The Evidence for Human Caused Climate Change Part II

[Murky]

Since nobody else created it I will do the honors.

The old thread is here.

All comments are welcome in this thread.

Here is a good little video on Trend and Variation to restart the dicussion


Link to video.

 

[peter grimes]

Good video - I especially liked the narrator's accent

Small quibble - I think a more appropriate title to this thread might have been "The Evidence AGAINST Human Caused Climate Change".

 

[Murky]

Can someone answer why AGW is different from the Milankovitch Cycles?

http://www.ncdc.noaa.gov/paleo/milankovitch.html

 

[tokala]

Milankovic cycles are on the timescale of millenia, AGW on the timescale of decades.

Milankovic cycles do not change the total energy balance of earth, but the seasonal and latitudianal distribution of insolation.
The large temperature changes observed during ice age cycles are thought to be produced primarily via feedback reactions of the northern icecaps to those changes, and to a lower order by secondary feedback of the atmospheric composition.

Anthropogenic greenhause gas emissions are directly changing the atmospheric composition, increasing the heat content of the lower atmosphere, cryosphere, upper oceans and landmasses even without any feedbacks.
The details of the various feedback effects are one of the main topics of climate research, with best estimates of about doubling the warming effect of initial greenhouse gas emissions.

 

[BasketCase]

The pertinent question is, how much of an effect are humans actually having? Even assuming our current measurements are accurate (which is a stretch), we still can't be sure what's causing current temperature trends. If we see a warming trend, is it human-caused, or part of the Milankovic cycles, or something else entirely....?

 

[peter grimes]

The pertinent question is, how much of an effect are humans actually having?

Indeed.
But the consensus is that human activity is having a huge effect. This is comprised of electricity production, deforestation, industrial livestock production, transportation, and likely a few I can't name off the top of my head.

Even assuming our current measurements are accurate (which is a stretch)

Why do you claim this? What measurements are suspect? For that matter, what degree of precision do you need to claim a measurement is accurate?

 

[BasketCase]

Indeed.
But the consensus is that human activity is having a huge effect. This is comprised of electricity production, deforestation, industrial livestock production, transportation, and likely a few I can't name off the top of my head.

Add pollution cleanup to the list. Our efforts since the 70's to eliminate particle-based pollution had a net warming effect. (nobody cared about greenhouse gases at the time)

Also add breathing to the list. Ten percent of all the CO2 produced by the human race comes out of the mouth. (pretty please, no jokes about greenhouse gases humans produce at the other end?? thanx)

Anyway: you say human activity is having a "huge effect". This claim cannot be considered "fact" until it's tested. The testing is still in progress (seeing as how we don't have a laboratory planet to work with, the real Earth is the only possible testing ground). And so far, past predictions (and computer modelling) have returned results far too dicey to be considered better than a coin flip. When we can predict future climate reliably, then I'll be convinced. Not before.

And even that's not enough. Only after we know for certain how much CO2 we need to produce or eliminate to keep temperature stable without turning the planet into a popsicle--only then we can act. Without that, there's simply no way you can make a case with me. I'm far more worried about accidentally setting off the next Ice Age than about any Doomsday scenario the global warming alarmists could ever come up with.

Why do you claim this? What measurements are suspect? For that matter, what degree of precision do you need to claim a measurement is accurate?

Two problems: first, most of our measuring stations are in and around cities (which are warmer than average). Second, we don't have enough coverage in the open ocean.

I always hated statistics--and guess what, statistics was a required curriculum in college. The fact that I hated the topic is probably precisely the reason the rules of statistics are now burned forever into my brain like a disfiguring scar. And we don't have enough measuring points to achieve statistical reliability. It should be a simple matter to resolve, too: just plop a lot more temperature buoys into the oceans, and make sure the spacing is correct.

 

[G-Max]

The pertinent question is, how much of an effect are humans actually having?

By my estimates, we're responsible for about a quarter of the warming that has occurred in the past 200 years.

 

[BasketCase]

Question #1: any thoughts on what's responsible for the other three fourths? (I would guess solar cycles)

Question #2 (actually, this one's rhetorical): any way we can test your estimate? Say, plop a billion people with the requisite industry and cars down on a clean planet, and see how much it warms up? Unfortunately, no. This is the core of the problem with global warming. In order to test a factor, you need a test environment where all other factors except the one being tested, remain the same. I've heard all the claims by climate scientists about "oh, we're accounting for all the other factors" and those claims are bollocks. The entire reason we do tests in actual laboratories is to see if our accounting for the other factors is accurate--or if there are other factors we didn't know about and forgot to account for.

It cannot be called "fact" until it's properly tested, either in the lab or in the real world.

