My sources say 288 Kelvin. What figure do YOU have for the current temperature of the Earth? Mine say 285 Kelvin. Simply put - thermodynamics indicates that the Earth CANNOT get much hotter, as it is NOT a perfect "black body" and is already near the theoretical maximum temperature for a balck body radiator.
I was ignoring your posts due to your inability to understand the very basic material relevant to CO2 sampling. In all honesty your sources aren't the most reliable. But when someone says "Well said richyoung." I have to respond. Your sources say 285 kelvin? That's 12 ºC which is lower than what the IPCC claims current temps are:
http://www.grida.no/climate/vital/17.htm1. I understand the CO2 data fine - you persist in trusting sources I don;t and vice-vera. That is NOT the same as one of us not "understanding", but thanks for the subtle personal attack in lieu of actual discussion...
2. As should be understoof by ALL now, the IPCC is a political group with little credibility now.
3. from:
http://www.ianschumacher.com/maximum_temperature.htmlHypothesis 1: The average temperature of a body in thermodynamic equilibrium with an external energy source can never exceed the temperature of a black body in the same environment.
Hypothesis 1, does not seem particularly revolutionary and to most people with a physics background they probably seem rather trivial and obvious. However, this statement up front is unfortunately necessary in order to overcome the common misinterpretation of the greenhouse effect that allows for conditions to violate Hypothesis 1. When trying to determine the maximum temperature of the Earth, it is important to know which mechanisms limit this maximum. The parallels between our high-pass filter example and the greenhouse effect are obvious, so does this mean that the greenhouse effect does not exist? No, it does not mean any such thing. The greenhouse effect is real, however it does mean that the greenhouse effect can never produce a temperature that is higher than the temperature of a black body in the same environment.
Hypothesis 2: The greenhouse effect can never produce a temperature that is higher than the temperature of a black body in the same environment.
For many readers this will cause a great pause and some reflection. It has become conventional wisdom that the greenhouse effect has essentially no limits, but this is clearly not true. The greenhouse effect works exactly as previously described. High-energy high-frequency light enters through the atmosphere and is absorbed by the surface and atmosphere to produce low-energy low-frequency thermal radiation. This low frequency thermal radiation is more readily absorbed by the atmosphere and is radiated back to the surface and out to space. The result of the greenhouse effect is to raise the equivalent absorptivity of Earth closer and closer to unity (but never exceeding it). To those having trouble believing Hypothesis 2, I recommend they work through Hypothesis 1 in their mind until it becomes clear that this must be the case.The sun, the moon, and the earth
It should now be clear that the maximum temperature of Earth can not be higher than the maximum temperature of an equivalent black body. We will now try to evaluate what that maximum is. For simplicity, all values and graphs have been obtained from Wikipedia unless otherwise stated.
The moon is quite close to a black body. It is estimated to have an absorptivity of 0.88. Conveniently the moon is nearly in the same environment in space as the Earth. The maximum temperature found on the moon is approximately 390° K. Using the Stefan-Boltzmann equation described earlier the maximum flux on the moon is
aS=oT^4
which for our values gives a flux of 1491 W/m^2. Already we have a problem. The flux on Earth from the sun as measured by satellites is widely reported to be around 1366 W/m^2, or significantly lower. Why the discrepancy? It is interesting to note that even with only these three elements, moon data, sun data, and the Stefan-Boltzmann equation, we end up with slightly inconsistent results, which may give us some insight into the level of uncertainty in the data that still remains in this area. Since we are interested in the maximum temperature we will take the maximum value of 1491 W/m^2.
The earth is approximately spherical and receives light from the sun on a cross-sectional area of a circle, but radiates thermal energy from the area of a sphere. The ratio of the spherical area to the circular area is 4. Dividing the incoming energy flux by 4 gives the Earth an approximate maximum temperature of 285° K. Again we have another inconsistency as this maximum temperature is below the widely reported global average temperature of 288° K. Also the earth has an uneven distribution of temperatures and therefore an uneven distribution of flux, the end result of which would be to lower the average temperature even more. Still the result is quite close and it suggests that the Earth is behaving very closely to a black body and is operating very close to its maximum possible temperature.
