Dear Martin,

Thanks, as always, for zeroing in on the key challenges. I'm grateful that you've stipulated two main areas of provisional agreement: a globally coordinated attack on extreme poverty and a revived effort to promote voluntary fertility reduction, aiming to stabilize the world's population. My previous book The End of Poverty laid out the case that market forces, combined with a mere 0.7 percent of rich-world GNP (now around $280 billion per year), can get the job done on extreme poverty by 2025. I'm more than satisfied with your judgment that while such an approach might not work in all cases, "there is nothing else plausible on the table."

In the end, the key is to try. We'll learn, I believe, that much more is achievable much more rapidly than is widely suspected. We have deep reserves of powerful technologies—for food production, water management in dry lands, disease control, and infrastructure—that can be deployed rapidly and at modest cost to break poverty traps. If we do this, I think we will also find that the need to rely on the military is decisively reduced. There are no doubt occasions, very few in number, when a military intervention can end or prevent a bloodbath. But the military alone can never solve the deeper and chronic problems of instability in Africa, the Middle East, and Central Asia. Our mistake is to be vastly overinvesting in military approaches while tragically neglecting our opportunities to address the challenges of poverty and demography, which are at the crux of the matter.

I also agree with you that the bigger uncertainties lie in the challenge of combining environmental sustainability and continued global growth. The challenge is probably greatest on the question of energy. The modern world has been created by fossil fuels, but they will no longer suffice, at least not with today's technologies. And we can't even be sure whether our most urgent problem will be the dangerous climate change that fossil fuels induce or the limited supply of these fuels at reasonable costs. The new $105-per-barrel price of oil is an appropriate backdrop to our discussion.

I argue in the book that, as with extreme poverty, we have sustainable technologies waiting in the wings that can make the continued use of fossil fuels environmentally safe and progressively replace them altogether as their low-cost supply is depleted. Carbon capture and storage, or CCS, is the most promising way for us to continue the large-scale use of fossil fuels, especially coal-fired power plants. Each component of the technology—capture, pipeline transport, and underground sequestration—is proven on a small scale but certainly not on a large scale. New sources of energy—including wind, geothermal, and even a little bit more hydro—can play their role, with the big and long-term players likely to be nuclear and solar.

But such sweeping statements are easy. The essence of the problem lies in the cost of bringing about such a transition and the agility it will require. On cost, I am indeed relying on relatively optimistic engineering. I am impressed not only by the engineering reports on CCS, concentrated solar thermal, concentrated PV solar, plug-in hybrids, green buildings, and other low-emission technologies, but also by the ironic fact that most of these and other promising technologies have not yet been tried on a large scale. It's not as if we have knocked our heads against the wall for two centuries on this problem and must therefore pray for an as-yet-unimagined breakthrough. Carbon emission reduction is a relatively new problem, which the world's engineering talent has yet to aggressively tackle; there are a great number of exciting potential angles of technological attack with some huge successes likely to be found, relatively close at hand and at a surprisingly low cost. The same has been the case, at a vastly lower scale, with cuts in sulfur emissions, deleading of gasoline, and the phasing out of ozone-depleting chlorofluorocarbons.

The hardest point of all, we'd probably agree, is global agility. The book emphasizes at great length that markets alone will not solve this problem. Even putting a price on carbon emissions—through emissions taxation or tradable permits—is only a piece of a much larger institutional problem. We must engineer large-scale technological change. We need to conceive of sustainable development as a matter of global-scale directed technology policy, using an interplay of public and private institutions to spur RDD&D, meaning the research, development, demonstration, and diffusion of new core technologies. And we will have to do this globally and cooperatively. China alone now accounts for more than half of the world's coal consumption, for example, so that the United States, Europe, and Japan have a strong interest in helping China to develop local capacity in CCS technology and to begin CCS demonstration projects. The world's climate may well depend on it.

Currently our global energy system is tied up in knots. Should we build coal-fired power plants at all if they are not capturing their carbon? What about nuclear? What about large-scale liquefaction of coal in the face of tightening oil markets? What about bio-fuels and their environmental and social costs? There is little global leadership and even less global consensus, just an intensifying scramble for the resources at hand and the prospect of growing conflict zones if we don't raise our sights. The financing of energy infrastructure is gripped by uncertainty, though the readiness of vast sums to flow into new energy technologies is also evident.

We are at a time when ideas will count—technical ideas to be sure, but also ideas about cooperation and conflict. The frames of reference of our political leaders will matter greatly. If they view the world as us versus them, we will indeed live in a world of growing conflict. If they view the world as facing a science-and-technology-based transition at a global scale, we can achieve spreading prosperity and sustainability. And in the end, interestingly, the politicians will be listening and responding to the world public. Perhaps as in all ages, our fate is truly in our hands.

Thanks again,

Jeff