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    How Did Earth Avoid Runaway Global Warming In The Past?
    By News Staff | June 11th 2014 04:31 PM | 2 comments | Print | E-mail | Track Comments

    There have been times in our geological history when CO2 levels were 10X what they are today, yet warming was only slightly higher.

    Unlike what you often read in simplistic media accounts, there are a lot of variables in climate and weather and temperature. It takes a lot of things going wrong to turn Earth into Venus and we have never come close. 

    At the Goldschmidt geochemistry conference in Sacramento, geochemists discussed one such period, but they say we just got lucky - a vast mountain range formed in the middle of the ancient supercontinent, Pangea. 

    Around 300 million years ago, plate tectonics caused the continents to aggregate into a giant supercontinent. The sheer size of the continent meant that much of the land surface was far from the sea, and so the continent became increasingly arid due to lack of humidity. This aridity meant that rock weathering was reduced; normally, a reduction in rock weathering means that CO2 levels rise, yet in spite of this CO2 levels – which had been falling prior to the mountain formation- continued to drop, eventually undergoing the most significant drop in atmospheric CO2 of the last 500 million years. This phenomenon has remained unexplained - and still is, but a group of French scientists from the CNRS in Toulouse have come up with a conjecture based on a model which seeks to explain this contradiction.

    The period coincides with the rise of a vast series of mountains in the interior of Pangea, the "Hercynian" mountains". These mountains arose in a wide belt, running from what is now the Appalachians, through to Ireland, South-Western England, through Paris and the Alps into Germany, and on further East. 

    According to team leader, Dr. Yves Godderis, "The formation of these mountains meant that the rock weathering, which was threatening to slow to a walk through much of the supercontinent, was able to continue. The steep slopes of these Hercynian mountains produced physical erosion. Occurring in a humid equatorial environment, this physical erosion promoted rock weathering and removing CO2 from the atmosphere.

    "We believe that it is this which led to the dramatic drop in atmospheric levels of CO2. We estimate that if it hadn't been for the formation of the Hercynian mountains, the atmospheric CO2 levels would have reached around 25 times the pre-industrial level, meaning that CO2 levels would have reached around 7000 ppm (parts per million). Let me put that into a present-day context; the current atmospheric CO2 levels are around 400 ppm, so this means that we would have seen CO2 rise to a level around 17 times current levels. This would obviously have had severe effects on the environment of that time. But the formation of the mountains in fact contributed to the greatest fall in atmospheric CO2 in the last 500 million years."

    The team believes that even if the mountains had not formed and CO2 levels rose sharply, this would not have led to a runaway greenhouse effect as happened on Venus, because the increasing temperatures would have led to rocks being ultimately weathered, heat compensating for the scarcity of water.

    Rock weathering would have removed CO2 from the atmosphere, thus stopping the rising temperatures.

    "So it would eventually have been self-correcting," said Dr Godderis, "but there's no doubt that this would have stalled Earth's temperature at a high level for a long, long time. The world would look very different today if these mountains had not developed when they did.

    "This is a new model which explains some of the events in the 80 million years following the start of the Carboniferous period, and of course the ideas need to be confirmed before we can be sure that the model is completely accurate. The take-home message is that the factors affecting atmospheric CO2 over geological periods of time are complex, and our understanding is still evolving."




    Comments

    JohnK.
    Frustratingly, a great deal of simple science on this topic is routinely ignored, because of the political ramifications.  Specifically in this instance, large changes in the ocean, will cause large changes in the atmospheric CO2 concentrations.  This is because the solubility of CO2 in water, is inversely proportional to temperature. 

    For example, the Eocene to Oligocene transition that occurred 34.5 million years ago, took place as the Antarctic Circumpolar Circulation started to form.  This geological change was driven by the widening/formation of the gap between the Antarctic Archipelago and Australia/South America.  This thermally isolated Antarctica, which is why it got colder.  The formation of a large, cold ocean, in turn reduced atmospheric CO2.  Technically speaking, the Earth has been in an Ice Age for the past 34.5 million years.
        
    Anytime a geologic change alters the main ocean currents, the climate changes as well.  The real problem is that this argument cannot be used, because the answer to all climate science must be forced into the CO2 explanation, when in reality, it is not that simple.  Rock weathering is not as important as ocean currents.
    I am waiting for some climate scientist to publish a paper on what the optimum climate is for our biosphere. The first question that would naturally flow would be where is our current trend in relation to this finding.

    That nobody seems interested in this vital comparison indicates that the climate is being studied for other purposes. Since all the urgent demands that flow from today's climate science all converge on policy solutions that involve statism, bigger government, higher taxes, less personal liberty, the bigger picture tells me all that I need to know about "climate science". It is socialism and Gaia worship by other means.

    I am also curious about how deep the ice got during the last serveral periods of glaciation of the northern hemisphere, but that is a question for another time.