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Is it Man or a Milankovitch Cycle?

Pam Sornson

Posted on March 5, 2019 12:47

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Despite an overwhelmingly large global agreement by science that humans are causing climate change, there remain people who either don't believe that assertion or who believe something else is causing the planet to warm precipitously. It's important to understand why some people still legitimately question the science

 

There always have been skeptics in every field. In many cases, they base their contrary opinion on what, to them, appears to be equally valid science that 'disproves' the more widely accepted position. In the case of climate science, there are many naysayers around the world, each of whom has a different perspective (or in some cases, motive) as to why human activities aren't the driving cause of the warming atmosphere.

At least a few of these skeptics rely on the scientific theories of Milutin Milankovitch (1879-1958), a German astrophysicist who attributed the cause of changing climates to the rotation of the Earth around the Sun.

Sound Science = Different Conclusion?
And, in truth, his theory is sound. His math and analytical skills revealed that the planet's orbit around the sun does change on a regular basis and that those changes significantly influence the climate.

Milankovitch discerned that there were three cyclical variations to the planet's rotation, which he called its 'eccentricity,' its 'obliquity' or axis tilt, and its 'precession.'

Eccentricity
Eccentricity relates to the shape of the orbit, which changes over the course of 100,000 to 413,000 years. Those changes cause the orbit to expand and contract from a fairly round shape to a fairly oval shape. The shape of the orbit influences how much of the planet is exposed to solar radiance (sunshine) which heats or cools it depending on how close to the sun the earth is at any given time.

Obliquity (Tilt)
Obliquity refers to the angle of tilt of the planet's north/south axis toward the sun. The tilt swings from 21.5 to 24.5 degrees with a full cycle of one to the other occurring over 41,000 years. Steeper tilts shift the poles closer to the sun, which exposes those regions to more sunlight and higher temperatures. A more verticle tilt shifts that heat exposure more to the equator and evens out the total solar exposure across the planet.

A recent study confirmed the effect of the Earth's tilt on climate change.

Precession (Wobble)
Precession refers to the planet's wobble on its axis. The tides driven by the Sun and Moon and their influence on the Earth's oceans cause it to bobble a bit in its rotation. That bobble also affects how much sunshine hits the varying surfaces of the planet. Milankovitch's precession cycle completes every 26,000 years.

So, if we accept that Milankovitch's conclusions are true and accurate, are they sufficiently significant to 'disprove' the alternate scientific conclusion that human activity is the leading cause of climate change?

From my perspective, the two views of the issue are not incompatible. Yes, there is definitely science backing up Milankovitch's theories so I believe we can assume that the Earth's orbit and rotational elements are contributing to the phenomenon of climate change.

However, tune in next week to see why those theories alone aren't significant enough to explain the climate, weather and temperature extremes that we are experiencing today.

Pam Sornson

Posted on March 5, 2019 12:47

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Source: Phys.org

Scientists have long posited that periodic swings in Earth's climate are driven by cyclic changes in the distribution of...

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