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Twelve Tipping Points

When the Caribbean and Florida were hit by multiple big hurricanes last month, the question on the lips of many people was whether global warming was at fault. Climatologists had the scientifically correct answer: hard to say, probably not, but quite possibly a contributing factor. Because the environment is a complex system of system, it's very difficult to pinpoint precise cause-and-effect for specific weather or environmental effects. But that doesn't mean we can't see particular signs of change.

John Schellnhuber, research director at the Tyndall Centre for Climate Change Research in the UK, has helped to develop a list of twelve "tipping points" where small increases in average atmospheric temperature due to global warming could produce "sudden and dramatic environmental damage." The list varies from locations where changes could have significant global effects to locations where the changes would be more "canary in a coal mine" warnings. What's most troubling is the manner in which such disruptions would very often trigger positive-feedback loops -- environmental changes which would in turn serve to accelerate the effects of global warming.

Follow the link for the full list; read on for a couple of excerpts.

Sahara desert

Occupying some 3.5m square miles of northern Africa, the Sahara desert is expected to shrink with global warming as more plentiful rain brings a flourish of vegetation to its southernmost reaches.

For those on the edge of the desert, the fertile land will undoubtedly be a boon, but the Sahara plays a broader role in the health of the planet. The dry dust that is whipped up from the desert by strong prevailing winds contains crucial nutrients that seed the Atlantic and may even help fertilise the Amazon.

As the Sahara turns from brown to green, the flux of nutrients into the ocean is expected to drop, restricting food available for plankton, the smallest of links in the marine food chain.

As the number of plankton falls, so does food for aquatic creatures further up the food chain.

That's not the only knock-on effect. Plankton lock up the greenhouse gas CO <->2 from the atmosphere, and so help counter global warming. With fewer plankton, the oceans will take less of the gas from the Earth's atmosphere.

Dust from the Sahara has other, more subtle influences. When blown out over the Atlantic, clouds of Saharan dust act to stabilise the atmosphere, suppressing the formation of hurricanes.

A greener Sahara could mean more frequent, or more severe hurricanes slamming into the Caribbean, parts of central and southern America and the south-eastern US.

Meanwhile, the now wetter Saharan regions of Sudan, Morocco and Algeria could become more prone to infestations of locusts, such as the swarms that have devastated crops in the region this year.


The monsoon

During March and April, the Indian subcontinent begins to heat up, reaching some of the highest surface temperatures of the year by May. The hot land produces a sharp temperature gradient between the land and sea which causes an abruptreversal of the winds from seaward to landward.

As the winds strike the Himalayas and are deflected upwards, they create a low pressure system, forcing rainclouds to release their stores of water. While the monsoon season can cause incredible flood damage, local populations are largely adapted and to some extent reliant on the weather.

If global warming has the expected effect of heating India even more, the monsoon season could become far more severe. What happens will be influenced by the level of pollution in the region. Sulphur dioxide and even dust make rain droplets smaller and so diminish overall rainfall. These substances also increase the reflectivity of clouds, which prevents the ground from heating up so much.

Both of these factors would weaken the monsoon, causing havoc for Indian agriculture, with serious consequences for food production.

Comments (11)

Stefan Jones:

I'm interested in another sort of tipping point:

What kind of disasters will it take to force various parts of society that something really bad is happening and doing something about it?

What would have to happen to get the Bush administration to drop their current line of B.S.?

What would it take to get Americans out of their S.U.V.s?

How many miles of coastline would have to be scrubbed clean of millionaires' homes for the Coalition of Growth to face reality?

Heh... well... the Ozone Hole got effective, rapid action because the science was pretty clear, and the effect scared the mortal crap out of everybody involved... "sterilizing cancer rays from the sky could scorch the world? Holy heck, we better do something!"

What we lack is clear cause-and-effect. If we had it, I think people would act. And by clear, I don't mean "disputable", I mean **CLEAR**. Clearer than that. Clearer than order of magnitude guesses, estimated carbon sinks, kilometer resolution computer models.

