posted several articles on the just-released IPCC reports. One of those summarizes 6 key results. In that post, they provide the following graph from the IPCC report, which shows the estimated temperature response due to a variety of factors over the last 100 to 150 years. "Land use reflection and irrigation" is the second-last bar on the right. Note that the calculated effect is minor cooling, not warming.
Michael Sweet's suggestion to read the IPCC reports is a good one. I often suggest that people start with the first 1990 report, as this covers a lot of the basic climate science principles in a manner that is easier to understand for the non-expert. In the 1990 report, they mention the Sagan et al paper I linked to in my first comment. Google Scholar can probably help you fnd a free copy.
https://science.sciencemag.org/content/206/4425/1363.abstract
Also in response to blaisct's comment #66 posted over on the Urban Heat Island discussion.
The albedo is relative ... and depends primarily on the wavelength of the light that hits the body. We should therefore always specify a wavelength range for Albedo. Otherwise, strictly speaking, the entire spectrum of the sun is decisive. This relativity to the albedo is particularly important for an element as widespread worldwide as H²O.
As water vapor, it absorbs (28W / m²) largely only in the long-wave range and lets most of the visible light pass through.
As liquid water on the surface, it absorbs long-wave and short-wave light very strongly, although as a cloud in the same aggregate state, finely distributed in the atmosphere, it again reflects a high proportion (-47W / m²) of the high-energy, short-wave radiation.
As solid ice or snow on the surface, it reflects short-wave radiation as well as clouds. On the other hand, in the long-wave range it behaves like a black body and a layer of ice over the open sea isolates the one below
warmer water and prevents it from emitting its heat radiation to the atmosphere and space which in turn relativizes the ice albedo effect.
So @bleisct is not that wrong if he ascribes the Earth's albedo a major influence on global temperatures. The atmosphere (and every single component - including CO² molecules) also has an albedo if the solar spectrum is viewed holistically across all wavelength ranges and light refraction and transmission are taken into account as factors. Higher levels of GHG lower earth`s albedo by absorbing ~20% of radiation energy.
@MA Rodger is right when he remarks that the cloud albedo ingeniously has the strongest albedo and the global albedo(change) is of very minor importance over urban areas.
With a global mean surface albedo of 13.5% and net shortwave clear-sky flux of 287 Wm−2 at the TOA this results in a global mean clear-sky surface and atmospheric shortwave absorption of 214 and 73 Wm−2, respectively. From the newly-established diagrams of the global energy balance under clear-sky and all-sky conditions, we quantify the cloud radiative effects(CRE) not only at the TOA, but also within the atmosphere and at the surface.
When assessing the earth`s albedo, it`s also helpfull to have a look to the different radiation balances from land and sea and the fact that the cloud albedo is very closely interlinked with latent heat flux of evaporation in the radiation balance.
Do not confuse the strongly cooling CRE (-19W / m²) with the warming cloud radiative feedback CRF of ~ + 0.42Wm-2 ° C-1, which is a missing +RF in the above graphic by @Bob Loblaw as is also the radiative forcing of the ice Albedo effect.
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[RH] Reduced image size.
The discussion diagrams provided by coolmaster in the preceeding comment are a useful expansion of the traditional "Trenberth" diagram that shows global averages.
Add geographical differences related to latitude, continentality, global circulation patterns, etc. and you see even more variation.
Complex? Yes.
Incomprehensible? No.
This complexity is what general circulation models of the earth-atmosphere system do. Divide the planet up into small areas, model all radaition and other forms of energy transfer, the water cycle, etc. and watch the atmosphere and oceans respond.
Summary diagrams are summary diagrams - not detailed models.
@Bob Loblaw
"useful extension"
They are not only a useful extension of the understanding of climate - but also the basis for recognizing where and how humans intervene (or could intervene) in the climate.
Fighting the causes of an evil (GHG emissions) is important and right - but is it actually enough? - I would say - NO. After decades of meditation on Mauna Loa Observatory / Hawaii GHG concentrations are still rising steeply.
So we urgently need a second, additional strategy that is potent enough to stop further global warming.
