Marble in space
Main influences on Earth's temperature
By Dr J Floor Anthoni (2010)
(This chapter is best navigated by opening links in a new tab of your browser)
Planet Earth 'hangs' by an invisible thread between a sun of 6000ºC and outer space of -273ºC, its temperature depending on solar radiation, Earth's reflectivity (albedo) and outgoing re-radiation. How do these change? The atmosphere also influences the temperature of Earth's surface. How does it change? 
An introduction to this important chapter
Earth is the third planet from the sun. How does it compare to its neighbours? The atmosphere to 800km altitude, the radiation balance, temperature gradients, how is the temperature of a planet measured?
Earth's reflectivity or albedo is the most important climate factor after solar irradiation, also because it can change drastically and suddenly.
The Earth wobbles in both its rotation and orbit, and this causes small changes in the amount of sunlight it receives, and in the intensity of summers. The effects are very slow and small but add up.
The effect of imaginary atmospheres with various properties such as convection, heat re-radiation and more.
How does a living planet contribute to regulating its temperature?
The biggest change to our planet comes from deforestation and changing land use. It has had a profound effect on climate, often mistaken as caused by global warming.
The properties and effects of Earth's atmosphere, reviewing the science. Radiation budget and balance.
Although the sun's radiation has been very constant over a long period, it may not always be so, as suggested by sunspots and their cycles.
Quite recently, more attention is paid to cosmic radiation from outside our solar system, because correlations look promising.
Other influences on solar radiation are: volcanoes, condensation trails, black soot, and maybe more.
Important tables
& related chapters
Geologic time table: the development of Earth and its life
Back to climate index and introduction

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When viewed from outer space, our planet Earth appears like a blue-green-brown marble with white swirls of cloud. It is a spectacular sight which reminds us of how special this planet is, and perhaps also how vulnerable.
Little does one realise that this blue/white blanket around the world, and everything that lives within  it, is so preciously thin. Imagine planet Earth the size of a billiard ball (6cm diameter). Then the whole biosphere from the deepest oceans (-10km) to the tallest mountain top (+10km) is merely as thin as a human hair (0.1mm). Within this thin smear, everything happens in layers: the deep ocean circulation, the shallow sea surface circulation, the winds, clouds and rains, and all air traffic. Above the troposphere of 10km thick, very little else happens.

Understanding this thin smear upon which our lives depend, is therefore important. This chapter looks at Earth hanging in the balance between a solar skin of 5800 degrees Celsius and the cold black outer space of -273 degrees. Earth's temperature depends not only on its position (which varies) but also on the sun's light output (which also varies). And life as we know it, depends on a small range of temperature (the Goldilock zone "just right"). Not surprisingly, the planet has evolved with mechanisms to stabilise its temperature, although this can't prevent the sudden swings between ice ages and the warm periods in-between.

We are still living in an inter-glacial warm period which began some 10,000 years ago and stabilised some 7000 years ago. So the entire known history of human civilisation happened in a single warm spell between ice ages. It simply could not have happened in the 50,000 years of cold beforehand. We are thus very privileged.

In this chapter we'll have a close look at our atmosphere and how it works as a stabilising blanket. We'll study the variations in our position relative to the sun and how the sun varies its intensity, and also at influences caused by humans.

Planets compared
comparing mercury venus earth marsOur nearest planets are all like Earth, 'rocky' rather than 'gassy'. None produce enough heat by themselves to make a difference (it is thought), such that their temperatures are determined by the heat from the 6000ºC (5800ºK) sun and how much they re-radiate back into space. The graph shows the positions of these planets relative to the sun, measured in Astronomical Units (AU), equivalent to the distance between sun and Earth (150 million km or 8 light-minutes). The vertical scale is logarithmic and represents solar irradiation, the solar constant in Watt per square metre, but also the planet's temperature in degrees Kelvin (1K=-273ºC). For details see the table below.Note that the degree sign º is omitted for Kelvin.
Surprisingly, the average temperature of Venus stands out due to its dense carbon dioxide atmosphere (96% CO2) (it is thought) covered with a white cloud of sulfur dioxide (SO2), acting like a white body.

planets of our solar system
Our solar system from left to right: Sun, Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, Pluto
distance to sun (AU) solar constant (W/m2) average temperature (ºC) without atmosphere, with zero albedo (ºC) without atmosphere (ºC) mass of atmosphere
Mercury 0.387 9147-9449 167 (440K) 173 (446K) 167 (440K) ?
Venus 0.723 2620-2688 464* (737K) 55 (328K unknown 4800E18 kg
Earth 1.000 1370-1402 16 (289K) 5  (278K) -17 (256K) 5.1E18 kg
Mars 1.524 590-612 -63 (210K) -47 (226K) -58 (215K) 0.025E18 kg
* The Russian Venera7 measured 475ºC before failing.

Every planet reflects some sunlight, which is the part that does not heat the surface and atmosphere, and it absorbs the remaining sunlight. The absorbed light interacts with the planet's surface and atmosphere, warming it in the process (otherwise the temperature would be like that of dark space, -273ºC). During this interaction, sunlight changes to heat, and this is re-radiated back into space. The amount of re-radiated energy depends on the temperature: the warmer, the more radiation. Thus a planet absorbing all sunlight (a black body) will re-radiate all light as warmth, by becoming warmer than a white planet. As a planet rotates, the incoming radiation happens on one side only while the outgoing radiation happens all around.

Thus all planets are in a state of balance such that:

incoming radiation = reflected radiation + outgoing re-radiation

Earth's atmosphereBut what is the 'average' temperature of a planet with an atmosphere? Look how the temperature varies from 15ºC at the surface to -60º at Mt Everest (10km), back to 0º at 50km and even up to 2200º at 400 km height? Because the atmosphere thins considerably with height, the upper levels do not have enough mass (and thus re-radiation) to play a role. Looking from the outside in, Earth's 'average' temperature lies somewhere between 1 and 40km, and is reported by satellites as 5º even though Earth's average surface temperature is 15ºC. (click on diagram for a larger version)
The diagram shows Earth's atmosphere to a height of 800km, higher than where earth-orbiting satellites are found. The pressure here is for all practical purposes zero (1E-50 bar). Note that the 'atmosphere' here is made up of the two lightest gases on Earth, helium and hydrogen which are continually gassed off to space by the solar 'wind' (a stream of particles from the sun).

From 100 to 600 km extends the ionosphere where sparse charged atoms (ions) move around at high speed, hence the high temperatures of 2200º to 750ºC. In the ionosphere one finds bands that are important to shortwave radio, as they bounce the electromagnetic signal back to Earth, thus enabling around-the-world radio transmissions. The higher F2, F1 and E bands are active only during the day, disappearing by night. Thus radio programmes and their frequencies for world radio change according to the availability of these ionised bands. At the altitude of the E band, the atmosphere is dense enough to burn up incoming meteorites, thus preventing most from reaching the ground. Notice that the composition of the sparse air here is very similar to that on the ground, but rare helium is far more common (it is a very light gas). At these heights auroras can be seen in the polar regions, caused by fast particles colliding with gas molecules.

At about 100km the 'temperature' has cooled to -80ºC (the mesopause) after which it begins to rise again to 0ºC in the stratopause. In-between is the mesosphere with the ionised D band which is active all day and night, reflecting radio waves but not very far.

Between 50 and 10km extends the stratosphere where the temperature climbs from -60º to 0ºC. It can be considered the 'lid' on the climate atmosphere, with a composition much like that on the ground. But there is enough oxygen for ozone to be produced here, particularly in the ozone belt between 20 and 30km. Underneath it extends a mysterious sulfuric acid belt at about 20km (sulfuric acid is a much heavier molecule than the normal air molecules).

Temperature is at a minimum of -50 to -60ºC in the tropopause, another 'lid' on the troposphere where the weather reigns.
In the troposphere the air is dense enough to trap and transfer heat, to spread it around and to even out temperature extremes.

Whereas average ground temperature (skin temperature) is about 15ºC, it diminishes at a predictable rate of 6.5ºC per kilometre altitude (the lapse rate). This decrease in temperature corresponds somewhat to the adiabatic cooling (cooling due to expansion without loss of heat) a parcel of air experiences when rising and expanding, and is a fixed property of gas. It seems as if the upper troposphere with the tropopause acts like a pane of glass, a lid over the atmosphere. Underneath it, conduction and convection of heat matter most, whereas above it in the stratosphere, the air is too thin for that, and re-radiation (dark radiation or infra-red) to space matters most.

Note that the atmosphere stores 1000x less energy than the oceans. The total heat capacity of the global atmosphere corresponds to that of only a 3.2 m layer of the 3000m deep ocean.

