Here Pacala speaks to environmentalresearchweb about how emissions and the planet have changed since publication of the wedges paper, the potential effects of a recession, how easy it might be to invent our way out of the problem, and his new work on calculating fair national emissions caps by assigning individual carbon allowances.

You published your paper on "Stabilization Wedges: Solving the Climate Problem for the Next 50 Years with Current Technologies" in Science four years ago, how have things moved on since then?

In my view there are four main developments since the fourth IPCC report about a year ago. One is a rapid economic and emissions growth, which I remain hopeful is just a blip. Emissions have risen since 2000 at about 3% per year. Over the previous 30 years they had grown by 1.5% per year, but during the previous six-year economic expansion they rose by an average of 2.7% per year.

The analysis by Canadell et al [which showed a rapid growth in carbon emissions since 2000] was for the period since the last global recession and ended right before the one that’s happening now. So the important thing to find out is what happens during this recession. If the world really has changed phase and emissions continue to go up through a recession because China is in such a different state, then we’re in the soup. We’ve only got 30 years instead of 50 to deploy existing technology, and we may have to invent something not two generations from now, but now.

It will astonish me if in the next recession we don’t see a massive fall in emissions. Look at every other one we’ve had – emissions have been level or they’ve decreased. It really depends on how severe this one is.

Secondly, there’s a report that the southern ocean has reduced its carbon dioxide uptake because of a change in the winds. Thirdly, there was a claim that the terrestrial carbon sink is decreasing. The last point is that the more that’s known about ice sheet dynamics, the more worrying it becomes.

The first change since the IPCC report has to do with emissions growing too quickly, the second and third have to do with carbon sinks being weaker than they were before, but ice sheet dynamics says "no, even if all those things were the same, the target that we need to reach is actually more stringent than we thought it was".

There’s no good news in the mix and there’s plenty of bad news but the jury’s still out, we’ll have to wait and see.

Is there anything you wish you’d done differently?

The purpose of the stabilization wedges paper was narrow and simple – we wanted to stop the Bush administration from what we saw as a strategy to stall action on global warming by claiming that we lacked the technology to tackle it. The Secretary of Energy at the time used to give a speech saying that we needed a discovery as fundamental as the discovery of electricity by Faraday in the 19th century.

We also wanted to stop the group of scientists that were writing what I thought were grant proposals masquerading as energy assessments. There was one famous paper published in Science that went down the list [of available technologies] fighting them one by one but never asked "what if we put them all together?" It was an analysis whose purpose was to show we lacked the technology, with a call at the end for blue sky research.

I saw it as an unhealthy collusion between the scientific community who believed that there was a serious problem and a political movement that didn’t. I wanted that to stop and the paper for me was surprisingly effective at doing that. I’m really happy with how it came out – I wouldn’t change a thing.

That doesn’t mean that there aren’t things wrong with it and that history won’t prove it false. It would be astonishing if it weren’t false in many ways, but what we said was accurate at the time.

What are you doing now?

I’m working on pure science and administrative initiatives to improve climate modeling by building a new type of institution. Also, a group of us at Princeton including Rob Socolow and I and several others, led by a young physicist named Shoibal Chakravarty are trying to disaggregate emissions data and estimate how many emissions everyone in the world is personally responsible for.

Right now, we have China pointing at the US and saying it’s not fair to expect us to curtail our emissions when you’ve done most of the emissions so far. You already had your economic growth and now it’s our turn. And the US points its finger at China and says it’s not fair to expect us to do that laterally when you’re the largest emitter in the world now.

There’s this rhetoric of fairness that reminds me a little bit of the former rhetoric of technological unreadiness. It’s just a gigantic stalling gambit.

But what concept of fairness are they actually using here and is it congruent with the concepts of fairness we use in our everyday lives? I reckon if you think about it, you’ll see that the answer is no. In what sense do the past emissions in the US necessarily have anything to do with the people there today? My people are immigrants while the wealthy in China have bank accounts that come from an export economy. Those dollars and the emissions that go with them have exactly the same robber baron roots as the money in your bank account. Money is promiscuous – it travels around the world.

You receive the benefits of your western standard of wealth and you distribute the emissions costs to everyone in the world. The same is true of the Chinese person who has your income. It’s not that I have anything against China, but I don’t see why the wealthy in Shanghai ought to get a free ride.

So could there be some other strategy that would have the rhetorical value to stop this argument? It’s a similar gambit to the wedges paper, which was never really intended as a practical scheme for deploying technology but rather as a way to get people to think about the problem so that those who were stalling with obfuscatory language would have to stop. We’ve figured out a way to do that – it’s a fancy-schmancy statistical thing.

Let’s suppose that instead of having a national cap we assemble national caps from individual caps. To make it as simple as possible, we take a single number in any one year and say this is your emissions allowance as a person. If you’re under, you’re under and if you’re over, somehow it’s got to be cut back to the limit. You’d line up everybody in the nation in order of their emissions. Everybody who was under this single global target would just get their emissions added up, while everybody who was over would get the target added up for them. The sum would be the target for the nation. If the nation emitted its target it would be as though those that were over came down to the limit and those that were under just emitted business as usual.

