Somewhere around the end of the 20th century the world's human population reached 6 billion. At least, it probably did. There are many countries where no population census is taken at all and others where a census is taken but the results are not made public. Even in the US and other sophisticated countries, estimates of population are good to no better than 2% or so. Still, within the next few years the world's population will certainly exceed 6 billion, if it hasn't already. The best present estimate is 6.1 billion with an uncertainty of a quarter of a billion. That is, the uncertainty in the estimate of the world's human population is about the size of the population of the United States. Nevertheless, the date on which the world reached 6 billion human inhabitants was "predicted". It might be better to say that it was announced because there is no way of verifying whether the prediction was true. For that matter, there is no value at all, no real point in making such a prediction other that as a way of raising awareness about the growth of population in the 20th century. It did achieve that point.

    Joel Cohen, of Rockefeller University and Columbia's Earth Institute has pointed out many curious and some alarming derivative facts that underlie this simple number. For instance, it took from the dawn of time until about 1830 for the Earth to acquire its first billion people. It took only 12 years for the Earth to acquire its last billion people. Every one who is more than 39 years old has seen the population of the world double. Anybody born before 1930 has seen the population triple. And the rate of population growth has, until very recently, steadily increased. Put another way, the doubling rate has steadily decreased. As Cohen puts it, that's like a bank account in which the interest rate keeps increasing the more money you have in the bank. The growth rate is much steeper than exponential. Nobody predicted it.

    Had it been predicted, would we have been able to anticipate that of the 6 billion people on the planet fully half would exist on less than $2 a day and that perhaps 2 billion exist on less than $1 a day? Yes, costs and standards of living and expectations differ in different parts of the world, but no matter how one looks at it, almost a third of the world's population is "poor" by any reasonable definition.

    There are, in fact, two worlds - the world of the rich and the world of the poor. In the poor world a child is seven times more likely to die before the age of 12 months. That child will have 2 siblings on average, while in the rich world a child has 0.6 siblings. In the poor world you probably don't have anywhere to go to the toilet. If you are an adult woman you are probably illiterate. In the rich world you are more likely to live in an urban area and in a square kilometer around you there will be about 20 other people. In the poor you probably live in a rural area and despite that, in the a one kilometer square around you there are about 60. Of the 60 people in the poor persons square kilometer 20 or so are chronically hungry. They will wake up hungry, spend the day hungry and go to sleep hungry, only to wake and repeat the cycle day in and day out until they die at around the age of 25. Had we scientists been able to predict that the population would rise to 6 billion, would we have been able to anticipate and mitigate the miseries of the poor world of which I have noted only a very few?

    As scientist we hold a belief that the better we understand Nature the better the world will be. J. Robert Oppenheimer said that you couldn't be a scientist unless you believed that the act of understanding Nature is fundamentally an act of "doing good". The belief that doing science equates to doing good is deeply in place in western science. But, given the bald facts summarized above it is very hard to see how doing science has accrued to the good of the poor world. "Good for whom", one might ask.

    In the rich world science and technology have allowed humans to become the dominant species. Even though Cohen points out that the biomass of domesticated animals exceeds the biomass of humans, and that there are more chickens (17 billion) than people on the planet, we are the masters of the planet in the rich world. We have impounded so much water that the associated change in the earth's angular momentum has altered the length of the day. We shape the landscape more than any other natural force. We have put under our management all the surface biomass. All water, whether it flows on land or in the deepest parts of the oceans, bears the imprint of human activity. And it is well known that the technologies that have brought the rich the level of comfort they enjoy, also emit materials that alter the chemistry of the atmosphere. We have become managers of the planetary system with a singular management focus on control.

    Almost all of this remarkable innovation happens in the rich world. Very little happens in the poor world and very little adoption of rich world innovations is taken up in the poor world - just because they are too poor. The poor world is far less in command of Nature. There the relationship between humankind and Nature is characterized more by desperate struggle than by management. Environmental degradation is greatest in the poor world, not because of willful neglect or the excesses of control, but because it is consequent on the necessity to survive.

    So, respecting the topic of this session - Insights from Recent Global Challenges - and arguing that 20th Century population growth and the associated distribution of rich and poor are recent global challenges, one insight is that the science conducted in the rich world has had little if any affect on improving the poor world.

    Perhaps this is so vast a problem that it is not the business of science anyway, especially the sort of science that we are discussing in this session; the science of global climate or atmospheric change. Is it even reasonable to suppose that our science could change the balance of rich and poor? Our science aims at an understanding of the nature of the physical Earth, its atmosphere and climate system. I know no physical scientist who considers it his or her work to aim at redressing the imbalance between rich and poor. But perhaps it does; or it could.

