Reinventing the Wheel


I research the cause of ice ages and yesterday I read a manuscript written in 1867 that made me feel like I am trying to reinvent the wheel.  James Croll was a failed hotel innkeeper and when appointed to the Geological Survey in Edinburgh, failed the Civil Service exam, but now he is known as one of the first people to link differences in the Earth’s orbit to changes in global climate that resulted in ice ages.  I am seeing more and more the importance of the ocean as a heat sink and transporter, but perhaps this is obvious to someone living in the path of the Gulf Stream:

“A greater quantity of heat is probably conveyed by the Gulf Stream alone from the tropical to temperate and arctic regions than by all the aerial currents which flow from the equator” -Croll, 1867

My current research focus is on Uganda’s climate, which is greatly influenced by the Indian Ocean monsoon and the passing of the Intertropical Convergence Zone (ITCZ, basically a belt of rain clouds near the equator).  Changes in ocean currents and sea surface temperatures have a huge influence on the monsoon and therefore rain or snow in Uganda.

“if the equatorial current of the Atlantic, the feeder of the Gulf-stream, were removed merely a few degrees to the south of the present position, the entire current would be turned into the Brazilian branch and flow into the Southern Ocean, and thus probably stop the Gulf-stream altogether.” -Croll, 1867

Croll’s ideas are very similar to those debated today to explain the connections between tropical and polar regions and climate feedbacks that can amplify the temperature change in an area.  A simple shift in ocean currents could make southern France feel like Toronto, for example.

Croll’s contributions are typically dismissed or omitted from present-day discussions about past climate because he attributed the occurrence of ice ages to maximum eccentricity, times when the Earth’s orbit causes COLDER than normal WINTERS allowing large quantities of snow to fall.  Instead, the timing of interglacials (warm periods similar to what we experience now) in the northern hemisphere appear to be linked to WARMER then normal SUMMERS, when the summer temperatures cause all the snow that fell during the winter to melt away.

Anyway, fascinating stuff, to learn more about Croll and others, I recommend reading: Ice Ages: Solving the Mystery by Imbrie and Imbrie.

Croll, J. (1867) On the excentricity of the Earth’s orbit and its relations to the glacial epoch.  Philosophical Magazine, February, 1-13.

Yes, the image of the moon is a bit fuzzy, but I still like it because that is the best photograph of the moon I have ever taken!  Look at those craters!


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