All possibilities that humans could have available are shown in the changing global radiation balances. There you not only find the disturbed carbon cycle, but also the energy flow of the global water cycle.
When looking at the actual problems (decreasing biodiversity, SLR, droughts, record temperatures, floods, ...) that humans and creation have to suffer with global warming, it is noticeable that they all mainly have to do with the presence or absence of water. The idea of influencing the climate via the water cycle is therefore only logical, more direct and, above all, much faster. (All firefighters in this world nod their heads understandingly)
Let me now briefly explain this alternative climate protection strategy, which does not care much about the causes (mainly CO² & other warming GHG), but should at least noticeably alleviate the above-mentioned effects and problems of climate change:
- 3.7mm SLR = 9mm over the land area = 1335km³ of water = 2.7% of the global runoff via the rivers.
- This volume can be retained by a wide variety of measures before it flows into the oceans and converted into evaporation.
- 9L / m² corresponds to ~ 1% of the average annual rainfall over land and should therefore create ~ 1% additional clouds over the land mass. Also a multiplication effect arises because there is a high probability that these clouds will in turn rain down again over a (different) area of land.
- The net effect of the clouds(CRE) is given by Prof. M. Wild (ETH Zurich) as -19W / m². + 1% additional cloud cover over land (-0.19W / m²) corresponds globally to -0.07W / m² and is therefore a lot more than the current annual increase in radiative forcing.
!!! The rise in sea level and the rise in earth temperature would thus (in theory) be stopped. !!!
In the graphic below I tried to show the simulated additional amount of clouds and water(red numbers) in the radiation balance. I look forward to your criticism and assessment. - Thanks
[RH] Adjusted image size. Please keep your images down to a width of 450px because otherwise it breaks the page formatting.
coolmaster @71,
There is something like 500,000 cu km of annual global precipitation (and the preceding evaporation) which might suggest the addition of 1,335 cu km evaporation per year is small on a global scale but a big volume in terms of SLR.
But water doesn't stay so long in the atmosphere with the atmospheric water content just 13,000 cu km suggesting an average residency time of less than 10 days. Thus if the continual addition of 1,335 cu km evaporation per year into the atmosphere were achieved, it would pro rata result in the removal of some 34 cu km from the planet's surface/oceans, reducing sea level by 0.1mm, the equivalent of about ten-day's-worth of today's SLR. And that would be a one-off reduction requiring the evaporation of 1,335 cu km each and every year to maintain.
@ MA Rodger
"500,000 cu km of annual global precipitation"
Humans can only influence evaporation over the oceans indirectly (via climate change) by higher temperatures and stronger, drier winds. The amount of precipitation over the sea is therefor also irrelevant because it cannot be held back there.
Over land, the average rainfall is only 100,000-120,000km³ - approx. 100xSLR. An intensification of the water cycle by at least 1% will also increase cloud formation over land by ~ 1%.
A share of ~ 8% of the SLR consists of the water that the continents lose every year. Wetlands are drained, glaciers, permafrost areas, groundwater and aquifers are juiced. This promotes the spread of deserts, which are generally characterized by the fact that there are few clouds, little precipitation, little plantgrow(CO² absorption) and little rH. A third of the land area (~ 50 million km²) is already desert and it is spreading rapidly.
After the last Pacific Northwest heat wave at the latest, it should be common knowledge that drought acts as a temperature driver.
The year-round retained amount of 1335km³ is mainly used & transpired in spring and summer after it has been stored in soil moisture and groundwater. Assuming that it is largely transpired through plant growth, an additional 4.9-9.8 Gt of CO² are extracted from the atmosphere every year.
This climate protection strategy may seem Spanish to one or the other - and that is exactly what it has been - for centuries. Equipped with sufficient global water cooling over land, the earth's temperature will fall - not rise !
SLR & global warming will remain a problem as long as neurotic, uncreative CO2 budget-oriented people determine the public's climate protection strategies.
This is also intended as a criticism and is addressed to the Intergovernmental Panel on Climate Change and climate science in general.
Coolmaster:
You seem to be trying to claim that there is some sort of method of controlling climate by increasing evaporation over land, leading to increased cloud cover?
