Thanks for the post, Andrew. I'm having a hard time understanding the statement: *Only these homogeneously formed cirrus clouds can be effectively influenced by artificial ice nucleating particles[...]*
The bacterium* P. syringea <https://en.wikipedia.org/wiki/Pseudomonas_syringae> *produces a high temperature ice nucleation triggering enzyme which can be effective within areas of both heterogeneously or homogeneously formed clouds. Why would it not? As such, I also find it difficult to understand the premise that: "*An ideal geoengineering scheme would dissolve the cirrus clouds completely or prevent their formation in the first place. This, however, is not possible." *On one hand, dissolving cirrus clouds (or creating large holes) through accretion/precipitation, triggered by the high temperature ice nucleation enzyme, can not be ruled out. On the other hand, increasing albedo through the same means is also plausible. The dose makes the poison (or cure). The author's call for field expeditions to generate much more empirical data on these issues is highly justifiable and there may be ways to do this on the cheap. The artificial snow production industry can provide the enzyme in bulk and a simplistic dispersal system can be designed for use with typical weather balloons. Once at altitude, the enzyme would be dispersed and the results recorded through various means and methods. If this simplistic experiment can produce holes in the high cloud cover, commercial autonomous airships can eventually be used as cirrus cloud engineering platforms while possible earning money through providing platform space for communication equipment such as being proposed by *Google* <https://www.google.com/loon/>. For the general reader, I've included some basic information on the general cloud cover subject. *Per: http://www.climate4you.com/ClimateAndClouds.htm* <https://lh3.googleusercontent.com/-VplYc4JIWLU/V4adgNaBgsI/AAAAAAAAE3s/QuQ8ZRLpCTMmztLNtc3ypyMX-itcR-3XwCLcB/s1600/Clouds%2BCloudFraction20080101-31.jpg> Total Cloud Cover <https://lh3.googleusercontent.com/-oKuHUOrZDvM/V4adk2AFusI/AAAAAAAAE3w/JXmucaJyQz40F_Q1Eeu1WXUaAccKvQOggCLcB/s1600/Clouds%2BCirrusFreflectance20080101-31.jpg> Cirrus Cloud Cover <https://lh3.googleusercontent.com/-pE5pyKLKkHo/V4ajjo-tf_I/AAAAAAAAE4A/417h4woAp141r8ndJthmNP0HGbpPvxnswCLcB/s1600/CloudCoverAllLevel%2BAndWaterColumnSince1983.gif> *"Diagram showing monthly variations in global cloud cover for high, middle and low clouds since July 1983. The uppermost panel shows the variation of the total amount of water vapour in the atmosphere. During the period of observations, the amount of low clouds (net cooling effect on global temperature) has been decreasing from about 29 percent in 1986 to about 25 percent in 2007. A secondary low and peak were recorded in 1990 and 1994, respectively. The amount of middle clouds (no clear net effect on global temperature) has been slowly increasing from about 20 percent in 1984 to about 22 percent in 2007. The amount of high clouds (net warming effect on global temperature) decreased slightly until around 1999, and has since then again increased somewhat. The time labels indicate day/month/year. Data source: **The International Satellite Cloud Climatology Project <http://isccp.giss.nasa.gov/index.html> (ISCCP). The ISCCP datasets are obtained from passive measurements of IR radiation reflected and emitted by the clouds. Please note that **the step-like change in atmospheric water content 1998-1999 may be related to changes in the analysis procedure used for producing the data set, according to information from ISCCP. The cloud cover data, however, should not be affected by this. **Last data: December 2009. Last figure update: 4 September 2011."* In brief, engineering cirrus clouds as a form of GE does hold great potential and small scale field expeditions are highly justifiable. The first balloon launch, testing '*Dose Levels*' of the enzyme on cirrus clouds, can be achieved with minimal funding. Further experimentation, such as testing enzyme release from contrail (artificial cirrus) generating aircraft, can also be achieved with minimal funding. As such, a proposal should be prepared for NCAR/UCAR <https://www.mmm.ucar.edu/> (Dr. Latham, your input on this would be invaluable). Best regards, Michael On Tuesday, July 12, 2016 at 2:08:22 PM UTC-7, Andrew Lockley wrote: > > Poster's note : I don't normally share press releases, but this is a > complex and important paper that merits explanation > > > http://www.cscs.ch/publications/highlights/2016/can_cirrus_cloud_seeding_help_to_save_the_climate/index.html > > Can cirrus cloud seeding help to “save” the climate? > > Researchers at ETH Zurich used ‘Piz Daint’ to simulate how cirrus cloud > seeding, a novel geoengineering method, might impact the Earth’s radiation > balance. Their findings are sobering. > > July 4, 2016 - by Simone Ulmer > > Cirrus clouds look like giant feathers wandering around the blue sky; In > fact, they consist of numerous tiny ice crystals. They form in our > latitudes at heights of 5-13 km, where temperatures can be as low as -70°C. > Although they may seem light as a feather and translucent, these clouds > contribute to the greenhouse warming effect of Earth's atmosphere. This is > because incoming short-wave solar radiation easily passes through the thin > cirrus clouds, while they block a large fraction of outgoing long-wave > terrestrial radiation. > > The interaction of cirrus clouds with radiation is a complex one, which > depends on the concentration of ice crystals, their size, as well as on > properties such as the temperature of the cloud and the underlying surface, > and solar insolation. Model calculations indicate their radiative effect > accounts for about 5 Watts per square meter in global average. “Were one to > eliminate all cirrus clouds, that would immediately counteract a CO2 > doubling which adds a ‘warming’ impact of 3.7 Watts per square meter”, says > atmospheric physicist Ulrike Lohmann of ETH Zurich. This is what makes > cirrus clouds a potential target for geoengineering methods. > > Geoengineering by means of larger ice crystals > > An ideal geoengineering scheme would dissolve the cirrus clouds completely > or prevent their formation in the first place. This, however, is not > possible. Nevertheless, their radiative effects could be reduced by seeding > them with some very effective ice nucleating particles. These ice > nucleating particles are thought to decrease the number of ice crystals in > the cirrus cloud and make the remaining ones larger. This would allow more > long-wave radiation to escape to space, decreasing their warming impact on > climate. The effectiveness of such measures has now been investigated by > Lohmann and her graduate student Blaž Gasparini using simulations with the > ECHAM6-HAM global climate model on the CSCS supercomputer ‘Piz Daint’. > > A key issue that needs to be addressed to understand the efficacy of > geoengineering, says Gasparini, is whether a cirrus cloud and its ice > crystals have formed heterogeneously or homogeneously. Heterogeneously > formed ice crystals develop on a solid particle, called an ice nucleating > particle, such as a grain of dust. On the other hand, water droplets or > sulphuric acid droplets lead to homogeneously formed cirrus clouds. Only > these homogeneously formed cirrus clouds can be effectively influenced by > artificial ice nucleating particles, ideally at locations where the > humidity is relatively high and the cirrus clouds are still in the process > of formation. > > To date there exists only three studies on this topic, says Lohmann. These > offer some hope that the radiation effect induced by cirrus clouds could be > cut by 2 watts per square metre – which is to say, up to 40 percent of > their estimated overall effect. However, the simulations by Gasparini and > Lohmann on the CSCS supercomputer ‘Piz Daint’ paint a less optimistic > picture. Their simulations show that only a small fraction of cirrus clouds > has been formed homogeneously and is therefore susceptible to artificial > seeding. Furthermore, it was found that more cirrus clouds formed under the > influence of artificial ice nucleating particles and, rather than > increasing, the diameter of their ice crystals actually decreased. Their > conclusions show no significant effects of cirrus cloud seeding on climate. > > More data needed > > Gasparini and Lohmann note that their model predicts more heterogeneously > formed cirrus clouds, and also a larger radiative warming effect from > remnants of thunderstorm clouds, compared to previous studies. These > so-called anvil cirrus clouds, say the researchers, have similar radiative > effects to locally-formed cirrus clouds but cannot be influenced by > introduction of artificial ice nucleating particles in these altitudes. Due > to the lack of studies as well as the uncertain data available on the > global distribution of cirrus clouds, Lohmann admits that the results > currently obtained in this area are contradictory and will remain so for > the time being. The researchers advocate for better observational data of > the properties of cirrus clouds and ice crystal formation mechanisms to > improve their computer models and strengthen the results of their modelling. > > Reference > Gasparini B, and Lohmann U: Why cirrus cloud seeding cannot substantially > cool the planet, J. Geophys. Res. Atmos. (2016), 121, > doi:10.1002/2015JD024666. > -- You received this message because you are subscribed to the Google Groups "geoengineering" group. 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