This post looks at the central pillar of the climate change mania, which says that the “greenhouse effect” is responsible for us having a habitable planet by increasing the “global temperature” by 33 degrees C from a dismal -18C to the mythical “global average temperature” of 15C. I write this after a lot of reading and research and certainly do not claim it as an original idea. One of the sources was the book “Slaying the sky dragon”, written in 2010 and available on the net for free in pdf form. There are also numerous blogs where this claim, central to the IPCC propaganda, is examined.
The greenhouse effect posits that without an atmosphere the “AGT” would be -18C or 255 Kelvin. This is computed using black body radiation equations based on a total energy flux impinging on the earth of about 240 watts per square metre. The solar energy flux at earth’s distance from the sun is around 1,340 watts per square metre and at “top of atmosphere” it is 1,000 w/M2.
The classic greenhouse explanation divides the solar flux by 4 to simulate an “average” over the entire surface of the earth and treats it as a static situation 0 no revolutions and no night/day. They take a disc that is equal to the surface area of the earth and “spread” the solar flux over it evenly and declare that this is “equivalent” to the real world. The 240 w/M2 is said to be equivalent to a “black body” temperature of 255 K or -18 C. When the earth re-radiates energy equivalent to -18 C somehow this gets “trapped” by the miniscule amount of CO2 in the atmosphere which then “back-radiates” the “trapped heat” back to the surface of the earth raising the temperature by 33 C. Really??? This is the boiling a kettle on a block of ice scenario.
The days of “heat” being thought of as some sort of mysterious fluid that “flows” are long gone. Caloric and frigoric do not exist. As Flanders and Swan sang, “work is heat and heat is work”. A body’s temperature is changed by doing work on it by energy exchange, not by heat “flowing” from some external source.
The earth is a sphere, (near enough), and it rotates once every 24 hours. The axis of rotation is inclined to the orbital plane by somewhere around 23.5 degrees, depending on where we are with the Milankovitch cycle for axial tilt – it varies from 24.5 degrees to 21 degrees over a 41,000 year cycle. What I looked at was the 24 hour “energy” trip for a place on earth’s surface as the solar flux varies from zero to a maximum and back to zero in 12 hours and then remains at zero for the next 12 hours. Note that in the charts below they refer to a 1 square metre area as it passes through the sun’s radiation in a day. The suns radiation is always parallel to the plane of orbit but the effects on the earth’s surface vary because of the spherical shape.
For simplicity I calculated the solar flux for various latitudes and then used the appropriate value to calculate the changes around a full circle of longitude for certain latitudes. For simplicity again I chose the Equator, the Tropics, 45 degrees, the Arctic/Antarctic circles and the poles. The longitude is divided into 15 degree segments as this is the “distance” travelled in one hour, (360 divided by 24 = 15).
Because the incident radiation from the sun is considered to be parallel and the earth is a sphere the normal and tangential components need to be calculated. The normal component does the work and as latitude increases from the equator the incident normal radiation varies with the cosine of the angle. The sun is directly overhead at the equator twice a year when we have equinoxes and directly overhead one of the tropics once a year. If it is over the tropic of Cancer then it is summer solstice in the northern hemisphere and winter solstice in the southern and vice versa. Note that these are “one day” events as the earth is revolving around the sun at a constant rate so the sun angle changes each day.
The calculation tables for each chart are not included for the sake of space however they are available if anyone wants them.
