Quote:
Originally Posted by Harlan
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Eurgh.
A: World Coal consumption: 5.3 * 10^12 kg
B: Molar mass of Carbon: 12
C: Molar mass of CO2: 44
D: C/B * A = 1.94 * 10^13kg
So burning coal emits about 1.94 * 10^13 kg of CO2 every year
E: Total mass of the atmosphere: 5.3 * 10^18kg
F = D/E = 3.67 * 10^-6
I.e we emit an amount of CO2 equal to about 0.000367% of the earth's atmosphere every year.
Over 50 years, this gives
E = F * 50 = 0.0184%
Which is more than 30% of the current CO2 concentration.
This was Coal alone, at pressent consumption levels. If you in addition factor in Oil, Gas, Deforestation, Methane from agriculture, CFCs ... it gets even worse.
As for the solar radiation effect...people keep throwing around the nonsense claim. Basically the compelling bit of evidence against the solar variation theory is that the rate of warming increases even while solar activity decreases.
Assumption 1: Definition of temperature. The rate of change of temperature is proportional to the rate of change of internal thermal energy.
dT/dt = A * dE/dt
Here A is a constant representing the thermal inertia of the planet. E is the net thermal energy of the planet and T is temperature.
Assumption 2: The thermal energy in the earth's atmosphere and surface is almost exclusively down to the amount of radiation received from the sun and the amount of radiation emitted into space.
dE/dt = A * F - G
F is the amount of energy received by the planet, and G is the amount of energy emitted by the planet. Taking the time derivative on both sides:
d^2T/dt^2 = A * dF/dt - dG/dt
That is, the rate of change of temperature change ( the rate of increase of the rate of warming ) is just the difference between the rate of change of incoming radiation and the rate of change of outgoing radiation. From the above it follows that
dF/dt < 0 , |dG/dt| < |dF/dt| ==> d^2T/dt^2 < 0
That is, if the amount of radiation received by the earth is decreasing, and at the same time the amount of radiation leaving the earth does not change even more rapidly then the rate of warming MUST decrease. Now the claim was that variations in solar radiation ( i.e the amount of radiation the earth receives) is much more important than the greenhouse effect. I.e the change in radiation received is at least as large as the change in how much radiation is emitted. Thus when solar radiation decreases, we have:
dF/dt < 0
|dG/dt| < |dF/dt|
So from the above
d^2T/dt^2 < 0
This is not what we observe. We observe steadily increasing rates of warming even when the solar activity decreases, which imply that at least one assumption above is incorrect. Since this occurs when solar activity decreases we know that dF/dt < 0, meaning that the only assumption left to discard is the following:
|dG/dt| < |dF/dt|
Therefore
|dG/dt| > |dF/dt|
That is:
The rate of decrease of radiation leaving the earth is greater than the rate of change of radiation received by the earth.
Or, put slightly differently
Changes in radiative forcing due to greenhouse gases contribute at least as much to global warming as observed changes in solar radiation received by the earth.
Note that the magnitude of the thermal inertia ( the constant A ) doesn't make a difference. This is why I looked at the rate of change of warming rather than warming in itself. Because the planet's thermal inertia is largely constant it doesn't significantly affect weather the planet warms or cools, only the extent to which it does so, and thus observing changes in radiation received and emitted is sufficient to reach the conclusion above. This is why the above derivation is so much simpler than the more detailed climate models, and this is also why it doesn't tell us how much larger that impact is as compared to solar variation. It also doesn't tell us how much warming to expect, nor where the main uncertainties are, nor which greenhouse gases are most important. The only thing my derivation above is able to show is that solar variation is not the sole cause of global warming.
There are more advanced models that can extract more information from the observations. In particular, highly accurate numerical simulations, which take into consideration variations in atmospheric temperature, variations in greenhouse gas concentrations, and the impact of aerosols and cloud formation, are able to derive fairly certain estimates of radiative forcing components. The results look something like this:
http://en.wikipedia.org/wiki/Image:R...e-forcings.svg
No one is denying that the earth warms and cools naturally; the problem that human emissions cause is the rate at which the changes are taking place, and that humans are changing the equiberium which will have devastating long-term effects. I'm not pretending that the impact of global warming is completely clear. Different models give different predictions, but for the business as usual scenario all of the top- eight climate models predict a 2 - 5 centigrade increase during this century. This may not sound much, but since 5 centigrades is simply the average there will be occasional peaks that are far higher, about 10 centigrades or even more. Furthermore the warming is not uniform. The equator will experience the least warming while countries further north or south will experience more. Land areas will also experience more warming than the seas. The amazonas is probably the most scary example, and wille xperience an average increase of 8 centigrades. Now given that a significant amount of the earth's vegetation is located in the amazon rainforest, a 8 centigrade increase is really not something tot ake lightly. If you ruin the rainforest, leading to irreverasble deforestation, this will amplify the warming causing even more problems.
http://en.wikipedia.org/wiki/Image:G...ions_Map_2.jpg
Note that this is the impact without the doomsday predictions. If you start looking at the impact for sea-level rise, huricanes, draughts, starvation due to failing crops etc, things quickly start reaching a level of disaster that quite frankly has no historic presedence. This could easily give pandemic virus infections a hard time keeping their position as the biggest killer of all time.
It's extraordinarily easy to calculate the variables that I'm talking about in relation to global warming. Considering we know a lot of the effects of pumping CO2 into the atmosphere, a lot of which I've already stated earlier, there are very few unknown variables, unless you can think of any? I'm quite sure I would've heard of them and people who made the documentary would be keen to highlight problems with methodology. One such claim I've recently heard is that the researchers of GW "orthodoxy" often freely interchange dependent and independent variables. Well, I don't think I've done that in my calculations.
These are the ones from the top of my head...
Amount of greenhouse gases we emit ( basic chemistry once you know fossil fuel consumption ).
Amount of radiation the sun is emitting, and how much of it reaches the earth (measured by satellites and observatories for decades now ).
The spectrum of solar radiation. (has been known for a century or so )
The spectrum of radiation emitted by the earth. (same as above )
Atmospheric composition. ( Easy to measure, basic chemistry).
The absorption and emission spectrum of the gases in the atmosphere (has been known to great detail for a century).
The extent to which the ocean absorb CO2 (CO2 reduces the pH of the ocean, we can measure this).
The amount of CO2 emitted by volcanic eruptions and geological activity ( it is orders of magnitude smaller than human emissions).
The effect of radiative forcing on steady state temperature (follows from thermodynamics).
When the above is considered ALL of the top 7 climate models predict that greenhouse gas emissions will cause global warming. The uncertainty is to what extent and arises primarely from:
Cloud formation.
Feedback effects. (warmer temperatures affect vegetation and algae etc..)
Aerosols that reflect sunlight.
The impact of aerosols on cloud formation.
Note that solar radiance is not a major cause of uncertainty. We know it to great accuracy, and whereas there are some uncertainties, they are very small.
I haven't sourced these claims because there is quite a lot of material, but I am able to do so if need be. If there is a particular issue you doubt, just ask me to source it and I will.
Linear Mode