Leaving the effect of an atmosphere aside for a moment, the temperature of a planet can vary because of:

Try to remember the following rules of thumb:
If the distance Earth to Sun becomes 1% smaller, Earth's temperature increases by 2% or 6ºC
If the diameter of the sun increases by 1%, Earth's temperature increases by 2% or 6ºC
If the sun becomes 1% warmer, Earth''s temperature increases by 1% or 3ºC
A 1% increase in albedo cools the planet by 1% or 3ºC
About 99% of the atmospheric mass lies below an altitude of 30km

Main constituents of Earth's atmosphere
(*) concentration near the surface
In red the greenhouse gases. In blue the noble gases.
constituent ppm by volume constituent ppm by volume
Nitrogen N2
Oxygen O2
Argon Ar
Carbondioxide CO2
Neon Ne
Helium He
Krypton Kr
Xenon Xe
Hydrogen H2
Methane CH4
Nitrous oxide N2O *
Carbon monoxide CO *
Water vapour H2O
Ozone O3
Ammonia NH3
Sulfur dioxide SO2 *
Nitrogen dioxide NO2 *
other gases
aerosols, dust, 
trace amounts
highly variable

Temperature gradients
temperature gradients: atmosphere, ocean crustThe diagram shows the temperature gradients of the atmosphere, ocean and crust. Where a gradient (gradual change) exists, there must also be a transport of heat along that gradient from warm to cold (right to left in the diagram). This heat transport also depends on the density of the medium. The crust is 3 times denser than water, which is 800 times denser than air, but it transfers only about 0.06W/m2, which is negligible in the planet's heat budget. The oceans (blue curve) have a steep gradient and good mixing in the first 100m, but from 800m down, they are all equally cold to a minimum of 4ºC, corresponding with water's highest density. The only way for this cold water to surface, is to be replaced by equally cold water from the thermo-haline circulation. So for practical purposes, only the first 100-200m matter in climate change (perhaps not true as water as deep as 3000m shows temperature fluctuations).

The red curve shows how Earth's surface has an enormous range in temperatures, narrowing down in the first km, such that above 3km most of the atmosphere is equal all around the world. The gradient ends at about -55ºC in the tropopause which marks the end of the troposphere (sphere of mixing). All climate and weather occurs in the troposphere which is thickest around the equator (12km) and thinnest at the poles (7km). The brown line (sorry, here shown in red above the word "crust") shows how temperature increases under the surface, at a rate of 25-30ºC per km. By comparison the 'lapse rate' (cooling of the atmosphere with altitude) is 6.49ºC per km.
How is the temperature of a planet measured?
incoming and outgoing radiationWhen a thermometer cannot be placed directly on a planet, scientists determine its temperature from the heat it radiates out. For instance, this graph shows the incoming light (yellow) and outgoing heat radiation (green) of Earth. Because the atmosphere absorbs some 'colours', both spectra look rather frayed. Vertical is the light intensity and horizontal the wave length (= 'colour') in microns. Visible light runs from 0.4 to 0.7 micron, a narrow band, whereas infrared runs from 0.8 to 50 micron, a very wide band. The red envelope belongs to a body of 6000ºK and the green envelope clumsily fits around the outgoing heat radiation, but with enough uncertainty that we can't say for sure what precisely the temperature is seen from outside the Earth: somewhere between 260 and 300K (-13 to +27ºC). Keep this in mind when interpreting the table above. 

What would the temperature be of a mirror? If the mirror reflects the sunlight, then our space 'thermometer' would interpret the temperature of the mirror equal to that of the sun: 6000ºK. Venus has a very dense atmosphere consisting almost entirely of CO2. At 25km above its surface, a temperature of 50ºC was measured, and on its surface 450-475ºC under a pressure of 80-90 bar (80-90 times that of Earth). See Venus' atmosphere below.

Note also that the yellow curve must be in balance with the green one, as incoming radiation must equal outgoing radiation, or otherwise the planet would continuously either grow warmer or cooler. The reason that the two curves look unequal in size, is that both scales are logarithmic and not linear. The incoming radiation envelope is narrow but high whereas that of outgoing radiation is wide but low.
It is important to remember that the law of conservation of energy demands that  no total energy is lost, even though at any moment radiation (=flow of energy) may be out of balance.For instance, Earth is warmed on one side only during the day as its night side only cools.During the day the atmosphere cools the planet whereas during the night, it warms. One cannot average these opposing effects, as the IPCC scientists all too happily do in their computer models and temperature series.

Another important point is that the incoming light comes from a small spot in the sky (the solar disc), but is very bright (one billionth of the sun's energy, 1E-9), whereas outgoing radiation radiates out to space in all directions over almost a hemisphere (half sphere), but is rather weak. On any part of the skin, incoming radiation is only by day whereas outgoing radiation happens day and night.

The peak of the spectral envelope is according to Planck's laws:
peak wavelength (µm) = 2897 / T (ºK)
Example: peak wavelength of incoming radiation (sun) = 2897 / 5780 = 0.50 µm
peak wavelength of outgoing radiation (Earth) = 2897 / 300 = 9.65 µm
Earth's effective temperature is estimated with great uncertainty, between 255 and 300K
It is not certain whether our atmosphere is warming or cooling the surface.

Orbiting thermometer: can an orbiting satellite measure temperature accurately?
An orbiting thermometer can only measure the radiation coming from the planet in relation to its distance from the surface. Its advantage is that it can cover the entire surface of the planet many times each year, even though physical thermometers are missing from large tracts of the planet (like the oceans). Another advantage is that it does so entirely automatically, not needing human intervention (and error), and that it is not influenced by the Urban Heat Island (UHI) effect. 
In a polar orbit its measurements must be corrected for the fact that it 'sees' more of the poles than the equator, but this is relatively simple. However, its main difficulties remain:
Satellite temperature guesswork
The only instrument capable of 'measuring' temperature at a distance is a radiation meter or radiometer. Apart from being subject to the problems mentioned above, these instruments drift (vary) over time and need to be recalibrated and brought into agreement with measured temperatures on Earth. Thus a radiometer is good for measuring rapid variations, but useless for measuring slow ones. Thus despite the availability of temperature data from space for some 40 years, this data cannot be used to show slow decadal changes in solar intensity. What's more, their slow variations come from recalibrations against manual surface temperatures, and are not independent of these, and are equally subject to fraud. See the last point above, a massive 4.6W/m2 downward correction in 2011!!!

It is not surprising then that the resulting heat signal is almost impossible to calibrate to an 'average' temperature, and even then to correlate with actual surface temperatures. In the process, some arbitrary corrections need to be made, corrections that can be wrong or subjected to fraud.
For instance, if a "temperature difference" is observed, was this real and not caused by a change in cloud formation, or a change in water vapour?

Fortunately water vapour and rain are transparent to Earth's microwave out-radiation in the 5.0 mm band. Using this property, satellites can measure land and sea surface temperatures, subject to some of the difficulties mentioned above.

Note that one cannot 'average' the surface temperature because what one really wishes to know is the surface's heat/cold content. For instance a glacier at -3ºC contains vastly more 'coolth' than a desert at -3ºC by night. Likewise the sea at 20ºC contains much more available warmth than the land at the same temperature. Yet this is not taken account of in present-day temperature measurements from which world 'averages' are calculated. As a result, 'average' temperatures are quite deceptive and quite meaningless.
The global warming 'science' centres mainly on the radiation buget, the ins and outs of an accountant's balance sheet, but rarely discuss what is inside the balance sheet, the latent heat or stored warmth and coolth in oceans and ice caps. These by far overwhelm the annual heat balance, and no amount of mathematics can assess their influence.

There is no adequate physics or physical understanding of the circulation and key role of this latent form of energy in the atmosphere, nor a real understanding of the energy conversions into and from it.  All arguments (IPCC) are reduced to radiative treatments of electromagnetic energy, plus the mechanics of the movements of cold and hot air masses.

Important points:

Earth's albedo
The proportion of light reflected from the Earth's surface back to space is called albedo(whiteness) after the Latin word albus for white. It is identical to the Outgoing Shortwave Radiation (OSR) in the radiation budget, with spectral properties in the range of those of the incoming light from the sun. However as light interacts with substances on the surface, it changes colour (its spectrum) and intensity. Light coloured objects like snow have high albedo (see table below) whereas dark objects like forests and oceans have low albedo. When albedo increases, more light is reflected back to space, resulting in cooling of the atmosphere. Albedo thus has a large influence on global temperature. As Earth's average is around 30%, there remains ample scope for increases and thus temperature regulation.

Albedo and emissivity
surface type
Earth average (!)[2]
water (*)
desert sand
bare soil/loam
granite (mountains)
ploughed field
green grass
deciduous trees
conifer forest
asphalt, worn
black asphalt
black body
cirrus cloud
stratus cloud
cumulus cloud
cumulonimbus cloud
albedo %
emissivity [1]
0.969 - 0.997
0.993 - 0.998
0.949 - 0.962
0.975 - 0.986
(!) at equator 19-38%; at poles ~80%; varies with cloudiness
(*) water reflects like a mirror at low light angles and is wind (wave) dependent
[1][2] see links below
The world maps show how large the influence of clouds is. Data from CERES satellite.
In top earth picture: Note how the deserts and grasslands have high albedo. Of all the types of cloud, the rainstorm cumulonimbus (equator) is most reflective. Note also how water absorbs nearly all light, but at low angles, reflects almost all light.
Planetary albedo is the ratio of reflected radiation divided by the total incoming radiation. Thus the emitted longwave radiation is what is left over in order to balance incoming and outgoing radiation:
E = ( 1 - A ) x S / 4
Where A=planetary albedo; S= solar constant; 4= the ratio of the cross section to the surface of a globe: The amount of sunlight falling on Earth is that intercepted by a disc the size of the Earth. This energy is then spread over the whole surface of the globe (not evenly though): area of disc divided by area of globe:
pi x r x r  / 4 x pi x r x r = 1 / 4
If Earth's albedo = 0.30 and S = 1380 W/m2, then E = 0.7 x 1380 / 4 = 241 W/m2
From the Stefan-Bolzmann equation (below) it follows that T=255K. Consensus centres on 4-5ºC=277-278K
Reader please note that this leaves a lot of guessing and uncertainty.

