From a Press Release from the Max Planck Institute for Meteorology
Do dust particles curb climate change?
A knowledge gap exists in the area of climate research: for decades, scientists have been asking themselves whether, and to what extent man-made aerosols, that is, dust particles suspended in the atmosphere, enlarge the cloud cover and thus curb climate warming. Research has made little or no progress on this issue. Two scientists from the Max Planck Institute for Meteorology in Hamburg (MPI-M) and the American National Oceanic and Atmospheric Administration (NOAA) report in the journal Nature that the interaction between aerosols, clouds and precipitation is strongly dependent on factors that have not been adequately researched up to now. They urge the adoption of a research concept that will close this gap in the knowledge. (Nature, October 1st, 2009)
Greenhouse gases that heat up the earth’s atmosphere have their adversaries: dust particles suspended in the atmosphere which are known as aerosols. They arise naturally, for example when wind blows up desert dust, and through human activities. A large proportion of the man-made aerosols arise from sulfur dioxides that are generated, in turn, by the combustion of fossil fuels.
The aerosols are viewed as climate coolers, which compensate in part for the heating up of the earth by greenhouse gases. Climate researchers imagine the workings of this cooling mechanism in very simple terms: when aerosols penetrate clouds, they attract water molecules and therefore act as condensation seeds for drops of water. The more aerosol particles suspended in the cloud, the more drops of water are formed. When man-made dust particles join the natural ones, the number of drops increases. As a result, the average size of the drops decreases. Because smaller drops do not fall to the ground, the aerosols prevent the cloud from raining out and extend its lifetime. Consequently, the cloud cover over the earth’s surface increases. Because clouds reflect the solar radiation and throw it back into space, less heat collects in the atmosphere than when the sky is clear. Climate researchers refer to this mechanism as the “cloud lifetime effect”.
To date, however, it has not been possible to quantify the influence of the cloud lifetime effect on climate. The estimates vary hugely and range from no influence whatsoever to a cooling effect that is sufficient to more than compensate for the heating effect of carbon dioxide.
According to Bjorn Stevens from the MPI-M and Graham Feingold from the Earth System Research Laboratory at NOAA in Washington D.C the enormous uncertainty surrounding this phenomenon is indicative of the fact that the explanation of the cooling mechanism generated by aerosols is oversimplified. The two cloud researchers have analyzed the specialist literature published on this topic since the 1970s. In their survey of the literature they encountered observations that disagree with the cloud lifetime effect: for example, a field study carried out a few years ago found that clouds in the Trade Wind region rain out more quickly rather than more slowly in the presence of virtually opaque aerosols.
On the completion of their analysis of the literature, Stevens and Feingold came to the following conclusion: “Clouds react to aerosols in a very complex way and the reaction is strongly dependent on the type and state of the cloud,” says Stevens. Therefore the aerosol problem is a cloud problem. “We climate researchers must focus more on cloud systems and understand them better,” he stresses.
As the researchers write, processes in the clouds that counteract or even negate the influence of the aerosol particles have not been taken into account up to now. One example: when a cumulus cloud comes into contact with aerosols, it does not rain out. However, this has certain consequences: the fluid rises and evaporates above the cloud. The air that lies above the cloud cools down and becomes susceptible to the upward extension of the cumulus cloud. Higher cumulus clouds rain out more easily than lower ones. This is what causes precipitation. Therefore, in such situations the aerosol does not prevent the cloud from raining out.
Stevens and Feingold believe that due to such buffer mechanisms the cooling effect of the aerosols is likely to be minimal. They admit, however, that the cloud lifetime effect is not unsuitable per se as a way of explaining the processes triggered by aerosols in the clouds. “All cloud types and states cannot, however, be lumped together,” says Stevens. He calls for rethinking aerosol research and makes a comparison with cancer research: “People used to think that cancer was based on a single mechanism. Today, it is known that each type of cancer must be researched individually,” says the scientist.
According to Stevens and Feingold, research must first identify the cloud systems on which aerosols have the greatest influence. They suggest starting with particularly common types of cloud, for example flat cumulus clouds over the oceans (Trade Wind cumuli), which cover 40 percent of the global seas.
