The Idiots Guide to CO2
If we are going to talk about CO2 in the context of Global Warming, let's see where the GW alarmists and the GW skeptics agree:
1. The level of CO2 in the atmosphere has been increasing since the beginning of the industrial revolution in an almost linear fashion.
2. CO2 is a greenhouse gas and as such is able to increase global temperature.
3. The relationship between CO2 and temperature is logarithmic. What does this mean? For example, let's say that going from 250 ppm CO2 to 500 ppm CO2 causes global temperature to rise 2 deg C. Then in order to get another 2 deg C of rise, CO2 would have to go from 500 ppm to 1000 ppm. And to get another 2 it would have to go from 1000 ppm to 2000 ppm.
4. The temperature increase that is caused by a doubling of CO2 - without any positive or negative feedback - is about 1 deg C per doubling.
So where do GW alarmists and GW skeptics disagree? They disagree on the amount of global temperature rise that is caused by each doubling of CO2.
1. GW alarmists believe that each doubling of CO2 causes global temperature to rise about 3 deg C. plus or minus 1 deg C.
2. GW skeptics believe that each doubling of CO2 causes global temperature to rise about 1.2 deg C. plus or minus .6 deg C.
Why does this difference in opinion exist? Basically it exists over the estimated amount of positive feedback that comes with CO2 warming. What do we mean by feedback? For example, let's say that you doubled CO2 in the atmosphere and it gave you a 1 deg C temperature rise. That rise in temperature would make the air hold more moisture( H2O). H2O is also a greenhouse gas and it would therefore cause even more heating. In other words, it would amplify the effects of CO2 heating.
But here is an example of estimating the problem. H2O also forms clouds, and clouds increase the earth's albedo (reflectivity), thereby lowering temperatures. There are dozens of factors involved in estimating feedback - many of them poorly understood.
The basic difference between the GW alarmists and the GW skeptics is then this. GW alarmists believe that positive feedback causes the natural effect of about 1 deg C rise for each doubling of CO2 to be boosted to about 3 deg. C. GW skeptics believe that positive feedback is very small and causes the natural 1 deg C rise from CO2 doubling to increase to about 1.2 deg C.
Who is right? The evidence seems to favor the GW skeptics. Here is why.
1. Since the beginning of the industrial revolution we have had about a 50% increase in CO2 above what it was before the industrial revolution. In other words, we have had about half of a doubling already. The amount of temperature increase that accommodates this amount of CO2 increase is about .6 to .7 deg C. Because of the logarithmic effect of the CO2, we would expect less temperature increase for the second 50% of that doubling. So, let's say that the second half of the doubling yields from .3 to .5 deg C. Adding this to the first half's temperature increase we get about .9 to 1.2 deg C for that CO2 doubling. This is empirical evidence that favors the GW skeptics.
2. We are able to generate computer models that take a given number for positive feedback for CO2 increase and generate temperature charts of the result that should come from such a feedback number. We find that when we use large feedback numbers, such as 2 to 3 degree positive feedback for each CO2 doubling, the resulting temperature charts simply do not look like our real temperature records. The positive feedback takes over to such a degree that it shoots temperature up in a way that cannot be seen in any portion of the temperature record. When using a smaller feedback number, like .2 deg C for each CO2 doubling, the resultant chart looks much more like what we find in the temperature record. This computer modeling then also favors the GW skeptics.
Congratulations, you now understand more about Global Warming than 99% of the population of the earth.
1. The level of CO2 in the atmosphere has been increasing since the beginning of the industrial revolution in an almost linear fashion.
2. CO2 is a greenhouse gas and as such is able to increase global temperature.
3. The relationship between CO2 and temperature is logarithmic. What does this mean? For example, let's say that going from 250 ppm CO2 to 500 ppm CO2 causes global temperature to rise 2 deg C. Then in order to get another 2 deg C of rise, CO2 would have to go from 500 ppm to 1000 ppm. And to get another 2 it would have to go from 1000 ppm to 2000 ppm.
