By the end of this century, temperatures around the globe are on track to be the hottest at any time since the last ice age. A new study in Science magazine says that, from the 19th century on, emissions from extensive burning of fossil fuels have led to temperatures rising to levels nearing those 5,000 years ago and to even higher levels.
After stabilizing at relatively warm temperatures in the Holocene Age some 10,000 years ago, the earth’s climate plateaued until around 5,000 years ago. From 1450 to 1850 B.C.E., a long and slow cooling trend began, the result of shifts in the amount of incoming sunlight. There was a “brief spike” (as the New York Times puts it) in the Middle Ages, the Medieval Warm Period, when the Vikings settled Greenland; this ended as the cooling trend returned.
In fact, the Northern Hemisphere would be on course to freeze over in several thousand years and to go back towards another ice age, but the Industrial Age has changed and seemingly reversed this. The earth has been as hot as it now is before but with one significant difference: the rise in temperatures is now occurring at an “exceedingly rapid clip on the geological time scale.”
As study author Shaun Marcott, a climate scientist at Oregon State University in Corvallis, tells the New York Times, if this increase in temperatures continues, the earth is likely to become even warmer than it was at the start of the Holocene, some ten thousand years ago.
How Do You Figure Out How Hot It Was 11,000 Years Ago?
Since we only have records from scientific instruments from the 19th century, scientists rely on data from tree rings and isotope ratios from formations in caves to determine temperatures in the distant past. But these can only tell us so much, says Nature.
For the Science study, Marcott and another researcher looked at data from 73 other sets of records. These included measurements from sediments cores drilled from the bottoms of lakes and seas around the world, including Antarctica and Greenland. The scientists measured ratios of magnesium and calcium ions in the shells of microscopic creatures who had fallen to the very bottom of the ocean floor.
From all of this, Marcott and his colleague found that average global temperatures rose and then plateaued between 7550 and 3550 B.C.E. A cooling trend followed but, from the start of the 20th century till now, average temperatures have gone from their coolest point to what is among their hottest and at a “dramatic clip.” In our lifetimes, the average temperature anywhere on earth has been higher than these have been for about 75 percent of the past 11,300 years.
The Industrial Age, though a blip in time relative to earth’s existence, has made the planet hotter than ever. If we keep consuming oil and other fossil fuels for energy at the same rate, the earth is on the track to be the hottest in its long history — and a hotter than ever earth could put the survival of numerous species, including our own, at risk. It is (excuse the irony) a chilling thought to think that, in just around two to three hundred years, we have not only reversed the cooling trend the earth was on, but are setting it on a course to break the records for all time.
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