Ground albedo and cloudiness by latitude
Earth's average albedo from north to southThis graph shows how average albedo on Earth changes with latitude (red curve). In the background a map of the earth showing normal (light green, plains/grass) and extra dry (yellow, deserts) or wet (dark green,forests) areas The sea was left white but should have been dark-blue. Albedo is low (dark) at the equator, and high (light) towards the poles. There exists a marked difference between northern and southern hemispheres mainly because there is more ocean down south. The desert bands (20-35º) do not make much impact because at their latitudes, still a lot of ocean is found. Between -60 and -70 degrees latitude, albedo increases steeply because Antarctica is a white continent surrounded by dark oceans. The south pole is also whiter than the north pole because the north pole is an ocean surrounded by continents, and in summer with less sea ice.
The average cloudiness by latitude is the blue curve, obtained from the IPCC. It somehow disagrees with the average Earth albedo of 0.3, so consider it somewhat lower. It shows that there is little cloud over Antarctica but much over the Arctic. The desert bands now show up in the form of dips on both sides of the equator (not precisely?). Now remember that all rain comes from the sea, which means that we cannot expect the clouds over land to contribute much to temperature regulation. Neither can we expect the deserts to contribute (no cloud, reflective already), nor can the southern hemisphere because it is already rather cloudy. Also both poles disqualify because they see little sunlight. Thus the Earth's capacity to regulate its temperature must come mainly from the tropics where most light falls and where warmth contributes to evaporation. It appears then that Earth's temperature self-regulation is rather limited.

On any given day, about half of Earth is covered by clouds, which reflect more sunlight than land and water

Energy radiation from a less than black body
An 'ideal' black body is both a perfect absorber as well as radiator; absorbs ALL incident radiation; and emits in all directions equally.
The energy radiated out to space from a body with emissivity is proportional to the fourth power of its absolute temperature in ºK, according to the Stefan-Boltzman equation:
j = emissivity x sigma x T^4 (Watt/m2)

where emissivity is 1 for a black body and 0.99?? average for Earth
and sigma = 5.6703 10-8 (W/m2/K^4), the Stefan-Boltzman constant
sun's radiation = (5.6703E-8) x (5800 ºK) ^4   = 6.42E7 W/m2 at its surface

Incoming radiation at Earth = sun's radiation / ( radius of sun / orbit of earth ) ^ 2 = 6.42E7 / (125)^2 =
= 1389 W/m2 = solar constant [1,2]

A 1ºC change in Earth's average temperature, could be caused by a change in: solar constant 1.4% (incoming radiation) or albedo 3.3% (day) or effective emissivity 1.4% (night). (1.4 = square root of 2)

[1] Gerlich & Tscheuschner (2009)
[2] several values of the solar constant have been quoted, depending on the estimated temperature of the sun.

Sea temperature and albedo
variation in Earth's albedoThe albedo of Earth has been reconstructed from overlapping satellite images (blue line, Pallé E et al. 2004), here graphed upside down because an increase in albedo makes the planet more reflective, thus cooler. Note how albedo diminished (less cloud cover) a massive -10% in as little as 15 years, corresponding to a radiative 'forcing' of +10W/m2 or 0.6W/m2 per year. By comparison, the IPCC worries about a warming effect of 2.4 W/m2 in a century. In red, the sea temperature from Endersbee. Note the strong correlation between albedo and temperature. Note also that most of the sun's radiation ends up in the sea from where it escapes more slowly than from the land. 
CERES is the Clouds and Earth’s Radiant Energy System instrument, operational since 2000. Nasa mentions that a 1% reduction in albedo would equate to 3.4 W/m2, which conflicts with the above diagram. A recent publication estimates increased effective radiation at 0.15 W/m2 per year [3].
The purple curve is the total increase in global cloudiness (%), which tracks very well the increase in albedo [4].

Important points:

[1] Engineering Toolbox. link. link2.
[2] Note that emissivity is often confused with the complement of albedo: (1 - albedo). Simply put, albedo gives the amount of reflected visible light (by day), whereas emissivity gives the correction in infrared 'dark' radiation affected by the nature of the substance (by night). Values quoted: 0.612, 0.75, are wrong. World average emissivity is not accurately known, but is close to 0.99.  Emissivity also varies with wavelength for each substance, much the same as absorption does. link.
[3] R. T. Pinker, B. Zhang, E. G. Dutton (2005): Do Satellites Detect Trends in Surface Solar Radiation? : "Solar radiation at Earth's surface from 1983 to 2001 increased at a rate of 0.16 watts per square meter (0.10%) per year; this change is a combination of a decrease until about 1990, followed by a sustained increase." Agrees roughly with blue curve above.
[4] cloud cover web site using data from the ISCCP D2 dataset (International Satellite Cloud Climatology Project).

Milankovic cycles
summer and winterIn order to understand Milankovic cycles, it is important to first understand how summer and winter arise. In the diagram, Earth is shown rotating around the sun in a counter-clockwise direction when looking down from the north. The planet itself rotates around its axis in the same direction, but at a slight angle of 23.5º. Northern hemisphere summer occurs when the northern half tilts towards the sun in June, and likewise for the southern hemisphere in December. In the northern summer, Earth is also 1.7% closer to the sun, thus the northern summer gets 3.4% more sunlight (= 3.5% more heat) or 1.7x3= 5 degrees C (see above), and the difference between northern and southern hemispheres amounts to 7 % in heat or 10 degrees C. These differences are quite large and have an influence on the climate system.

Milankovic variationsMilutin Milankovic (28 May 1879 – 12 December 1958), was a Serbian civil engineer and geophysicist, best known for his theory of ice ages, relating variations of the Earth's orbit and long-term climate change, now known as Milankovitch cycles. The diagram (from Wikipedia) shows the nature of the cycles and how these influence solar radiation (solar forcing). Milankovic thought that the ice ages could be explained this way. However, the planet has known ice ages only during the Pleistocene, back to 1.6 million years ago whereas the Milankovic cycles must be very much older. Note also that there is no hard correspondence between the oscillations shown and the recorded ice ages. 
Remember also that the effects of the Milankovic cycles is very small (max +/-50W/m2 of 1370 W/m2 or +/- 3.5%), much smaller than changes in albedo can achieve. Note that the Milankovic cycles all assume that the power of the sun remains constant, but is this so?

Important points:

The mystery of the faint young sun
mystery of dimming sunOver thousands of millions of years (eons), the sun has become brighter, and during the 4.5 eons that Earth had a crust, its luminosity increased by about 25% (red curve). Plotting Earth's temperature back in time (blue line), Earth should have been a snow ball earlier than 2 eons ago, but ancient rocks show neither such low temperatures, nor excessive CO2 to balance the heat. To make matters worse, at that time, life had not invaded the land, and it looked like a large bright desert, reflecting much of the solar radiation back to space. However, back then, the oceans were also larger, which is where most solar radiation was absorbed. Thus the surface temperature shown in the diagram (blue line) must be adjusted upward, above 273ºK (0ºC, the freezing point of water), following the early accretion of Earth's crust(brown shape) consisting of high albedo rock and desert. 
The dashed blue curve shows our graphical adjustment of surface temperature for the sea/land ratio, dipping below the 0ºC line at 4 eons ago when Earth was still hot without life, while staying above it all along. Ironically, the formation of ocean and continents had a stabilising effect.
The brown area is the amount of continent relative to today (%) and the light blue area the relative amount of sea. The grey area shows the temperature of the atmosphere from the surface (top) to the 'average' seen from space. The red curve shows the solar irradiation relative to today (%).
Note that Earth's hot interior has also been cooling and that the amount of heat lost through its crust (and through volcanism) must have been diminishing noticeably (not shown). Today, heat loss from the interior is estimated at 0.1 W/m2, or 0.01% of incoming sunlight. Even so, there are places where thermal energy can be exploited.

Minik T Rosing, Dennis K Bird, Norman H Sleep, Christian J Bjerrum (2010): No climate paradox under the faint early Sun. Letter to Nature 464, 744-747.
The diagram contains information from  Kasting & Catling (2003) and the accretion of Earth's crust.See soilgeo/crust formation.
Variable solar activity
Variable solar activity: carbon-14, temperature, sun spotsThis diagram brings three factors together: sun spots, carbon-14 ratio and average temperature. Note that the scale of C-14 is upside down. Carbon-14 is produced by normal nitrogen-14 absorbing a low-energy ('thermal') neutron and releasing one hydrogen ion in the upper atmosphere:
1n + 14N => 14C + 1H
Carbon-14 is radioactive and decays (beta radiation of electrons) in about 5700 years to half of its radioactivity, and can thus be used for carbon-dating of biomatter like wood, bone and shell. But it occurs in trace amounts of trillionths (1E-12) in the atmosphere. Shown here is its variation over time. Note that recently natural C-14 has been polluted by nuclear tests (making lots of it) and fossil fuel burning (lacking it). The brown curve shows that solar activity has been changing over time, and that it bears some correlation with surface temperature. However, it varies for only a few percent over long time scales.

In the recent millennium two climate periods stood out: the warm Medi-eval Warm Period (MWP), during which Vikings roamed the seas and Greenland was inhabitable, and the cold Little Ice Age (LIA 1350-1850), when the Thames froze over and Europe suffered famines and emigrations (to the USA).