4. The temperature increase that is caused by a doubling of CO2 - without any positive or negative feedback - is about 1 deg C per doubling.
So where do GW alarmists and GW skeptics disagree? They disagree on the amount of global temperature rise that is caused by each doubling of CO2.
1. GW alarmists believe that each doubling of CO2 causes global temperature to rise about 3 deg C. plus or minus 1 deg C.
2. GW skeptics believe that each doubling of CO2 causes global temperature to rise about 1.2 deg C. plus or minus .6 deg C.
Why does this difference in opinion exist? Basically it exists over the estimated amount of positive feedback that comes with CO2 warming. What do we mean by feedback? For example, let's say that you doubled CO2 in the atmosphere and it gave you a 1 deg C temperature rise. That rise in temperature would make the air hold more moisture( H2O). H2O is also a greenhouse gas and it would therefore cause even more heating. In other words, it would amplify the effects of CO2 heating.
But here is an example of estimating the problem. H2O also forms clouds, and clouds increase the earth's albedo (reflectivity), thereby lowering temperatures. There are dozens of factors involved in estimating feedback - many of them poorly understood.
The basic difference between the GW alarmists and the GW skeptics is then this. GW alarmists believe that positive feedback causes the natural effect of about 1 deg C rise for each doubling of CO2 to be boosted to about 3 deg. C. GW skeptics believe that positive feedback is very small and causes the natural 1 deg C rise from CO2 doubling to increase to about 1.2 deg C.
Who is right? The evidence seems to favor the GW skeptics. Here is why.
1. Since the beginning of the industrial revolution we have had about a 50% increase in CO2 above what it was before the industrial revolution. In other words, we have had about half of a doubling already. The amount of temperature increase that accommodates this amount of CO2 increase is about .6 to .7 deg C. Because of the logarithmic effect of the CO2, we would expect less temperature increase for the second 50% of that doubling. So, let's say that the second half of the doubling yields from .3 to .5 deg C. Adding this to the first half's temperature increase we get about .9 to 1.2 deg C for that CO2 doubling. This is empirical evidence that favors the GW skeptics.
2. We are able to generate computer models that take a given number for positive feedback for CO2 increase and generate temperature charts of the result that should come from such a feedback number. We find that when we use large feedback numbers, such as 2 to 3 degree positive feedback for each CO2 doubling, the resulting temperature charts simply do not look like our real temperature records. The positive feedback takes over to such a degree that it shoots temperature up in a way that cannot be seen in any portion of the temperature record. When using a smaller feedback number, like .2 deg C for each CO2 doubling, the resultant chart looks much more like what we find in the temperature record. This computer modeling then also favors the GW skeptics.
Congratulations, you now understand more about Global Warming than 99% of the population of the earth.
posted by Tilo Reber at 12:04 PM
2 Comments:
Where do you obtain your 50% figure for C02 rise? At the beginning of the Industrial Era, concentrations were on the order of 280ppm; now 380ppm (give or take) which puts the figure at only 35%.
That being said, however, why would you assume that anthropogenic greenhouse gases haven't also been accompanied by given negative feedbacks such as aersols (indirect and direct)during the 20th century? You seem to be basing your case on the assumption that temp trends in the 20th century are due solely to C02 (and its equivalents). But establishing climate sensitivity would require more than a simple comparison of that type.
Watchmaker, I have seen pre-industrial era numbers ranging from 260 to 280. The current level is closer to 390 than 380.
I don't assume that temperature trends can be based soley on CO2. But what are you going to use as a baseline trend without CO2. It could be going up, which would mean less CO2 forcing, or it could be going down, which would mean more. The 80s and 90s had strong solar cycles, so some warming may have been expected. This would further reduce the portion assigned to CO2.
It doesn't seem like we know enough about aersols to be sure of their effect.
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