GHG Bulletin No. 9 released

Whoa there, if by "buffering capability of the earth to handle CO2" you mean that some (half) released to the atmosphere is promptly sequestered at land and sea, this is not at all the case.

If such sequestration switched off, CO2 would be now increasing at ~4 ppm/yr instead of ~2 ppm yr.

The methane figure appears to have the highest increases at the most northerly latitudes. This is not quite consistent with fracking. It is consistent with permafrost or marine clathrate exhalation, which is not really a cheerful thought.

 

No one knows what those levels are, but the governments have been calling out 80% reductions for ghg to maintain their same forcing. There is feedback not yet in the system The only good news is perhaps sensitivity is lower than many thought a decade ago.

Here is the US governments take on it.
Methane Emissions | Climate Change | US EPA

I don't trust the numbers, but they are as good as I can get quickly.

EPA says over 60% of methane is from man made sources less than 40% from natural. Agriculture and landfills seem to be the places with the easiest fixes. Globally agriculture is the biggest contribution of anthropological methane (Amethane), far beyond fracking. All in all though methane is responsable for only about 9% of the ghg produced in the US. The US has dropped ghg by over 6% between 2005 and 2011. Increased fracking reducing the price of natural gas, then natural gas being substituted for coal is a major source of that reduction. Coal mining is also a source of Amethane.

 

I lost you on the first line AustinG. Please say what "No one knows what those levels are", and because I am slow please use and not pronouns.

I agree that the standard view about methane sources is as stated, but the most rapid increases at the highest latitudes would not easily follow from that.

Bob, current carbon sequestration is just about what you say. But the capacity may be related to [CO2] in a positive way, if land pant productivity increases and decomposition does not increase. It may be related in a negative way, if marine biological uptake is reduced as surface water pH goes down. In summary, difficult to predict the near-term course of CO2 sequestration processes, as CO2 will increase and climatic factors will change in different ways in different areas. It may be that was the meaning of AustinG's first line?

 

There are no experts that actually know with a high degree of certainty, how high human generated ghg can be with no increase in temperature above X. The only thing certain is wide disagreement in the amount of sensitivity and the amount of natural sequestration. Numbers like 50% reduction, and 80% reduction are political not scientific. Even at an 80% reduction temperature increase from average 1880-1900 temperatures could easily exceed 2 degrees C, and that 2 degrees C is anouther arbitrary political line.

Absolutely fracking and leaky pipelines is not causing much of the ghg forcing. There is wide disagreement on the amount of natural and agricultural methane, and these are the two biggest sources.

+1

 

Bob,

Here's one helpful way to view carbon sinks. Prior to the industrial revolution there was about 600 gigatons of carbon (C) in the atmosphere, and this was roughly in equilibrium with the rest of the biosphere. In particular, the ocean and the atmosphere were roughly in equilibrium with respect to exchange of CO2. Now there's roughly another 240 gigatons of C in the atmosphere, creating disequilibrium. Every year, Man puts out roughly another 10, and of the entire 240 in excess of equilibrium, Nature absorbs 5. So it looks like Nature absorbs half our annual output, but in fact, Nature absorbs a small fraction of the 240 gigatons in excess of the equilibrium amount in the atmosphere. Which by coincidence, right now just happens to amount to half of what we produce.

Because that absorption by Nature is driven by the 240 tons in the atmosphere, not the 10 or so we produce annually, in the short run, Nature would continue to absorb its 5 gigatons no matter what we did. So, if we could instantaneously cut CO2 emissions in half, yes, in the short run, atmospheric CO2 would stabilize. But that's a very limited statement. A: By contrast, if it's going to take half a century to reduce emissions, then we'd be talking about a much different world, and likely the needed reduction would be larger. B: And with that 50% cut, we wouldn't be "in equilibrium", we'd still have 240 gigatons of excess carbon in the atmosphere. We just wouldn't actively be pushing the atmosphere toward even greater disequilibrium, as we are now. C: So even with that 50% emissions cut, the natural sinks would still be "filling up" at the (exact) same rate as they are now. So you can see that there's no guarantee that stabilizing CO2 in the short run would in fact keep it stable in the long run. D: And in keeping with that, we are now far enough from equilibrium that there's no guarantee we havent' started other processes snowballing (e.g., arctic methane), so again, stabilizing CO2 at current levels right now does not guarantee long-run stability. E: And even if we had long run stability of the CO2 level, temperatures would continue to rise for another 30 years or so (there's that much lag in the system).

