He approached the series with profound humility and the hope of a global conversation that might move us toward a safer world. The series is about momentous choices to be made.

His favourite speech by John F Kennedy was his commencement address at American University 10 June 1963. It changed the course of history, away from the path of self-destruction represented by the Cuban Missile Crisis. He quoted passages from the speech:

Ours is the generation that must learn to live in an extraordinarily crowded world. It’s bursting at the seams in human, economic and ecological terms. We must learn to live in an interconnected world of unprecedented pressures of human society and human impact on the physical environment. J Sachs will talk of concrete actions, effective arguments and Peace as a way of solving problems.

We’re not on that path now, but one of increasing risk and instability. By all objective measures, it’s a path of increasing hate as well.

One fundamental change is needed: to see that the challenges are not Us versus Them ( Islam/ Iran/ Terrorists). They are in fact All-of-Us versus a set of increasingly urgent problems. We need to understand those problems in depth and face the challenges, then we can find Peace.

There are three common challenges: they are interconnected and build on one another in ways that amplify, accumulate and create abrupt change -

1. Anthropocene – for the first time in history, the physical systems of the planet (chemical fluxes, climate, habitat, biodiversity and evolutionary processes) are "under human forcings". The hydrological, carbon and nitrogen cycles are all being modified by human activity – "we are uniquely in the anthropocene".
2. Geo-politics – it is also an age of Convergence, which is wonderful in many ways. In this interconnected world, economic development is driven by technology that can be rapidly diffused worldwide and give fabulous improvements, with the prospect of closing the gaps between rich and poor. There will be a great shift of economic and political power in our time. This decade began with the fantasy of the United States as sole superpower – the sole indispensable power, the New Rome. It was urged by some who should have known better to take on the Imperial mantle. Meanwhile China, India and other regional power have expanded their economic and political weight in the world. There is a shared capacity to benefit from technology. Jeffrey Sachs was influenced by Adam Smith on these matters and one of his lectures will be given in his home city, Edinburgh.
3. The Weakest Links – in our interconnected world all parts are affected by everything that happens, everywhere, sometimes in surprising ways. In such a world, we have great need and responsibility to attend to the weakest links. Places that suffer poverty, early death and climate stress face horrific challenges to get onto the ladder of development – a billion people are too poor, too hungry, too disease-burdened and too bereft of even the most basic infrastructure to get onto the bottom rung. Despite some fine speeches, we believe they don’t really matter because we’re leaving 10 million to die every year from the effects of poverty. We are not acting.

The challenge is to understand the common challenges. Do we think Avian flu won’t pass through Iran because we don’t want to talk to Iran? Can we not see the commonality of our problems? Can it really be that the solutions to the problems of Darfur are sanctions and peacekeepers and troops when we know that the crisis began with rebellion in the West, because there’s not enough water there to keep people alive; because livestock have no vets and there’s no basic infrastructure – the nearest power grid may be 1,000 miles away. Do we really think that sanctions and troops can solve this problem?

There is fundamental re-thinking needed in each area. China is already water-stressed, and if the glaciers in the Himalayas melt it will affect the seasonal timing of the snow melt from the Himalayas and so influence the flows of the Yangtse and Yellow rivers and others in Asia. And it’s not just one problem. As Nicholas Stern (in the audience for this lecture) said, we face not only mass extinctions, but the mass destruction of fisheries in the North Atlantic and elsewhere. We’re weighing so heavily on the earth’s systems with CO2 emissions, the acidifying of oceans and over-fishing, over-hunting, over-gathering: if we can catch it, we kill it.

The illusions of geo-politics keep us from solving the problems. Americans have the fantasy of "going it alone" in a global world of shared problems. How do we think we can be safe while allowing a billion others to struggle for daily survival? The American military budget is $650 billion, and $4.5 billion for all assistance to Africa. How can we think that is a prudent choice? Remember AIDS, and the linkages there.

John F Kennedy spoke of a new and hopeful politics – Peace as a way of solving problems. Jeffrey Sachs will speak of Open Source Leadership – a new way to address and solve global problems. It is possible to get global cooperation without global government using the Millennium Development Goals/ MDGs as the organising principle. There is no need for a single implementing authority.