 

[Crezth]

Anyway: you say human activity is having a "huge effect". This claim cannot be considered "fact" until it's tested. The testing is still in progress (seeing as how we don't have a laboratory planet to work with, the real Earth is the only possible testing ground). And so far, past predictions (and computer modelling) have returned results far too dicey to be considered better than a coin flip. When we can predict future climate reliably, then I'll be convinced. Not before.

So what is it about the current body of evidence and the proposals by the scientists that is insufficient, specifically? That it can't predict future climate "reliably?" What is reliably?

Two problems: first, most of our measuring stations are in and around cities (which are warmer than average). Second, we don't have enough coverage in the open ocean.

Cite this. What's a hard number for enough or not-enough coverage?

 

[tokala]

For the debate of recent climate developments, the important point of orbital forcing driven climate change is its astronomical timescale. Orbital forcings act hundreds of times slower than what is observed in the last decades. They are completely irrelevant for the discussion of the recent climate change.

Changes in solar irradiation would be on the right timescale, but its amplitude is too low to be a major contributor, unless the feedback effects are seriously underestimed.

If the feedback would indeed be high enough for solar activity to play an important role, those same feedback effects would also amplify the climate effect of the recent increase in greenhouse gases, so the relative contributions wouldn't change.
I.e. greenhouse gases would still have a much large effect than solar activity fluctuations.

The basic physics of AGW is really straightforward:

On the geological timescale, CO2 levels are rising extremely fast.
The amount of additional carbon is roughly the same as what would be expected from the amount of burned fossile fuels.
The isotopic composition of atmospherical carbon is changing in line with what would be expected if massive amount of fossile Carbon would be added to it.

Higher CO2 levels change the way in how the earth reradiates the energy received from the sun as infrared radiation.
This changes in outgoing infrared radiation can be detected, and a reduction in outgoing energy is measured.
Average global temperature, night/day temperature cycles and the temperature gradient from the tropics to the poles are changing in line with what would be expected from this radiation deficit.

Of course the devil is in the details, and there are alot more other effects at work (other greenhouse gases, volcanoes, ENSO, aerosols, feedback effects etc.).
But those play already second fiddle to CO2, and with continously rising CO2 levels, those will play an even smaller role in the future.

Now, the question if something should be done about it, and what should be done about it is politics, not science.

 

[tokala]

By my estimates, we're responsible for about a quarter of the warming that has occurred in the past 200 years.

Somehow the professionals beg to differ.

Also add breathing to the list. Ten percent of all the CO2 produced by the human race comes out of the mouth. (pretty please, no jokes about greenhouse gases humans produce at the other end?? thanx)

You are apparently not aware that even if that would be the case (which I somehow doubt) it would be completely irrelevant for the debate on AGW.
Think for a moment about where the carbon we exhale originated from

 

[G-Max]

Somehow the professionals beg to differ.

I said 200 years. That chart says 50-65 years. Your argument is invalid

 

[BasketCase]

So what is it about the current body of evidence and the proposals by the scientists that is insufficient, specifically?

The fact that it hasn't been tested in the real world. (normally I would say "tested in a lab" but we don't have a planet-size lab at the moment, so the real Earth is going to have to be the testing ground)

That it can't predict future climate "reliably?" What is reliably?

What is the planet's average temperature going to be in five years, ten years, fifteen years, and twenty? Make predictions, and let's use a ten-percent margin of error. And let's see if your predictions come true.

So far, the predictions by science have fallen far short of that.

What's a hard number for enough or not-enough coverage?

On open ocean, one sensor every fifty to one hundred miles (since open oceans don't see a lot of human activity). On land, more density is needed. Around five to ten miles should be enough. Plus enough satellite coverage so we can measure the total amount of energy departing the planet (I don't know if our current satellite technology can measure that sort of thing--is infrared photography enough?)

We need the satellites so we can measure total energy coming out as well as total energy coming in. The Earth absorbs about 90,000 terawatts from the Sun. How much is the Earth radiating back into space? If the second is equal to or larger than the first, then global warming is not possible at all! If the second is smaller than the first, we need to know where the energy is being stored (in oceans, in land, or sequestered in plants) before we can say how much humans are heating up the planet.

Of course the devil is in the details, and there are alot more other effects at work (other greenhouse gases, volcanoes, ENSO, aerosols, feedback effects etc.).
But those play already second fiddle to CO2

Third fiddle. CO2 plays second fiddle to other factors such as methane.

You are apparently not aware that even if that would be the case (which I somehow doubt) it would be completely irrelevant for the debate on AGW.
Think for a moment about where the carbon we exhale originated from

Could have come from anywhere. Could have been absorbed out of the atmosphere by plants six months ago, or maybe it came from decayed plants in the soil the crops were grown in, or maybe it came from fertilizer fed to the crops (which would have been produced by oil which had formed a billion years ago).