At this point, I hope it's clear. Stabilizing atmospheric CO2 still leaves us 240 gigatons in excess of equilibrium. It just means that we aren't actively adding to that amount.

And there is annual variability in all of this. The land-based natural sinks can be quite variable from year to year, due at least due to the importance of rainforest. So if there's a drought in the Amazon, that entire portion of that continent goes from being a carbon sink to a carbon source, and that matters materially for that year's absorption of CO2. Here they cite the 2010 Amazon drought as eliminating 1.5 gigatons CO2 absorption (= about 0.5 gigatons C absorption) for one year. So that, by itself, would about to a one-year 10% reduction in natural carbon sinks. Another Amazon Drought Spurs Greenhouse Gas Emissions: Scientific American

There is variability to a lesser extent in ocean absorption. Oceans require turbulence to absorb the CO2 and mix it downward, and ocean currents to mix it down to the deep ocean, so year to year variations in that affect the rate of absorption of CO2 out of the air. As does variation in surface temperature, as CO2 is less soluble in warmer water.

The upshot is that even if human CO2 production were fairly steady, you would see upticks and downticks in the rate of growth of atmospheric CO2 due to natural variability in absorption by Nature. I know I've seen a good, concise summary of this somewhere, but can't quite put my hands on it.

In terms of hitting limits, for the ocean, at least, we probably have quite some time to go. For the ocean, think of the absorption as having two pieces: First, the simple, purely chemical process of gas diffusing into liquid. If you raise the CO2 concentration in the gas that is sitting on top of the liquid, and agitate it, some will diffuse into the liquid. That's simple to grasp and fairly predictable. Then there's the vastly more complex biological absorption by the plants in the ocean. For that, who knows. But the point is, at present, almost all the ocean absorption of CO2 is due to the simple physical process -- it's just CO2 being absorbed in water. And it will take a very long time before we saturate the ocean with CO2, although (e.g.) the predicted slowdown in the thermohaline circulation (Gulf Stream et al.) would slow that down. Wikipedia's description is good:
Carbon sink - Wikipedia, the free encyclopedia

 

There is some strange belief contained in these numbers that 600 gigatons is a "natural" number and when god or maya set the scene in motion and nature always has the same amounts of sources and sinks. Its a convient idea for the religious or the greek idea of the unchanging universe. It also is far from the truth.
Atmospheric Concentrations of Greenhouse Gases | Climate Change | US EPA


You can see as we go through the glacial cycles ghg drop, and rise in the inter-glacial. Go further back than that first chart, and you would see ghg higher than today. Look at the peaks of the last 2 inter-glacials, and they are much lower than today. During each of those last 2 inter-glacials sea levels and we think temperatures were higher than today. We can also see that prior to industrialization ghg were rising, slightly curbed by the lia, but rising like the last 2 inter-glacials. Nature and climate change, sometimes in quite violent ways. It was not static before we industrialized.

We have destroyed many of the sinks through deforestation. Burning fossil fuel is not the biggest change to the planet man has done. We have paved over it, polluted it, over hunted, and over fished.

Now if we turn it down 50% will ghg concentrations naturally fall back to 280 ppm? It is extremely doubtful. One mechanism of increased ghg is heating of the oceans releases them both reduced carbonic acid concentration (equilibrium with atmosphere is temperature dependant) and release of natural methane. Many think that if we cut to 50% even today, concentration would continue to go up. It may drop for a couple of years, but then keep rising. Nature is neither static or angry, attempting to change the planet to Venus with run away feedback. But there is feedback in the system, and changes are slow.

 

The permafrost is melting, and giving off methane. There's a lot of permafrost, and a lot of methane. As we know, methane is a more potent GHG than CO2. As bad as the CO2 increases are, the bigger effect is triggering the methane.

And then there are the consequences to sea life from all that carbon uptake. Nope, not a pleasant thought at all.

 

I'm not sure I understand the 'carbon sink' correctly, although I view it in analogy to an acid titration into a buffer that anybody who has taken a first year college chemistry lab will remember: the pH trends slowly downward until the buffer is 'used up', and then drops rapidly.

