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Contents
- Infection time: Disease is more severe when it hits in the morning, at least in mice
- Explainer: Our bodies’ internal clocks: Biological clocks determine hunger, sleepiness and other daily rhythms
- Flu in the air: Germs tiny enough to pass through surgical masks may cause half of all cases
Web edition: October 13, 2011
Print edition: November 5, 2011; Vol.180 #10 (p. 12)
MINNEAPOLIS — By sailing to the New World, Christopher Columbus and other explorers who followed him may have set off a chain of events that cooled Europe’s climate.
The European conquest of the Americas decimated the people living there, leaving large areas of cleared land untended. Trees that filled in this territory pulled billions of tons of carbon dioxide from the atmosphere, Stanford University geochemist Richard Nevle reported October 11 at the Geological Society of America annual meeting. Such carbon dioxide removal could have diminished the heat-trapping capacity of the atmosphere and cooled the climate, Nevil and his colleagues have previously reported.
“We have a massive reforestation event that’s sequestering carbon … coincident with the European arrival,” said Nevle.
Tying together many different lines of evidence, Nevle estimated how much carbon all those new trees would have consumed. He says it was enough to account for most or all of the sudden drop in atmospheric carbon dioxide recorded in Antarctic ice during the 16th and 17th centuries. Such a depletion of a key greenhouse gas may have helped augment Europe’s so-called Little Ice Age, centuries of cooler temperatures that followed the Middle Ages, Nevle's team has argued.
By the end of the 15th century, between 40 million and 100 million people are thought to have been living in the Americas. Many of them burned trees to make room for crops, leaving behind charcoal deposits that have been found in the soils of Mexico, Nicaragua and other countries.
About 500 years ago, this charcoal accumulation plummeted as the people themselves disappeared. Smallpox, diphtheria and other diseases from Europe ultimately wiped out as much as 90 percent of the indigenous population.
Trees returned, reforesting an area at least the size of California, Nevle estimated. This new growth could have soaked up between 2 billion and 17 billion metric tons of carbon dioxide from the air.
Ice cores from Antarctica contain air bubbles that show a drop in carbon dioxide around this time. These bubbles suggest that levels of the greenhouse gas decreased by 6 to 10 parts per million between 1525 and the early 1600s.
Reforestation fits with another clue hidden in Antarctic ice, says Nevle. As the population declined in the Americas, carbon dioxide in the atmosphere got heavier. Increasingly, molecules of the gas tended to be made of carbon-13, a naturally occurring isotope with an extra neutron. That could be because tree leaves prefer to take in gas made of carbon-12, leaving the heavier version in the air.
“There’s nothing else happening in the rest of the world at this time, in terms of human land use, that could explain this rapid carbon uptake,” says Jed Kaplan, an earth systems scientist at the Federal Polytechnic School of Lausanne in Switzerland.
Natural processes may have also played a role in cooling off Europe: a decrease in solar activity, an increase in volcanic activity or colder oceans capable of absorbing more carbon dioxide. These phenomena better explain regional climate patterns during the Little Ice Age, says Michael Mann, a climate researcher at Pennsylvania State University in State College.
Kaplan points out that there’s a lot of uncertainty in isotope measurements, so this evidence isn’t conclusive. But he agrees that the New World pandemics were a major event that can’t be ignored — a tragedy that highlighted mankind’s ability to influence the climate long before the industrial revolution.
Citations
R.J. Nevle et al. Ecological-hydrological effects of reduced biomass burning in the neotropics after A.D. 1500. Geological Society of America Meeting, October 11, 2011. Abstract available: [Go to]
R.J. Nevle et al. Neotropical human–landscape interactions, fire, and atmospheric CO2 during European conquest. Holocene, Vol. 21, August 2011, p. 853. doi:10.1177/0959683611404578. [Go to]
Suggested Reading
A. Witze. Climate meddling dates back 8,000 years. Science News. Vol. 179, April 23, 2011, p. 17. Available online: [Go to]
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It seems more likely that the oceans cooled due to well-documented diminished solar activity and the cooler oceans absorbed more CO2.