In recent times more attention is paid to the number of sunspots counted on the sun's surface facing us. It also shows that the sun is restless. Particularly long periods of low sunspot numbers are correlated with cold periods in the world's climates. Not shown on the diagram is the very recent drop in sunspot numbers and their unusual extended absence. At the same time, cold winters are experienced. We may be in for another little ice age and hopefully not a full ice age. See the restless sun, further down.

minimum duration what happened
Dalton 1790-1820 crop failures, mass migration to USA; 
Maunder 1645-1715 more severe than Dalton; Imperial colonisation; Thames freezes over;
Spörer 1450-1550 collapse of Machu Picchu civilisation in Peru
Wolf 1280-1350 begin of Little Ice Age
Oort  1040-1080 dark middle ages; pests and famines
Mayan 600-800 collapse of Maya civilisation
Greek 350-450BC collapse of the Greek civilisation
Homeric 650-750BC .collapse of the Minoan (Crete) civilisation (?not sure)
Egyptian 1500-1400BC collapse of the 18th Egyptian Dynasty

Imaginary atmospheres
the glasshouse experimentIn order to deepen our understanding of how Earth's actual atmosphere works, we'll study a number of imaginary atmospheres, but first the glasshouse experiment (Robert W Wood 1909, Businger [1]). It is a simple experiment with three well insulated identical boxes A, B, C. A is open. B is covered in glass which lets light through but which blocks infrared light. Most glasses do this. C is covered with a special window made from salt (NaCl) which is known to be transparent to both light and infrared. Many plastics do this too. After exposure to sunlight, container A remains a little warmer than outside but the covered containers warm up considerably, reaching identical high temperatures of 55ºC with "hardly a degree difference". If the greenhouse effect were caused by blocking infrared radiation, container B would have become much warmer than C. In fact C becomes a little warmer because glass still blocks a little of the incoming solar infrared radiation. When the experiment is left to cool, the cooling rate is determined by the thickness of the glass. Conclusion: at Earth's temperatures and air densities, outgoing infrared radiation is negligible compared to conduction and convection. The greenhouse effect is not caused by infrared-blocking gases. Later we'll come across other reasons why this is so. The experiment has also been replicated by others [2] and with balloons [3] and very thoroughly here.Nevertheless, a large number of 'authorities' make false claims about this as it has become an entrenched belief [7]

At mid-day, a fully insulated box as above would receive 1368W/m2 solar radiation to reach a temperature of (Stefan-Boltzman law):  T = {1368/0.000000056704}^0.25 = 394.1K = 121.0ºC. Thus Earth can never become this hot.

  • Ramanathan and Coakley pointed out in their 1978 paper: "convection is what determines the temperature gradient of the atmosphere but solving the equations for convection is a significant problem – so the radiative convective approach is to use the known temperature profile in the lower atmosphere to solve the radiative transfer equations." In other words, an oversimplification of the real physics, and an acknowledgement of the importance of conduction and convection. The temperature profile is not calculated and explained, but is used to bolster the (false) radiative transfer theory, also in use by the IPCC.
  • Nasif S Nahle: “The warming effect (misnamed "the greenhouse effect") of Earth is due to the oceans, the ground surface and subsurface materials. Atmospheric gases act only as conveyors of heat.” We concur.
  • Ångström's experiment (1900) showed: 1. CO2 is transparent to 90% of infrared radiation applicable to temperature variation. 2. Those infrared bands that CO2 readily obstructs are already almost totally blocked by atmospheric CO2.
  • NASA: “Certain gases in the atmosphere behave like the glass on a greenhouse, allowing sunlight to enter, but blocking heat from escaping (false).” This is the whole (false) basis for the IPCC models. See also Hall of Shame/realclimate. Many textbooks repeat this argument. How could so many scientists have been so wrong for so long?
  • [1] R.W.Wood from the London, Edinborough and Dublin Philosophical Magazine, 1909, vol 17, p319-320. Cambridge UL shelf mark p340.1.c.95, i
    [2] Nasif  S Nahle and John O'Sullivan confirm Robert Wood's experiment, quoted in Chapter6. link(PDF).
    [3] Berthold Klein's experiment quoted in Chapter6.
    [4] Alan Siddons (March 2010): The Hidden Flaw in Greenhouse Theory,
    [5] Gerhard Gerlich and Ralf D. Tscheuschner (2009): Falsification of the Atmospheric CO2 greenhouse effect within the frame of physics,  International Journal of Modern Physics B, Vol. 23, No. 3 (2009) 275{364 }.
    [6] Postma Joseph E (): copernicus meets greenhouse effect. link. explaining two important mistakes in our thinking. Greenhouse effect cools rather than warms.!?
    [7] John O'Sullivan (2012): Our Atmosphere ‘Like a Greenhouse:’ 53 Crass Authority Statements. link.disgusting.

    Important points:

    no atmosphere and nitrogen atmosphereAbsence of an atmosphere
    The leftmost picture is that of Earth without an atmosphere, a bit like the moon, but with the presence of a warm inner earth (magma) and a crust above it. Earth's crust is by itself a magnificent blanket, only 20-40km thick compared to the magma which goes 6300km deep. Of course, this is all very simplistic. In the absence of an atmosphere, the incoming radiation is either reflected back into space from light coloured areas, or is absorbed to heat the surface of the crust. The red and purple bands signify some infrared and ultraviolet in the incoming radiation. The amount of infrared re-radiated into space is proportional to the temperature of the surface, reason why it cools rapidly by night. On average, the temperature is as low as it can get (-17ºC). The cold crust pushes the magma further down, allowing only a trickle of heat through. Note that a dead planet has high reflectivity (albedo), not shown. Note also that the crust acts as a miniature atmosphere by storing and conducting some heat. The 'centre' of this 'atmosphere' lies underground.

    Nitrogen atmosphere
    A nitrogen atmosphere is chosen as an example of an atmosphere which does not absorb radiation and is completely transparent to both incoming and outgoing radiation. It is just a cushion of gas resting on the crust. The amount of light re-radiated is the same as before, depending on the colour of the (dead) crust. But this kind of atmosphere has mass and contributes to conduction and convection by which warm air rises as cold air sinks. Also surface winds help to spread the heat more evenly. Thus heat is spread over the atmosphere without escaping. Such a blanket spreads the temperature more evenly and it also moderates extremes from day to night. The warm atmosphere then re-radiates most infrared from higher altitudes. As a result, the surface of the crust becomes warmer on average (5ºC). This invites the crust to warm through, as if the magma rose somewhat but this is inconsequential.

    Convection or re-radiation?
    There exists a great deal of confusion about how the warmth of the planet is reradiated to space and how the greenhouse effect works. It is thought that water vapour, carbondioxide and a few other heat-trapping gases control Earth's temperature. But a pure, transparent nitrogen atmosphere without them, does (almost?) the same. We think that our atmosphere is different from a greenhouse, but it is not. The troposphere is 'capped' like the glass on a greenhouse, by the adiabatic lapse rate which is independent of whichever gas is inside.
    It is thought that the skin re-radiates out to space through the transparent air, according to its temperature and the Stefan-Boltzman equation (above), but this is not so. Reradiation can occur only from a warmer to a cooler body, and happens at a rate depending on the difference in temperature between the two bodies, to the fourth power (Twarm ^4 - Tcold ^4).
    For example, a warm 30ºC skin reradiating to a 10º cooler air above it (exceptional case), radiates heat proportional to 300^4 - 290^4 = (81 - 71)E8 = 10E8, whereas reradiating to space which is 300º cooler, loses heat proportional to 300^4 = 81E8 or 8 times faster. With small differences in temperature, as is the case in air, re-radiation to space becomes negligible [1].
    It is also important how 'easy' it is to cool the skin by warming the gas above it, compared to re-radiation, as water vapour plays also a very important role [1].
    The consequence of this is that re-radiation plays a very small role inside the atmosphere, as long as it remains dense enough. But in the  stratosphere, reradiation does more to cooling than convection.
    In the troposphere and between skin and air, heat is (mainly) transferred by contact (conduction) and by movement (wind, convection), and within this moving air, by evaporation and condensation of water. Air movement happens both horizontally and vertically.
    Ironically, the radiation-trapping gases like CO2, and even water VAPOUR play almost no role. However, water vapour's latent heat and condensation into cloud, rain and snow, are of utmost importance to Earth's greenhouse effect.

    [1] Nasif S Nahle (2007): Heat stored by greenhouse gases a bit complicated but very important.

    Conduction and convection
    example of conductivity and convectionAir is a paradoxical substance. When you are standing in a freezing gale, the wind is trying to freeze you while at the same time the air in your clothing is keeping you warm. Why? Air (nitrogen and oxygen) is an excellent insulator for heat when it is not allowed to move, such as in woollen clothing. But once it moves, it becomes a good conductor of heat. Why?
    The diagram attempts to illustrate this. It has four layers of different temperatures, illustrated by different shades of red. A cubicle A is sandwiched between two layers. As it receives heat from the warmer layer below, it passes an equal quantity of heat to the cooler layer above, but it cannot exchange heat with the layer it is located in because it has the same temperature. It is a slow process caled conduction.

