Global Warming Question

I can't really answer your question directly, but all the evidence that I see is,,, not good.

Science stunner: On our current emissions path, CO2 levels in 2100 will hit levels last seen when the Earth was 29°F (16°C) hotter | ThinkProgress

 

There are many sources of information on recoverable crude oil, methane (in those geological traps) and recoverable coal. They seem to span quite a wide range.

I do not think there are similar estimates for tar sands, shale oil, or oceanic methane clathrates. But my impression is that this group could include much more carbon than the previous.

I have no doubt that uncontrolled burning could put the atmosphere at 1000 ppm in the 21st century. After that the path would be much more speculative.

But there are two other major issues to consider, at least. Will we continue to receive the same level of ecosystem services from the marine and terrestrial biosphere? Specifically, half of anthropogenic emissions are now taken out of the atmosphere by biological sequestration. If that service wanes, CO2 in the atmsphere would go much higher with the same burn rate.

Also there are large pools or organic matter in soils (especially high-latitude soils). Probably 4 times what is in the atmosphere at present. Dissolved inorganic carbon in the surface ocean is also a large quantity, but I'd have to look that up.

For both of these, the point is that we are quite uninformed about the stability of those C pools under climate change. They represent feedbacks that could send atmospheric CO2 to a level that nobody wants to have.

So the original question is difficult to address. Asking it does neatly summarize why people are putting substantial effort into understanding the carbon cycle.

My response leaves out several things, including geological sequestration by mineral weathering and ocean net trapping by large-scale changes in circulation patterns. These are among the leading processes that have greatly reduced atmospheric CO2 in the past. I have no doubt that they will 'help us out' some time in the future. But it may be a distant future.

I do not think we will have another coal-forming period like 350 to 320 million years ago. The decomposer fungi have gotten too smart to let that happen. It really drew down the atmospheric CO2 though.

 

All three of your questions depend upon a number of factors, some of which have already been addressed.

As already stated, weather or not the biosphere continues to soak up as much of our CO2 as it does now will be a huge factor.

But the bigger one, is 'how much oil is burned' in each of your 3 questions?
Secondary to that is, 'how much energy/fossil fuels are required to be burned to get to that oil/shale, etc.

As cheap oil is used up, it requires more and more energy to get to the tougher to get oil. Emitting yet more CO2 than just burning the oil itself.

 

See also Tar Sands Oil!

 

21% oxygen is pretty nice for us. I reckon most could get by on 18%. Much below that could be trouble.

The element ratios work out that O2 should go down as CO2 is (net) produced by combustion. I mentioned this in a recent thread, and a few groups have actually measured the -2 ppm that is now happening to oxygen.

A 21% to 18% reduction in O2 would correspond to CO2 increasing from the current 400 (almost) ppm range to 3%. There is no doubt enough carbon stored somewhere on the earth to cause that, but it is far beyond what anybody is planning on doing. We'd all die 6 different ways before it happened.

So, I advise you to not be concerned about an impending oxygen shortage.

Inside a closed garage, though, your mileage might vary.

 

We used to vary O2 in submarines a bit, but I don't recall how low they used to let the values get. I'm thinking 19.something.

-----yeah....I know. Didn't hurt me a bit, huh?

 

I agree with your conclusion.

I think it is the O2 partial pressure in the atmosphere that matters the most. Seems like it would be the partial pressure, or aviators using pure oxygen at high altitudes in unpressurized aircraft wouldn't work.

The fact that most people can acclimatize to 10,000 feet elevation would indicate that we humans can get along on a lot less oxygen. At 10,000 feet the O2 partial pressure is about the same as it would be with 13% O2 at sea level.

There are places where people live at 18,000 feet but that is extreme.

 

You need to clarify a lot of things before you can even guess an answer the question. Just the concept of "all fossil fuels" is ambiguous -- there's total reserves (all the molecules in the ground), proven reserves (the fraction of that you guess you have a good chance of extracting with current technology), and then there's the fraction of that you can extract at a profit.

That said, if you look around, everybody seems to give a figure in the 1000 to 1500 ppm range as an answer to your question. No clue as to the detail there.

Here's a discussion. It's a little dated but is easy enough to follow:
U.S. Global Change Research Information Office

Here's one of our national labs, they say nearly 1500 ppm, but they explicitly model a slowdown in uptake by nature:
What If We Burn Everything?