So your claim that it's irrelevant, is irrelevant.

 

[tokala]

It's not much of a difference.
(red/green=anthropogenic)

And before you come up with, "oh there are still 40 years missing", please look up the historical temperature data.

 

[Crezth]

The fact that it hasn't been tested in the real world. (normally I would say "tested in a lab" but we don't have a planet-size lab at the moment, so the real Earth is going to have to be the testing ground)

On a microcosmic level, however, the suppositions have been demonstrated to be based in sound theory. Obviously it's not experiments done on a planet-wide scale, but in principle there is data that suggests AGW furtively.

What is the planet's average temperature going to be in five years, ten years, fifteen years, and twenty? Make predictions, and let's use a ten-percent margin of error. And let's see if your predictions come true.

So far, the predictions by science have fallen far short of that.

So what would correct predictions say about the capacity of our scientists to judge global warming? Does that change what past trends have suggested?

On open ocean, one sensor every fifty to one hundred miles (since open oceans don't see a lot of human activity). On land, more density is needed. Around five to ten miles should be enough. Plus enough satellite coverage so we can measure the total amount of energy departing the planet (I don't know if our current satellite technology can measure that sort of thing--is infrared photography enough?)

What makes you qualified to say that this is an optimal density, especially compared to whatever it is we already have?

We need the satellites so we can measure total energy coming out as well as total energy coming in. The Earth absorbs about 90,000 terawatts from the Sun. How much is the Earth radiating back into space? If the second is equal to or larger than the first, then global warming is not possible at all! If the second is smaller than the first, we need to know where the energy is being stored (in oceans, in land, or sequestered in plants) before we can say how much humans are heating up the planet.

I don't know any of the specific details about this, but I'd say if the Earth reflected more energy than it took in from the Sun, there would be no life on this planet. In fact, it'd lose energy.

But as that's not the case, it's a little more complicated than that. Normally there's an equilibrium between the energy of the planet and the surrounding cold sink, and the work that stuff on the planet does with all of that energy which is obtained directly from the sun. But the total energy, of all the work and all the energy that is radiated and reflected, will equal the amount of energy the earth takes in from the universe.

The question is if the Earth is taking in more energy and reflecting less of it than before. That's central to the theory of greenhouse effect.

 

[tokala]

We need the satellites so we can measure total energy coming out as well as total energy coming in. The Earth absorbs about 90,000 terawatts from the Sun. How much is the Earth radiating back into space? If the second is equal to or larger than the first, then global warming is not possible at all! If the second is smaller than the first, we need to know where the energy is being stored (in oceans, in land, or sequestered in plants) before we can say how much humans are heating up the planet.
...
Third fiddle. CO2 plays second fiddle to other factors such as methane.

Here you go:
http://www.skepticalscience.com/empirical-evidence-for-co2-enhanced-greenhouse-effect-advanced.htm

Could have come from anywhere. Could have been absorbed out of the atmosphere by plants six months ago, or maybe it came from fertilizer fed to the crops (which would have been produced by oil which had formed a billion years ago).

So your claim that it's irrelevant, is irrelevant.

"Could have been absorbed out of the atmosphere": That was the point I was driving at, meaning a zero net effect. And AGW is all about net effects.

"came from fertilizer": very unlikely, as fertilizer is mostly about everything else but carbon.

 

[BasketCase]

What makes you qualified to say that this is an optimal density, especially compared to whatever it is we already have?

Tell you what, I'll answer your questions when you stop doing the ad hominem fallacies.

It's not much of a difference.
(red/green=anthropogenic)

That chart is seriously short on captions. Needs more detail on which colors mean what.

Here you go:
http://www.skepticalscience.com/empirical-evidence-for-co2-enhanced-greenhouse-effect-advanced.htm

Good site. Problem is, I've seen many others, in many global warming threads, and they all give widely varying figures. Enough to convince me that water vapor and methane are larger factors than CO2.

"Could have been absorbed out of the atmosphere": That was the point I was driving at, meaning a zero net effect. And AGW is all about net effects.

"came from fertilizer": very unlikely, as fertilizer is mostly about everything else but carbon.

A lot of modern fertilizers are made from fossil fuels.

Also, living plants get a lot of nourishment from dead plants in the soil. Dead plants in the soil could have been there for one year, or a decade. Or those dead plants may get buried and end up turning into peat moss which we'll never see again.

There's no way to know where the carbon that comes out of your mouth actually originated.

 

[tokala]

Now with text + caption.

Moar detail and compilation from several papers (lower part of the article)

 

[BasketCase]

Much better. Reading time.