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 water vapor possible 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 (homogeneous nucleation).  Rather liquid drops form only when water vapor nucleates on 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 depend on such incongruous phenomena as ionization trails of galactic cosmic rays 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 less 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 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 on millimeter scales rather than the many kilometer separations now employed.  So the equations of fluid flow, i.e. Navier-Stokes, are supplemented by arbitrary curve fitting polynomials to make model predictions match historical records.  This corruption of the science is called “parameterization”.  This is unfortunate because the most of the energy flow in the troposphere is regulated by clouds [3].  But this is necessary, because even with infinite computer resources, wind, weather, and clouds are “chaotic” and theoretically impossible to predict.




While we can estimate magnitudes, we have few precise measurements of global cloud statistics much less their evolution.   Nevertheless clouds are crudely observed to provide negative feedbacks reducing warming from all sources.   This is in stark contrast to alarmist predictions which require an runaway positive feedback to increase modeled CO2 warming predictions to anything we could possibly observe.  Fortunately, with the advent of satellite measurements we have the first unequivocal observations and as expected the feedback is negative cooling the earth.  In particular, 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 increase the temperature of nearby regions of the sun raising the solar irradiance by about a watt per square meter over the entire earth, i.e. on the order of 0.1%.  But this is not of sufficient magnitude to cause much change in temperature.  Rather the more important effect is the modulation of cosmic rays which provides nucleation sites for water vapor.   This increases cloud cover and since clouds have a significantly greater effect than greenhouse gases, it wouldn’t take much to overwhelm every other consideration [7].  But the bottom line is that sunspot frequency is a strong predictor of global temperature cycles while CO2 levels are not [8-9].  


Global warming advocates dismiss these manifest facts by focusing only on simplistic estimates of direct solar heating.  This red herring, ignoring the undisputed correlation with sunspots, continues to demonstrate a political rather than a scientific agenda.




Because the effect of clouds is so great, small uncertainties in their behavior ceates large and exponentially increasing errors. [9]


figure 1

Figure 4. The Special Report on Emission Scenarios (SRES-SPM-5) A2 projection from Figure 1 showing the physical uncertainty of the projected temperature trend when including ±10.1% cloud error (light shading), or the uncertainty in greenhouse gas forcing (dark shading). Inset: A close-up view of the first 20 years of the A2 projection and the uncertainty limits.


“This shows the A2 SRES projection as it might have looked had the IPCC opted to show the minimal ±10.1 % cloud error as a measure of the physical accuracy of their GCM-scenarioed 21st century temperature trend. The result is a little embarrassing. The physical uncertainty accumulates rapidly and is so large at 100 years that accommodating it has almost flattened the steep SRES A2 projection of Figure 1. The ±4.4°C uncertainty at year 4 already exceeds the entire 3.7°C temperature increase at 100 years. By 50 years, the uncertainty in projected temperature is ±55°. At 100 years, the accumulated physical cloud uncertainty in temperature is ±111 degrees. Recall that this huge uncertainty stems from a minimal estimate of GCM physical cloud error.


In terms of the actual behavior of Earth climate, this uncertainty does not mean the GCMs are predicting that the climate may possibly be 100 degrees warmer or cooler by 2100. It means that the limits of resolution of the GCMs — their pixel size — is huge compared to what they are trying to project. In each new projection year of a century-scale calculation, the growing uncertainty in the climate impact of clouds alone makes the view of a GCM become progressively fuzzier”


Does anyone think that perhaps we need more science education and fewer new taxes for the general fund?





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 …