Ancient catastrophic drought leads to question: How severe can climate change become?

Feb 24, 2011
A boat on Lake Tanganyika today; the lake's ancient surface water level fell dramatically. Credit: Curt Stager

How severe can climate change become in a warming world? Worse than anything we've seen in written history, according to results of a study appearing this week in the journal Science.

An international team of scientists led by Curt Stager of Paul Smith's College, New York, has compiled four dozen paleoclimate records from in and other locations in Africa.

The records show that one of the most widespread and intense droughts of the last 50,000 years or more struck Africa and Southern Asia 17,000 to 16,000 years ago.

Between 18,000 and 15,000 years ago, large amounts of ice and meltwater entered the North , causing regional cooling but also major in the tropics, says Paul Filmer, program director in the National Science Foundation's (NSF) Division of Earth Sciences, which funded the research along with NSF's Division of Atmospheric and Geospace Sciences and its Division of Ocean Sciences.

"The height of this time period coincided with one of the most extreme megadroughts of the last 50,000 years in the Afro-Asian monsoon region with potentially serious consequences for the Paleolithic humans that lived there at the time," says Filmer.

The "H1 megadrought," as it's known, was one of the most severe climate trials ever faced by anatomically modern humans.

Africa's , now the world's largest tropical lake, dried out, as did Lake Tana in Ethiopia, and Lake Van in Turkey.

The Nile, Congo and other major rivers shriveled, and Asian summer monsoons weakened or failed from China to the Mediterranean, meaning the carried little or no rainwater.

What caused the megadrought remains a mystery, but its timing suggests a link to Heinrich Event 1 (or "H1"), a massive surge of icebergs and into the North Atlantic at the close of the last ice age.

Previous studies had implicated southward drift of the belt as a localized cause, but the broad geographic coverage in this study paints a more nuanced picture.

"If southward drift were the only cause," says Stager, lead author of the Science paper, "we'd have found evidence of wetting farther south. But the megadrought hit equatorial and southeastern Africa as well, so the rain belt didn't just move--it also weakened."

Climate models have yet to simulate the full scope of the event.

The lack of a complete explanation opens the question of whether an extreme megadrought could strike again as the world warms and de-ices further.

"There's much less ice left to collapse into the North Atlantic now," Stager says, "so I'd be surprised if it could all happen again--at least on such a huge scale."

Given what such a catastrophic megadrought could do to today's most densely populated regions of the globe, Stager hopes he's right.

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gvgoebel
3.9 / 5 (14) Feb 24, 2011
And now here comes the obligatory denunciations of the climate science community.

Interesting article anyway.
GSwift7
4.4 / 5 (9) Feb 24, 2011
No. I would say that the questions they are asking are good ones. I'm glad to see that they are asking questions. If they were making grand proclaimations about the future then I would be questioning their lack of questions, not really denuouncing them. Questions=Good Science, right?

You are probably right though. This kind of study usually gets the knees jerking pretty good.
geokstr
1.8 / 5 (19) Feb 24, 2011
How severe can climate change become?

As severe as the warmists computer models can make it.
And now here comes the obligatory denunciations of the climate science community.

I see that the obligatory apocalyptic apologistic got here first though.
gvgoebel
4.3 / 5 (12) Feb 24, 2011
I see that the obligatory apocalyptic apologistic got here first though.


Actually I have my reservations about the climate change case. But nowhere near as many as I have about you.
axemaster
3.9 / 5 (15) Feb 24, 2011
How severe can climate change become?

As severe as the warmists computer models can make it.


"Warmists"? You are aware that it isn't a political party that you get to support, right? It's something called reality, as confirmed by decades of data.
GaryB
4.1 / 5 (15) Feb 24, 2011
Our Earth is an ill-understood dynamic system. It is subject to weird, non-linear events. Doing things that change the composition of the atmosphere or sea isn't wise. It wouldn't be crazy in such case to tax carbon fuels and use the income to push other sources such as nuclear/thorium, solar etc.
Shelgeyr
3 / 5 (4) Feb 24, 2011
The bulk of the article does not support the sub-title of:
How severe can climate change become in a warming world? Worse than anything we've seen in written history, according to results of a study appearing this week in the journal Science.


