As many of you have undoubtedly seen in the news since last week, research published in the journal Science extends to work of Antarctic ice core gas sampling back from its previous record of 440,000 years to 650,000 years ago. This week, I am going to look at a pair of papers published together that analyze, separately, the cycling of CO2 and Methane/Nitrogen Oxides over the last 8 glaciations. The results, and a graph that I am displaying from a Perspectives piece also in Science this week show fairly conclusively that the recent increases we have seen in greenhouse gases are not part of a natural cycling, at least not one seen in more than half a million years. Plus, we’ll take a brief look at the process of sampling gas from tiny bubbles that have presumably been in place for hundreds of millenia.
Brief Citations: (full citations [1, 2, 3] at CiteULike.org)
1: Siegenthaler, U. and others. Stable Carbon Cycle-Climate Relationship During the Late Pleistocene. Science 310(5752), 1313-1317.
2: Spahni, R. and others. Atmospheric Methane and Nitrous Oxide of the Late Pleistocene from Antarctic Ice Cores. Science 310(5752), 1317-1321.
3: Brook, E.J. Tiny Bubbles Tell All. Science 310(5752), 1285-1287.
Synopsis:
The two papers by Siegenthaler and others as well as Spahni as others are best read as two parts of a larger document. Siegenthaler and others present results of sampling CO2 concentrations in Antarctic ice, and Spahni and others present their sampling results of CH4 (methane) and NO2 (nitrogen dioxide). The two papers are separate because the groups doing the analysis are themselves separate, but are part of a larger consortium. The Antarctic ice core (pictured above, right, photo credit L. Augustin, LGGE) used for these two separate analyses was obtained from a region of Antarctica known as Dome Concorcodia (Come C). This particular region is ideal for such ice coring because of very low snow accumulation rates and low mean average temperatures. Their 3+ km long core records a record of approximately 650,000 years of snow and ice accumulation.
The results of these two studies are displayed in a composite figure (left) by E.J. Brook. There are six primary features of this graph: 1) The age increases to the left, 1950 is year 0 on the horizontal axis, 2) methane, CO2, NO2 and temperature rise and fall in sync, i.e. changes in their levels are coupled, 3) there is a natural period of cycling from maxima to maxima on the order of 100,000 years, and 4) across cycles, for each gas there is a minimum and maximum level that remains relatively unchanged. For CO2 this range is 180-290 ppm (parts-per-million), and 5) at the left-most end of the graph there is an anomalous increase in the levels of all three gases, methane levels double and CO2 levels increase from 290 ppm to more than 360 ppm, and 6) those anomalous increases in gas levels have not been accompanied by an equivalent increase in temperature, thus the coupling that once existed has now been broken. This means that whatever natural influence was forcing changes in all four parameters has within the last 150 years been overtaken by something else.
Context:
These Antarctic Ice Core records are the premier data on past climate change, because unlike other methods of determining CO2 and temperature levels such as tree-rings or marine sediments, the ice in which the gases are preserved is unchanged, and with the exception of temperature, no proxy is needed to establish gas concentrations. In other words, we don’t need to relate tree-ring thickness to CO2 and temperature levels, because CO2 can be measured directly from those pockets of trapped gases (more on that below). There is some uncertainty as to the exact dates of measurements taken because a model is needed to establish them relative to the exact techniques for determining temperature dates. However, these uncertainties do not affect the gas concentration measurements themselves, indeed the authors report measurement uncertainty of the order of 2 ppm for CO2, far smaller than the range of concentrations they report.
These results are further evidence that the rises we are seeing in atmospheric gases today are not due to natural processes. If that were, in fact, true, then that natural process would have needed to kick in right as we began dumping millions of tons of CO2 into the atmosphere from our 19th century factories. Also, this supposed natural process would have been dormant for 650,000 years at least before that very coincidental restart. No, the rises we are seeing in CO2 are human-induced, and the effects that they are having on the energy balance of our planet are not nearly as complicated as climate change opponents would suggest. The planet is warming, and the results presented in this paper provide a marquee result in a year full of extremely important work in climate change research.
General Explanations:
The tiny bubbles that were trapped 650,000 years ago only to be extracted and analyzed this year are miniscule time-capsules of the ancient atmosphere. They are formed when the snow that falls onto the Antarctic ice sheet finally turns into ice by a process called firnification. This process, at Dome C, takes as much as several thousand years, thus the gases preserved in the ice core are that much younger than the ice itself. The temperature proxy mentioned in the figure above is obtained by analyzing the composition of the ice itself, while the CO2, CH4, and NO2 all come from the trapped gases. Thus, in order to match up the time scales, a model is used that estimates how long the firnification process takes based on the temperature record and accumulation rates (how much ice formed each year). This model introduces some uncertainty into the dating of the gases, but the 2,000 year average offset is very small compared to the 650,000 year timescale being considered. In general, trapped gas analysis from Antarctic Ice core is the most certain, contamination-free, means we have of measuring the ancient climate.
