Wallace S. Broecker
Newberry Professor of Geology
Lamont-Doherty Earth Observatory of Columbia

(interviewed by Gil Cunha, senior, School of Visual Arts, for Artist As Citizen)


My position at Columbia University is Professor in the Department of Earth and Environmental Sciences.

I’m a geochemist. I’m interested in climate change and geochemical cycles on the surface of the Earth, particularly the cycle of carbon.

I was probably the first one to realize that in the past the Earth’s climate system has undergone these complete changes of state – in other words, jumped from one way of operating to another -- and these jumps can occur in something like a couple of decades. And while they were occurring, during the transition period, the system flickered back and forth.

And so, much of my research in the past twenty years has been trying to understand this phenomenon.

We found that these abrupt changes have impacts across the entire Northern Hemisphere and through much of the tropics. And we think that it has to do with a turning on and off of a major loop of the Atlantic circulation. And when it’s off, sea ice can form in the North Atlantic, and that cools – that makes much of the Northern tier of the Northern Hemisphere like Siberia, because there’s no heat coming out of the ocean.

So that explains why these changes [in the past] caused Europe to really have cold, cold winters – I mean really cold, like Arctic conditions in Scandinavia, which has reasonably mild winters now.

And also, we now understand through models that if you make the northern tier of the Northern Hemisphere really cold, it pushes the rainbelts, the equatorial, tropical rainbelts, to the south. Because they want to be sort of at the average temperature, so if you make one hemisphere colder, [the rainbelts] move towards the other hemisphere.

And that affects rainfall in the places that are on the edges of the current rainzone, because the rainbelt swings back and forth with the seasons, so it’s furthest north in the summer and furthest south in our winter.

Also, it’s thought that if you have really cold winters across Eurasia, and have more extensive and long lasting snow cover, then that weakens the monsoons, which is another thing that’s seen in the record.

So this stopping of the large scale circulation, the freeze-over of the ocean north of Ireland – probably the whole damn thing – has repercussions all over the world.

The question is: as we add greenhouse gases to the atmosphere, what will happen?

Will it be a smooth warming, or will the warming have big bumps in it?

And in particular, is there a danger that we will shut down this circulation system? So then, the movie “The Day After Tomorrow,” the Pentagon report , all those things play on the fact that global warming would bring an ice age. Which is kind of like an oxymoron, you know, why should this be?

Well we now think that in order to shut down the conveyor by global warming you have to heat the climate by four to six degrees. Which would mean, that’s almost the worst scenario, to get it that warm. And hopefully it will never do that. And then it does shut down the conveyor circulation because fresh water, extra rain in the high northern latitudes, does the job.

But – if the planet were four to six degrees warmer, no sea ice would form, and if sea ice is the big amplifier, then we luck out – there’s no big amplifier, so the impacts would be much smaller.

Nevertheless, the lesson we’ve learned is that the Earth’s system is capable of doing these reorganizations and we’re far from understanding the whole thing. So prudence would tell us, “hey, wait a minute – don’t take a chance because you really don’t understand enough to do it.”

Other people say until you can prove that the effects will be bad we’re not going to do anything about it. I say that’s ass-backwards. I mean, any other environmental problem, you have to show what you’re going to do to the earth – do an impact statement that shows the environmental consequences will be acceptable.

But in this case, it’s turned around.

And it’s very hard to prove that. I mean the range of possibility is large.

I have a feeling that the world is going to run on fossil fuels, oil and coal, and natural gas. And therefore our idea of taking CO2 back out of the air says “OK, if you want to pay the costs of taking the CO2 back out of the air, you can produce it.”

And therefore we remove in some way the threat --  we say you can have your cake --fossil fuel energy -- and eat it too, which would be using all the energy you want.

Some people say it’s a bad idea to take CO2 out of the air because you empower the Hummer. And I say, well what we ought to do with Hummers is:
Immediately in the short term, we start to make them pay for all the extra CO2 they produce, if they had instead driven, you know, like I do, a Toyota. So whatever that median mileage is, if they only get half of that, they pay when they buy the vehicle for its lifetime of extra CO2 production.

That’s a way to start. You know, you’re not going to go from nothing to full tilt.

And it turns out that probably for a cost of fifteen percent extra on fossil fuel, we could extract the CO2 that we’re putting into the atmosphere, and take it back out and store it. So it’s not as if we have to cripple our economy in order to have a bail out. And this is possible; a company is now developing the wherewithal to do this. It’s just basic chemical engineering.


The problem is this immense amount of CO2 we produce. And to produce all of the -- to change the whole infrastructure to do this is a huge job. So if you start to figure out the time it will take, it’s hard to believe you could do it before 2060 or 2070 no matter how hard you tried.

Which means we’ll probably double the CO2 content from its pre-industrial level no matter what we do. But we’re sort of – that’s built-in to our world.

But if we don’t do anything, we’ll triple it. And the damage will be, you might say, twice as bad, twice as much.

And so my hope is that we’ll get behind sort of an effort to say, “OK, double is an awful lot. We shouldn’t really do that, but there’s probably no way we can prevent it from doubling. But let’s make sure that we don’t triple it.”

You know, so once it gets to double, and we get our hands on the whole problem, we can always bring it back down again. Because if we leave it even at 560 [parts per million, or double pre-industrial levels of CO2] for a hundred years, we’re going to melt a lot of polar ice, and it’s not going to be a catastrophe but all beachfront property, Bangladesh, the Netherlands, Florida, either you’re going to have to dike them off, which is expensive and sort of ruins the coastline, or you have to abandon the land and just move inland.

And that’s, you know, that’s worth a lot of money. All the beachfront property in the world, if you add up the price, it’s high.

Since we’ve grabbed the planet and taken over as its manager, we’re the ones that are going to determine what the climate is going to be like and what a lot of things are going to be like. We have a responsibility as self-appointed stewards not to allow this to happen.

So it’ll be interesting to see what happens. It’s a political nightmare right now. There are a lot of people dedicated to making sure that we don’t do anything, saying it’s “junk science,” that it’s a hoax, and it’s not.



1 – the Pentagon report referred to is titled:
An Abrupt Climate Change Scenario and Its Implications for United States National Security October 2003

By Peter Schwartz and Doug Randall



2 - The global temperature on both land and sea has increased by 0.6 ± 0.2 °C over the past century [5]. At the same time, the volume of atmospheric carbon dioxide has increased from around 280 parts per million in 1800 to around 315 in 1958 and 367 in 2000, a 31% increase over 200 years. Other greenhouse gas emissions have also increased. Future carbon dioxide levels are expected to continue rising due to ongoing fossil fuel usage, though the actual trajectory will depend on uncertain economic, sociological, technological, and natural developments. The IPCC Special report on emissions scenarios gives a wide range of future carbon dioxide scenarios [6], ranging from 540 to 970 parts per million by 2100.

[source, Wikipedia]

[FROM 3.13.06]
BBC News has learned the latest data shows CO2 levels now stand at 381 parts per million (ppm) - 100ppm above the pre-industrial average.

[source: http://news.bbc.co.uk/1/hi/sci/tech/4803460.stm]