It's a curious article. I would like to get a look at the study they are talking about. Earth's orbit has been providing cooling for the planet for about 6000 years now. Perhaps the orbit forced various wind patterns to change bringing a greater amount of precipitation to the region?

Here is a more in-depth article about it. It points to the lead researcher as well.

http://www.coloradonewsday.com/news/regi...

Here is the lead authors University of Reading webpage. Unfortunately they don;t have the study in question up yet.

http://www.reading.ac.uk/ges/Aboutus/Sta...

And I'm sure we are all blocked from answering Cyclops question. I have been for a long time now. No big deal though.

Edit: I did find an early print version.

http://www.pnas.org/content/early/2014/0...

I don't see anything in the abstract or significance stating anything about changes in solar forcing. I do see the following though: "Our unexpected findings reveal a surprising third scenario, in which earthwork builders took advantage of a naturally open savanna landscape, which existed under drier-than-present climatic conditions before ～2,000 y ago."

Here is the supplemental material: http://www.pnas.org/content/suppl/2014/0...

Edit: They have known of the dried amazonian climate during the early-mid-holocene for some time now.

http://rstb.royalsocietypublishing.org/c...

This paper states that there are other more serious threats to the amazonian forest other than climate change, such as deforestation, as much of the amazon vegetation faced harsher and drier conditions.

Edit: Perhaps it was caused by SST changes? http://www.captura.uchile.cl/bitstream/h...

Apparently orbital forcing may have lead to a suppression of El Nino during this time.

http://www.ldeo.columbia.edu/res/div/ocp...

And more on orbital forcing during this time period and the changes it caused.

http://onlinelibrary.wiley.com/doi/10.10...

Edit: Orbital forcing appears to have affected monsoons as well. I have been searching and find most discussion surrounding northern Africa. However this paper relates that orbital forcing that affected monsoons in northern Africa to changes in the southern hemisphere as well.

http://www.knmi.nl/publications/fulltext...

And here is more on orbital forcing during this time period again dealing with the African monsoon.

http://aos.wisc.edu/~zliu/publications/9...

Yeah, 'clops posts and blocks. Climate change deniers are that way: they have hot dogs in the ears, don't want to learn anything. The whole idea that a media outlet is left-wing because it has a science section is telling. 'Clops is like JimZ who is constantly posting here that scientists are Marxist just because they are scientists. It is a mindset, a need to attack what they don't understand.

The interesting thing about the study is the proposal that the growth of the Amazon forests may have absorbed enough CO2 to create the Little Ice Age. If 'Clops had actually read the article he linked he would have realized he is publicizing one more climatologist who has calculated and who is telling the world that changes in the CO2 levels have a powerful affect on the amount of heat the atmosphere retains.

***********

JimZ, I believe climate change is real because I follow the news and research that is published in the science journals. You label me a "leftist" for no other reason than that. You have stated here that our National Academy of Sciences are Marxist. And you don't even know what the NAS is -- obviously you have not received your nomination. You have stated here that all of America's greatest sciences and conservative anti-communists such as the Reagan administration are followers of the writings of Carl Marx and actively working for the working class to over-throw the free-enterprise system. You are an important example of how climate change deniers are whack-job reactionaries. You claim to be some look-in-wellologist who looked in wells and denied that California was having much of a drought after the driest year in the history of the state. You have no clue of facts, you only react out of anger at what you perceive is an entire world that has become Marxist.

I thought the same thing. 2000 years is pretty short time to have much of an effect.

I do think there is a bias but it isn't as bad as some places and entities. For example, someone on YA asked what you get when you cross a primate and a sheep. My answer was Obaaaama and it was deemed offensive. If my answer were Saaaaaraaaa Palin, it wouldn't have been. There is a double standard but most of us have grown used to it. Personally, I find it offensive that some don't know all humans are primates.

Baccheous, I am a scientist. I am not a Marxist, therefore all scientists aren't Marxists. Glad we cleared that up. The real issue is that those who are predisposed to being Marxists, or statist, or leftists, or Progessives or whatever you feel like calling yourselves are also predisposed to believing in significant or harmful AGW. I realize you don't like to face the fact that you believe in harmful AGW primarily because you are a leftist. Who would? You fantasize it is because of your flawed belief that all scientists agree with your cherry picked facts. In fact, they don't.