Clear like four decimal places clear. Cause-and-effect need to be demonstrated as clearly as they were for the Ozone Hole and we're a long way off yet. I wonder myself "what if we're wrong about CO2 and it's just some long baseline cycle?"

I'm not confident enough not to have doubts myself at time. Harder science is required.


US news outlets were definitely not linking the hurricane assault on Florida to Global Warming. If there was any public discussion of the possibility, it was happening in the green community and no where else that I know of.

And if I am remembering correctly, ozone skeptics like S. Fred Singer were pooh-poohing the Montreal Protocol for at least a couple of years after it was enacted.

My guess is that the Chinese are going to step up to the plate and discover that greenhouse efficiency equals business efficiency and start to eat (even more) of our (US) lunch. Then American businesses will start howling.

In re: comments upthread about harder science required -- the challenge is the complexity of this global system. No one topic of the global climate can be studied in a vacuum, making absolute proof difficult at best. Earth is computationally irreducible. The challenge is further complicated by the insufficiency of commitment and funding required to obtain softer science, let alone harder science.

Can we really afford to wait until we have hard science in hand? Do we need to be dead right?

Word to Stefan, via Jason.

It would be worth mention the work of the Resilience Alliance here. They are doing excellent work on "tipping points" in social-ecological systems around the world. Very worth reading over.


Also, for an overview of "tipping points" in ecosystems (or, as they're called sometimes, "regime shifts"), readers may want to look at the following article in Nature (full disclosure: I am one of the co-authors of the paper):

Scheffer, M., S. Carpenter, J.A. Foley, C. Folke, and B. Walker (2001). Catastrophic shifts in ecosystems. Nature 413, 11 October 2001, 591-596.


All ecosystems are exposed to gradual changes in climate, nutrient loading, habitat fragmentation or biotic exploitation. Nature is usually assumed to respond to gradual change in a smooth way. However, studies on lakes, coral reefs, oceans, forests and arid lands have shown that smooth change can be interrupted by sudden drastic switches to a contrasting state. Although diverse events can trigger such shifts, recent studies show that a loss of resilience usually paves the way for a switch to an alternative state. This suggests that strategies for sustainable management of such ecosystems should focus on maintaining resilience.

I'd like to green the Sahara, just on principle.

I'd never heard of seeding the Atlantic, before. Certainly the Med doesn't need that, does it?



Oks ill answer your questions Stefan.

1 What kind of disasters will it take to force various parts of society that something really bad is happening and doing something about it?

Global warming isnt bad for everyone and as a result you cant expect everyone to try and stop it. You can expect people are preping for it.

Only those that have a reason to want it to stop would care enough to spend money to stop it and even of those only those that think and feel it can be stopped would expend much energy on trying to stop it as apposed to say trying to prep to survive it and live with it and maybe even take advantage of it. I mean think of it if your a developer or a mega corp and your being held up because the wibble skink is on your property wouldnt you look at global warming killing off your skink as a boon not a bane?

2 What would have to happen to get the Bush administration to drop their current line of B.S.?

Bad question as it isnt bs its a very different point of view and a very different way of dealing with what is to come.

In simple terms it took alot to convince some that people actauly had enough power to actauly move the world. We now have a FEELING we actauly did move the world and as typical we now think we moved it the wrong way. But we arnt realy realy sure and its a big world and we dont wana move it the wrong way trying to corrent a bad move we may or may not have done.. specialy when the road is foggy the headlights are busted the windshield whipers never worked and we have no breaks or car insurance and we dont know how to drive and happen to be drunk legaly blind and deaf and whoever dies take the wheel will be at fault if we screw up.

Now to an environmentalist this is a horror we MUST fix. To an island nation this is a terror that must be stopped.

To bush and friends this is something looming on the horizon they need to keep in mind and start the plans rolling so someone down the line can decide what to do when THEY know what it is THEY can actauly DO. Its not a horror its not something that MUST be fixed and its not the end of all. Its just a very bad situation that will build over the years.

So what does bush do.. being that hes not conversant with the issue and of course doesnt know what to do? He ordered some people to advise him and study it and make recomendations. That he did early on and that report you can read today.

Now what does he do based on it and what hes advised and all that?