A research project to be undertaken jointly by the Max Planck Institute for Meteorology and the Caribbean Institute for Meteorology and Hydrology in Miami will make a start on this. The two-year empirical field study will commence on the Caribbean island of Barbados, which is located in the Trade Wind region, in 2010. The researchers will install remote sensing instruments on the island’s windward side that will focus on the clouds coming from the open ocean. The land measurements will be complemented by measurements taken in the clouds themselves by HALO, the German research aircraft. The data from this measurement campaign should help the scientists to reach a better understanding of the relationships between cloud cover, precipitation, local meteorological conditions and aerosols.
Related links:
[1] Aerosols, Clouds, Precipitation and Climate: Barbados Field Study
[2] HALO Website (The High Altitude and LOng Range Research Aircraft)
Original work:
Bjorn Stevens, Graham Feingold
Untangling aerosol effects on clouds and precipitation in a buffered system
Nature, October 1st 2009, Volume 461, pages 607 – 613
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Interesting. Does this not also lead to the factor of decreased rainfall, if rain does not reach the ground? What do the experts say?
And we also now have Prof. Henrik Svensmark’s new report as noted on sciencedaily.com
“Cosmic Ray Decreases Affect Atmospheric Aerosols And Clouds
ScienceDaily (Oct. 6, 2009) — Billions of tonnes of water droplets vanish from the atmosphere in events that reveal in detail how the Sun and the stars control our everyday clouds. Researchers of the National Space Institute in the Technical University of Denmark (DTU) have traced the consequences of eruptions on the Sun that screen the Earth from some of the cosmic rays — the energetic particles raining down on our planet from exploded stars.”
The piece concludes with this quote:
“The evidence has piled up, first for the link between cosmic rays and low-level clouds and then, by experiment and observation, for the mechanism involving aerosols. All these consistent scientific results illustrate that the current climate models used to predict future climate are lacking important parts of the physics”.
http://www.sciencedaily.com/releases/2009/08/090801095810.htm
‘To date, however, it has not been possible to quantify the influence of the cloud lifetime effect on climate.’ Nice bold highlight. In contrast to ‘NOAA understands and predicts changes in the Earth’s environment, from the depths of the ocean to the surface of the sun, and conserves and manages our coastal and marine resources.’
The science is settled! We are just not sure if clouds are a significant influence but we are sure that CO2 is ……. trace gas verses water vapor ….. but we need money to study.
Hmm, nice job in the tropics for a lucky few German “climate scientists”.
Sorry if I appear cynical; but hey, at least they are making empirical studies. Maybe inadequate, but a start.
Ever was it so…These very same issues have confounded nearly every climate analysis in the last twenty years.
Waiting for Kim’s ‘message in a cloud’…..
I’m interested to see the result of that new study. Here in the Philippines, we hardly see the Sun the past few weeks and months. With or without a typhoon, clouds are everywhere. Sometimes the Sun would show up in the morning, only to disappear in the afternoon. Most clouds are low-lying, but sometimes they are thinly dispersed from the higher atmosphere to low level, perhaps hust half kilometer up from the surface. And yet we are near the equator.
We should get Dylan Ratigan to moderate the current state of the global warming debate. He shows real promise in getting to the truth about the issue.
Here is how he dealbt with a specific health reform issue.
I know, it’s a link to Huffington Post. Please forgive me.
http://www.huffingtonpost.com/2009/10/06/betsy-mccaughey-dylan-rat_n_311044.html
Our climate is incredibly complex. To say that CO2 controls everything is a huge oversimplification.
SNIP – we don’t allow discussions of chemtrails on WUWT
If I recall correctly, a large cooling effect of aeresols is presumed by the global circulation models when calibrated/validated against present and past climate. If the actual cooling effect is minimal, as argued above, then a reasonable conclusion is that the warming effect from CO2 is quantitatively overestimated by the models.
I take it these aerosols also compensate for the greenhouse effect of the water they create?
Sounds like perpetual motion.
Help, I need a budget, I want to go to Barbados!
I ask a simple question:
We all have seen the sat images from ship tracks.
If they measure the emission output of an individual ships engine and measure the moisture levels and temperature of the surrounding air mass and the residence time of the chimney plume, they can use that data for models.
