The Science of Clouds




The earth’s oceans supply copious amounts of water vapor to the air through the process of evaporation.  Globally water vapor amounts to about 1-4% of all air molecules.  The local percentage depends strongly on temperature with humid warm air able to hold much more water vapor than drier cold air.    When the temperature drops, as at night or as one goes higher into the sky, at some point the air contains the maximum possible amount of water vapor which then condenses into liquid drops creating both the morning dew and clouds.  While water vapor is invisible, liquid drops and ice particles are not as they scatter and reflect light.


Clouds are thus made from small drops of water or tiny ice crystals, typically 1-100 microns in diameter.  These initial drops are small enough to be pushed around by turbulent convection currents which give them long residence times at all altitudes.  If there aren’t many drops around or if they gradually fall to warmer air, they mostly evaporate again. But if their density is high enough, they bump into each other and form larger blobs which are heavy enough to precipitate in the familiar forms of rain and snow and hail.


An additional, but oft neglected consideration is that the vapor to liquid transition never happens spontaneously even when it is energetically favorable to do so (homogeneous nucleation).  Rather liquid drops form only when water vapor nucleates on things like dust particles, or aerosols, or small cluster of sea salt ions, or highly oxygenated molecules (heterogeneous nucleation).   And the aggregate of these nucleation rates, which vary over many tens of orders of magnitude, are not only notoriously difficult to calculate but also strongly dependent on such seemingly incongruous phenomena as ionization trails of galactic cosmic rays from distant supernova as modulated by the sun’s magnetic activity.


In any event, clouds have very many different forms characterized mostly by their height and water content and whether there is any precipitation [1].



At any time on average, most of the world’s surface [about 60-70%] is covered by clouds [2].  Clouds are thus the primary regulators of the earth’s temperature because they block (i.e. scatter and reflect) sunlight and re-radiate infrared heat in all directions.  The direct effects of global warming gases are insignificant in comparison.


Although the dynamics of clouds is complex, nevertheless high clouds tend to warm and low clouds tend to cool the earth.  The net effect by far is to cool.   And these effects and their feedback loops are orders of magnitude greater than the “greenhouse” effect of trace gases in the atmosphere.





Not one single weather or climate model yet developed, or likely to be developed, anywhere in the world actually calculates the effects of clouds.   This would require grids finer than millimeter scales rather than the many kilometer separations now employed.  So rather than employing the equations of physics, i.e. Navier-Stokes, that are the only way to numerically create clouds, arbitrary and gross curve fitting polynomials are used to approximate the effect of clouds on global temperature in a crude joke called  “parameterization”.  This is unfortunate because in general, the amount of heat controlled by clouds and their effect on global temperatures vastly overwhelms the “greenhouse” effect [3].  Nevertheless, this is necessary, because even with infinite computer resources, the effects of clouds are theoretically impossible to predict because the system is “CHAOTIC”.




We have very little data on global averages of clouds much less on their evolution in a warmer world.   Nevertheless clouds are thought to provide a NEGATIVE feedback greatly reducing the initial effect of any increased warming from any source.   This is in STARK contrast to alarmist predictions of end of the world scenarios.  With the advent of satellite measurements, global cloud cover has decreased by perhaps 5% and average altitude has decreased by perhaps 100 feet [4].




While 60-70% of the earth is always covered by clouds, the humidity, or amount of water vapor, is greater over the world’s oceans.   For the continental United States for instance, we have the following average cloud cover statistics [5].






While it is true that the temperature of the sun does not change very much, its activity has proved highly variable over more than four centuries of observations.   Sunspots are irregular dark patches on the surface of the sun in which magnetic field lines become entangled thus reducing convection currents.  They appear dark because they are cooler than the sun’s protosphere by perhaps 1500 degrees Kelvin.   They may persist from as little as a few hours to as long as several months.


There is a strong correlation between observed sunspot activity and average global temperatures on the earth both over the centuries as well as with the shorter 11-year cycle.  In particular, the earth entered a global phase of cooling called the Little Ice Age starting around 1300 A.D., reached its peak about 1675 A.D., after which it began warming to end roughly in 1850 A.D.   This Ice Age almost exactly matches an absence of sunspots in the so-called the “Maunder Minimum” [6].  Very strong correlation continues to the present day as seen in the temperature plot of the world published by the IPCC in 1995.






Sunspots actually increase the temperature of nearby regions of the sun increasing the solar irradiance by something on the order of a watt per square meter over the earth, i.e. on the order of 0.1%.  But the likely cause of the correlation with temperature is the modulation of cosmic rays which provide nucleation sites for water vapor in clouds.   And since cloud cover has several orders of magnitude more effect on global temperatures than greenhouse gases, it wouldn’t take much to overwhelm every other consideration [7].


Please note that while the observed change in the solar irradiance of the sun is not of sufficient magnitude to directly cause the change in global temperatures, the CORRELATION is manifest and undeniable.    This is in dramatic contrast to rising CO2 in the atmosphere which is NOT correlated. [8]   Likely causes are changes in the ACTIVITY of the sun which also has a minor effect on solar irradiance but a much larger one on cosmic rays and consequent nucleation of clouds and a minor effect on heating of the upper atmosphere and changing wind patterns [9].


Global warming whackos of course dismiss the obvious scholarship by focusing only on simplistic estimates of direct solar heating.  This red herring, ignoring the undisputed relative correlations, again demonstrates a political rather than a scientific agenda.  Think we need more science education and not more “magic” DS (democrat-science)?





See also F. Blanchi, et. al, Science, Vol. 352 Issue 6289, 27 May 2016, page 1109.   Interestingly sulfuric acid and iodates, contrary to Global Warming Whacko propaganda over the last many decades do not seem to be important for cloud nucleation but rather highly oxygenated molecules.









as sourced in Rossow, W.B., and Y.-C. Zhang 1995, "Calculation of surface and top-of-atmosphere radiative fluxes from physical quantities based on ISCCP datasets”,  J. Geophys. Res. 100, 1167-1197.



For a more lighthearted education, see especially “The Politically Incorrect Guide to Global Warming and Environmentalism”, Christopher C. Horner, Regnery Press (2007); page 146.





Variation of cosmic ray intensity and monthly sunspot activity since 1958 according to the

Germany Cosmic Ray Monitor in Kiel  (GCRM) and NOAA's National Geophysical Data Center (NGDC),

respectively. High sunspot activity correlates with low cosmic ray intensity, and vice versa. Last month

incorporated: August 2009 (GCRM) and October 2009 (NGDC). Last diagram update: 6 November 2009.




The 6-fold increase in hydrocarbon use since 1940 has had no noticeable effect on atmospheric temperature or on the trend in glacier length…  Solar irradiance correlates well with Arctic temperature, while hydrocarbon use does not correlate …