Several things occur to me.

Zippi thinks I, and scientists, need to consume a bit of humble pie.

And, in his humble opinion, scientists run amok .... Pie???

The Atacama desert is dry because prevailing wind blows over the Andes, and is bone dry on the west side. If wind were to blow from the west, across the Andes and then across Brazil, that would turn the rainforest into savanna pretty quickly. Maybe even desert.

Trying to figure out ancient climate, and the reason it existed as it did, is pretty interesting. And challenging.

JimZ, "Progessives ... are also predisposed to believing in significant or harmful AGW. I realize you don't like to face the fact that you believe in harmful AGW primarily because you are a leftist. Who would? You fantasize it is because of your flawed belief that all scientists agree with your cherry picked facts. In fact, they don't. "

OH my. Where to start?

- We are aware that "all scientists" don't agree that global warming is a problem. On the other hand, a very large majority, particularly of scientists who study global warming, do think it's a serious problem.

- We don't think global warming is a problem, "because we're progressives". We think it's a problem because that's what the science indicates.

- We don't "cherry pick" our facts. Clearly we don't get them from fox or breitbart or Limburger or climatedenial or the Koch brothers. We do like NOAA. We also find that wikipedia is often pretty correct.

- I might suggest that your attitude that being concerned about global warming implies that a scientist, or anyone, is progressive, possibly to the point of Marxism, seriously undermines your contention that you're a scientist.

Climate Realist: "What do ice cores say about carbon dioxide over the last 2000 years? If rapid growth of the Amazon rain forest had caused the Little Ice Age, carbon dioxide would have had to have led the temperature during that time."

- Not to sure what you're trying to say. "If the rain forest caused the Little Ice Age, then a change in CO2 would have had to cause the little Ice Age"?

a) The timing is off by 1,000 years, and (b) if the rain forest absorbed CO2 from the atmosphere, then the partial pressure of dissolved CO2 in the oceans would have replaced that which the rain forest took out. One might somehow try to look at the CO2 levels in the ocean to see if there was a change, however, I suspect that there's more to this story that I, at least, haven't heard yet.

" ... "The scientists said that a shift toward wetter conditions, perhaps caused by natural shifts in the Earth’s orbit around the sun, led to growth of more trees starting about 2,000 years ago. "

That would imply a change in earth's orbit that is much faster than I would have thought possible. ... "

Humble Pie maybe, but the problem with researching the past is that science uses it to promote the future, especially when it comes to Climate Science. "Extremist-run Climate Science" does need some "Humble Pie" from time to time IMO. The environmentalists (science and media) seem to run amok with any inferences that blame human existence as a cause for anything that "seems" wrong with the world.

What do ice cores say about carbon dioxide over the last 2000 years? If rapid growth of the Amazon rain forest had caused the Little Ice Age, carbon dioxide would have had to have led the temperature during that time.

I agree with Jeff M, Earths warm wet period was 9000 to 6000yrs ago so it is a bit peculiar.

If you look at the amazon's latitude you could expect some of it to be savannah, I think a lot of its precipitation is recycled water (by trees) fed by the Amazon river, maybe there was a change in the river (direction or flow)

Apparently, I’m blocked also; but I am curious what kind of brain would ask that question based on an article that has nothing to do with global warming. Why would you need to sneak a story about a PNAS article suggesting that climate change might have caused environmental change past a “left wing climate propaganda promotion team"?

That is the kind of thing that would have prompted old women in the South to say, "you know, that poor little cyclops boy is Touched."

Does the Huffington Post have a left wing propaganda promotion team? I think CO2 blocking you from answering.

A no-brainer, folks. This has to be at least the 1000th example of a nitwitted fossil fuel industry duped anti-climate-science liar-denier trying to use the "logic" of "there was once a fire caused by lightning, therefore arson is a leftwing, coolist, fire-insurance-conspiracy hoax."

Why worry about a village idiot like cyclop?

It would appear that cyclop has blocked me.

At least, that's my assumption, since I don't have an opportunity to answer his question.

Not real sure why, don't think I've been mean to him lately. Maybe just not able to handle a rational post.

At any rate, he has found an interesting article.

And rather than comment on the content, he complains about yahoo.