One important piece of understanding is the amount of our suns (Sol) energy that interacts with the earth, When we understand what a very small amount of its energy actually comes towards the earth we can begin to get a feel of what effect that even a very minor change could affect us.
To this end I asked my good friend Richard Heathfield of CPAX to help enlighten us with the calculation below, as you can see that approximately just less than 30 Billionth of 1% of the suns energy come into the Earth, even if this level is sustained the earth would quickly evaporate all its atmosphere into space as it has on the planet Mercury. The Earth compensates for this vast energy by transmittance (see black-body radiation theory) the warmer the planet gets the more it compensates. "The flow of energy into the atmosphere must be balanced by an equal flow of energy out of the atmosphere and back to space" NASA.
The point of this page is to prompt more thought on how carefully we need to be when we look at some of the figures that so easily get used without understanding of their true significance.
Approx % amount of solar energy to fall on earth.
By Richard Heathfield
Okay, let's take this one step at a time.
The Sun emits energy in all directions. There is no particular reason
for any one direction to be favoured over another, so the energy is
spread evenly (with variations sufficiently tiny that they can be
ignored). This energy radiates outward from the Sun, forming a colossal
sphere that expands at the speed of light. A tiny fraction of it is
absorbed by Mercury and Venus, but this can more or less be ignored
too, for our purposes.
The Earth is, on average, 149,597,871,000 metres from the Sun. This is
so close to 150,000,000,000 metres that we can take the simpler number
without serious loss of precision.
By the time the Sun's energy has radiated as far as Earth's orbit, it is
dissipated over an area equal to that of a sphere of radius
150,000,000,000 metres. The area of a sphere is given by the equation
A=4PRR (where A is the area we are trying to calculate, R is the mean
distance of Earth from the Sun, and P is "pi", the ratio of a circle's
circumference to its diameter, a universal constant that has a value
just over 3.14159).
As we shall see, for this exercise the precise value we take for "pi",
or P, is of no consequence. In fact, it wouldn't matter if we used 1,
or 1000, or 1000000.
Earth can be considered to be a circle drawn on the energy sphere. The
mean radius of Earth is 6,371,000 metres. The area of a circle is given
by a=Prr (area = "pi" * radius * radius). Note that we use lower-case
'a' for Earth's cross-sectional area, to distinguish it from A (the
area of the energy sphere), and lower-case r for Earth's radius, to
distinguish it from the energy sphere's radius.
The value we want is the percentage of solar energy reaching Earth. The
fraction of energy reaching Earth is simply a/A, and the percentage
(units per hundred) is 100a/A. Since a=Prr, and since A=4PRR, the value
we want is:
100 * P * r * r
-----------------
4 * P * R * R
The Ps cancel (which is why the value doesn't matter), giving us:
100 * r * r
--------------
4 * R * R
Taking the top first: 6371000 * 6371000 is 40589641000000, and 100 times
this value is 4058964100000000.
Now for the bottom: 4 * R * R = 4 * 150000000000 * 150000000000, which
comes to .90000000000000000000000.
So the percentage of solar energy reaching the Earth is
4058964100000000 / 90000000000000000000000, which comes to 0.000000045%.
This is such a tiny number that it doesn't make much sense to us. It may
be easier to picture it as a fraction, which we can easily get by
forgetting about percentages and turning the equation on its head. This
gives us a value of 2217314511. The precision is a little misleading,
so let's lose a few significant figures, and call it 2200000000.
This means that, for every Joule of energy that reaches Earth from the
Sun, 2200 MILLION Joules don't strike Earth at all - they are just lost
into space.
So - how many Joules of energy reach Earth each second? Answer: 174
petaJoules. (About 30% of this is lost to reflection from the
atmosphere, and about 20% is absorbed by the atmosphere, so only about
half reaches Earth's surface, but 174 petaJoules is the amount of
energy that Earth actually gets each second. A petaJoule is
1000000000000000 Joules. So the amount of energy we DON'T get from the
Sun is roughly 380000000000000000000000000 Joules every single second.
That's enough to power 127600000000000000000000 three-bar electric
heaters, which is 18000000000000 three-bar fires PER PERSON currently
living on Earth.
When you play with the Sun, it's just impossible to grasp the true
immensity of the numbers you get.