    If the cubicle moves to a layer of lower temperature, it will pass twice the quantity of heat to the next cooler layer, while at the same time also passing four quantities (it has four sides in this layer) of heat to its present layer. The same happens in reverse, when a cubicle B enters from a cooler to a warmer layer. Thus by moving around, which is named convection, air becomes many times more effective in conducting heat. It so happens that windy days are more common than calm days, and every wind also has much turbulence. Also warm air rises as cold air sinks. Thus convection is a major influence on the distribution of heat.
    Note that this applies to every kind of gaseous atmosphere on any planet.
    The mysterious lapse rate
    Above we saw that the troposphere is capped by the tropopause and that the temperature diminishes at a constant rate (the lapse rate) of -6.49ºC/km, despite the fact that the air becomes progressively thinner. It is strange that the temperature diminishes linearly (at constant rate) with altitude. So there is loss of heat, but not at a constant rate because the air has progressively less heat content. Then suddenly at 10-12km altitude, the loss of heat becomes zero (lapse rate = 0), which means heat is neither coming in, nor going out. Stranger still, from here on into the stratosphere, the very thin air becomes warmer, which means that heat is coming in.
    The lapse rate is poorly understood, even though it is a general property of gaseous atmospheres. Some think that it is caused by air rising and cooling while it expands (adiabatic cooling), but up there exists no spare space for rising air, and for every parcel of air rising, there must be a corresponding parcel of air sinking, accompanied by counter-acting adiabatic warming. Every time a parcel of air warms or cools, some heat is lost permanently due to thermodynamic losses. Is the heat transferred upward by convection, and is the air moving ever faster as it becomes thinner? Or is most of the heat re-radiated across the tropopause into space? Evidently there is much uncertainty here.

    Important points:

    CO2 atmosphere
    The two diagrams show a CO2 atmosphere at Earth's conditions (low concentration with nitrogen) and the situation on Venus. CO2 has only little effect on the incoming radiation and some effect on the outgoing radiation. At 300ppm it is already almost fully opaque ('black') for the wavelengths it blocks, within one metre! Within a few metres it has stopped all the infrared it could possibly stop, and converted this energy to heat, radiating again over a wide spectrum in all directions. In other words, CO2 mainly contributes to convection. In the upper atmosphere an increase in CO2 concentration (say, from 400 to 800 ppm at the surface) could have an effect, but there's little it can do here because all the radiation it could absorb has been absorbed and retransmitted at other wavelenghts. Besides, the cooler air here cannot warm the warmer air below it. The situation on Venus which is surrounded by almost pure CO2, is entirely different for other reasons.
    Note that much ado is made about CO2 as a greenhouse gas, supported by model calculations, but actual measurements do not support this. CO2 is just far too potent to have any effect left [1]. At this point it is important to remember that CO2 cannot ever have a measurable effect on temperature, despite what has been published to the contrary. We'll come back to this later.

    A computer simulation program MODTRAN (not an experiment), assuming that there still exists infrared emissions in the CO2 band, from the stratosphere, leads to a similar but weaker conclusion:

    "The effect of carbon dioxide on temperature is logarithmic and thus climate sensitivity decreases with increasing concentration. The first 20 ppm of carbon dioxide has a greater temperature effect than the next 400 ppm. The rate of annual increase in atmospheric carbon dioxide over the last 30 years has averaged 1.7 ppm. From the current level of 380 ppm, it is projected to rise to 420 ppm by 2030.
    The projected 40 ppm increase reduces emission from the stratosphere to space from 279.6 Watt/m2 to 279.2 Watt/m2. Using the temperature response demonstrated by Idso (1998) of 0.1°C per watt/m2, this difference of 0.4 watt/m2 equates to an increase in atmospheric temperature of 0.04°C.
    Increasing the carbon dioxide content by a further 200 ppm to 620 ppm, projected by 2150, results in a further 0.16°C increase in atmospheric temperature." [2]
  • Another way of looking at carbondioxide's impotence is: it occupies less than 0.001 of air. Suppose it was 'black' to outgoing infrared radiation, only 1‰ of the air would be heated. The heat is then passed on to the other 999‰.
  • Gerhard Gerlich (2009) [3]: "within CO2's absorption wavelength of 10µm in air with 300ppmv CO2, one finds 8 million CO2 molecules. To talk of heat transfer as done by radiation is nonsense. Conduction and convection dominate by far. CO2 conducts heat only half as well as either O2 or N2."
  • Gerhard Gerlich (2009) [3]: (freely translated) "there exists no mechanism whereby carbon dioxide in the cooler upper atmosphere exerts any thermal 'forcing' effect on the warmer surface below. To do so would violate both the First and Second Laws of Thermodynamics ... heat rises, it does not fall."
  • Alfred Shack (1972): "the radiative component of heat transfer of CO2 ... can be neglected at atmospheric temperatures. The influence of carbonic acid on the Earth's climates is definitely unmeasurable."
  • Important points:

    [1] Hug, Heinz (1998): The climate catastrophe - a spectroscopic artefact?. simple spectrometric measurement on a column of air with variable amounts of CO2. CO2 is just too strong an absorber of infrared to have any effect on AGW, which makes it just part of convection. One simple experiment that proves many theoretical considerations wrong.
    [2] Archibald, David (2008): Solar Cycle 24: Implications for the United States. International Conf on Climate Change, March 2008. link.
    [3] Gerlich, Gerhard & Ralf D Tscheuschner (2007): Falsification of the atmospheric CO2 greenhouse effects within the frame of physics. In J Modern Physics Vol 23, 3 275-364. link. Very important reading but a bit difficult. It completely demolishes the greenhouse effect as propagated by the IPCC and most textbooks. Any gaseous atmosphere has a greenhouse effect. This paper has caused quite a stir among climate scientists. An easier to read 6-page summary by Hans Schreuder, 24 June 2008.

    Venus' atmosphere
    Venus is totally different from Earth with its much bigger atmosphere. The atmosphere there is some 90 times denser, which conveys heat even more so by convection (this is not so on Earth). In addition, its outer layer consists of white sulfurdioxide (SO2) which reflects incoming radiation by over 65%. Whatever light penetrates further into the atmosphere, is absorbed until a very dim light reaches the crust. The very dense CO2 atmosphere supports fierce convection of gas, distributing heat effectively. Because of its isolating blanket, Venus' interior has remained warmer than Earth's. As a result, its crust conveys much heat from its interior to its very dense atmosphere. The surface temperature on Venus is some 470ºC.

    How does Venus differ from Earth?

    Important points:

    [1] It is rather counter-intuitive that a gas (CO2) which is only 60% heavier than air (N2 + O2), over a planet slightly smaller than Earth, and with 20% less gravity, contributes to an atmosphere which is 90 times denser than Earth's. Add to that its higher temperature, which means that gases are more prone to be 'vented' (lost) to space. This paradox has been explained by Dr Hartwig Volz, and is accessible here: The significance of Venusian climate.
    [2] Venus isn't our twin!  April 2006

    CO2 has no influence on the greenhouse effect
    Venus Earth comparison at 0.2 to 1 barHarry Dale Huffman [1,2] discovered that at Earthly tropospheric pressure (sea level 1000mBar to 200mBar at the top of the troposphere), the temperature gradients of Earth and Venus are identical as shown by this graph (Earth blue, Venus purple). Horizontally the tropospheric pressure from the surface up, and vertically the temperature, corrected by 1.176 because Venus is closer to the sun [1]. So an atmosphere with almost 100% CO2 behaves identically to one with almost 0%!!! Likewise, an atmosphere without any water vapour (Venus) behaves like one half saturated in it (Earth).

    This has a number of very important consequences:

    • 'greenhouse gases' have no influence on the 'greenhouse effect'. Thus methane, carbon dioxide and even water vapour have no effect on how heat escapes from a planet with a gaseous atmosphere.
    • the tropospheric temperature gradient or lapse rate (=the real greenhouse effect) is caused by thermodynamic behaviour of any gas, combined with conduction and convection.
    • Anthropogenic Global Warming from CO2 is not possible !!!!
    • the importance of this fact cannot be overstated. Take note!
    [1] Huffman, Harry Dale (2010): Venus: No Greenhouse Effect.
    [1a] If the above link fails, here is a mirror in climate6.
    [2] Robert Fritzius (2001): Venus Atmosphere Temperature and Pressure Profiles

    Nitrogen atmosphere with water
    nitrogen atmosphere with waterAdding water to the nitrogen atmosphere discussed above, changes the picture quite radically as two very reflective substances are added: ice caps and clouds. Of these the ice caps store a very large amount of latent heat (coolth), changing in size only slowly.  By comparison, clouds are ephemeral (short-lasting). In addition, convection with water vapour is much more effective because water vapour has high latent heat and condenses at altitude, raining down rapidly, and thereby conveying heat upward and cold downward. Even though air contains only 2-3% water, its ability to convey heat and cold increases considerably. See also our next chapter on water and ice. The large ocean however, is by far the largest circulating store of heat, moderating Earth's temperature through day/night and seasonal temperature swings and even in between ice ages.

    Water has given our planet an ability to regulate its temperature in the following ways:

    warming => more evaporation => more cloud => more light reflected => cooling

    However, a small positive feedback may occur, feared by some to become a 'run-away' self-reinforcing loop:

    warming => more water vapour => traps infrared light => stores heat in atmosphere => more warming

    But we now understand that water VAPOUR does not play a role in the radiation budget for the same reasons that CO2 doesn't.
    In addition:

    cooling => less moisture in air => less snowfall => shrinking ice caps => less light reflected to space => warming

    But also runaway cooling:

    cooling => more ice extent => more reflected light => more cooling

    Please note that the respective magnitudes of the above four effects are not known, which lies at the centre of the global warming scare. But there is more to the planet's self-regulation as we will see below.