    Jeffrey Sachs, writing in the Economist in 1999, has pointed out something that we all already know, or could easily conclude from studying a map of the globe while keeping in mind where the poor live. Most of the rich live in temperate climates; most of the poor live in the tropics or arid environments. With the exception of a relative few who are homeless, everyone in North America has a place to go to the toilet and no one is chronically hungry. Even in the U.S. the poorest people live closest to the tropics. So in a highly averaged, first order, global sense, climate determines whether we are rich or poor. In fact, it is a very reasonable proposition that the inability of poor countries to cope with their hostile climate and the consequences of severe climate variations, is a major inhibiter to their development. Sachs describes it as the Ecology of Underdevelopment. In other words, poor countries are poor because of their climate and tend to stay poor because they cannot adapt effectively to their climate.

    One could criticize this globally averaged statement as an oversimplification that ignores the many realities and nuances of the real situation. Certainly there are rich people in densely populated tropical regions and poor in sparsely populated temperate zones. Most of us in North America don't feel very rich. Nevertheless, we are quite happy to use the globally averaged surface temperature of the planet as a valuable measure of the state of the planetary system, and I don't think the statements made by Sachs are oversimplified when cast in the light of that comparison. They are global statements meant to bring attention to global issues, and as such they are not wrong.

    Accepting the simple premise that climate and poverty are linked, albeit in a complex manner in detail, and knowing that science has developed a great understanding of climate, we can ask a specific question in the context of the central question of my discussion "If Science could Predict the Future could we Prepare the Earth for Future Generations"? In this case it is the climate future we are asking about, and the future generations are those in the poor world. Asked a little differently, is it possible to realize the social value to the poor world of innovation in climate science in the rich world?

    I think the only way to correctly address that question is to express the hope that the answer is affirmative, because we certainly have no evidence that this can be done. Roberto Lenton has pointed out that there is good news and it comes in two parts. First, some elements of the climate future can be predicted with what we believe to be useful skill. Second, and more important is that skill is greatest in those parts of the world where the impacts of climate variations are most severe; and they are in the poor world. Two scientists from Columbia's Lamont-Doherty Earth Observatory, Mark Cane and Steve Zebiak, established that it was possible to use simple models of the El Nino Southern Oscillation (ENSO) to predict the phase of that climate phenomenon. That would have been of purely academic interest were it not for the fact that the phase of the ENSO profoundly affects temperature and rainfall in frequently drought-stricken parts of the poor world. Furthermore, predictions could be made with sufficient lead-time that, in principal, decisions could be made about crop type and planting time that the great harm of droughts could be averted or at least greatly reduced. In other places El Nino leads to heavy rains with attendant flooding. We know that warm wet conditions often promote mosquito breeding and may lead to malaria and dengue fever outbreaks. Heavy rain may trigger landslides. In all these cases loss of life can be very large. While the loss of life is tragic, the economic setbacks are also huge. Hurricane Mitch caused US$4billion worth of damage in Honduras. Such a loss would be problematic but manageable in the US but, in Honduras, that loss is equivalent to one year's GDP. Honduras has no hope of internally managing that loss. If you have to spend all your money repeatedly recovering from the ravages of Nature it is not possible to progress toward development.

    At Columbia we have set up an entire university-wide institute, The Columbia Earth Institute, whose mission is to understand the Earth for the purpose of enhancing its sustainability. Within the Earth Institute is the International Research Institute for climate prediction, whose central mission is to realize the social value of the ENSO prediction skill that has been gained by science in the last decade or so. It is not an aid agency. Its focus is on research into producing the best, most useful forecasts of ENSO events, and devising ways in which forecasts can be used by societies in affected regions. The IRI has only been operating for about three years so it's a lot to expect much to have come from it yet, but there is an important insight that has come from the early work. It's a lot harder to usefully apply a forecast than it is to make the forecast.

    Most of the reason it's hard is that what we face is a problem in social and political science, not physical science. What we need to do is develop policy and other tools that will induce societies to change their normal behavior. One thing they need is to believe the forecasts we issue. In developing societies where our information can be used to greatest affect, communication systems are crude and unreliable. Most people won't even know that a forecast has been issued. People who exist on a dollar a day or less can't flip on the TV and watch the weather channel. In many places people make decisions based on religious factors or on the advise of a local village sage. If changing people's behavior means changing what they believe in, the task becomes very difficult indeed. People may be powerless to do anything anyway even if they know about the forecast and may want to act. In the US a farmer in the mid-west will consider a drought forecast, for instance, and plant drought resistant genotypes, or more likely the farmer will plant some drought resistant types, but will hedge by planting some acreage in crops suitable for more normal conditions just in case the forecast is wrong. This type of portfolio approach is just not an option for poor subsistence farmers in many regions of the world. Furthermore, forecast information can be misused, or used for private gain rather than for the common good. When an El Nino forecast is issued in Peru one response has been that the privately owned canneries that buy fish from the numerous small fishermen will close, putting the fishermen out of work. Banks stop lending because they fear that people will not be able to re-pay their loans (and they would be right, of course). The cannery owners and the banks have many options; the fishermen have very few, if any. So, should one not issue a forecast because one suspects it might be misused? If we know or suspect that a government will not act for the good of all its people in using the forecast information, should we not issue the forecast? The ethical questions raised by these considerations are very new to our science, and we do not have answers to them.