The "Little Ice Age" began long BEFORE 1492. The Pope in Rome sent Columbus a letter (after 1492) asking for Columbus to investigate, "what had happened to the Bishop of Greenland,"
because Rome had not had any letters from Greenland for many years. N.B. -- There were so many Catholics living in Greenland, that the Pope appointed a Bishop to live there.
The Middle Ages Warm Period had ended decades before, and could no longer sustain the European-style agrarian life-style.
Also, bear in mind that post-1500, World exploration meant required an exponential increase in wooden ships, both in number and in size. As a result, not only did population increase, but so did de-forestation. Indeed, perhaps the main export of the American Colonies was LUMBER. Even the export of tobacco,and then cotton required de-forestation.
By 1608, the well-known, but un-mapped 'Northwest Passage'
had frozen over to such an extent that Henry Hudson was un-able to complete his mapping. Re-forestation must have been exceedingly rapid to effect the entire Earth in such a short time.
Richard Nevle is proof of the adage that, "If the only tool you have is a Grant to prove A.G.W.(tm), then everything in the result of A.G.W.(tm)"
The key phrase here is "in terms of human land use". I think the theory is interesting, but it appears he was specifically looking for a way to tie this to a man-made event.
An additional question would be whether there is any correlation between the climate and the progress of the black plague across Europe (given that northern forests do not recover as fast as those in the tropics.
The author, given the dates, could suggest that Columbus had some responsibility for the Maunder Minimum (period of reduced sunspots believed to have affected climate). It would make as much sense.
Good Lord! I thought I was reading science when I logged onto sciencenews.org.
Do you work for the Heritage Foundation? Or are you just another NeanderCons existing beyond the rightfield fringe?
@Paul Noel, you are also on trying to trampoline on quicksand.
"Good Lord! I thought I was reading science when I logged on.." as @Johnson opined applies to you as well.
"As a result massive "virgin forrests" erupted all over the place. If anything there was a massive CO2 uptake as a result of the Spanish arrival"
Erm yes that's what the article is proposing, that there was CO2 uptake, thus atmospheric CO2 levels diminished, thus less greenhouse effect thus global cooling
Forest has one l
It's best to remain silent and be thought a fool, than to open one's mouth and resolve all doubt!
Just keep giving them the rope.....only a matter of time.
"We are finally beginning to realize the seriousness of the educational misinformation promulgated to us, including the physical atrocities imposed on us for centuries by conquering Europeans. Philosophers and scholars have begun to study indigenous values and belief systems with the aim of integrating western philosophical thought into the more ancient codes. Five hundred years after the first great wave of European colonization in the western hemisphere, we have entered a new phase in the cycle of history -- the conquered peoples are influencing the invaders' perceptions of themselves and their values."
Science is not about whose ideological "team" is winning. It's about looking the evidence- all of it- WEIGHING its relative importance, and arriving at the best interpretation, without ignoring or blatantly misrepresenting important pieces of evidence which don't confirm your political philosophy. There's a reason why most Ph.D climate change deniers aren't published climate scientists. It's because, when all of the blowhard and outsized claims they make are actually subjected to serious, competent scrutiny under peer-review, they're found to be bogus, weak, or largely irrelevant to the understanding of serious and competent climate scientists who have looked at all the data. See "evolution" and "natural selection" for how this stupid neocon game is played by deniers. Climate change is just another bird of a feather.
Now if only these people would apply that same objective brilliance to the subject of, say, trans fat consumption and human health, we all might be rid of this plague on the collective human intellect a lot sooner.
What is even more funny - while it was presented recently at a conference this was published in December 2008 - and it is only now making Science News - what a joke!
Marcus Rezende
What a lot of hot air out of Stanford---must have added half a degree to the earth's temperature already.
I was listening to an official Australian government spokesman and carbon tax advocate on a radio interview. He said any proposed CO2 reforms would not affect climate for at least 500 years.
So, I am thinking that 50 years to cause the Little Iceage is just Magical thinking.