    The most important thing to remember is that water vapour, an innocent potential warming gas, can instantaneously become cloud, a potent cooling agent. With about 20% of incoming radiation reflected by cloud, the planet has a very powerful 'throttle' to control its temperature. For instance, in the morning when the sun is weak, clouds disappear and as the earth warms, water vapour enters the air. By mid day clouds begin to form, just as the sun is becoming hot, resulting in moderation of incoming heat and retention of heat between cloud and skin. For the surface to become cooler, clouds simply need to begin a little earlier in the day. A similar thing can happen at night where a cloudless sky loses more heat.

    When a cloud forms, a large amount of heat is freed, warming the cloud as it forms, but not enough to re-evaporate it. Thus clouds also act like blankets. A dense cloud reflects more light, before it can be absorbed by the water in the cloud (water also absorbs light, see underwater photography/light). Clouds keep the surface cool by day and warm by night.
    Snowball Earth
    Snowball Earth refers to the hypothesis that the Earth's surface became nearly or entirely frozen over, at least once during three periods between 650 and 750 million years ago (the Pre-Cambrium), because glacial deposits were found in sediments located rather far from the poles, as shown on the map below of what is thought to be the location of the continents at the time. [image Wikipedia] See also Geologic time table
    glacier deposits of snowball Earth

    The idea that it could have been possible that the entire planet was covered in ice and snow, comes from:

    cooling => more ice extent => more reflected light => more cooling
    and conversely:
    warming => less ice extent => more absorbed light => warming
    but also:
    cooling => less evaporation => less ice => warming
    and Earth may well teeter in the balance between ice formation and evaporation, with oscillations between each phase (ice ages).

    Off course the hypothesis is shrouded in uncertainties related to the nature of sediments found, their magnetic orientation, transport of glacial debris, location of continents, and so on. For understanding present climate, it is sufficient to understand that glaciation can cause more glaciation in a run-away effect such as an ice age, and that ice ages last longer than their warm interglacials. See chapter2/ice ages.

    For an extensive treatise see Wikipedia/Snowball_Earth. - a lot of wild speculation.

    Temperature regulation by a living planet
    It is too tempting to consider the Earth's temperature and climate regulated by physical non-living factors. But life on Earth has existed for a very long time, changing its environment gradually to suit itself. So life has co-evolved with the climates it created, on the one hand adapting to the existing climate, and on the other hand improving it. 

    Independent scientist James Lovelock and Andrew Watson in a paper published in 1983 [1], first suggested the idea that life and climate evolved together, the one influencing the other, in such a way that the planet can be thought of as a single organism, even though it is made up of millions of species. For if life did not evolve this way, it would have remained very primitive indeed. Daisy World illustrates the idea. 
    DaisyworldSuppose the world is mainly barren, with a patch of black daisies and a patch of white daisies of the same species. Because black daisies absorb more heat, they can live in the colder parts of the planet, while the white daisies live in the warmer parts, reflecting more light, and making these parts more inhabitable. The word will soon be covered in black and white, and grey in the area where both survive, as shown in the left image.
    Suppose the sun becomes hotter. This makes the grey area less suitable for black daisies and they retreat to the poles, as white daisies take over, spreading from the equator. The effect is that more sunlight is reflected back into space and that the overall temperature of the world stays much the same, which is indeed borne out by computer simulations.

    In the same theme, deserts could be stabilising the climate as follows:

    warming => more desert, less green => more light reflected to space + more night cooling => cooling

    Alas, during an ice age the CO2 concentration in air reduces and life becomes rather desert-like, which adds to the ice age effect (see climate chapter 2)

    life on Earth during an ice age and interglacial
    The difference in life on Earth, between an ice age and what it is today, is massive. Then the world was mainly desert and grassland.

    Earth albedo seen from space by CERESThe problem with Earth is that its albedo is rather the opposite of Daisyworld, as shown in this image from the CERES satellite. Thus daisyworld cannot counteract the ice age drivers:
    more ice => cooler => more ice
    cooler => less CO2 => more desert => cooler
    which is why Earth is stuck in a multiple million year epoch of repeated ice ages (see Chapter2/ice ages) and why Earth's temperature has been gyrating long before that. Read our carbon pipe hypothesis in the ocean acidification chapter.


    This temperature graph obtained from sediment cores, shows that the climate on Earth has become progressively less stable.

    [1] Watson, A J & J E Lovelock (1983): Biological homeostasis of the global environment: the parable of Daisyworld. Tellus B (International Meteorological Institute) 35 (4): 286–9.
    [2] Lovelock, James E (1987): GAIA, a new look at life on earth. Oxford University Press.
    [3] See Wikipedia/daisy_world.
    [4] Schneider, Stephen H and Randi Londer: The Co-Evolution of Climate and Life. 1984

    Dimethylsulfide and climate
    dimethylsulfide from eutrophicationJames Lovelock, in trying to find the circulation of sulfur from sea to land, discovered and measured the molecule dimethylsulfide DMS (CH3-S-CH3), produced by plankton [1,2]. Although much bigger than the water molecule (H-O-H), it has a similarly polarised form, which attracts water molecules. Because water molecules are already attracted to one another, dimethylsulfide acts as a condensation nucleus, assisting water to change into cloud.
    The diagram shows how the plankton releases DMS which attracts water to form cloud. The diagram also shows how excessive erosion and wasteful land use (over-use of fertilisers) could accelerate cloud formation and produce denser rains, leading to more erosion, etc. (which is not proved)
    Scientists claim that DMS first needs to be oxidised to sulfuric acid before it can act as a condensation nucleus (which is not proved). The concentration of DMS in the sea is rather low (2-4 nanoMol/litre).
    DMS could be involved in stabilising world temperature by stabilising plankton productivity:

    more light => more plankton => more DMS => more cloud => less light
    and also:
    warming => faster growth of plankton => more DMS => more cloud => cooling


    more people => more intensive land use => more run-off
    more runoff => more plankton => more DMS => more and heavier rains => more run-off

    Reader note that this is still an area of speculation as the behaviour of DMS and other cloud condensing substances is not known in very low concentrations.

    [1] DMS has been associated with various plankton organisms such as coccolithophores, but it may well be that DMS is not produced during photosynthesis by the phytoplankton, but by bacterial decomposition especially of short-lived phytoplankton. [our hypothesis, J F Anthoni]
    [2] Charlson R J, Lovelock J E, Andreae M O, Warren S G (1987): Oceanic phytoplankton, atmospheric sulfur, cloud albedo and climate. Nature 326: 655-661. [not free]
    [3] See Wikipedia/dimethyl_sulfide: DMS is insoluble in water and boils at 37ºC, yet it is produced in water by life. In the atmosphere it is oxidised to sulfur compounds that form cloud condensation nuclei (CCN)
    [4] Timothy Bates, Patricia Quinn, Derek Coffman, Drew Hamilton, James Johnson, & Theresa Miller: Oceanic Dimethylsulfide (DMS) and Climate : DMS concentrations in the ocean are not changing, steady at around 3nM (~0.2ppm). World-wide measurements of DMS emissions and concentrations are now in progress.

    Land use and climate change
    shorting the water cycleThe effects from land use on climate, have not had extensive coverage, and they do not feature in IPCC climate change models either. However, the effect of changing a forest cover into arable lands, and the building of cities, houses and roads, has had a major effect on climate and is still continuing as world population grows. Once upon a time,  the lowlands near ocean coasts were lush forests and swamps. Moisture from the oceans (all rain comes from the sea) would rise and cool above the lowlands, and the rain would be sponged up by forests and deep soils. The forests in turn would re-evaporate moisture only to fall as rain further inland, and so on. In the end, even the central deserts of the continents would get some rain.
    But urbanisation and cropland changed all that. Cities and roads do not sponge up water at all, but drain it straight into local rivers, back to the sea. Cropland has lost the deep forest soils and standing lush foliage, and can store only a small amount of moisture, and excess water immediately drains away into rivers, back to the sea. As a result, the midlands and highlands receive significantly less water, resulting in droughts, expanding deserts, empty aquifers and shrinking glaciers. All are symptoms of major change in climate, keeping pace with world population [1,2].

    more people => less forest => less re-evaporation => drier continents => more light reflected => cooling
    less cloud => warming

    Thus ironically, the ultimate effect of land use changes is unpredictable even though its symptoms have been associated with 'global warming':

    Reader please note that this huge climate factor (land use change) has not received enough attention by mainstream scientists. Also that it is too difficult to simulate in computer models [3].

    [1] Wilhelm Ripl: Management of water cycle and energy flow for ecosystem control. 1994.
    [2] Wilhelm Ripl, Christian Hildmann (1994): Wasserhaushalt und Basenverluste aus der Landschaft....  (in German) Water and energy drive all life processes. Energy occurs as 'alternating current' in daily and seasonal cycles, the properties of which have been under-rated. In the past 2 millennia, the water storage capacity of the land has been reduced considerably, with consequent losses in soil quality and quantity. Also resulting in flooding. Next phase could be universal desertification.
    [3] Wilhelm Ripl, freshwater scientist (limnologist) at the Technological University of Berlin, is highly critical of the IPCC computer models because the most important factor on climate change, the change in land use, is not even looked at.

    Earth's atmosphere and energy budget
    As seen from our imaginary atmospheres, just about any atmosphere has a tempering 'greenhouse' effect on Earth's temperature, while acting like a blanket. The collective name for these effects is the greenhouse effect but a better name would be atmospheric effect
    It is generally thought (IPCC) that the gases in Earth's atmosphere block outgoing radiation, such that the atmosphere heats up (which is easily proved false by experiment). The diagrams below may illustrate the problem.

