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Global CO2 Levels Set to Pass 400 ppm Milestone

By John Vidal, The Guardian

The concentration of carbon dioxide in the atmosphere has reached 399.72 parts per million (ppm) and is likely to pass the symbolically important 400 ppm level for the first time in the next few days.

Readings at the U.S. government's Earth Systems Research laboratory in Hawaii, are not expected to reach their 2013 peak until mid-May, but were recorded at a daily average of 399.72ppm on April 25. The weekly average stood at 398.5 on Monday.

The Mauna Loa Observatory, located on Mauna Loa volcano, on the big island of Hawaii.
Credit: NOAA.

Hourly readings above 400ppm have been recorded six times in the last week, and on occasion, at observatories in the high Arctic. But the Mauna Loa station, sited at 3,400 meters (11155 feet) and far away from major pollution sources in the Pacific Ocean, has been monitoring levels for more than 50 years and is considered the gold standard.

"I wish it weren't true but it looks like the world is going to blow through the 400ppm level without losing a beat. At this pace we'll hit 450ppm within a few decades," said Ralph Keeling, a geologist with the Scripps Institution of Oceanography which operates the Hawaiian observatory.

"Each year, the concentration of CO2 at Mauna Loa rises and falls in a sawtooth fashion, with the next year higher than the year before. The peak of the sawtooth typically comes in May. If CO2 levels don't top 400 ppm in May 2013, they almost certainly will next year," Keeling said.

CO2 atmospheric levels have been steadily rising for 200 years, registering around 280ppm at the start of the industrial revolution and 316 ppm in 1958 when the Mauna Loa observatory started measurements. The increase in the global burning of fossil fuels is the primary cause of the increase.

One year of CO2 daily and weekly means at Mauna Loa. 
Click image to enlarge. Credit:  NOAA

The approaching record level comes as countries resumed deadlocked U.N. climate talks in Bonn. No global agreement to reduce emissions is expected to be reached until 2015.

"The 400ppm threshold is a sobering milestone, and should serve as a wake up call for all of us to support clean energy technology and reduce emissions of greenhouse gases, before it's too late for our children and grandchildren," said Tim Lueker, an oceanographer and carbon cycle researcher with Scripps CO2 Group.

The last time CO2 levels were so high was probably in the Pliocene epoch, between 3.2 million and 5 million years ago, when Earth's climate was much warmer than today.

Reprinted with permission from The Guardian

Comments

By Eric Peterson (Front Royal, VA 22630)
on May 2nd, 2013

The “milestone” won’t be passed for a couple of years.  The black line on this chart http://www.esrl.noaa.gov/gmd/ccgg/trends/ is the CO2 level adjusted for the yearly fluctuation.  It is ludicrous to use a seasonal fluctuation to claim that CO2 hasn’t been this high in umpteen million years.  For one thing, the ice cores and other proxies used for that claim cannot show such seasonal fluctuations.  Nor a 10 year fluctuation or even a 100 year fluctuation.  All they can show is smoothed data points at around 500 to 1000 years resolution.  So a spike in CO2 like the current manmade spike would not show up in the older ice cores (prior to the present interglacial).

Anyway, it’s all pretty much irrelevant since the distribution of water vapor (i.e. weather) determines the global average temperature in the short, medium and long runs with only a minor role for increased CO2.

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By Dave (Basking Ridge, NJ 07920)
on May 2nd, 2013

Eric,
Technically the 400ppm level for average atmospheric concentration of CO2 will of course actually be passed. I think it also happened briefly last year too at about this time. Then as all the nice new plants and new green leaves on all the trees in the NH start sprouting and gobbling up CO2, the level will swing down again - just as it does every year – only to a new level a couple of ppm higher than last year. So, the background trend level is around 395ppm or so and that trendline will indeed probably extend pass 400 ppm in a couple of years.

In climate change, it is of course very relevant what the CO2 concentration is and what it means. CO2 is the trigger gas that raises the Earth’s thermostat so that the powerful water feedback can kick in.  Without any CO2 in the atmosphere, the Earth would indeed be a lot colder (about 30C)  and the water would freeze out and stay out, as it has done many times in the distant past when the CO2 levels naturally fell due to rock weathering and so on. So in that respect CO2 is the main greenhouse gas. It is apparently irrelevant to you.  But it is most definitely not irrelevant to the planet’s climate.

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By Peter C. Osborne (East Hampton, NY 11937)
on September 28th, 2014

Water vapor is the principal “greenhouse” gas, 95% of the effect, CO2 a distant second at under 4%.  CO2 does not drive climate change, no matter how much is there. The Sun drives the change principally.

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By Eric Peterson (Front Royal, VA 22630)
on May 2nd, 2013

Dave,  CO2 is not a thermostat nor a trigger, it is an amplifier.  When the relatively weak Milankovitch forcing creates a cooler northern hemisphere, the decreased albedo from unmelted snow and ice starts the cooling process (a positive feedback), and the decrease in CO2 from cooling oceans is another positive feedback.  As an amplifier in the other direction the increase in CO2 from warming oceans helps turn the glacial into interglacial.