While it is tempting to view the pH change before rapid change as almost flat or linear that is actually not the case; the buffer itself becomes less and less able to take up the acid. Ignoring time scale, the point of this is realize that the Earth does not have a fixed carbon uptake ability.

 

Austingreen,

It never occurred to me to preface my remarks about Bob's post (last 40 years) by saying "for the 10,000 years prior to the industrial revolution". So, let me correct that now. Looking at the middle graph above, for the 10,000 years or so prior to the industrial revolution, there was about 600 gigatons of C in the atmosphere, and it was roughly in equilibrium with the biosphere. E.g., there was little net flow of CO2 between ocean and atmosphere.

It didn't occur to me to caveat my remarks because the CO2 changes over the ice age cycle are both well known as to cause, and --- here's the key point --- slow. E.g, the buildup of atmospheric CO2 at the end of the most recent ice age is two orders of magnitude slower than the buildup from burning of fossil fuel. Those process are so slow they are irrelevant for discussion of Bob's original point. Bob's point, and my attempt to add some useful information, is about the vertical segment that terminates that 10,000 year roughly horizontal line, in the middle graph.

 

During recent glacial minima, the atmospheric CO2 pool was about 400 gigatons or petagrams Pg of CO2 carbon. During the minima, about 400. I just used the 180 and 280 ppm (ice core) values to get that. The 'swing' of 200 is smaller than the 240 Pg of anthropogenic increase (including deforestation). Interesting by itself; more so if you consider the time scales involved.

Chogan2 @7, the classic reference for this is Heimann and Reichstein 2008, doi:10.1038/nature06591 Required reading for all students interested in 'carbonology', put that doi into google scholar and your free copy pops up.

BobW @8 I think it is simple interest until some strong positive feedback may develop on CO2

 

I feel better talking about concentrations than gigatons or pentagrams (PG), since sequestration methods are easier to understand in terms of ppm. My problem with your post was it seemed to convey the idea that nature would try to have negative feedback to aim for such a level. Looking at the historical record and models often we get a positive feedback loop then negative feedback, with carbon dioxided concentrations moving regularly between approximately 180 ppm to 300 ppm, often with positive feedback with temperature going from ice age to interglacial. There is no reason to believe that if man cut back emissions by 50% that feedback would go completely negative.

The biggest negative feedback is disolving carbon dioxide in the oceans. Here we have a simple matter of physics to determine how much carbon dioxide will dissolve, based on concentration, temperature, and pressure. It is a slow process though for it to flow to deeper waters, so all the sequestration for this years additional ppm in air has not been sequestered yet. Let's say the ocean's uptake of carbon dioxide simply from uptake of disolved carbon dioxide and carbonic acid is 20%, Drop sources from adding 10ppm to the air to 5ppm, will drop uptake from 2ppm (net 8ppm) to 1ppm (net 4ppm). This is going out on a much further limb than I find plesent. It is likely dropping the addition in half, would add around half. Deforesting would add more concentration.

Now on sequestration in soil and sea creatures and plants we may do 30%, these are guesstimates, and perhaps tochachu can correct them. The ability of the earth to sequester as much has been harmed by pollutants and deforestation (land use). Perhaps we can reforest and clean up pollution to get these things in ballance, but there are giant smog clouds over asia, and forests are still being cut down. Will these drop us 3 ppm regardless of how much carbon dioxide we produce. I doubt it but let us put that in the equation. Now the 10ppm -2ppm-3ppm stays at anouther 5ppm in the air, and the 5ppm-1ppm-3ppm is at 1ppm. We have dropped the amount going into the air, but the amount will still be going up. How low do anthropologic sources need to go to net 0 increase? That is where I say no one knows. We don't know the negative feedbacks, but do know some positive ones. We likely have incresase from natural methane built into the system. Populations are eating more meat, and the manure and cammel and cow farts will increase this source. If you reduce fossil fuel by increasing deforestation, you may actually increase problems.

Again we can lie with statistics a great deal. We have the graph in that inconvient movie, with ghg following temperature, and sometimes it leads, and these feedbacks are slow. If you ignore the feedbacks you misunderstand the problem. We have positive and negative feedbacks, and you do need to look at the long term to figure those out. Otherwise you would look at that first graph I presented, see the spike and think something crazy like we are going to turn into venus if this keeps up, ok a septagenarian climate scientist made exactly that mistake.