    Diagram from Wikipedia (above) and NASA (on right). One has average heat fluxes in Watt per square metres, the other gives relative values. But conduction and convection (rising air) hardly play a role.

    Earth's radiation budget according to Kiel & Trenberth
    Trenberth - Earth radiation budgetThe diagram shown here is perhaps the most detailed available today (Kiel & Trenberth). All quantities in W/m2. Average incoming radiation is 342 of which 76+29 (31%) is immediately reflected back and 10+58 (20%) absorbed by the atmosphere, leaving 29 (8%) reflected by the surface and 169 (49%) absorbed. Heat convection by air and water vapour 22+76 (29%) heats the lower atmosphere (troposphere). The surface radiates 392 out but receives 321 by back radiation 392-321 (21%). Of this 71, 53 (15%) penetrates the troposphere, etc. etc. Finally 237 (69%) leaves the planet as infrared radiation. Note that the 'atmospheric window' (surface to space) for infrared is a mere 40 (12%) and that highly variable clouds account for 76 (22%). This diagram also appeared in the IPCC AR4 report, and the name Trenberth is exposed through climategate. Take care, for the nonsense can be clearly seen as follows:.
    Absorbed by the surface: 196. Re-emitted by the surface 392. This is not possible because energy transfers within a passive closed system cannot exceed the energy entering the system. Thus a surface cannot re-emit more than it gets. In the diagram it re-emits even more than the total energy from the sun (342). Also the idea of back radiation is false because it comes from a cooler source, higher up in the atmosphere. One cannot get more back radiation than what was absorbed by the surface and the atmosphere (169+58). The whole diagram is guess work or fantasy, not based on actual measurements, and all global climate models are based on it!
    No part of the 'global energy budget' can be greater than the incident energy. - Harry Dale Huffman link

    Wallace & Hobbs energy balanceA diagram from Wallace & Hobbs in the late 70s. Note how these figures disagree with those from other authors. The science of the radiation budget is far from settled, but there is another problem - these figures are not constant, but vary enormously from place to place, year to year, season to season, day to night and so on. The fear of manmade global warming comes from the notion that, all things remaining equal (which is not likely), increasing levels of CO2 will alter the energy budget such that more heat stays in the atmospheric 'blanket'. For that to happen, we need to look at the radiation absorption of CO2 and other greenhouse gases.

    radiation absorption spectra of greenhouse gases
    The incoming radiation is bounded by the red bell curve for 5525K, the temperature of the sun. What reaches Earth is shown as the ragged red shape. A large part of the UV side of the bell won't reach the surface because it is filtered out by oxygen and ozone, and by interacting with atmospheric molecules, the light is scattered in all directions (Rayleigh scattering), reason why the sky looks blue. Water vapour also halts some of the infrared incoming light, which one can feel varying on a sunny day. 
    What the Earth radiates out is shifted to the right by an amount accounting for the difference between 5525K and about 300K. The purple, blue and black bell curves show how much uncertainty exists about how warm Earth seems as seen from space (210 to 310K or 100ºC uncertainty !!). Important is that only 15-30% gets through the greenhouse blanket. Note that the wavelength scale is logarithmic and the blue curve and shape should be very much wider on a linear scale. So the blue shape should be identical in size (surface area) to the red shape.
    However, it is important to notice that nitrous oxide, methane and oxygen have only a negligible role to play, as their spectra mostly overlap those of water vapour. CO2 weighs in at second place, but where it is effective, it is nearly 100% effective in the first 10 metres, so any increase will have very little effect. Thus water vapour and clouds are the great variable in the climate equation, far outweighing any incremental effect of the rather constant CO2.
    Note (blue curve) that the atmosphere is relatively transparent to IR radiation from 8-13 µm, which is commonly used for IR imagery and meteorological satellites.

    Atmospheric data
    Solar irradiation
    Increase since 18th century
    Average for day/night, season & location
    Lapse rate (cooling with altitude)
    Height of troposphere (mixed sphere)
    Mean surface temperature
    Density of air at sea level is about
    1366 W/m2
    ~ 0.1 W/m2
    342 W/m2
    -6.49 ºC/km
    8-12 km
    14-15 ºC
    ~1.2 kg/m3 (1.2 g/L)
    • pressure decreases by a factor of two approximately every 5.6 km
    • 50% of the atmosphere by mass is below an altitude of 5.6 km (18,000 ft).
    • 90% of the atmosphere by mass is below an altitude of 16 km (52,000 ft). 
    • 99% of the atmosphere by mass is below an alitude of 30km 
    • The common altitude of commercial airliners is about 10 km (33,000 ft) and Mt. Everest's summit is 8,848 m (29,029 ft) above sea level.
    • 99.99997% of the atmosphere by mass is below 100 km (62 mi; 330,000 ft), although in the rarefied region above this there are auroras and other atmospheric effects. 
    • The total heat capacity of the global atmosphere corresponds to that of only a 3.2 m layer of ocean.

    Important points:

    [1] Florence J M et al. (1950): Absorption of near-infrared energy in certain glasses. J Res Nat Bureau of Standards, Vol 45 No 2.
    [2] Gerlich, Gerhard & Ralf D Tscheuschner (2007): Falsification of the atmospheric CO2 greenhouse effects within the frame of physics. In J Modern Physics Vol 23, 3 275-364. Very important reading but a bit difficult. It completely demolishes the greenhouse effect as propagated by popular consensus. (free) Rebuttal (not free) disagreement (free). An easier to read 6-page summary (free)by Hans Schreuder, 24 June 2008. Do not miss it!

    Radiation budget and heat transfer
    radiation budget and heat transferThis diagram shows incoming and outgoing radiation, averaged by longitude, from north to south horizontally. Note that the poles are very much smaller than the equator. On the left vertical scale the radiation in watt per square metre and on the right-hand scale heat transport in PegaWatt (1E15 Watt, purple). Alas only that for the northern hemisphere could be found. 
    The radiation budget shows that the equator enjoys an excess in radiation (green curve), and this would result in a continuous build-up of heat were it not transported to the poles where a radiation deficit exists. The way this heat is transported is shown in the purple curves. At lower latitudes, around the equator, the ocean does most of the transfer through large ocean gyres, and because the trade winds blow towards the equator. At mid latitudes the atmosphere takes over, eventually equalising the small polar deficit. Note that the poles are much smaller than the diagram suggests.
    ocean and air heat transport after trenberth&caronThere exists considerable uncertainty about how much the tropical heat is transported pole-ward, as this more recent graph from Trenberth & Caron differs from Pearson's. Here the influence of ocean transport (OT) is estimated to be considerably less than that through the atmosphere. Note that North and South on this graph are the other way around. Note also the bogus transit of the curves through the equator, where heat transport reverses suddenly, rather than gradually. One should also ask why so much heat is transported through air, whereas according to Trenberth and Kiehl, most heat is radiated upward and out of the atmosphere. 

    The restless sun
    total solar radiation seen by satelliteThe sun may not be as stable as has been thought. After all, it is a nuclear reactor whose energy is made by a run-away process of nuclear fusion, like a hydrogen bomb. But natural forces such as gravity and pressure keep the process reasonably constant. What we see from Earth is the energy peeping through the sun's gaseous 'crust'.
    This graph shows a composite of various satellite observations over three decades. It shows that the sun's irradiation varied by no more than 5 W/m2 but that a period of cooling occurred in the early 1980s, followed by gradual warming in the 20 years since, at a rate of 0.05% per decade, enough to explain most of the recently observed warming. Notice that the sun's cool periods have much less variation than its warmer periods. Notice also  that the graph is vastly expanded and shifted from the zero axis.
    Various satellites are now observing Total Solar Irradiation TSI, and once their instruments were recalibrated, a consistent and accurate behaviour emerged, shown here, and agreeing with observed cooling and warming periods, to such extent that most if not all observed "warming" (after fraud was eliminated) can be explained by variability in sunshine, thus from natural causes. Remember that the IPCC rejected this "because humans cannot change the sunshine". They were looking for, and blaming a human factor, e.g. CO2. The debate should have ended here.
    solar activity from beryllium-10 and sun spotsHowever, when using a more recent proxy for solar irradiance, as measured in an annually layered ice core from Dye-3, Greenland (Beer et al. 1994, blue curve), the variation in solar irradiance is much larger than previously presumed when observing a longer time period. The various cool periods of the past co-incide well with the sun's dips in brightness. See also Chapter7, Normal climate change.

    The swinging sun
    the swinging sunAlready mentioned by famous scientist Isaac Newton, the sun does not spin around its centre but around a centre which moves outside its diameter at times. This swinging or shaking is caused mainly by the massive planets Jupiter, Saturn, Uranus and Neptune, and has an effect on the material inside the sun, spinning the way water in a glass spins when the glass is swung or shaken. It can thus affect the sun's magnetic fields, sunspot cycles and the way radiation exits from the sun. It can change the sun's equatorial rotational velocity (spin) by 7%. The main cycle duration is 83-84 years, with multiples thereof. Accelerations in the sun's spin correlate with past cool periods [4]. Indeed Scafetta [6] discovers main cycles of 60, 20 and 9.1 (moon) years in the known temperature record. 
    Theodor Landscheidt [4]: "change in the UV radiation of the Sun is much greater than in the range of visible radiation.  The UV range of the [electromagnetic] spectrum lies between 100Å and 3800Å.  Wavelengths below 1500Å are called extreme ultraviolet, EUV.  The variation in radiation between extrema of the 11-year sunspot cycle reaches 35% in the EUV range, 20% at 1500Å and 7% around 2500Å.  At wavelengths above 2500Å, the variation reaches still 2%.  At the time of energetic solar eruptions, UV radiation increases up to 16%." [Note: the Aengstrom Å is 0.0001 micrometre or 0.1 nanometre or 1E-8m] Thus shortwave UV could have a measurable influence on gobal temperature.
    With regularity, holes appear in this solar 'crust', called sunspots, and through these sunspots energy pours out in swirls and loops, some of which reaches Earth as fast particles. Such particles could produce condensation trails in the thin upper atmosphere, causing high cloud and thus cooling.

