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How do we know where the carbon is coming from?

Keeling curve

Keeling curve vs prediction based on fossil fuel origin (from Scripps)

In 1957, Charles Keeling of Scripps Institution of Oceanography began regular measurements of carbon dioxide concentration at Mauna Loa, Hawaii. By 1960, he was already in a position to report a steady increase, together with seasonal variations. In the northern atmosphere, CO2 concentration falls during the spring and summer growing season, but recovers during autumn and winter as vegetable matter decays. This sawtooth pattern is superposed, however, on a steady overall increase.

The Keeling curve and beyond

Scripps Institution of Oceanography

Scripps Institution of Oceanography, from Birch Aquarium ((Invertzoo via Wikipedia)

Charles Keeling died in 2005, but the work is being continued by his son Ralph. When I visited Scripps in 1995, I saw Charles Keeling’s original curve, ink on graph paper, on the wall in the corridor outside his office. That curve has now been designated a National Historic Chemical Landmark, and there are commemorative plaques both at Scripps and at the Mauna Loa Observatory. Charles Keeling’s original paper, freely available here, goes into meticulous detail regarding sample collection, calibration, precautions taken to prevent local contamination, and comparisons between the Mauna Loa data and those that numerous other sites, including the Antarctic and samples collected from an aircraft.

By 1985, the record had been extended backwards in time by analysis of air bubbles trapped in ice cores, with dates ranging from the 1980s to the 1600s and earlier. These dates overlap Keeling’s data, and take us back to pre-industrial times. Before long, the ice core record had been extended to an 160,000 years, taking us into the Ice Ages, while further work has pushed it back to 800,000 years. We have estimates going back far beyond that, but employing indirect methods and with higher uncertainty.

Ice core record

Atmospheric CO2, 1700 – 2014; NASA via Forbes. Click to enlarge. Note that the zigzags for atmospheric data are not error bars, but annual fluctuations.

During the Ice Ages, carbon dioxide played a dual role, as product and as agent. The temperature oscillations at this time were driven primarily by subtle changes in the Earth’s motion (so-called Milankovitch cycles). But carbon dioxide is less soluble at higher temperatures (which is why your carbonated drink fizzes inside your mouth). And so in the first place the rise and fall of temperature led to a rise and fall of carbon dioxide in the atmosphere, as the oceans released and reabsorbed the gas. But then, the changes in carbon dioxide concentration amplified the original effect, since more carbon dioxide acting as a greenhouse gas makes the Earth lose heat less efficiently into space.

To summarise the results, current levels of CO2 are the highest they have been for over twenty million years. In the centuries leading up to 1800, Read the rest of this entry

AiG is just silly, but global warming denial is serious

Update: just in from NASA: “In Greenland, Another major glacier comes undone”  

Firstly, who do you think said this:

CO2 emissions must be reduced to avoid serious climate change. To manage CO2, governments and industry must work together. Government action is needed and we support an international framework that puts a price on CO2, encouraging the use of all CO2-reducing technologies.

Answer at end.

Evolution denial, as AiG’s declaration of faith (recently posted, with brief commentary, here) shows, is merely absurd. Climate change denial is deadly serious. Although there is an overlap; AiG says the climate is safe because God’s looking after it, and many creationists, including Jay Richards of the Discovery Institute, are fervent climate change denialists. Although in the last case, the reason seems to be a touching faith in the Free Market, rather than in God.

The video below has already had over 34 million views, but deserves a few more before the Paris conference on climate. A good use of 4 minutes of your time. But don’t be unduly alarmed; it really took 75 minutes, not just 4.

The commentary is also interesting: e.g. “The glacier has retreated further in the last ten years than it had in the previous 100”.

I would say “Be afraid, be very afraid”, but someone might call me an alarmist. Enjoy the show!

In case you haven’t noticed what’s happening (Indonesia’s burning; Ethiopia is running out of water; the Maldives are disappearing), see here:

And if someone tries to tell you that it isn’t happening, or that it’s natural, or that it’s happened before, or that it doesn’t matter, or that nothing can be done about it, or (as I recently came across) all of these at once, see here. As to how we know what the causes are,

Refer to caption

if you try to work out what’s happening without anthropogenic CO2 you get it wrong; if you include it, you get it right.

Has it happened before? Check the record:

File:2000 Year Temperature Comparison.png

And remember that all but one year in the last decade has been warmer than 2004, already up and away ahead of the curve, with 2015 set to be the warmest yet for something like 100,000 years.

h/t my friend Kim Johnson. Global Temperature Anomaly by NASA Goddard Institute for Space Studies; licensed under Public Domain. Other images created by Robert A. Rohde / Global Warming Art. Literature references for Climate change attribution  here; for reconstructed temperature here. Links to easily accessible sources for brevity and convenience; primary literature links embedded therein, and at Skeptical Science. Quotation at beginning from Shell official policy statement.

Earth’s Climate Evolution – a Geological Perspective on Climate Change

Summerhayes-cover-designYes, climate can change naturally. No, that is not why it’s changing now.

Earth’s Climate Evolution – a Geological Perspective on Climate Change

From Geological Society of London blog via my friend Michael Roberts

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