In fact, during the late 1400's and early 1500's (and continuing into the early nineteenth century in places like North Dakota) the American continent suffered a pandemic of infectious diseases that reduced the population by some 90%, from a previous stable average of some 40 to 90 million persons. This pandemic was so virulent that "first contact" frequently caused the immediate elimination of the entire native population exposed. Coincident with the loss of population, native manipulation of forest cover by burning nearly ceased. In fact, the natives had kept forest cover down by periodic burning for many years (in order to increase game, for one reason) and when they died off, the cessation of active management resulted in the reappearance of extensive forest cover.
These are simple facts, but until recently they have been unrecognized by historians.
The occurrence of the Little Ice Age chronologically matches the reappearance of extensive forest cover on the American continent, there is no doubt, and additional lines of confirming evidence are cited in the article, for example, the loss of charcoal deposits and the reduction in carbon dioxide levels with a preferential loss of carbon-12, which forest leaves take up more quickly. Those who deny the relationship of these events to each other simply do not understand what really happened during the European colonization of America, perhaps because the facts about the population of America before Columbus have not been widely disseminated until recently.
This is all just science, and doesn't imply anything else, no matter how much you don't like its conclusions.
Meanwhile, back at the ranch... the key words for spin control contained in the article are "may have contributed." Personally, I think trying to make a causal relationship is a bit farfetched. For one, it's a very short time frame, even in terms of the life cycle of a forest.
It could, however, lead to some needed research into the carbon sequestering capacities of different flora, if only to contribute to the economics of ecology.
As to "global warming"... climate change is constant. That does not mean that people today should wantonly waste resources and spew waste everywhere they can in order to cut expenses and make more of a profit.
Proposal for a scenario...
Warming is a necessary prelude to the next event in the Ice Age we have been living through. How else would there be enough snow and ice to grow a glacier? (I think we can rule out a bombardment of comets from outer space.)
The water needs to be heated to evaporate and fall as snow in the polar and alpine climes. That snow will reflect sunlight from those areas, causing changes to atmospheric circulation patterns that would result in more moisture being blown that way by the storms that become increasingly violent as the present imbalances (that currently make the world climate go round) increase and are accentuated and the snowfields would last longer each year, increasingly augmenting those imbalances.
The (literally) ice-cold runoff from the snowpacks and later from under the glaciers themselves then contributes to paving the way for their expansion by further cooling the nearby areas.
Over the millenia, sea-levels drop, exposing more land all around the world, which then acts as a heat trap for sunlight, eventually contributing to a warming of the atmosphere overall and the retreat of the glaciers. And then people can repopulate those areas and "contribute" to starting the cycle all over again.
The obvious colorado had snow in May this year. Lake Powell went from 20% filled to 50% filled due to heavy winter snow fall in the Rockies. as the artic ice melts Ocean effect snow will cover more land for longer periods.
Because of the difference in time frame I beleive Nevle has put the cart before the horse. The decrease in population is dued to the little ice age. Late spring melts and early snow falls of the little ice age leads to less agriculture heavy snows in winter leads to less game animals to eat in the winter. what a wonderful way of reducing the population. from 1200 to 1400. in a reasonable amount of time. In the midwest the Hopewell culture 800 - 1200 was reduced to the small Fort Ancient 1400.
A climate change such as this is what has to be understood to base long term p[lans on.
Nevle I invite you to go to Buffalo this winter to experience Lake effect snow and extrabloate that to Ocean effect snow from the Artic Ocean, Northern Pacific and Northern Atlantic Ocean.
I also want to point out that many of the commentators have a simplistic single-cause/single-effect mindset. Some seem to think that climate scientists claim that all climate change is caused by human activity, so when they find some other contributing cause (among other ways, by pointing to change that happened before humans and thus could not have been caused by human activity), they have disproved all of climate science. Nothing could be sillier. This is like saying that your fever last month resulted from a common cold, so your new fever this month could not possibly result from an infected toe. Just as many things can contribute to a fever, many things can contribute to climate change. Why do scientists and historians have to investigate the causes of each case instead of assuming a blanket cause once and for all? For the same reason your doctor has to investigate what's causing your fever right now.
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