He helps push h2 along as after all EVERYONE in industry says its the goal and well your not gona get far if you ignore everyone in industry now will you?

He puts in tax credits to help all sorts of altenate fuel sources.

He does various other very boring things that will help do boring things that help us do whatever boring things in the future I was too bored to keep reading on but which sounded somewhat important if too boring to read... God I wish there was a cliff notes for these things.

Anyhoo he did stuff.

Is it enough? prolly not but its what he was advised to do and you cant realy expect him to do what he doesnt know to do now can you?

If you want global warming to be delt with quickly and "smartly" why are you voting for a politician for pres? When at war you want a warrior when in danger of nasty weather.... who do you call? Not kerry not bush.... sure as hell not nader.... THAT is the problem. Not bush not kerry we simply dont have anyone to call. Well at least we dont have anyone stupid enough to want to be pres that is.

3 What would it take to get Americans out of their S.U.V.s?

Something better then the suv.

Its like asking what would get fliers out of a twin engine sesna... a better plane.

What would get boaters out of a twin motor boat? A better boat.

What would get people out of helicopters.. something better then a helicopter.

In order to get people out of the suv you need to know why they went into it in the first place and then design a BETTER car to supply what they needed and wanted out of the suv.

Size? Design a lighter car thats as big as an suv but not as heavy as one.

Confort in long roadtrips? design a very comfy long haul car that seats a family for 6-7-12 hour trips that is better then the suv.

Manlyness. design a car that looks more manly then typical suvs but is lighter then them and or uses less fuel to get around.

4 How many miles of coastline would have to be scrubbed clean of millionaires' homes for the Coalition of Growth to face reality?

Quite alot since no one realy cares about people stupid enough to live that close to the ocean in hurricane prone areas any more then people care these days when idiots live in flood prone areas or slide prone or fire prone or quake prone areas.

Oh and no one cares about millionares homes not even the millionares themsevles many times. All they are is a disposable toy to them no more then a fast computer is to you or me.

So why is it that soo many dont seem to care? Because they dont need to... yet.

John Laumer:

Toyota Prius is already the best selling car model in last three quarters. It outsold Hummer 7 X last year. US Corporations are slowly waking up to the fact the Japanese and EU societies comsume a quarter of the energy per unit of GDP that we do. First response is parallel to labor cost driven decisions: they move operations over seas. But because cheap labor and efficient processes/cheaper energy do not at all overlap, they are now torn or in denial about the obvious trends. IF oil is sustained in its upward creep, reality will hit them in 2005.

As for tranportation, a person can move closer to work, get a job closer to home, take transit, and so on. But the best choice is to get a far more efficient car for a whole lot less money and in doing so be able to roll that saved money into energy efficiency choices at home. The market shift won't happen on a large scale until gasoline goes well over $3.00 per gallon and/or actually gets scarce, making commuting difficult. The small segment of the market that has already bought into "conspicous conservation" are working out the bugs from the designs that everyone else will be hankering after in a few more years. Smile when these pioneers drive by. We need them.

Previous commenters well pointed out that the SUV replacements will have to be better in many respects: so goes the Prius with built in Bluetooth to let drivers talk hands free for example. What's missing is simple and cheap for a 4 mile drive to the Grocery. FOr that we need more scooter and bike trails, which means better road and path design.


Ah be careful of statistics they can be tricky beasts.

The hummer doesnt sell in number because it never sold in number. For all the hoopla about it and suvs like it the number of massive beefy suvs sold each year is less then the number hearses sold each year likely:)

The issue with getting closer to work is realy that the closer in you go the vastly more spendy the house is. Poeple simply cant afford it and in many cases wouldnt want it because crime ALSO goes up closer to work.

As for shopping... one BIG reason many will use an suv/mini suv in shopping is many americans shop every other week as they get paid... and so instead of like in europe or japan where many shop daily for the days needs they need a car capable of holding 14 days supply.

Now at issue there and a fatal issue at that is these families often vacation by DRIVING not flying and as such the suv is needed for that for twice monthly shopping AND as few have alot of spare cash or driveway/garage space they dont have ROOM for 3 cars.


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