And, as with anything in this area, you will find some nuts who say this is all wrong, everything will be OK, and yada yada yada. Believe them if you want.

Getting an accurate answer is hard and will have some high degree of uncertainty.

But you can get a feel for it yourself, by answering the simpler question. If we vaporized all our fill-in-the-blank (fossil fuels, all biosphere carbon, etc.) tomorrow, what would that do to atmospheric C02? That's easy enough to answer.

For that, all you need is the ratio of carbon in the reservoir to carbon in the atmosphere. Using the first cite above, about halfway down the page is a list of the carbon reserves. Based on that, there's 6.6x as much carbon in fossil fuel as there currently is in the atmosphere. Vaporize that tomorrow and you'd get atmospheric C02 just over 3000 PPM (assuming I did the math right, that's 7.6 (no typo) times current C02 of 392). (392? The conventional figure is 380, but ... that was five years ago. Now it's 392.)

The fact that the actual estimates are in-the-neighborhood-of-half of that tells you that either they start with a lower estimate of "reserves", or, more likely, on net they assume Nature ultimately absorbs about half of what we emit, pretty much the same as today.

So you get roughly the correct answer by vaporizing existing fossil fuels today and assuming Nature absorbs half.

None of those assumes significant positive feedback from nature -- the carbon in the arctic soils and in the methane clathrates noted above. If we get that positive feedback started in earnest, and then its hard to see where this would stop. The clathrates, in particular, have been implicated in past extinctions. Warming to methane to more warming, until all the carbon stored there comes out into the atmosphere.

OTOH, all of these estimates assume that there will still be a civilization burning fossil fuels at some fairly advanced points in the future. Given that the same models that project the temperature rise also project that most of North America and much of Europe will be uninhabitable desert by the year 2100, I'd say that's unlikely. Google "UCAR Drought" if you want to see the best available projection of what's going to happen to America's bread basket. Tough to mine coal if you can't eat.

So:
1) I don't think you have to go even close to the endpoint to get (the scientific community's best estimate of) outcomes that we, as Americans, really do not want to see. Just Google UCAR Drought, and realize that the current situation in West Texas is a -4 on the scale they are plotting there. They appear to the eye to over-predict actual drought in the base period (you'd need to read the research to understand it in detail), but its the change between 2000 and 2100 that is of interest.
1a) I think it's an academic exercise to calculate an estimate that assumes industrial society will survive the point of extracting the last bits of fossil fuel. There will be a breakdown in the social order long before then. "Let them eat cake", "bread and circuses" -- there are reasons those phrases survive. Violent revolutions correlate strongly with starving populations.
2) With no positive feedback from nature, looks like 1000 to 1500 PPM or so covers most estimates. The Livermore National Lab projection above was something like 15 degrees F warmer than now, based on that. I hope I don't need to explain how screwed up the world would be, at that temperature.
3) With positive feedback from nature, it's hard to place an upper limit on it. Hansen talks about Venus syndrome on earth, but I've seen some pretty smart people say that's not possible. (Basically, it gets so hot you evaporate the seas, and water vapor, being a greenhouse gas, keeps the planet locked in at that temperature.) But there's good paleological evidence for the potential for extinction from release of carbon stored in clathrates, which in this case would presumably be our extinction.

 

Read "Storms of my Grandchildren " by James Hansen US Climatologist. for an easy to understand analysis.

 

We need water, food, functioning infrastructure at a variety of levels (thinking both about politics and medicine here), and manufacturing, service industries and trade to pay for it all. We have all that now, although it can easily be argued that the 'bottom billion' on the Earth don't have very much.

If rain falls somewhere else, it will not necessarily be in the right place for crops, direct consumption or other uses. If the best climates for agriculture move poleward, they may not line up as well with suitable soils, water supplies, and all the infrastructure. Some diseases clearly follow climate, and just recently you may have read that river flooding can trump climate change in that regard.

Humans are a unque species on earth because they depend on all these things. Cognition, agriculture, indistry and civilization are all dandy; they have allowed us to become 'Kings' and to populate much beyond what hunter/gathers could do. Not to mention all the gadgets...

But still we are uniquely dependent. The risks of climate change on all that remain highly disputed, and perhaps fairly so: We just can't yet pin the details down to everyone's satisfaction.