 

The interaction of atmospheric CO2 with ocean surface waters has a great deal to do with windspeed, so that has to be included with temp, press, and conc. There have been decadal changes in windspeed in some areas apparently. So this is not a constant that falls out of the equation. Fortunately there are microwave scatterometers that can monitor such things globally from orbit. We simply need to keep the satellite fleet healthy and adequate.

I have not seen any strong evidence that either terrestrial or marine carbon sequestration have changed. The Heimann and Reichstein 2008 showed very well that sequestration is inversely related to 'ENSO state'. Now we are close to neutral in that regard. If it turns out that this century favors positive ENSO (El Nino), then there will be less than hoped-for sequestration.

AG: "If you reduce fossil fuel by increasing deforestation, you may actually increase problems." That is truly a horrible idea and I am sure you are not suggesting it. Forests are not just buckets of carbon, they are home for many species. Not just the charismatic ones used to squeeze donor money, but also smelly unattractive things that may benefit us in ways we cannot yet imagine.

There is a new study suggesting that mercury pollution in China could be reduced by burning wood pellets instead of coal. As the pellets have to come from somewhere, you can imagine that I don't think it is a good pan.

 

I thought the physics of equilibrium concentration only depended on temperature and pressure. Now temperature and pressure do depend on how the ocean waters mix, but wouldn't wind speed and ocean currents only affect the rate at which we reach equilibrium? That is it would take n number of years (IIRC decades but if you have a good number let us have it) to get the caronic acid and diffused co2 to depth. We also do have calcium carbonate that acts like a buffer.

We do have non-physical things too such as the calcium carbonite critters and algea blooms, and evolution, pollution, fishing, cycle of life that changes. I didn't mean to imply that we can calculate those effects from physics.

Yes I was only pointing out that some schemes are all about the fossil fuel, but seem to forget about land use change in reducing sequestration. To me the land use change is worse because it destroys biodiversity.

I agree. If the power demand is low enough renewable tree farms (also remove biodiversity) and waste wood can be use. Increase demand will cause more deforestation, and demand in china is quite high. ccgt with proper pollution controls reduces mercury to very low levels, even igcc coal, but this costs much more than a fuidized bed for burning biomass.

 

Yes, surface wind and advection in the water control rates. But I am a bit stingy with the word 'equilibrium'. Atmos CO2 is going up, water pH and aragonite saturation are going down. If those things were stable, then the system would work towards equilibrium. Perhaps, the oceanographers could specify the time required.

 

Increasing atmospheric CO2 should increase water [H+] (hydrogen ion concentration) in sea surface water accoding to the formulas, so yes increasing [H+] means decreasing ph. I definitely agree that currently atmospheric carbon dioxide is rising faster than it is mixing into lower depths. We also don't know the mix rate, and if rising temperatures have passed a tipping point where methane in the oceans will outgas faster than disolved carbonate (CO3-) ions mix into lower waters.

Aragonite is super saturated, so we need some help here to see what is happening, and its tough to figure out in the long term. We do know the atmospheric CO2 is a source of CO3- ions, but also a source of acidity (H+ ions), magnesium and calcium in the water as well as biological systems are involved. We are seeing in the short term that shells and corals are disolving faster than they are being constructed, but in the long term evolutionary pressure may change this.

 

New in PNAS "Anthropogenic emissions of methane in the United States"
(still in the early view section; naturally copies are available from various sources )

Annual US emissions set at 35 teragrams ( 0.035 petagrams ) by this work. Quite a bit higher than the USEPA or EDGAR (bookkeeping models ) estimate of about 20. It is not so easy to obtain these totals as one might suppose.

New in Nature Climate Change, by Miller et al. a coupled climate model (the typical way such things are done) suggesting that +2 oC happens at 650 petagrams cumulative CO2 emissions. Previously that had been set at 1000 Pg. Neither is very good news (by my definition) but there you go. I emailed Miller for the article just now, but I presume that he is not waiting by his computer to respond to such requests instantly.

 

Since agricultural interests do not self report methane, I would not trust the EPA number. Maybe we are in a ballpark between 10-70 tg

Miller seems to have turned to a higher ghg sensitivity than the old one. How much does 650 petagrams carbon dioxide correspond to ppm