Man, you really work hard on these research synopses. Here is an ice-related question: In the movie Kingdom of Heaven, this one dude in the desert offers this knight a glass of ice water as a luxury gift. How would people in the desert a thousand years ago have obtained and kept ice? How did anyone have ice for that matter?
Tom,
Thanks! I do work hard on them, but I’m finding that forcing myself to read more papers is helping to improve my research and writing skills as well, so I guess it all pays off in the end. So far, the papers have all been good reads, too, so hopefulyl there won’t be a week where I have to venture into the scary world of biology for a good paper (just kidding, I like biology but all of the bio papers in the big journals are extremely specific and jargon-rich).
About the ice, I don’t think that there was any ability of ancient desert folks to make ice. There is a really cool natural refrigerator that was probably used extensively in ancient times. If you take a double-walled clay pot in which the outside wall is made more porous, for instance by adding straw or something that burns off in the firing process, you can refrigerate foods down into the 40 degree F range or so. The key is that you fill the space between the walls with water which is able to evaporate from the outside of the pot, this then cools the water down and keeps the contents of the interior cold. But, this wouldn’t get you ice. If people did have ice I imagine that it was somehow carried in a well-insulated wagon or something, but this seems doubtful as well. Maybe it was just a Hollywoodification, but they wouldn’t make something up, would they?
Thanks! You should be the new Bill Nye because you seem to know all things related to interesting science.
And bio is crap.
Seriously.
Dear Anthony.
This from Australia. A very fine site. As an aside, very sorry to see that the US is bringing back the Inquisition. No doubt we will soon mimic. Maybe the French should ask for the Statue of Liberty back?
But, to the excuses and then to the main game. I have had a go at being a geologist for the past 30 years, which basically means, I have a license to be more confused about such things than most other folk. And I am. I find it is rather difficult, in a complex universe, to describe exactly what happened yesterday, never mind back in the geological past; I missed the prac where they handed out 20-20 rearview vision. I once arranged for a fairly ordinary sort of paddock to have 600 holes drilled into it, each to 50 metres. We then sampled every metre, for ten elements; it was a bit expensive. It was not complex geology. At about hole 590, I tried guessing what we would get next. Never came close. But folk far more perceptive than I will ever be, drill one hole and can then tell you the history of all the flat ground to the horizon and back to the Proterozoic. Ho hum.
And so with ice cores. I will get to those shortly, though I fear I am too thick to follow it all.
Sure, the climate is changing, remarkably, and the trees and the fish and the mammals are going down. But maybe it is all natural and cyclical, at least fundamentally.
Perhaps we panic too easily. When the world was first abuzz with ozone flap, opme years back, a zoologist friend in the habit of going down south pointed out that the whole thing revolved around seven uncalibrated instruments in Antarctica, operating erratically. I also read somewhere that Mt Erebus, just upwind of the new hole in the air, was then putting out about 35 million tonnes of chlorine annually, which was almost exactly a hundred times the amount of chlorine in the world’s aerosol cans’ cfc’s, for that year. I have no idea if that is true, I admit aand have been unable to find the reference again.
An aside. An old aborigine was arrested and went to the lockup for breaking up a cart, somewhere near Melbourne, early on. He needed the steel for an ax, to cut the replacement poles for the ones that where holding up the sky, but were rotting. Nearby, a solar array will soon save the sky, we are told.
We are currently in a flap about CO2 levels, predominantly because of the interpretation of maybe a dozen long ice cores all up, mostly those of Vostok and Dome C. I stared at the CO2 and methane and temp graphs from those for many hours, as they surfaced on the net.
First, they do seem to support the notion that we have had interglacials before. Next, it seems that the temperature rises, then the carbon dioxide, a few hundreds or thousands of years later. But the arrow of time is a fairly constant thing, at least at this end of the universe. If CO2 drove all the previous interglacials, whose exhaust gas produced it? The people of Atlantis? If so, where are their Coke cans? What drove the medieval warm period? The Vikings’ 2-stroke outboard motors? The IPCC does not like the medieval warm, but they did run cows in Greenland. The IPCC’s hockey-stick graph is deeply flawed, as any conversation with Google will show.
What I wish to put up for consideration is that the IPCC’s model was a fine try, but maybe it was wrong. All sorts of derivative science, by folk who are very good in their own fields but a little unaware of the complexities and uncertainties of geology, climatology and physical oceanography, has bought its tenets, lock stock and barrel. I observed exactly the same re the NASA model for a warmer, wetter past Mars, which offends most of the basics of first year geology, (like, liquid water does not easily flow very long distances uphill), yet is mostly unchallenged. Science, as you know, is an industry that lives largely by singing the simpler popular ditties. When you hear all scientists agree and there is now no debate on a topic, look out. You have just been told that tribal group-think has cut in.
