Mike, Stephen, and others: Evidently, regarding the new 400 ppm arctic readings, this group (including me) needs help. Here's what I think I understand, followed by what I don't understand.
Every year for several decades, in April and May, the concentration of CO2 at Point Barrows, Alaska, has exceeded the concentration of CO2 at Mauna Loa. It seems that the highest concentrations on the planet for the whole year are these spring-time arctic readings -- if one excludes readings where there is a local fossil-fuel source (as in a city) or a local biogenic source (as in the interior of a forest). The world's first readings above 400 ppm in the past million or more years were the April readings this year at arctic stations -- once one requires 1) readings from the marine boundary layer, where a local anthropogenic or biological signature is nearly absent, and 2) monthly averages to remove outliers. The large peak-to-valley annual oscillation in Arctic CO2 concentration is the reason 400 ppm happens first in the arctic. The peak to valley oscillation at Point Barrows is about 18 ppm, and at Mauna Loa it is about 7 ppm, with the peak around May and the bottom of the valley around November. The large arctic oscillation allows an annual average at Mauna Loa to exceed that at Point Barrows (by about 2 ppm) while the April-May readings at Point Barrows are higher than at Mauna Loa (by about 4 ppm). I think the main reason the annual average is higher at Mauna Loa than at Point Barrows is because the Mauna Loa latitude is closer to the anthropogenic fossil-energy source, which is centered at mid-latitudes in the northern hemisphere. Perhaps this isn't the main reason. I hope someone knowledgeable will comment. As for the 18 ppm swing at Point Barrows, and the higher April-May values in the Arctic than at lower latitudes, I hope someone in this group can clarify the underlying science. Many existing models must contain the answers: they must quantify zonal photosynthesis and respiration, superimposed on freezing and thawing and accompanied by importing to and exporting from lower latitudes. What does a zeroth order model look like, with just the most important terms? (My guess is that the methane terms are small.) What fraction of that 18 ppm swing has anything to do with people? One way of asking the question is to ask what the CO2 pattern looked like in pre-industrial times. My guess is that the large arctic amplitude has very little to do with anthropogenic sources, and that the highest concentration of CO2 in the Year 1600 would have been in the Arctic in April-May. Who can set us straight? Rob -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Mike MacCracken Sent: Tuesday, June 05, 2012 9:30 AM To: Stephen Salter Cc: Geoengineering Subject: Re: [geo] 400 ppm and rising Hi Stephen--Not at all--I am just saying that the meteorological situation is also a very important factor to consider. Mike On 6/5/12 6:10 AM, "Stephen Salter" <[email protected]> wrote: > Mike > > Both diffusion and oxidation are involved. Are you saying that > methane released from the Arctic does not get oxidised? > > Stephen > > Emeritus Professor of Engineering Design Institute for Energy Systems > School of Engineering Mayfield Road University of Edinburgh EH9 3JL > Scotland Tel +44 131 650 5704 Mobile 07795 203 195 > www.see.ed.ac.uk/~shs > > > On 04/06/2012 14:46, Mike MacCracken wrote: >> Hi Stephen--I think there is a simpler explanation, and that is that >> the planetary boundary layer is shallow due to the typical inversion, >> so CO2 tends to build up near the ground during the non-growing >> season. My guess is that the late summer values also tend to be a bit >> lower than Mauna Loa due to the CO2 being pulled out from a thinner >> layer (you see a much larger seasonal variation in high latitude CO2 than at >> Mauna Loa). >> >> Mike >> >> >> On 6/4/12 6:30 AM, "Stephen Salter"<[email protected]> wrote: >> >>> Hi All >>> >>> There are not many large coal-fired power stations in the Arctic and >>> so the question arises about where this extra CO2 in the Arctic has >>> come from. One possibility is that it is the product of methane >>> decomposition and would be in line with the report to this group >>> from Greg Rau of 22 May. >>> >>> We know that the atmosphere weighs about 5 E18 kilograms. If we >>> know the plan area represented by the observing stations and the >>> decay rate of methane to CO2 we could get an approximate figure for >>> the mass of methane causing the rise in CO2. We could then compare >>> this with the scary rate of methane increase reported by Semiletov and >>> Shakhova. >>> >>> Stephen >>> >>> >>> Emeritus Professor of Engineering Design Institute for Energy >>> Systems School of Engineering Mayfield Road University of Edinburgh >>> EH9 3JL Scotland Tel +44 131 650 5704 Mobile 07795 203 195 >>> www.see.ed.ac.uk/~shs >>> >>> >>> On 02/06/2012 17:41, Rau, Greg wrote: >>>> Greenhouse gas levels pass symbolic 400ppm CO2 milestone Monitoring >>>> stations in the Arctic detect record levels of carbon dioxide, >>>> higher than ever above 'safe' 350ppm mark Associated Press >>>> guardian.co.uk, Friday 1 June 2012 07.50 EDT >>>> >>>> The Arctic Ocean with leads and cracks in the ice cover of north of Alaska. >>>> Photograph: Courtesy Eric Kort/Jet Propulsion Laboratory/NASA The >>>> world's air has reached what scientists call a troubling new >>>> milestone for carbon dioxide, the main global warming pollutant. >>>> >>>> Monitoring stations across the Arctic this spring are measuring >>>> more than >>>> 400 >>>> parts per million of the heat-trapping gas in the atmosphere. The >>>> number isn't quite a surprise, because it's been rising at an accelerating >>>> pace. >>>> >>>> Years ago, it passed the 350ppm mark that many scientists say is >>>> the highest safe level for carbon dioxide. It now stands globally >>>> at 395. >>>> >>>> So far, only the Arctic has reached that 400 level, but the rest of >>>> the world will follow soon. >>>> >>>> "The fact that it's 400 is significant," said Jim Butler, the >>>> global monitoring director at the National Oceanic and Atmospheric >>>> Administration's Earth System Research Lab. "It's just a reminder >>>> to everybody that we haven't fixed this, and we're still in >>>> trouble." >>>> >>>> "The news today, that some stations have measured concentrations >>>> above 400ppm in the atmosphere, is further evidence that the >>>> world's political leaders with a few honourable exceptions are >>>> failing catastrophically to address the climate crisis," former >>>> vice president Al Gore, the highest-profile campaigner against >>>> global warming, said in an email. "History will not understand or >>>> forgive them." >>>> >>>> Carbon dioxide is the chief greenhouse gas and stays in the >>>> atmosphere for >>>> 100 years. Some carbon dioxide is natural, mainly from decomposing >>>> dead plants and animals. Before the industrial age, levels were >>>> around 275 parts per million. >>>> >>>> For more than 60 years, readings have been in the 300s, except in >>>> urban areas, where levels are skewed. The burning of fossil fuels, >>>> such as coal for electricity and oil for gasoline, has caused the >>>> overwhelming bulk of the man-made increase in carbon in the air, >>>> scientists say. >>>> >>>> It's been at least 800,000 years probably more since Earth saw >>>> carbon dioxide levels in the 400s, Butler and other climate scientists >>>> said. >>>> >>>> Readings are coming in at 400 and higher all over the Arctic. >>>> They've been recorded in Alaska, Greenland, Norway, Iceland and >>>> even Mongolia. But levels change with the seasons and will drop a >>>> bit in the summer, when plants suck up carbon dioxide, NOAA >>>> scientists said. >>>> >>>> So the yearly average for those northern stations likely will be >>>> lower and so will the global number. >>>> >>>> "It's an important threshold," said the Carnegie Institution >>>> ecologist Chris Field, a scientist who helps lead the Nobel >>>> Prize-winning Intergovernmental Panel on Climate Change. "It is an >>>> indication that we're in a different world." >>>> >>>> Ronald Prinn, an atmospheric sciences professor at the >>>> Massachusetts Institute of Technology, said 400 is more a >>>> psychological milestone than a scientific one. We think in >>>> hundreds, and "we're poking our heads above 400," >>>> he said. >>>> >>>> Tans said the readings show how much the Earth's atmosphere and its >>>> climate are being affected by humans. Global carbon dioxide >>>> emissions from fossil fuels hit a record high of 34.8 billion >>>> tonnes in 2011, up 3.2%, the International Energy Agency announced last >>>> week. >>>> >>>> The agency said it's becoming unlikely that the world can achieve >>>> the European goal of limiting global warming to just 2 degrees >>>> based on increasing pollution and greenhouse gas levels. >>>> >> >> -- You received this message because you are subscribed to the Google Groups "geoengineering" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/geoengineering?hl=en. -- You received this message because you are subscribed to the Google Groups "geoengineering" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/geoengineering?hl=en.