On the whole, the article itself seems pretty well done. Its speculations aren't presented as established facts, and it closes with kind of the opposite of the sub-title, i.e. with Curt Stager doubting that it could happen again, at least at such a scale.

I'm obviously a true blue, red-blooded, hard-core "AGW Denier". For that and other reasons have to say to GaryB that while I agree with the premise that the Earth is an ill-understood dynamic system, I disagree and think it would be crazy to tax carbon fuels more than is already being done in order to push nukes, etc. And I'm very pro-nuke.

The article, on the other hand, I'll give a thumbs-up and 4 stars.
Howhot
3 / 5 (12) Feb 24, 2011
Yeah, when the Arctic polar icecap melts just enough to be navigable by supertankers, then we can stop global warming. Unfortunately that is not what will happen. AGW is man made by CO2 emissions from fossil fuel burning. Only after we've burned up that 200yr supply will the deniers care.

unknownorgin
3.3 / 5 (7) Feb 25, 2011
The article states; "what caused the megadrought remains a mystery" This study and a lot of other research Proves that there is much to be learned about what really changes climate and it is too early to blame one cause when there are hundreds of things working together to cause changes in climate. It is foolish to think that simply not burning fossil feul will make this complex system do what you want it to do , just look what happened 15,000 years ago.
brianlmerritt
1 / 5 (1) Feb 25, 2011
The potential connection between icebergs and glacial melting in the North Atlantic and droughts from the Med across to China was interesting, given that is happening again now.

Assuming we are modelling the current climate changes, would it not be possible to also model (with less accuracy) different scenarios that could have caused the drought 16k or so years ago?
GSwift7
2.3 / 5 (6) Feb 25, 2011
Assuming we are modelling the current climate changes, would it not be possible to also model (with less accuracy) different scenarios that could have caused the drought 16k or so years ago?


That's a good question. The short answer is both yes and no. The models probably could be set up to simulate that time period, however they way the models work is that you have to know a lot of things about the state of the atmosphere before you can model it. The atmosphere was radically different at that time period, with much lower oceans, large continental ice sheets, etc. With a large and concentrated effort, you may be able to use successive model runs to tighten constraints on some of the well-understood variables enough to figure out some of the less understood variables. The time and work required to do that, versus the confidence you would have in the results probably doesn't justify the time and money to do it right now. And of course, what would it gain us?
GSwift7
2.3 / 5 (6) Feb 25, 2011
Continued:

The big models are set up in grids. Each grid has to be pre-conditioned with a few different variables. If you don't know the values of those parameters then you are stuck. With a lot of work, you can use the model itself to make some good guesses, but you have to understand how many parameters there are and also how many grids there are. If any parameter in any grid is off by a little bit, then what is the confidence in the model results. When they model the modern world, they can check model results against the real world and then do what is called "tuning" to get the model to match up with reality. When trying to reconstruct a time period 10k years ago, you can't do very much comparrison to the real world because many of those measurements just aren't available. For example, how many places around the world have been analyzed with tree ring studies, ice cores, stalagmites, sediment cores, etc. There are just too many grid cells that wouldn't have any data.
FrankHerbert
1.6 / 5 (7) Feb 25, 2011
@GSwift7

"Hey, let's not study things because we don't understand them very well." You took two posts to say virtually that.
Modernmystic
3.4 / 5 (5) Feb 25, 2011
@GSwift7

"Hey, let's not study things because we don't understand them very well." You took two posts to say virtually that.


