Question

Outline what you understand by the following terms in the context of climate change. Give an example in each case.  

-Milankovitch cycle

-Feedback loop

-Radiative forcing                                                    

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Answer 1

MILANKOVITCH CYCLE:

A Milankovitch cycle is a cyclical movement related to the Earth’s orbit around the Sun. There are of three types: eccentricity, axial tilt, and precession. According to the Milankovitch Theory, these three cycles combine to affect the amount of solar heat that’s incident on the Earth’s surface and subsequently influence climatic patterns.

ECCENTRICITY

The path of the Earth’s orbit around the sun is not a perfect circle, but an ellipse. This elliptical shape changes from less elliptical (nearly a perfect circle) to more elliptical and back, and is due to the gravitational fields of neighboring planets (particularly the large ones – Jupiter and Saturn). The measure of the shape’s deviation from being a circle is called its eccentricity.

That is, the larger the eccentricity, the greater is its deviation from a circle. Thus, in terms of eccentricity, the Earth’s orbit undergoes a cyclical change from less eccentric to more eccentric and back.

AXIAL TILT

Earth tilts at angles between 22.1-degrees and 24.5 degrees. Greater tilts mean that the hemispheres closer to the Sun, i.e., during summer, will experience a larger amount of heat than when the tilt is less. In other words, regions in the extreme upper and lower hemispheres will experience the hottest summers and the coldest winters during a maximum tilt.

PRECESSION

Aside from the tilt, the axis also wobbles like a top. A complete wobble cycle is more or less 26,000 years. This motion is caused by tidal forces from the Sun and Moon.

Precession as well as tilting are the reasons why regions near and at the poles experience very long nights and very long days at certain times of the year. For example, in Norway, the Sun never completely descends beneath the horizon between late May to late July.

The Milankovitch Cycles are among the arguments fielded by detractors of the Global Warming concept. According to them, the Earth’s current warming is just a part of a series of cyclical events that take thousands of years to complete, and hence cannot be prevented.

FEEDBACK LOOP:

In climate change, a feedback loop is the equivalent of a vicious or virtuous circle – something that accelerates or decelerates a warming trend. A positive feedback accelerates a temperature rise, whereas a negative feedback decelerates it.

Scientists are aware of a number of positive feedbacks loops in the climate system. One example is melting ice. Because ice is light-coloured and reflective, a large proportion of the sunlight that hits it is bounced back to space, which limits the amount of warming it causes. But as the world gets hotter, ice melts, revealing the darker-coloured land or water below. The result is that more of the sun's energy is absorbed, leading to more warming, which in turn leads to more ice melting – and so on.

RADIATIVE FORCING:

Radiative forcing is the change in the balance between radiation coming into the atmosphere and radiation going out.
A positive radiative forcing tends on average to warm the surface of the Earth, and negative forcing tends on average to cool the surface