The first chart shows the situation when it is equinox and the sun is directly above the equator. The chart shows North Pole and Arctic Circle but is equivalent for the southern hemisphere. I have done these as 3D line charts to show the individual lines a bit clearer and to show the 12 hours of night when the solar flux is zero. The vertical axis is solar flux in w/M2 and the horizontal axis is in hours – increments of 15 degrees longitude. The coloured lines show the changing flux over the day for each location, rising from zero at 0 to a maximum at 6 and zero again at 12 staying at zero for the next 12 hours. The maximum flux for each location is shown in the table below each graph. The table also shows the cumulative watts for the square metre over 24 hours and the theoretical “black body” temperature associated with that flux level.
|Location||Equator||Tropic of Cancer||45 N||Arctic circle||North Pole|
|Solar flux w/M2||1000||917||707||399||0|
|Total over 12 hours watts||7,596||6,966||5,371||3,029||0|
|Equiv BB temp degrees C||91||83||61||16||0|
|Location||Equator||Tropic of Cancer||45||Arctic circle||North Pole|
|Solar flux w/M2||917||1000||930||731||399|
|Total over 12 hours watts||6,966||7,596||0||5,555||3,029|
|Equiv BB temp degrees C||83||91||85||64||16|
|Location||Equator||Tropic of Capricorn||45S||Antarctic circle||South Pole|
|Solar flux w/M2||917||682||367||0||0|
|Total over 12 hours watts||6,966||5,180||2,788||0||0|
|Equiv BB temp degrees C||83||58||10||0||0|
Each of the charts shows the solar flux changing with the latitude and also the longitude. This energy is directed at a moving target as the earth rotates and the point at which the earth is normal to the suns energy flux varies from season to season. It is at the equator at the equinoxes and over either the tropic of Cancer or Capricorn at the solstices. As the earth rotates the energy flux above a point on the earth’s surface will change, increasing from sunrise to noon and then decreasing until it reaches zero at sunset and remains at zero until sunrise. This differs significantly from the “classic greenhouse” theory where the earth is depicted as a flat static plate subjected to a constant flux of 240 w/M2 over the whole day – there is no “night” in the classic theory.
The mechanism is that the sun heats the earth which heats the atmosphere. The heated air becomes less dense and is displaced by cooler air descending. As it rises it loses energy and becomes cooler. It cannot “radiate” back towards the earth with any appreciable effect because it would be a cool body warming a hotter one and physics prohibits this. Clearly all the energy is not retained by the earth as the heated atmosphere conveys the energy away as it rises into cooler climes however we all know that surface temperatures increase during the day and then cool off over the night. It is time dependent, when the sun sets it does not become “cold” instantly. The “Slayers” book has a very good chapter on this topic and shows the time delays in cooling.
The analysis above is simplistic and the purists might have a field day pointing out that I have not managed to sort out the change in the length of daylight/dark as seasons change but my maths has been challenged enough to get this far. There are other simplifications as well but the gist of the article is to demonstrate that the solar flux is much greater than the IPCC model shows and to attempt to show the day/night variations. It does show that the solar flux varies greatly depending on the latitude of the location and the season and shows that there is no need for a “greenhouse effect” to stop us from freezing. The primary band where flux is always high is between the tropics. This is the region that drives the “climate”, particularly with cloud formation.
The analysis makes no allowances for clouds which have a significant effect on how much radiation reaches the earth’s surface so any indicative temperatures need to be recognised as such.
I also had a go at summing the total watts received in a day for the region between the 2 Tropics by averaging the flux and multiplying by half the land area – which is around 100 million square kilometres. The numbers are large as shown below. The first table is at equinox.
|Location||Tropic of Capricorn||Equator||Tropic of Cancer|
|Max Solar flux w/M2||917||1000||917|
|Total over 12 hours w||6,966||7,596||6,966|
|Equiv BB temp degrees C||83||91||83|
The next table is at solstice.
|Location||Tropic of Capricorn||Equator||Tropic of Cancer|
|Max Solar flux w/M2||682||917||1000|
|Total over 12 hours||5,180||6,966||7,596|
|Equiv BB temp degrees C||64||83||91|
The total flux received only declines by 8% from equinox to solstice.
It is interesting that solar power systems show the same daily changes. The chart below comes from a study I did for a 100 MW solar farm proposed for SA. The charts show the “best day” and the “worst day”.