You read through two posts and missed his point.
GSwift7
2.6 / 5 (5) Feb 25, 2011
lol, Modern. You're exactly right. My point is that it would be possible but it would be very expensive and very time consuming and it would not do us very much good anyway. I was answering Brian's question in the best way I know how. Sorry that it took two posts. I could write a book about it and still not cover all the issues of trying to use a CGCM to model the severe droughts at the end of the ice age. A CGCM is a tool that is good for analysing modern climate. However, for studying the climate 10k years ago it's like trying to use a hammer to remove a bolt. It's just not the correct tool for that. Essentially, that's like asking if the climate models work well when you run them backward a thousand years. Of course they don't. They shouldn't. They were never designed for that. Again, the wrong tool for that job. I was trying to explain some of the most obvious reasons for that, which was Brian's question.
GSwift7
2 / 5 (3) Feb 25, 2011
Hey, let's not study things because we don't understand them very well." You took two posts to say virtually that


Actually, as I stated in my first post, I think this research is great. They are filling in some of the missing pieces that make it so hard to use a CGCM to simulate the climate 10k years ago. Over time, through good research like this, we can begin to fill in more and more of the missing pieces and gain a more and more complete picture of how our world works. What you said is actually opposite of my views. I was pointing out that computer models aren't the best way. Field studies like the one above are much better at this point.
Nonmythologist
1 / 5 (3) Feb 26, 2011
Everytime I read about another Climate Change/manmade globale warming (MMGW), I recall that approximatey 10 years ago there were volcanic eruptions found occuring under the artic ice cap. The eruptions have heated the water which rises to the bottom of the icecape warming it and causing it to melt. No Co2 involved, no MMGW. Occam's razor applies.
Shootist
2.3 / 5 (3) Feb 26, 2011
"Warmists"? You are aware that it isn't a political party that you get to support, right? It's something called reality, as confirmed by decades of data.


"The Polar Bears will be fine." - Freeman Dyson.
geokstr
1 / 5 (1) Feb 27, 2011
gvgoebel: Actually I have my reservations about the climate change case. But nowhere near as many as I have about you.

And I am supposed to give a rat's derriere about what reservations you have about me exactly why?
kivahut
not rated yet Feb 27, 2011
The Oceans are made of Water. Just because we don't desalinate now, doesn't mean we can't in the future.
gvgoebel
5 / 5 (1) Feb 27, 2011
And I am supposed to give a rat's derriere about what reservations you have about me exactly why?


Where's the problem? You have to take it precisely as seriously as anyone else takes you. This is not burdensome.
Moebius
2 / 5 (2) Feb 27, 2011
If it happened before it can happen again. If it happened before it can be worse than before. And that's not taking into account that our activities are a new factor in the equation. They can't predict what's going to happen from studying the past because our impact was minimal to nothing in the past.

That changed 100 years ago. Now we are busy populating the planet with CO2 and methane belching machines. Climate change is going to happen quicker than it ever did in the past because of us. It is no coincidence that climate change is happening now. Evidently skeptics think it is a coincidence which just goes to show how dumb they are.
Moebius
1 / 5 (1) Feb 27, 2011
"Warmists"? You are aware that it isn't a political party that you get to support, right? It's something called reality, as confirmed by decades of data.


"The Polar Bears will be fine." - Freeman Dyson.


What he means is the Canada bears because the pole will be nothing but bearless water.
GSwift7
1 / 5 (1) Feb 28, 2011
Just because we don't desalinate now, doesn't mean we can't in the future


There's plenty of desal plants around the world. Miami Florida gets a lot of its water that way already. I don't know the percent, but it could even be the majority of their water now. They have one of the largest single desal plants in the world. Other places have smaller ones. The real problem is money. Running a desal plant is expensive, so a wealthy area like Florida can afford to pay extra for water, but a poor place like Somalia can't. Even if you raised UN money to build one there, you would also have to build the entire water grid because there just isn't any public infrastructure there. Then you would also have to train thousands of people with the technical skills to run and maintain it. Transporting water long distances from the coast is also a problem if you don't have money. The US will never run out of water, but poor countries are already.

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