    Sunspots have been known for a very long time, and they have even been counted, and records kept of these observations. So the waxing and waning of sunspot numbers in regular 11-year cycles, has been known for a long time. At irregular times, the sunspots become fewer and fewer, sometimes disappearing for many years and it has been noted that this somehow coincides with periods of  cold, like  the Great Potato Famine (Dalton mimimum, 1845-1852) and before that the the Little Ice Age (Maunder minimum 1645-1715) which caused mass emigrations to the USA.

    sunspot numbers since Maunder minimum

    An even stronger correlation with temperature is found by observing the duration of a sunspot cycle - the longer the cycle, the colder it is on Earth. The relationship is -0.7ºC for every year (7-16 years) the next cycle begins later. The bottom graph shows the anomaly of sunspots, how they deviate from 'average' (or 'expected', or 'normal').
    It seems as if the new cycle is unwilling to begin, a possible sign of lower solar activity. Recent thinking is as follows: the Earth is subjected to a constant flow of (slow) solar particles, which shield it from high energy galactic cosmic radiation. With less solar wind, there will be more cosmic radiation which is capable of creating condensation trails around which clouds form, which in turn cools the planet.

    lower solar magnetic field => fewer sunspots => less solar wind => more galactic cosmic rays =>
    => more high cloud => more sunlight reflected to space => cooling

    sunspot cycle durations matching global temperature
    The graph shows how sunspot cycle length correlates with northern hemisphere temperature for over one century: the shorter the cycle, the higher is temperature. But the underlying mechanism is not fully understood. Note that the series is still rather short to be conclusive, even though it is much longer than that from satellite measurements. Note also the poor correlation with CO2 in atmosphere (green) and annual emission of CO2 (0-7 Gt/y, brown). The dotted part of the green line comes from a single (questionable) ice core (Siple Dome); the solid part from several (reliable) CO2 stations like Mauna Loa, all located by the sea.

    solar cycle 24 predictionsIt just so happens that the sun has ended a cycle (cycle 23 - purple squiggle), but the new cycle (24) is not beginning as expected. Instead, the sun spots are staying away. Notice how the predictions for solar cycle 24 have been shifting, both further away and lower down. Even so, observations remain below even the most dire prediction. We are obviously entering an area of great uncertainty.
    Could this mean a new cold spell like the Little Ice Age (1600-1800) when sunspot numbers were low in 1645-1715 [1]? And for how long? Could it herald the beginning of next ice age? Based on sunspot cycles, the world will face 2 degrees cooling within a couple of years - a profound disaster. Time is ticking . . . (Nov 2010)
    Study this map for what temperature means to the prospering of society: globaltemp4000yr.gif . Smile about NASA's predictions of solar cycle 24 and stay uptodate with Landscheidts Layman's sunspot count. Right now (Feb 2011) it is tracking below that heralding the Little Ice Age (SC5). NOAA's prediction, updated regularly: Animation of predictions vs actuals:

    possible future temperature developmentsPredicting the future is most frustrating because one will always be proved wrong. The graph here shows actual temperature (black) already deviating substantially from IPCC projections (red) since the late 1990s. Taking account of the sun's declining activity, new scenarios can be projected (blue), according to past cold periods. But it could become even colder for a longer period than shown here. Quite evidently, humans do not have a significant effect on Earth's temperature.

    “It’s tough to make predictions, especially about the future.” - Yogi Berra

    [1] Abdusamatov, K I (2005): Long-term variations of the integral radiation flux and possible temperature changes in the solar core. Kinematics & Physics of Celestial Bodies. Vol 21, No 6, pp 328-332, 2005. The sunspot varies its size, surface sunspots come and go, activity waxes and wanes, also evidenced by Mars' solar caps. Periodicity is 11, 80 and 200 years.
    [2] Friis-Christensen, Eigil, and Henrik Svensmark (1997): What Do We Really Know About the Sun-Climate Connection? Advances in Space Research 20: 913-921.
    [4] Theodor Landscheidt (2007): New Little Ice Age Instead of Global Warming? From solar cycles, predicts Gleissberg-type minima for 2030 and 2200 of the severity of a Maunder-type cooling, known as the Little Ice Age that lasted for almost a century (1600-1650).
    [5] Sharp G J (): Are Uranus & Neptune responsible for Solar Grand Minima and Solar Cycle Modulation? - - examines influence of planets on solar motion and temperature. (diffcult subject)
    [6] Nicola Scafetta (2010): Empirical evidence for a celestial origin of the climate oscillations and its implications - - analyses the power spectrum of known temperatures and finds important cycles. (difficult)

    Cosmic radiation
    correlation between carbon-14 and oxygen-18Recently more attention is paid to cosmic radiation originating from outside our solar system. The graph here shows a strong correlation between temperature (by its proxy oxygen-18) from calcite (CaCO3) in unpolluted cave stalagmites (dripstones), and carbon-14 from tree rings of some very old trees. The unstable isotope carbon-14 is produced in the upper atmosphere by cosmic radiation, and the quantity produced, varies slowly with time. It decays slowly and very predictively, such that after 5000 years, still about half of it can be found. Thus any variation from the expected value must have been caused by cosmic radiation. How it influences temperature, remains a mystery for now.
    Note that 14-C concentrations would be about 50% (on right) to 25% (on left), compared to today's values, and that 20‰ variation is only very little. We're talking about small variations having large effects.
    correlation between neutron radiation and low cloud coverCosmic radiation in the form of neutrons reaching Earth, interferes with the atmosphere in such a way that more cloud is formed when neutron radiation is less. Why, is not understood. It appears that the solar wind influences the Earth's magnetic field, while also shielding Earth from cosmic radiation. A change in solar wind could explain the above two correlations.

    An explanation goes like this: when the sun is active, it has more sunspots. It also sends out more particles (the solar wind). These form a protective shield around the sun and its planet, that is very large but thin. Within this shield, particles from the sun interact with those arriving from outside the solar system (cosmic radiation), scattering or diminishing them. When the sun becomes less active, more cosmic radiation reaches Earth where it forms condensation nuclei, which in turn form clouds. Thus Earth cools. This effect is larger than the actual changes in solar radiation, the solar constant.

    Please note that cosmic radiation is far more energetic (GeV, giga-electron-volt) than solar particle radiation (MeV, mega-electron-volt).
    The chilling stars
    global temperature while crossing galactic armsQuite recently [1] scientists have begun to see a link between cosmic particles from distant stars as a major influence on Earth's climate. The Sun rotates around its galactic centre (Milky Way) in around 226 million years (a solar 'year'). Because it travels faster than the arms of the Milky Way, it passes through one arm every 140 million years. The arms are called Perseus, Norma, Scutum-Centaurus and Sagittarius-Car). When our solar system is in such an arm, it experiences a higher density of cosmic radiation than in the gaps in-between. The cosmic ray flux in these spiral arms is ten times more intensive than that of the sun, penetrating its protective solar wind and causing major temperature changes on Earth. As the graph shows, there is a strong correlation. 
    Thus the distant stars combined with the sun's activity, may well have a more decisive influence on Earth's climate, than mankind. Note that the cosmic ray flux (flow) is plotted upside down, thus more cosmic radiation introduces cold and less radiation warmth.
    milky way spiral arms
    It has recently been discovered that our Milky Way has two main arms, Perseus and Scutum-Centaurus as shown on this artist's impression of our Milky Way, and which is also borne out by the above graph. Our galaxy has a bar-shaped centre, dense with stars, from which several arms spiral out. The artist's concept also includes a new spiral arm, called the Far-3 kiloparsec arm, discovered via a radio-telescope survey of gas in the Milky Way. This arm is shorter than the two major arms and lies along the bar of the galaxy, thus not in the Sun's path. Our sun lies near a small, partial arm called the Orion Arm, or Orion Spur, located between the Sagittarius and Perseus arms. 
    Note that much uncertainty remains.


    [1] rays and climate. By Nir J Shaviv (2006), for more information.
    [2] search the Internet for Svensmark.

    Other influences on radiation
    atmospheric absorption due to volcanoesSolar radiation is not only affected by the gases in the atmosphere, but also by volcanic activity and human activities. Large volcanic eruptions have always had an effect on climate, mainly in the first year following, and to a gradually lesser extent in the four years after that. The graph shows how two recent volcanoes absorbed up to 20% of the sunlight, for several years. The VEI number is a measure of the size of the eruption. 
    Undersea volcanoes are the invisible part of volcanic heat transfer, and their effect is unknown. At the mid-ocean ridges, the sea floor is spreading, which is accompanied with the release of heat. What is known, is that the world is going through a period of more active volcanism, both on land and in the sea.
  • Volcanoes emit mainly (link):