    I'll offer two unrelated examples. In Bangladesh, one of the poorest countries on Earth very large segments of the population are exposed to arsenic poisoning in groundwater. Millions of tube wells have been sunk to draw plentiful cool water from beneath the ground because of pollution of surface water that was causing cholera and other diarrhoeaic diseases. Surveys show that while many wells are contaminated at levels up to an order of magnitude greater than US standards, some are not. Furthermore, it can be shown that water drawn from depths greater that 50 feet is much less likely to be contaminated. This would seem to invite simple solutions - share the uncontaminated wells, and drill the contaminated wells deeper. Most wells are drilled by small private companies and although very cheap by our standards, cost individuals most of a years earnings to sink. Almost all are privately owned and greatly valued as possessions and there is little sharing. Most wells are also sunk to the depth where it starts getting difficult to penetrate further. Going deeper takes more time and costs more and is beyond that capacity of almost all individuals. So simple solutions that would perfectly well in a rich country, deny the financial situation and culture of the poor Bangladeshi villager.

    Another example comes from seismology. Scientists trying to assess earthquake hazard have made great gains recently by mapping the evolution of stress conditions along active fault systems that are known to produce deadly earthquakes. One such fault is the North Anatolian Fault in Turkey that produced the Izmut earthquake in 1999. We now know that the release of stress in that event redistributed regional stress fields in such a way that it is very likely that the next major earthquake will occur in the Istanbul region, perhaps in the Sea of Marmara. This conclusion was published in an academic paper and as a result a major reinsurance company pulled out of the property insurance market in Turkey, considering the risk of loss too high. Identifying the natural hazard in the publication actually put the people there and the Turkish government at greater risk than had the paper not been published.

    What we have learnt, and really should have known at the outset, is that the consequences of the Earth's behavior on people's well-being involve a complex interplay of many factors, so that the outcomes of forecasting can be highly unpredictable. We might, for instance, be able to see the future of the physical climate system's behavior, and even anticipate what that might mean for regional weather, disease and crop production, but being able to see the consequences on people's behavior from having information about the future state of the climate, cannot be so easily seen. Unanticipated consequences abound. We can predict the climate, but we cannot yet predict how people will react to knowing something about the future climate.

    Physical scientists, and I am one of them, are relentlessly naive about the interface between the outcomes of their research and the social good that might be derived there-from. We seem to have the idea that we should just do our work in splendid isolation (because that's how we think best) and then pass the results to social scientists who will put them into some sort of translator, out of which will emerge policy statements and other good things for all people. It's our job to do the science and someone else's to make it useful. This linear translator model has been with us a long time. It mirrors the model of basic science, to applied science, to new technology, to economic well being that was a long-held paradigm of modern science. From it follows the notion that the better science we do the more social good will follow. Just how this will happen we are never very sure because, of course, that's someone else's task. The Columbia Earth Institute has been established to study the processes by which climate forecasts might become of social benefit and works on the specific premise that it isn't someone else's problem.

    The principal insight I would offer from our work so far is that responding to the global challenge I outlined above will require a new science. Some people have called this Sustainability Science but I'm not sure if that's really the best term in this context because we are definitely not trying to sustain the poor world in it's present state. The objective is to use climate science to assist development efforts in those parts of the world where climate is a significant impediment to development. That means that the way in which the research outcomes will be used must be foremost and guide the research when it is being done. Michael Crow at Columbia has referred to this as outcome-driven science and is exactly the reverse of how we in the rich world have been driving science. We have the luxury of letting scientific inquiry run its unfettered natural course of free investigation. That's is the way the most inventive and creative insights happen. It has lead to astonishing discoveries about the nature of the universe, the structure of matter, the processes going on in Earth's deepest interior, and the origin of our species. Remarkable as these discoveries are there is little hope that they will accrue to the benefit of the poor countries of the world. That's not the motivation for this sort of research, driven as it is by a basic desire to understand Nature. But I think there is also little point in holding out hope that most research motivated this way might somehow diffuse from the rich world into the poor world to improve the human condition there. It might happen, but history tells us that the chances are slim. The pathway to sustainability cannot be charted by this approach.

    This leaves us with a great dilemma, but also with a great hope. For the first time science has been developed in the rich world that could have real benefit in the poorer, developing world, but we have not established how to realize that benefit. We know that simple approaches used in the past are unlikely to be successful. What we must do now is find the approaches that do work. That is the central mission of Columbia's Earth Institute.

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