What if CO2 leaks out of the ice core air bubbles in the first few days, months, years, hundred of years or millennia? Say the atmospheric CO2 levels were far higher close to the peaks of the previous interglacials, and it simply was not all trapped, or leaked away, or was chewed by lifeforms we have not noticed at work. We are assuming, I think, that newly fallen snow and firn are perfect traps for CO2 and are biologically inactive. Or are we? What if micro-shears, as from creep or compaction, allow some of the CO2 to escape? Maybe snow-loving algae or bacteria take it in and convert it to methane. As hydrogen takes up less space that oxygen, maybe the methane then escapes preferentially. Or, small things carry it away and the ice then refreezes around the depleted air bubble. Maybe the nitroous gases also escape. I do not say any of this is so. These are just the questions of the uninformed.
I tracked the data on the annual rainfall back to the first rain gauges, for Brisbane, Adelaide, Hobart and then Woodford, north of Brissie, where our now woeful local catchment is centred. The fifth order polynomial (Is that legit? I don’t know, but it panicked the Lord Mayor here, I am fairly sure) shows a long rolling wave for all of them, all different. For those, we can see only one full wave, Brisbane having a length of about 120 years. So, if this is tailpipe driven, what was the high of ‘74 all about? Or the low of 1915? I do not suggest or imagine this repeats regularly, as Erica Hendy’s coral isotope work a bit north of here shows rolling irregularities, taking it back into the seventeenth century. It goes around, erratically, seems to be the best observation.
The splendid and baffling set of abot 114 little maps of Australia, put out by Long Paddock, a fine government agency here, shows deviations from normal annual rainfall in colour. There seems to be no discernable pattern; it is just utterly baffling. If you are a farmer, you simply cannot plan. As we in Oz have national talkback radio, someone is always experiencing crippling drought and mentioning it. Next year, or ten years hence, when it buckets on his paddocks, out of genuine courtesy to the dust-covered folk who just sold him their stock, he has little to say.
On the basis of the sort doubts above, I am an optimist. This present climate change may just perhaps, not be a one-way trip to a global Namib Desert. If it gets hot, more water evaporates, more snow may fall, the albedo may rise, and the global temp may then come down. Something triggers very definite temperature declines, at the top of each interglacial, just as something starts them. I suspect the Milanko cycles are implicated and that this may all be driven by radiative forcing, rather than by our undoubted hubris.
I think we here in Oz should learn to mothball our towns or move them, like we do the cattle, to where the rain is. A transhumantes system is needed; plenty of other folk do it. Make the banks and post offices and houses truck-transportable, and get into this as a way of life and not a rolling disaster. Build the 270 solar power stations a TV journo was pushing for a few days ago. Get serious about solar-powered small electric vehicles and gas-powered semi-trialers. Test the notion of catching our water from wells along the seashore, just before the groundwater goes back to salt. Carefully. We also, I contend, we need public food trees, all over this planet. Hand-to-mouth mulberries and jaboticabas or whatever. No transport, no packaging, no cash required. War starts when folk start hunting each others daughters and gathering each other’s supplies. As long as we rely on the market mechanism entirely, someone will be always short of cash and ready to revert to older economics. I wish I could get the FAO to see it.
The climate news is bad, but not all so. It is just that evolution is far more dynamic than Charlie guessed, and extinctions are more frequent, in bigger runs, than we suspected. As we will almost inevitably not lead to derivative species, being too specialized, I think we should concentrate on helping other individual folk and species through this particular bottleneck, while also enjoying the sunshine. There is a stack to do, but maybe the most important is to think again about some of the basics of the drivers of the observed changes.
Maybe the problem is the heat we are generating directly, not the greenhouse gases. All those infernal explosion engines, old stamp-batteries running backwards. Or maybe it’s the new centrifugal pumps. Perhaps the drop in the world’s watertables and the decarb of the soils is releasing more carbon dioxide than we are directly, from the death of the upper layers of the deep biosphere. Maybe the oceans are buffering the CO2 system and we are a bit trivial. I also wonder if fishing or knocking off the whales, or just the drop in krill, might be looping back to the lower orders of marine life and changing the oceanic albedo, thus warming the surface of the western Pacific, inter alia, and depriving my macadamias of rain? Etc. If any of that is so, we may need to change our coping strategies.
Enough mumbling. A very fine website, as said. Keep going.
Best regards,
Peter Ravenscroft.
Closeburn, Queensland, Oz.