(PhysOrg.com) -- The eruption of the Laki volcano in Iceland in 1783-84 set off a cascade of catastrophe, spewing sulfuric clouds into Europe and eventually around the world. Poisonous mists and a resulting famine from loss of crops and livestock killed thousands in Iceland, up to a quarter of the population. An estimated 23,000 people in Britain died from inhaling toxic fumes. Acid rain, heat, cold, drought and floods have been attributed to the eruption, which lasted from June until February.
The recent earthquake in Japan shifted the earths axis by half a foot. You may be wondering if thats enough to change earths weather. No, not really, says Jerry McManus, a climate scientist at Columbias Lamont-Doherty Earth Observatory.
Earthquakes unleash a tremendous amount of energy, but not enough to upset the energy balance of earths atmosphere and oceans, which drive weather patterns in the short term, he says. Larger shifts of the planets rotational axis happen each year due to the fluctuating mass of earths atmosphere and oceans without changing the weather. These natural variations can push earths axis up to 39 inches, far more than the Japan earthquakes 6.5-inch nudge or the 2010 Chile earthquakes 2.8-inch shift.
Those shifts are tiny compared to long-term, cyclical shifts in earths movement that can raise or lower the planets thermostat. The planet currently leans at a 23.5 degree angle as it circles the sun, causing winter at one end of the globe and summer at the other, as its orientation toward the sun redistributes the amount of sunlight falling on each hemisphere annually. But the seasons can be greatly intensified depending on variations in earths tilt over long timescales. Every 41,000 years or so, earths tilt shifts about a degree in each directionthe equivalent of nearly 70 miles. At its highest tilt24.5 degreesmore sunlight falls on the poles; at its lowest22.1 degreesmore light falls on the equator.
Two other astronomical cycles shape earths climate: the changing shape of its elliptical path around the sun every 100,000 years or so, and the shifting wobble of its axismuch like a spinning topon average, every 21,000 years. All three cycles are caused by the gravitational tug of the moon and the planets in our solar system.
In the first half of the 20th century, Serbian mathematician Milutin Milankovitch painstakingly calculated how all three cyclesrespectively referred to as obliquity, eccentricity and precession influence the amount of seasonal sunlight falling over the planet. Though the calculations that were his lifes work can now be made in a few minutes by a student using a laptop, the name Milankovitch still describes the cycles that are so fundamental to earths climate.
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