In:
Elementa: Science of the Anthropocene, University of California Press, Vol. 3 ( 2015-01-01)
Abstract:
In connection with the Anthropocene, one might ask how climate is likely to evolve in the absence of man’s intervention and whether humans will be able to purposefully alter this course. In this commentary, I deal with the situation for very long time scales. I make a case that fifty million years ago, the collision between the northward drifting Indian land mass and Asia set the Earth’s climate on a new course. Ever since then, it has cooled. In the absence of some other dramatic disruption in the movement of the plates which make up our planet’s crust, on the time scale of tens of millions of years, this drift would cause the Earth to freeze over as it did during the late Precambrian. Evidence for this change in course comes from records of oxygen and lithium isotopic composition of foraminifer shells. It is reinforced by records of Mg to Ca in halite-hosted fluid inclusions and in marine CaCO3. In addition, the collision appears to have created abrupt changes in the sulfur isotope composition of marine barite and the carbon isotope composition of amber. Not only did this collision create the Himalaya, but more important, it led to a reorganization of the crustal plate motions. Through some combination of the building of mountains and lowering of sea level, these changes generated a mismatch between the supply of CO2 by planetary outgassing and that of calcium by the weathering of silicate rock. The tendency toward an oversupply of calcium has been compensated by a drawdown of the atmosphere’s CO2 content. This drawdown cooled the Earth, slowing down the supply of calcium. Although we are currently inadvertently compensating for this cooling by burning fossil fuels, the impacts of this CO2 on Earth climate will last no more than a tenth of a million years. So, if humans succeed in avoiding extinction, there will likely be a long-term effort to warm the planet.
Type of Medium:
Online Resource
ISSN:
2325-1026
DOI:
10.12952/journal.elementa.000061
DOI:
10.12952/journal.elementa.000061.f001
DOI:
10.12952/journal.elementa.000061.f002
DOI:
10.12952/journal.elementa.000061.f003
DOI:
10.12952/journal.elementa.000061.f004
DOI:
10.12952/journal.elementa.000061.f005
Language:
English
Publisher:
University of California Press
Publication Date:
2015
detail.hit.zdb_id:
2745461-7
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