What is the Milankovic Cycle?

Earth's orbit is currently fairly circular around the Sun. However, this is not always the case. Our planet experiences shifts from the current circular orbit to a much more elliptical one during which the difference between perihelion and aphelion is very marked. The entire cycle—from circular to elliptical and back again—takes about 95,000 years to complete. During the periods when the Earth is in its more elliptical orbit and ventures farther from the Sun, ice ages tend to occur. The theory was first formulated by Serbian geophysicist Milutin Milankovic (also spelled Milankovitch, 1879-1958), who was well known for his research into ice ages. His theories were later verified, in 1976, through the study of sediment cores taken during deep-sea explorations.

Who else formed theories that ice ages occur in cycles?

Before Milankovic , French mathematician Joseph Adhemar (1797-1862) published his book Revolutions of the Sea in 1842. In it, he suggested ice ages occur in 22,000-year cycles that matched the precession of the equinoxes. Scottish geologist James Croll (1821-1890) later elaborated on this theory. However, scientists did not know enough about the history of ice ages to compare this theory with actual data, and so the hypothesis languished for another century.

Why does the Earth's orbit change from circular to elliptical over time?

Like all the planets in our solar system, our world is subjected to the gravitational tugs of not only the Sun, but all the other planets as well. We know that our Moon causes tides and other gravitational effects that we can see every day, but Earth's orbit is also influenced by the gas giants Jupiter and Saturn. These planets are big

The Strokkur Geyser erupts in Iceland. Some scientists theorize that changing rainfall patters affect the frequency of geyser eruptions.

The Strokkur Geyser erupts in Iceland. Some scientists theorize that changing rainfall patters affect the frequency of geyser eruptions.

enough to pull Earth's orbit out of shape as they circle the Sun; then the Sun's gravity eventually pulls it back again in an extremely slow tug of war.

What is a nuclear winter?

Scientists Richard Turco and Carl Sagan made the world cognizant of the effects of a global nuclear war in the early 1980s, and Sagan published a popular book on the subject, The Nuclear Winter, in 1983. While most people were already terrified of the nuclear arms race that had been going on between the United States and the Soviet Union since the 1950s, the idea that ever major city on Earth could be obliterated by atomic and hydrogen bombs was just the beginning. Sagan and Turco showed that it wouldn't even take all of the then-50,000 nuclear warheads to kick up enough dust and debris to block out the Sun's warmth. Clouds of irradiated dust would be blown into the stratosphere, where they would circle the planet for months, plunging us into an artificial winter that would destroy crops and lead to a global famine.

Since the publication of The Nuclear Winter, many scientists have come to believe a similar scenario could happen if a large asteroid hit the planet. Indeed, this is one theory about how the dinosaurs may have become extinct 65 million years ago. Another possible cause of a nuclear winter would be planet-wide volcanic eruptions, which some scientists theorize led to a "Snowball Earth" hundreds of millions of years ago. Actually, when volcanoes are involved it would perhaps be more accurate to call these "volcanic winters."

How did Mikhail Ivanovich Budyko calculate the temperature of Earth's climate?

Mikhail Ivanovich Budyko (1920-2001) was a Belorussian meteorologist and physicist, as well as a pioneer in the specialized field of physical climatology. He was the author of the 1956 book Heat Balance of the Earth's Surface. In this work, he used the principles of physics to explain, as no one had done before, how energy from the Sun is absorbed and then radiated back into the atmosphere by the Earth. Budyko's research led him to become concerned about climate change, and he was one of the first to realize that a build-up of carbon dioxide created by human industry was causing the atmosphere to warm up. He predicted that by 2070 the average temperature on Earth would be 6.3°F (3.5°C) higher than 1950 temperatures. Budyko was also one of the first to predict that a nuclear winter would result from a nuclear war.

Where can I find reliable climate statistics online?

There are many websites about the weather available on the Internet; some are better than others. You can get lots of information from government websites, such as the National Weather Service at weather.gov and the National Oceanic and Atmospheric Administration at noaa.gov. There are also some online databases available. WorldClimate at worldclimate.com is a searchable online database that includes more than 85,000 climate statistics from all over the world. By typing in the name of a city, you can obtain data concerning rainfall and temperature. Weatherbase at weatherbase.com has information on nearly 16,500 cities around the world; it even lets you pick whether you want to see statistics in metric or U.S. units.

 
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