Posts Tagged ‘milankovitch’

August 9 2022 By Kimberly Mann

With all of the talk about climate change and CO2 levels reaching dangerously high levels according to certain political groups, a close evaluation of what a high level entails is in order.

Carbon dioxide is required in Earths atmosphere to create warming and cooling. A study led by Gavin Schmidt, who heads NASA’s Goddard Institute for Space Studies, showed that water vapor and clouds together account for 75 percent, with CO2 coming in at 20 percent, and other non-condensing greenhouse gases making up the rest.

According to NASA, in June 2022 the Earth’s atmosphere held 419ppm of CO2. During the Jurrasic period the “CO2 concentration in the range of ~ 750–975 ppm was calibrated from the fossil material, with a best-estimated mean of ~ 900 ppm.” No humans, No cars, no cow farts, and no manufacturers were available during the Earth’s Jurassic period.

If Earth’s CO2 level drops too low, glaciers form and starts an Ice Age. From an article titled “CO2 as a primary driver of Phanerozoic climate” they found:

“Here we review the geologic records of CO2 and glaciations and find that CO2 was low (<500 ppm) during periods of long-lived and widespread continental glaciations and high (>1000 ppm) during other, warmer periods.”

According to the findings of this research paper and NASAs calculation of Earth currently having 419ppm of Carbon Dioxide in the atmosphere, Earth is at a low CO2 level. If Carbon Dioxide isnt the primary driver of climate, what is?

The Earth changes both orbit and axis tilt. A change in Earths orbit is suspected of causing the last ice age over 20,000 years ago; the Milutin Milankovitch Theory which has been embraced by the National Research Council of the U.S. National Academy of Sciences.  More information on Milankovitch can be found on NASAs website at NASA.gov

The Milankovitch Climate Theory is “periodic changes in the orbital characteristics of a planet that control how much sunlight it receives, thus affecting its climate and habitability over hundreds of thousands of years.” space.com

In 1982, six years after the study was published, the National Research Council of the U.S. National Academy of Sciences adopted Milankovitch’s theory as truth, declaring that: “… orbital variations remain the most thoroughly examined mechanism of climatic change on time scales of tens of thousands of years and are by far the clearest case of a direct effect of changing insolation on the lower atmosphere of Earth.”

The change in the tilt of the Earth’s axis (obliquity) effects the magnitude of seasonal change. At higher tilts the seasons are more extreme, and at lower tilts they are milder. The current high axial tilt is 23.5° according to NASA on August 7 2022.  Over the last million years, it has varied between 22.1 and 24.5 degrees with respect to Earth’s orbital plane.  We are in a decreasing tilt cycle that lasts about 41,000 years. 41,000 years is the exact length of time between Earth Ice Ages.

Milankovitch examined how variations in three types of Earth orbital movements affect how much solar radiation (known as insolation) reaches the top of Earth’s atmosphere as well as where the insolation reaches. It was Milankovitch’s belief that obliquity was the most important of the three cycles (Eccentricity, Precession, Obliquity) for climate, because it affects the amount of insolation in Earth’s northern high-latitude regions during summer.

While CO2 does have an effect on our atmosphere, the primary driver appears to be Earths orbits and rotation around the sun, not human activities.

Credit: NASA

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