Here you have an example:
Ship Tracks in a Stratiform Cloud Layer
http://earthobservatory.nasa.gov/IOTD/view.php?id=1967
Just thinking scientific experiments on a poor man’s budget
I tell you in advance, the entire study won’t bring us a rats ass further because the human effects are dwarfed by natural events.
Just an example.
In all the European cities fine dust measurement are made.
One of the recent reports I read about the subject concluded that over 60% of the fine dust collected came from the Sahara desert and other natural sources.
Well golly-gee! Maybe clouds have something to do with global temperature? While these guys are working on aerosol effects the Swiss are onto cloud seeding via cosmic radiation (now at its highest levels since cosmic ray recording began; it’s sunspot related).
These breathless “scientists” are merely rediscovering what ancient climate prognosticators knew all along. Nature’s primary, near-term temperature control mechanism is low-level cloud cover (not the kind that makes rain). I expect they will eventually “discover” that global temperature is fundamentally “self-correcting” by way of “negative feedbacks” to any forcing function that tries to change temperature (greenhouse gasses, for example). History plainly records that the climate system is inherently stable over the short term (and long-term cyclic over a macro range of 12 deg C.) and that it is not subject to “runaway” situations and “tipping points” such as those programmed into the CO2 global warming computer models.
I find it interesting that so many big-time scientific institutions are suddenly easing themselves back off that “runaway global warming limb” (without actually saying so). We can now add the Planck Institute and the Woods Hole Oceanographic Institute to the list of scientific heavy-hitters who seem to realize they’re about to look really foolish if they don’t somehow get out ahead of what is rapidly becoming self-evident.
Global temperature peaked in 1998 (GISS data manipulations be-damned) and has since declined; that’s a FACT!
CH
In the 1970’s, my group was engaged in hydrologic study of runoff regimes of the Canadian Arctic Islands, especially for the snowmelt period. We wished to relate net solar energy inputs for the melt to the melt water runoff. To measure net solar radiation, we mounted two solid-state solarimeters, one pointing up, and one down to the smowpack. We thus obtained data for direct sunshine and the albedo. Our main concern was the substantial loss of snow water content via sublimation during the melt season. So, my question: Why could not weather satellites, properly instrumented, measure the same two parameters? That would, at the very least, provide some information for the short-wave energy components which could, in turn be linked to cloud cover beneath the satellite.
Hansen recently said that the Aerosols estimates were more-or-less just pulled out of a hat (and he was not kidding).
http://img58.imageshack.us/img58/855/modelaerosolsforcingp.png
You can multiply these numbers by 0.32 to approximate the temperature impact used.
I think I’ve never heard so loud
The quiet message in a cloud.
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REPLY: You’re late. People were beginning to talk. – A
Heh, DR, I saw the headline and jumped to my couplet.
Claude, sometimes I think that quiet message in a cloud is the magic self-centeringness of the whole system. Doubtless the real mechanism is even more complicated than just the convection, radiation and phase changes within a cloud, but it’s entertaining to imagine that there is just a simple process deep in the occult heart of a cloud.
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Kurt,
Ding, ding, ding – we have a winner! What separates ho-hum warming due to CO2 from alarming warming due to CO2 is the role of aerosols in the climate models. If you want to post at RC for the purpose of getting NO response, ask about aerosols and climate modeling. Crickets chirping.
Chris, the real irony is that by manipulating the once and future record of albedo the warmistas could explain any model output they’d care to push. I think the dissonance and demoralization in that community has caused them to miss the opportunity, and now, it may be too late. We are cooling, folks; for how long even kim doesn’t know.
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Isn’t this just a waste of time and money since the science is settled?
Do you suppose a hamster ever sees its own wheel?
‘Follow the Latent Heat’.
Signed, Deep Cloud
Re: Ken Roberts (20:15:39) :
“Do you suppose a hamster ever sees its own wheel?”
I never before heard or saw that profound observation and I hope you dreamed it up, because it far surpasses my “dogs chasing their own tails” description of most of this bunch of scientists. These people have no inertia. It’s not so much that they can change direction instantaneously that I find so bizarre, but that they can do so with an enthusiasm that does not wane despite repeated failures to gain any headway whatever.
As the Warmists sink into the west, the evidence is rising in the east,for them a cold,bad Moon on the rise.
Apologies to Creedence Clearwater…