Climate Change Before Humans
Why do glaciations, ice ages, and other long term climate changes even happen? There are both short-term and long-term processes that induce climate change. Some of these, like the eruption of a volcano in equatorial regions, can produce an ash cloud capable of lowering the global temperature for a year or two. This exact phenomena was observed in 1991, when Mt. Pinatubo (in the Philippines) erupted and caused temporary global cooling by injecting so much ash into the stratosphere that it reduced the amount of insolation to reach Earth's surface by 10%!
At the other end of the spectrum, one of the longest, slowest processes that produces climate change, as discussed in Module 2, is plate tectonics, or the slow movement of plates rearranging themselves on Earth's surface over tens of millions of years. Recall that the "Great Dying" extinction event that happened about 250 million years ago is thought to have stemmed from climatic change associated with the formation of the supercontinent Pangea.
In the middle of the spectrum are processes associated with orbital variation. In Module 1, you learned that the Earth's axial tilt is 23.5 degrees, and that the Earth's rotation around the Sun follows an elliptical path. That has not always been the case, however. Log in to the support website for the textbook and go to the Study Area. Click on Interactive Animations, and then under Chapter 8, select the animation titled "Orbital Variations and Climate Change." Use the animation to answer the following questions.
1) What are the processes described as eccentricity, obliquity, and precession?
2) What timescales do each of these processes occur? Which one takes the longest to complete a full cycle? Which one is the shortest?
3) Select the radio button for Eccentricity - All months. You'll notice that the Earths for June, July, and August change color when the shape of the elliptical orbit places them far enough away from the Sun. What do think this color change signifies climatically for Earth?
4) Obliquity and precession both alter the Earth's axial tilt, but in different ways. Which one do you think produces a bigger change in the Earth's climate? Why? (Hint: think about how tilt and wobble alter the amount and timing of solar insolation received across Earth's surface).
5) Consider each of these processes to have a scale. For eccentricity, for example, it would be a scale from most circular to most elliptical, for obliquity it would be between a 22 and 24.5 degree tilt, and for precession, it would be a 360 degree circle of where the North Pole points in relation to the Sun. What combination of the three scales do you think would produce the coldest climatic conditions for Earth? What about the warmest?
At the other end of the spectrum, one of the longest, slowest processes that produces climate change, as discussed in Module 2, is plate tectonics, or the slow movement of plates rearranging themselves on Earth's surface over tens of millions of years. Recall that the "Great Dying" extinction event that happened about 250 million years ago is thought to have stemmed from climatic change associated with the formation of the supercontinent Pangea.
In the middle of the spectrum are processes associated with orbital variation. In Module 1, you learned that the Earth's axial tilt is 23.5 degrees, and that the Earth's rotation around the Sun follows an elliptical path. That has not always been the case, however. Log in to the support website for the textbook and go to the Study Area. Click on Interactive Animations, and then under Chapter 8, select the animation titled "Orbital Variations and Climate Change." Use the animation to answer the following questions.
1) What are the processes described as eccentricity, obliquity, and precession?
2) What timescales do each of these processes occur? Which one takes the longest to complete a full cycle? Which one is the shortest?
3) Select the radio button for Eccentricity - All months. You'll notice that the Earths for June, July, and August change color when the shape of the elliptical orbit places them far enough away from the Sun. What do think this color change signifies climatically for Earth?
4) Obliquity and precession both alter the Earth's axial tilt, but in different ways. Which one do you think produces a bigger change in the Earth's climate? Why? (Hint: think about how tilt and wobble alter the amount and timing of solar insolation received across Earth's surface).
5) Consider each of these processes to have a scale. For eccentricity, for example, it would be a scale from most circular to most elliptical, for obliquity it would be between a 22 and 24.5 degree tilt, and for precession, it would be a 360 degree circle of where the North Pole points in relation to the Sun. What combination of the three scales do you think would produce the coldest climatic conditions for Earth? What about the warmest?