A few notes from Week 3 of Denial 101x: Making Sense of Climate Science Denial. These notes are mainly about the science and not the denialism part (unlike my last post, which addressed the central theme of the course, denialism, more.)
The Carbon Cycle
Atmospheric CO2 concentrations have gone up by about 40%. Simple explanation: Humans are releasing Carbon into the atmosphere by burning fossil fuel. More complex explanation: Humans are affecting the Carbon Cycle in a number of ways, releasing Carbon (burning fossil fuels) as well as affecting natural Carbon sinks.
This became known, observed, ca 1958. About half of the CO2 we release contributes to the extra atmospheric CO2. Myth: Since the amount of Carbon that cycles naturally through the system is so large, human influence must be negligible. Good analogy using a bank account. Nature has been a net Carbon sink over the last 50 years, but we are still seeing atmospheric CO2 going up.
A video by Gavin Cawley:
Andy Skuce discussed the role of volcanoes in comparison to human effects. Great discussion of the big picture for volcanoes. Did you know that most of the volcanoes are under the sea? But on balance the way undersea volcanoes work actually results in a lot of CO2 being consumed there. Mt Etna is one of the more prolific CO2 producers, but is still smaller than human fossil fuel burning in nearby Sicily. Also, 1/3rd of land based volcano CO2 is off set by weathering of volcanic surfaces. Humans release 60-100 times more Carbon than volcanoes.
Gavin Cawley talks more about the Carbon Cycle, asking the question, how long would it take the Carbon Cycle to return CO2 to pre-industrial levels is humans got out of the game today. Myth: CO2 has a short lifespan in the air. A given CO2 molecule may have a short lifespan but the amount of CO2 does not change quickly. Jelly Beans are invoked in a helpful analogy. Answer: It is a slow process that will take 50-200 years for much of it to return, but the total adjustment time is a long time, thousands of years. Also, Gavin Cawley and his wife need to talk more about heir checkbook and their private jelly bean stash.
Dr Joanna House, Corinne Le Quéré, Professor Tim Osborn, Professor Dan Lunt, Professor Lonnie Thompson, Professor Pierre Friedlingstein and Professor Mauri Pelto talk about the Carbon Cycle. Seasonal cycles, longer term cycles. Plants, ocean, etc. Natural fluxes are roughly in balance, human emissions provides a rapid positive flux. We have not had this CO2 level in 800 thousand years. NOTE: That does not mean that 800K years ago CO2 was at 400ppm. It is just that we have a good ice core record 800K long. To reach 400ppm you have to go back much farther in time, millions of years. The time scale for ocean mixing is thousands of years. About 65 – 80% of the human released CO2 will go away (if humans go away) in between 2 to 200 years. The remaining 35 percent (on average) will take thousands of years.
Mark Richardson: Pig picture, i.e., different planets. Good description of how the greenhouse effect works. Cool infrared camera demonstration. A pygerometer.
Mark Richardson: Looking at the first ever greenhouse effect myth, dates back to 1900. “Knut Ångström and his assistant did an experiment.” It seemed to show that the effects of CO2 could saturate. It does but not at actual relevant levels in the atmosphere.
Sarah Green about reinforcing feedback. Chicken-egg problems, causality. What do Ice Cores say about changes in the Carbon Cycle over long periods of time. Does warming increase CO2, or does increased CO2 cause warming? Yes. False dichotomy myth. This is pretty important and a bit complex, so I’ll just put the video here:
From the experts, Professor Naomi Oreskes, Dr Ed Hawkins, Professor Mike Mann, Professor Simon Donner, Professor Richard Alley, Professor Eric Rignot, Professor Jonathan Bamber and Professor Lonnie Thompson talk about the greenhouse effect, the history of research on the greenhouse effect, etc. Excellent video to show Uncle Bob:
Mark Richardson examines the fingerprint of changing structure of heat distribution in the atmosphere, (including the famous Tropical Hotspot, not a real fingerprint, though may be it is like a partial print). (See this recent post on a related topic.)
Sarah Green on Satellite measurements of outgoing radiation. This is a key fingerprint of changes in energy balance.
Are you taking the course? You should check it out, here.