What mankind has done now is short circuit the amplifier so the result will be warming.  But the warming from CO2 is relatively modest, maybe a degree C or so.  Water vapor is not a feedback, it controls the earth’s temperature.  Look at the fluctuations, 0.1 or 0.2 in a few weeks simply from changes in the distribution of water vapor.  Over time the water vapor doesn’t even out or redistribute itself, it does whatever the weather makes it do.  So if there are more storms or drought on average across the planet, that uneven distribution of water vapor creates global cooling for a day, week month, year, decade or century.  Conversely if there is relatively benign weather, the even distribution of water vapor (on average) creates global warming.

Thus the effect of our increasing CO2 will be about 1C of warming plus or minus whatever nature does with water vapor via weather.  Weather is mostly controlled by the sun.  Weather could also become more benign due to global warming (poles warming relatively faster thus less uneven water vapor, thus more global warming).  But that is model land and still not apparent in the real world.  In fact in the real world it is claimed that there is more storminess.  I don’t believe that, but if it were true, that is negative feedback.

The proof of warming via CO2 modulated by natural fluctuations in water vapor evenness is apparent from the graph: http://www.drroyspencer.com/latest-global-temperatures/  First flat in the 80’s to early 90’s from volcanoes then a rapid rise from stored up warmth mostly in the Pacific.  Part of that is the CO2 warming and the rest is the natural rise in water vapor mostly from El Ninos.  Since then flat again because nature has been doing some cooling things to offset the CO2 warming.  Mostly La Nina pushing heat into the deep ocean, more blocking (as measured by negative AO), etc.  The solar slowdown from 2008 and on has yet to be felt.

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By Dave (Basking Ridge, NJ 07920)
on May 3rd, 2013

Eric,
I appreciate your reply but my comment stands.  Parts of your comment look technically reasonable. But the key issue is that you do not connect the dots between warming due to long lived greenhouse gases like CO2 and water vapour levels in the atmosphere.

My thermostat analogy is of course a reference to papers that use that analogy in order to explain study results. Such as: http://pubs.giss.nasa.gov/abs/la09300d.html
There are also plenty of other established studies along with the generally held view from paleoclimatology identifiying atmospheric levels of CO2 and the subsequent greenhouse effect it produces as a major source of climate variability. Al of that is well established.

Roy Spencer is one of the very few denier climatologists. In that respect Roy Spencer stands somewhat alone in his thinking about the sources of climate variability. But we all know that

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By Eric Peterson (Front Royal, VA 22630)
on May 3rd, 2013

Dave, thank you for the reply.  The CO2 we are putting into the atmosphere is being absorbed by the ocean as we put it in.  Running through those numbers it means that if we stopped putting CO2 into the atmosphere, it would drop by 1/2 in 40 years or so.  So not very long lived.  However that is academic since we aren’t stopping.

Second the thermostat analogy is quite incorrect.  The paper says “control knob”, not thermostat but that is incorrect although less incorrect.  The notion that CO2 energy balance is controlling the water vapor worldwide is disproven every day, week, year, and longer time period.  It only takes a week or two to undo years or decades of CO2 warming because water vapor evenness, determined by weather, is the determiner of the overall energy balance.  Things that control the weather are thermostats.  One example is tropical convection.

Roy Spencer’s chart is a factual depiction of temperature measured by satellite, the most accurate way available to measure modern temperature change.  Attacking the man doesn’t change that fact.

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By Jeremy
on May 5th, 2013

Wonder at what level world leaders will panic and put in place drastic measures to curb emissions. My guess will be at between 475-500 ppm. It will not take that long to reach that becuae we are currently at 3 ppm yearly and I can see us jumping to 4-5 ppm in a decade.

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By Dave (Basking Ridge, NJ 07920)
on May 6th, 2013

Eric,

I just noticed your response today. I think it would be hard to construe my earlier comment as an “attack” on Roy Spencer. That’s not my style at all. The point I intended is that his views are not in line or representative of the established mainstream science. That is an important observation. It seems very likely that most readers here are not scientists or working climatologists. As with any profession, whether it is physicians, accountants, etc. or scientists, this type of background is, and of course should be, an important consideration to serious people in selecting whose professional advice to follow.

Regarding your other comments on the technical side: these are also clearly grounded in that outlier view so agreement / resolution in this conversation seems unlikely. On the other hand, I think it is important to talk openly and that has to be without rancor.

As far as I can see from the data, it seems quite obvious that the planet has warmed quite a bit. See for example this recent CC article which is relevant here:  http://www.climatecentral.org/news/why-the-globe-hasnt-warmed-much-for-the-past-decade-15788

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