You could have one number for the whole world, reducing it every year. Although I can’t tell you precisely what the answer is because the work is not yet published, I will tell you that it simultaneously passes the laugh test and offers sensible compromises with a few real surprises. One hint is that the climate problem turns out to be almost entirely a problem of the wealthy – 50% of emissions are caused by the top 700 million emitters. And a substantial fraction of those people – on the order of a fifth – actually live in developing countries.

It’s got a nice little feedback loop in it, if you grow faster economically and you have a whole bunch of rich people then your target comes down faster. If you grow slower and your people stay poor then you never hit the cap.

We did this to see what really would be fair – it’s the same number for everyone. I don’t get a credit because my ancestors were Romanian peasants. I’ve got money now and I’m the one that’s spending it. I’m getting all the pleasure but I’m distributing all the pain – I’m making some poor person in Bangladesh bear the cost of the rising sea level that it causes. It’s all about personal responsibility – that’s why I think that kind of scheme resonates. I don’t know what it means for a nation to be responsible for an industrial revolution within its borders 100 years ago, but I do understand personal responsibility and tightening the feedback between benefits and costs. I have no idea whether or not this will have rhetorical power, although you could imagine it in a negotiation of the G77, but we’re going to publish it and see.

Going back to the wedges paper, there’s been little action so far to implement currently available technologies to solve the problem. Why is that?

It’s because we don’t have strong binding agreements yet.

What would you like to see happen next?

The thing I want to happen immediately more than anything else is for the US to pass a stringent cap and trade bill, or any other equivalent. I’m neutral on exactly what the economic instrument is but I think that cap and trade bills are politically easiest to get through.

If the US will just get out in front and act unilaterally, it seems to me that’s a major msising element that would cause everyone else who’s missing their Kyoto targets to buck up and start to deliver on their own commitments. Although it’s been really slow to act in this case, historically when the US passes a set of environmental regulations it usually enforces them. And of course it’s in US interests once it’s passed regulations to make sure that everybody else enforces theirs. So I think that would do more to set the stage for a successful successor to Kyoto than anything else. Certainly it’s inconceivable to think of a strong successor treaty if the US is still dragging its feet.

And then I want a strong successor treaty to Kyoto, that brings everyone in.

Do you think that working on the development of new technologies, such as clean coal, is a distraction from implementing existing technologies?

To start with, I don’t think clean coal is 15 or 20 years down the line. If you put a price on carbon right now, there is any number of companies who will start building clean coal plants immediately. Clean coal bolts together three technologies already deployed at heroic scale. It’s not that we have all the science and technology worked out to do large amounts of carbon dioxide sequestration but we’ve got enough to get started.

When we talk about real blue sky technologies – that we shouldn’t do anything now because we want to develop nuclear fusion or a massively cheaper solar cell – that makes two errors. It misunderstands the magnitude of the problem that we face. If we fiddle around looking for blue sky technologies for the next generation we’re going to pass a doubling of greenhouse gas levels in the middle of the century. You can’t be sure that these new technologies are going to come in or when they’re going to. It’s why you put money in a retirement acount rather than just going to a casino when you’re 65 and hoping for the best.

Secondly, I think it misunderstands how you elicit new technologies. If one puts a price on carbon and starts deploying existing technologies, that leads to an enormous financial incentive. That’s then up for grabs by competitive people who want to figure out how to do it better, cheaper, and faster. The single best way to get new technologies is to start using existing technologies.

US columnist Tom Friedman claims that during the height of the IT boom $100 bn a year went into R&D in Silicon Valley. That’s a lot of money. There’s no way that the federal government is going to put $100 bn a year into blue sky climate research. The only way to get that kind of money in is to have a private market.

The question is, how easy is it going to be to invent our way out of this problem? That depends on the universe of possible inventions. We have no idea what that looks like. You can imagine that that universe is full of holes that are easy to walk through and discover all kinds of things. Maybe everyone’s been looking somewhere else – as soon as we draw the attention of humanity to the effort we will start to see all kinds of people punch into it and discover things quickly. On the other hand, there may only be one or two crooked little cracks that are really hard to find. It could be that even with a combined onslaught against it, nobody gets through for a long time.

If it looks like the former, we can just invent our way out of this problem and it will be over. If it looks like the latter, we’re in the soup. The world’s going to warm, we’re going to have trouble making our targets and it’s going to get a little bit desperate.

My imperfect armchair reading of the last decade is that it appears as though the number of things being talked about and the number of new ideas is increasing through time. That’s the fieldmark I would guess of a system that’s wide open, full of holes and that hasn’t really been paid attention to. Otherwise you would expect the number of new ideas to be forever decreasing as there are fewer and fewer opportunities.