So in the main it's 'business as usual'. Small increases in energy-use efficiency, small entry of renewable energy into the mix, and small efforts to sequester carbon in a variety of ways. So the infrared-absorbing gases increase, and we are effectively betting that this is for now the best course to follow.

Maybe it is, and maybe not. If it's not, then we can only hope to awaken to reality before adaptation and migitation become much more expensive.

If it is the best course to follow, then thanks will indeed be due to the fossil fuel industry and their friends for steering a steady course.

Speaking of which, that first oil gusher in Pennsylvania started a global revolution that arguably saved several whale species from extinction. I'm not sure we've properly thanked them for that.

James Hansen paints a much gloomier picture for the long term. But we'd better approach this a step at a time: what are the largest (and/or most reasonable) steps we ought to be taking this decade? Next decade, ask again, ideally with fuller knowledge and insights. And so forth...

 

This one is for austingreen..

while he advocating the real feedback is 1C and 6C is way too much apparently some think that 6C is too low and the real feedback is double of it.

 

I like your questions FL, but have no answers yet.

Re: O2, anything less than 19.5% is considered O2 defficient from safety perspective. We need full amount 21% if possible. Never heard anyone say burning fossil fuels could reduce O2. Maybe even increase O2 is the correct answer? Due to photosynthesis of the very high CO2. Don't know. See Wiki "atmosphere", O2 has been all over the place until it lined out at 21%. The atmosphere has a mass of about 5×10E18 kg. So put that in your pipe and smoke it. :smokin:

You can get estimates of how much fossil fuel burning is expected to 2050, and you could extrapolate.

 

Calculations (by me...so could be wrong...pls advise):

World Population = 7 Billion (this month!)
Crude Oil Use = 0.5 Gallon per person per day
Crude Oil - Total Supply = 18250 Gallons per person = 3000 x 10e9 Barrels
Crude Oil - Total Supply - Burned today = O2 depleted from 20.9 to 20.65 vol%
Crude Oil - Total Supply - Burned today = CO2 increase +175 ppm

Re: CO2, this equates to +1.75 ppm CO2 per year, since we currently burn ~1% of the total projected crude oil supply per year. I did not account for CO2 disappearance reactions (per Chogan's article).

 

All of the current fossil fuel burn (including oil) is now 8 to 9 petagrams of C. Half of that remains in the atmosphere and the other half is biologically sequestered (at land and sea). The current atmospheric CO2 increase is 2 ppm per year, now slightly more I think. Would need to get the most recent data from Scripps CO2 web site

So wjtracy estimate for crude oil alone seems too high.

 

Thank you, but I am only calculating CO2 released by burning.
I have no idea how much gets converted back to O2 by plants etc.
If you say 50% CO2 disappearance, then oil contributes +350 ppm CO2 total
If you say oil = 1/3 of fossil fuel = then 350x3 = +1000 ppm total CO2

This seems in general agreement with Chogan.

 

Tochatihu- Thank you, you are correct I was off 4x too high, divided by O2 volume instead of Total air volume.
Here are fixed numbers:

World Population = 7 Billion (this month!)
Crude Oil Use = 0.5 Gallon per person per day
Crude Oil - Total Supply = 18250 Gallons per person = 3000 x 10e9 Barrels
Crude Oil - Total Supply - Burned today = O2 depleted from 20.9 to 20.65 vol% (250 ppm O2 consumption)
Crude Oil - Total Supply - Burned today = CO2 increase +175 ppm

Re: CO2, this equates to +1.75 ppm CO2 per year, since we currently burn ~1% of the total projected crude oil supply per year.
If you say 50% CO2 uptake by Earth, then oil is approx. 0.8 ppm CO2 increase per year. This should be close enough for government work.

 

Since my name was included, I thought I might as well respond. Six seems to be as high as any legitimate scientist seems to put his finger on, this number is from Hanson. It is also a larger range than the IPCC includes. Think Progress seems to often play fast and loose with the facts. Alley has done a comparative analysis of the various historical modeling and has come up with a proxy data number of 2.8. Certainly there is a great deal of uncertainty on the feedback and even the feedback mechanisms, but multivariant analysis needs to be done on historic proxies.

This does bring us to the OPas question, if we burn everything easy to burn, what will CO2 do. IMHO negative feedback will kick in at some point, but this point won't happen without a large number of natural disasters. Certainly as all the artic ice melts and methane is released, the positive feedback will be reduced as there is nothing left to be released or end reflection.