Quote of the week: Genghis Khan should have driven a Prius

Ok that headline is not exactly what was said, but it is the flavor of the absurdity. The quote itself from the Carnegie Institution, distributed via  AAAS’s Eurekalert news service, is actually even more absurd.

Here’s the quote:

Genghis Khan and his Mongol hordes had an impact on the global carbon cycle as big as today’s annual demand for gasoline.

Given what happened on Eurekalert yesterday, I wonder about the veracity of this claim.

When Genghis Khan was alive (1162–1227), in this Wiki article it says he killed 40 million:

It has been estimated that his campaigns killed as many as 40 million people based on census data of the times.

Seems like a negative carbon footprint to me.

Here’s the graph of world population from the U.N. A true hockey stick:

It seems pretty much of a stretch to me to equate Genghis Khan’s 40 million low carbon footprint peasant deaths to todays automobile numbers:

That website goes on to say:

It is estimated that over 600,000,000 passenger cars travel the streets and roads of the world today.

600 million cars globally today -vs- 40 million people killed by Genghis Khan.

There’ been a lot of lecturing to us about the evils of the automobile. This website http://carsandpeople.sdsu.edu/ from San Diego State University Dr. Victor M. Ponce goes so far to calculate car to human equivalency:

In summary, in terms of energy consumption, one (1) car is equivalent to approximately 18 persons.

So…if one car = 18 people, then Genghis Khan killing 40 million people….

40 million Genghis Khan people divided by Ponce’s 18 people/car  figure = 2,222,222 Genghis Khan equivalency cars.

600,000,000 cars globally today / 2,222,222 Genghis Khan equivalency cars =  a difference factor of 270 by cars gasoline demand alone.

That’s hardly close to the equivalency of saying Genghis Khan and his Mongol hordes had an impact on the global carbon cycle as big as today’s annual demand for gasoline. And, we haven’t figured in trucks and motorcycles, and farm equipment, and a whole bunch of other gasoline consuming vehicles. Now maybe I’ve missed something in the reasoning behind the claim, but it sure seems way off to me. Beside the magnitude issue, there’s one of sign. It also doesn’t square with the fact that 40 million people removed by Genghis Kahn is a reduction in (negative) carbon footprint while 600 million automobiles are an increase (positive) carbon footprint.

Eh, but close enough for climate science publication news releases in Eurekalert. 😉

And here is the Eurekalert web source for this Carnegie Institution Press release, reprinted in full below. The author put her email address and tel# in that press release, so apparently she wants to be contacted. Who am I to quibble?

Addendum: Perhaps she is not looking at people so much, but only at forests. But how would you know accurately how much forest had been burned/impacted then to include in a  model today? Historical records are mostly anecdotal. Even so I still think it’s a bit more sensational than need be.

Here’s the Black Death Blip:

===========================================================

Contact: Julia Pongratz

pongratz@carnegie.stanford.edu

650-919-4358

Carnegie Institution

War, plague no match for deforestation in driving CO2 buildup

Stanford, CA— Genghis Khan and his Mongol hordes had an impact on the global carbon cycle as big as today’s annual demand for gasoline. The Black Death, on the other hand, came and went too quickly for it to cause much of a blip in the global carbon budget. Dwarfing both of these events, however, has been the historical trend towards increasing deforestation, which over centuries has released vast amounts of carbon dioxide into the atmosphere, as crop and pasture lands expanded to feed growing human populations. Even Genghis Kahn couldn’t stop it for long.

“It’s a common misconception that the human impact on climate began with the large-scale burning of coal and oil in the industrial era,” says Julia Pongratz of the Carnegie Institution’s Department of Global Ecology, lead author of a new study on the impact of historical events on global climate published in the January 20, 2011, online issue of The Holocene. “Actually, humans started to influence the environment thousands of years ago by changing the vegetation cover of the Earth’s landscapes when we cleared forests for agriculture.”

Clearing forests releases carbon dioxide into the atmosphere when the trees and other vegetation are burned or when they decay. The rise in atmospheric carbon dioxide resulting from deforestation is recognizable in ice cores from Greenland and Antarctica before the fossil-fuel era.

But human history has had its ups and downs. During high-mortality events, such as wars and plagues, large areas of croplands and pastures have been abandoned and forests have re-grown, absorbing carbon dioxide from the atmosphere.

Pongratz decided to see how much effect these events could have had on the overall trend of rising carbon dioxide levels. Working with colleagues at the Max Planck Institute for Meteorology in Germany and with global ecologist Ken Caldeira at Carnegie, she compiled a detailed reconstruction of global land cover over the time period from 800 AD to present and used a global climate-carbon cycle model to track the impact of land use changes on global climate. Pongratz was particularly interested in four major events in which large regions were depopulated: the Mongol invasions in Asia (1200-1380), the Black Death in Europe (1347-1400), the conquest of the Americas (1519-1700), and the Fall of the Ming Dynasty in China (1600-1650).

“We found that during the short events such as the Black Death and the Ming Dynasty collapse, the forest re-growth wasn’t enough to overcome the emissions from decaying material in the soil,” says Pongratz. “But during the longer-lasting ones like the Mongol invasion and the conquest of the Americas there was enough time for the forests to re-grow and absorb significant amounts of carbon.”

The global impact of forest re-growth in even the long-lasting events was diminished by the continued clearing of forests elsewhere in the world. But in the case of the Mongol invasions, which had the biggest impact of the four events studied, re-growth on depopulated lands stockpiled nearly 700 million tons of carbon absorbed from the atmosphere. This is equivalent to the world’s total annual demand for gasoline today.

Pongratz points out the relevance of the study to current climate issues. “Today about a quarter of the net primary production on the Earth’s land surface is used by humans in some way, mostly through agriculture,” she says. “So there is a large potential for our land-use choices to alter the global carbon cycle. In the past we have had a substantial impact on global climate and the carbon cycle, but it was all unintentional. Based on the knowledge we have gained from the past, we are now in a position to make land-use decisions that will diminish our impact on climate and the carbon cycle. We cannot ignore the knowledge we have gained.”

The Carnegie Institution for Science (carnegiescience.edu) is a private, nonprofit organization headquartered in Washington, D.C., with six research departments throughout the U.S. Since its founding in 1902, the Carnegie Institution has been a pioneering force in basic scientific research. Carnegie scientists are leaders in plant biology, developmental biology, astronomy, materials science, global ecology, and Earth and planetary science.

The Department of Global Ecology was established in 2002 to help build the scientific foundations for a sustainable future. The department is located on the campus of Stanford University but is an independent research organization funded by the Carnegie Institution. Its scientists conduct basic research on a wide range of large-scale environmental issues, including climate change, ocean acidification, biological invasions, and changes in biodiversity.