Hypothesis 3: The earth is operating very close to its maximum possible temperature.
Again, this will cause many to pause as it goes against the conventional wisdom. However we will attempt to provide two pieces of evidence to support this case:
ice ages and the runaway greenhouse effect
climate variability/stability
Ice ages and the runaway greenhouse effect
There is a surprising amount of debate about what causes ice ages and their ending. The core feature of ice ages is their remarkable periodicity. The figure below shows sample data for the last four ice ages.
{sorry - don;t know how to copy graph - go to the web site if you want to see it...}
The most likely cause of the ice ages is due to fluctuations in the intensity and the distribution of solar radiation caused by changes in the tilt in the Earth's axis. This theory was first described by the Serbian scientist, Milutin Milankovitch, in 1938. There are three major cyclical components of the Earth's orbit about the sun that contribute to these fluctuations: the procession (tilt of the Earth's axis), as well as Earth's orbital eccentricity and orbital tilt. The exact cause and effect relationship between orbital forcing and ice ages is still a matter of great debate, however the match of glacial/interglacial frequencies to the Milankovitch orbital forcing periods is so close that orbital forcing is generally accepted. Other theories include greenhouse gas forcing, changes in the Earth's plate tectonics, changes in solar variation, and changes in absorptivity due to dust and gases spewed by volcanoes.
The exact cause of the ice ages is not critical to our discussion other than to note that the Earth appears to have two metastable states: an ice age period and a warm period.
Of note in the above figure is the strong correlation between carbon dioxide and temperature. As the temperature increases, ice sheets recede, which increases the absorptivity of the earth, and more carbon dioxide, water vapor, methane, and other greenhouse gases are released. This increases the temperature further, which causes the ice sheets to recede further, and causes more greenhouse gases to be released, etc. This is a positive feedback loop and is the runaway greenhouse effect in action. The positive feedback also works in the opposite direction causing the earth to drastically fluctuate between these two metastable states. What causes this runaway greenhouse effect to end? The answer is that once the earth has achieved its maximum absorptivity (or very close to it), additional receding ice or greenhouse gases becomes irrelevant. The climate is pinned to the maximum possible value.
You say the earth can't get hotter than 288 Kelvin? Then why do rocks suggest the earth used to be 70 degrees C?
The geologic record tells a story in which continents removed the greenhouse gas carbon dioxide from an early atmosphere that may have been as hot as 70 degrees Celsius (158 F). At this time the Earth was mostly ocean. It was too hot to have any polar ice caps.http://www.spacedaily.com/news/early-earth-04h.htmlWhat was the solar output at that time? What was Earth's orbit at that time? What was the MOON's orbit, and how much tidal friction was heating the Earth's crust? What was the thermal contribution from vulcanism and the radioactive decay of elements in the Earth's crust? What was the thermal effect of chemical reactions then occuring?For someone who likes to accuse others of not "understanding", you seem unable to grasp that:
1. Correlation is not causation. Yes, it was hot back then, and CO2 was high. That doesn't mean one caused the other.
2. ALL discussions are "ceteris parabus". We can't have a meaningful discussion if you are going to use counter examples from billions of years ago with different orbits, solar flux, tidal conditions, etc. "Global Warming" theory is about NOW, under current and CONSTANT solar output - which is where it fails.
This took me about 15 seconds of googling. I will agree that the risk of a Venusian runaway is extremely small but to rule it out as a physical impossibility is to fail to understand history.
To rule a Venusian runaway IN is to ignore billions of years of fossil record history AND the laws of thermodynamics. I suggest you get a grasp of them before accusing OTHERS of a lack of cogitative ability....
