beej67 said:
I'm not making that argument at all. That's a dumb argument.
Apologies for not having understood your original premise. As I said, I have seen the UHI argument brought up a hundred times. But I have never seen anyone make the claim that you have, of urban albedo affecting the entire global temperature.
beej67 said:
You could throw all the data in the toilet and still make a very easy case for global warming, in fact a more solid case, by simply looking at glacial recession as your indicator.
Well, there are many skeptics who I suspect would like to throw feces at you for saying that. But I personally agree that glacial recession is just one of many observations indicating warming.
beej67 said:
But there's a difference between these two statements:
"The globe is warming" and
"The globe is warming completely because of CO2 emissions and no other reason."
I never said it was warming because of CO2 “and no other reason.” I simply think CO2 is the dominant factor.
beej67 said:
No, you need a link that says terraforming the planet to suit our purposes for agriculture and urbanization on such a massive scale that it's easily seen from space doesn't change the global energy budget.
We already agreed that it changes it; we just have disagreement on the magnitude and the sign of that change.
beej67 said:
That's about direct heat generated by human machinery, not about the changes in sunlight absorbed due to urbanization, deforestation, and agriculture. Try again?
You are the one making the positive hypothesis that the observed warming trend is due to anthropogenic albedo changes, so it really should be your responsibility to prove this claim, not mine to disprove it. But since it is a new argument, I found it interesting enough to work out. Anyone can feel free to correct my math where they see fit. (And yes, I am aware that this is a simplistic calculation. By omitting something I am not implying that it should not be considered, I am simply creating a baseline calculation and I welcome any added complexity you would like to contribute.)
Estimating the temperature change due to a change in albedo is relatively straightforward using Stefan-Boltzmann and assuming a blackbody.
Teff = [S0(1 – A)/4sigma]^.25
where Teff is the temperature of the surface in K, S0 is the solar constant, A is the albedo, and sigma is the Stefan-Boltzmann constant.
The Earth’s current albedo is approximately 0.30. The solar constant is 1370 W/m^2 and sigma is 5.67*10^-8.
Plugging that in, we get an effective temperature of 255.0 K. Lower than reality, but we are of course ignoring the greenhouse effect so this is expected.
Now, to calculate the effective temperature of urbanization we need an estimate of 1) The percent of the surface area that is urbanized and 2) the approximate albedo of an urbanized area.
Estimates for the first factor vary, but a recent estimate found it to be around 3% of all land area, so we will go with that. I make no judgment on how valid this estimate is compared to previous, lower estimates.
Of course, albedo extends beyond just land area, so this 3% needs to be translated to a global fraction, which makes it 0.876% of Earth’s total surface area, assuming the Earth is 70.8% water.
As for number 2, urban albedo ranges from 0.10 to 0.20, though some are much higher. From Table 2, here:
We will be very conservative and say it’s 0.10 everywhere, which is only slightly higher than the average albedo of pure asphalt.
Taking a weighted average, we get a new (urbanized) global albedo:
.99124*.3 + .00876*0.1 = 0.298
And a new Teff = 255.16
Compared to 255.0, that is a temperature difference of 0.16 C across the entire time span of human urbanization, under the very conservative assumptions of urbanized surface area and its average albedo. As compared to ~ 0.8 C observed over the past 100 years.
Of course I ignored agricultural lands in this calculation; since agricultural lands represent a much larger surface area, and since their albedo tends to be higher than what was previously there, I stand by my claim that direct anthropogenic albedo changes force a negative radiative forcing, not a positive one.
beej67 said:
A leaf does not produce the same warmth to its adjacent area as a slab of green asphalt does, because something else rather interesting is going on inside the leaf. It's capturing energy and using it in chemical reactions, and this goes on on a massive scale. If you believe the paleontologists, it's where the oil comes from. This very important process is ignored in every treatment of the effects of albedo on climate I've read. Got a link to one that takes it into account? I'd love to read it.
You emphasize that asphalt and a leaf of the same albedo do not have the same temp since the leaf does more than the asphalt, and I don’t disagree with that.
You get a double positive whammy by replacing a forest with a parking lot, but you get a double *negative* whammy by replacing a forest with a lighter agricultural field, since agricultural crops are better at photosynthesizing than most natural plants. And since global agricultural land represents an area more than ten times greater than urban land, I just don't see where there is any opportunity for a positive forcing. Interested to see your math.
beej67 said:
What does that tell you about a study that says "wind carries the urban heat away, so it doesn't affect the globe's mean temperature." ..?
Except that the paper was not talking about warming of the entire planet, it was talking about urban bias due to poor station siting. You were not making the urban bias argument, but there are many people that do.
beej67 said:
Not really. Ask a bunch of atmospheric chemists what the problem is, they're going to tell you atmospheric chemistry, especially when their research dollars depend on it.
Again, this is moving beyond skepticism and you are now making a positive claim that there exists an unfathomably large scientific hoax going on. A strong claim requires strong evidence, of which I see very little if any. I find arguments like ‘follow the money’ to hardly be convincing. Unless you can demonstrate a strong argument for why a real, existing problem would *NOT* logically receive research funding, then the mere existence of funding does not make me the least bit skeptical.
beej67 said:
And that's a separate discussion that I don't even want to bother having, because it gets into who's moving which money where (Goldman Sachs) to take advantage of "carbon trading."
That there might be businesses or governments seeking to take advantage of AGW for personal gain is a separate question irrelevant to the science. There are those who will try to gain and profit on absolutely anything that happens in the world, and I see no reason why we shouldn't expect people to take advantage of AGW too.
But seeing big businesses profit through greenwashing or carbon trading markets does not itself make me skeptical of the existence of AGW, any more than seeing businesses profiting on security guards and alarm systems would make me skeptical of the existence of crime.
beej67 said:
I'm an environmentalist. I believe it's important we reduce pollution, and CO2 is among the things we should reduce. I think the greatest damage CO2 is doing to our environment isn't even in the skies, it's in the oceans, which are slowly changing in pH as CO2 forms carbonic acid and dissolves the world's coral reefs. Google that, it's terrifying.
I’m familiar with ocean acidification and agree that it is of great concern, especially considering many agronomists believe that the only way we will feed (and power) 9 billion people is through massive-scale marine aquaculture.
beej67 said:
The backlash when the truth comes out will hurt all environmentalism.
It’s not a bogey man. For that matter it's also not Armageddon. It will not cause an ice age over night or send tidal waves of sea level rise flowing into NYC. But it is a problem that exacerbates many other problems that humanity will face throughout the 21st century. I do not know the magnitude of this problem, no one does. I believe it’s at least possible that the warming will surpass 3 C by the end of the century, and that concerns me. Even if it stays within 1 C it can cause problems. And considering that skeptics such as Spencer and Lindzen acknowledge at least a 1 C warming associated with 2x CO2, and that the planet is on par to greatly exceed 2x, I have yet to find any comfort from skeptical arguments.
By the way, I see you’re an environmental engineer. My degree was in environmental engineering too, from UF