In #72, you state "The amount of precipitation over the sea is therefor also irrelevant because it cannot be held back there."
You are wrong. The amounts of precipitation and evaporation over oceans is highly relevant. to global climate. Globally, oceans evaporate much more water than falls back iinto them as precipitation. The difference is the extra precipitation over land - where precipitation greatly exceeds evaporation for global totals.
The fact that lots and lots of evaporation from oceans is incapable of forcing ever higher and higher atmospheric water vapour and clouds should tell you that things other than evaporation limit both water vapour and cloud cover.
A 1% increase in evapoartion will not lead to a 1% increase in clouds over land. (Feel free to provide an actual scientific reference for your claim, should you have one.)
You may wish to read https://skepticalscience.com/water-vapor-greenhouse-gas.htm
Bob Loblaw@74
You seem to be trying to turn the word around in my mouth - you will not succeed. I have never said that precipitation over the seas is irrelevant to the climate - but I claimed that precipitation and evaporation over the sea cannot be held back or manipulated by humans - and that rain will fall into the sea.
You can stand on the beach or on a boat with a big bucket - but is that handy to hold back 1335 km³ per year - NO. Can you give me a practical, affordable way of enhancing evaporation over the sea ? - NO. Do you need proof of this? - I hope NOT.
Just note that I want to increase evaporation by 0,7W/m² over LAND AREAS with 9L/m² and year. This improves also the energy transport from the land surface to the atmosphere by 6.13KWh/m² in spring and summer when this water will be used as additional artifical irrigation.
I've posted some graphics(69) that you think will be a useful extension. There the energy transport from the oceans to the land areas is given as 19W / m² - you don't have to give me any tutoring in this regard.
BL: ... that things other than evaporation limit both water vapour and cloud cover.
Are you talking about desertification? 10% of global surface is desert spreading rapidly. Here I've put together some other graphics and links that can give you an idea of what I'm referring to:
https://climate-protecion-hardware.webnode.com/_files/200000017-9b9cc9b9cd/cloud_graphics.pdf?ph=02adf5ae1c
...From the totality of these findings I estimate the cooling radiative forcing resulting from additional evaporation through an improving cloud cover to approx. -0.2W / m² per year over land areas.(or even more due to multiplication effects)
It is suitable to compensate the current, global, annual radiative forcing of approx. + 0.04-0.05W / m² with ease.
In theory, this would stop the rise in earth temperature!
The use of additional "artificial irrigation" and retention measures with an annual, global total volume of 1335km³ = (3.7mm SLR) can reduce the predominantly CO²-related global warming with ~ -0.15W / m² "water cooling" by approx. -0,07 ° C / year.
If you take this additional volume from flowing waters and / or bank filtrate instead of using groundwater
- This also stops the rise in sea levels!
The global measures and changes in water management required for are
thus always an excellent regional protection against periods of drought, but at the same time also against heavy rain and floods.
Assuming that this water volume is completely withdrawn from global runoff and supplied to transpiration through plants or groundwater reservoirs and soil moisture, there is a potential for additional CO² absorption of ~ 4.9 - 9.8Gt / year (C3-C4 plants // 1-2Kg carbon / m³).
Overall, it can be assumed that biodiversity will benefit from additional amounts of water over land and counteract the extinction of species.
BL: A 1% increase in evapoartion will not lead to a 1% increase in clouds over land. (Feel free to provide an actual scientific reference for your claim, should you have one.)
Aristotle and I (and many others) believe in: What goes up - gets colder - and becomes a cloud - and must come down rapidly as water(~8,5days). A huge part of this additional evaporation will precipitate over a land area again (multiplication effect).
The link you sent is of little help. Here, too, the radiation-relevant net effect of clouds and water vapor (CRE = -19W / m²)), which is crucial for my strategy, is missing. You still seem to confuse CRE with the atmospheric feedback of the clouds, which consists in the fact that with increasing temperature less cloud cover, changed lapse rate and optical depth are determined (+ 0.42Wm-2 ° C-1).
May be it`s a good idea to work out this topic here together.
[BL] Link activated.
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