September 14, 2004
by Dennis T. Avery
Should America give up fossil fuels, cars, and air conditioning?
Should we ration electricity from noisy, erratic windmills, while ignoring trillions of barrels of low-grade petroleum in bitumen deposits that could cost-effectively power our society for another 200 years?
Should we vote for a Greenhouse Theory that can't explain Earth's recent climate changes?
Or should we examine the new but already-convincing evidence that the Modern Warming is part of the Earth's unstoppable, moderate, solar-driven 1500-year climate cycle?
There's no question the Earth has warmed over the last 150 years. We're no longer in the Little Ice Age-thank goodness. Glaciers are retreating and winters are a bit milder.
The real question is why?
Persistent voices say Earth is warming dangerously, due to human-emitted CO2. If that is the case, then why did virtually all of the Earth's warming occur before 1940--before the world had many factories or autos? CO2 emissions have soared since 1940, but today's temperatures aren't significantly higher.
The Greenhouse Theory says trapped CO2 will heat the atmosphere above us. That heat then will radiate down to warm the Earth. But that hasn't happened. The atmosphere is warming much more slowly than the Earth's surface--at 1 degree C per 300 years, according to the satellites.
The polar regions are supposed to overheat first. But the polar regions are cooling. Arctic temperatures were higher in the 1930s than they are now. Twenty-one Antarctic surface stations show a decline of 0.08 degrees C since 1979.
We know the Earth has a varied climate history. Medieval monks wrote that the 12th century was very warm; and humans prospered. During the Little Ice Age, in 1816, the Connecticut summer was 2.5 degrees C colder than the mean of 1780-1968. London held its last ice festival on the Thames River in 1814 because the river quit freezing.
Ice cores take us back through 900,000 years of Ice Ages--sudden coolings--and pleasant interglacials like our own. Through it all runs a moderate 1500-year cycle that raises temperatures in New York and Northern Europe about 2 degrees C above the long-term average during its warming phases--just like the Roman and Medieval warmings. Then it lowers temperatures about 2 degrees below the long-term average during the mini-Ice Ages. The temperatures at the equator change hardly at all, although the rainfall patterns do.
The 1500-year cycle was too long and too moderate to be sung in the Norse sagas, though the Vikings' Greenland colonies thrived during the Medieval Warming and froze to death in the Little Ice Age.
The cycle is tied to a tiny variation in solar activity that we can now measure from space with satellite instruments, and measure in history through carbon and beryllium isotopes in the ice cores.
We find the cycle globally--in the Greenland ice sheet, in Antarctic glaciers, in seabed sediments from the Atlantic and the Indian Oceans, in ancient tree rings from around the Northern Hemisphere, in the relocations of primitive Andean villages, and in cave stalagmites from Ireland, Arabia and South Africa.
The North American Pollen Data Base shows our vegetation completely reorganized by climate change nine times in the past 14,000 years. That's once every 1650 years.
The Antarctic ice cores say CO2 and temperatures have tracked closely together over the past 400,000 years. But CO2 changes have lagged behind the temperature changes by 200-800 years. More CO2 hasn't produced higher temperatures; higher temperatures have produced more CO2.
Humanity could stop burning fossil fuels tomorrow, but it wouldn't stop the climate cycle that has warmed the Earth slowly and erratically for the last 150 years. When the warming ends in another few centuries the cycle will give us colder temperatures. That's when we'll really need to worry about heat.
Dennis T. Avery is based in Churchville, VA, and is director of the Hudson Institute's Center for Global Food Issues.
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