Scientists can play a fundamental role in a world hungry for serious knowledge. Governments need to be reorganised – the structures of the 18^th and 19^th centuries are not right for today, and today’s governments don’t understand the problems we face.

Concrete Actions: all of us have a role to play and need to start acting to make a difference, starting today. He is an optimist: sit up, open your eyes, realise we’re not on an acceptable course right now, choose to change.

Eg, anti-malarial bed nets: there are 300 million sleeping sites in Africa which need protection from malaria. There are bed nets which last 5 years and cost $5. Often more than one child can sleep under a single net. Covering 300 million sleeping sites at $5 a net would cost $1.5 billion for 5 years. Divide the American military budget of $650 billion by 365 and you’ll see that we’re spending $1.7 or $1.8 billion a day on the Pentagon. One day’s military spending could cover every sleeping site in Africa with bed nets, but we haven’t chosen to get them.

Conclusion: a quotation from John F Kennedy, "among the most beautiful lines uttered by a world leader":

Sir Christopher Meyer (once Ambassador to the US, now Head of the Press Complaints Commission). He would love to be as optimistic as Jeffrey Sachs but thinks it’s pie in the sky; man does not change. JS disagrees – and many of the most important changes in the world have come from the UK: the end of the slave trade, and of imperialism, and the empowerment of women. We can make choices. CM was unconvinced; thinks the kind of change JS wants would require a step change in human nature, and that won’t happen.

Woman psychologist from Bristol doesn’t share JS’s optimism either, it is not infectious. Indeed, she feels more depressed. Existing poverty and deprivation is awful, but the root problem is over-population in her view. Buy mosquito nets and even more people will be lacking the food and water they need. They’re no solution. JS said the evidence is overwhelming that there can be a voluntary demographic transition to lower fertility rates – child survival is the best way to achieve that.

Jenny Russell (a Guardian journalist) sees no evidence at all that the rich will consume less to help the poor. JS argues that we can use existing knowledge and technology to improve the material conditions of the poor without deep cuts in the living standards of the rich. It would cost much less than people think.

Sue Lawley (Programme presenter) said the second half of the 20^th century was littered with goals that hadn’t been reached. What was JS saying that was different from those Grand Plans? JS said people had believed that war between the US and the Soviet Union was "inevitable" but it didn’t happen. The choices are better than you thin k, and cost much less than you fear. Stop rubbing your hands in angst, or turning your eyes away. Understand the real choices, costs and consequences and you might make the right choices.

Geri Halliwell (ex Spice Girl, now UN Goodwill Ambassador) "really supports" JS. She works for the UNFPA (Population Fund) and went to Zambia last year on Family Planning work: AIDS education, health and reproductive care. With education, women thrive and so do their villages. A tribal leader had made that point. JS agreed, empowering women helps a lot. The election of Ellen Johnson Sirleaf as President of Liberia (the first African woman elected leader) is cause for celebration. His experience with Millennium Villages is that when help is given with the basics of life, women are automatically empowered thereby.

Sue Lawley asked how tribalism, corruption, ignorance and fanaticism could be overcome. Eg, the President of Gambia expelling a UN worker who had challenged his claim to cure AIDS by herbal remedy and the laying on of his hands. JS said you don’t just say something should be done and expect it to happen – change requires effort. Eg Wilberforce in the 1770s – he was opposed then, but didn’t give up and go home. Eg also, early in 2001 when working for the WHO, J Sachs told Harvard colleagues that Africans needed anti-retroviral drugs to remain productive citizens. There was a great outcry, followed by the establishment of a global fund to fight AIDS, TB and malaria, rapid scaling up of treatment and commitment to have universal access to drugs by 2010. "Don’t tell me things can’t change, and change fast." We just need to fight for it, based on evidence.

Mark Goodall (Climate Change Capital) – is there a role for unelected, supra-national bodies to make decisions? Elizabeth Haydon Jones is an optimist – "if we don’t believe human nature can change, she would not have a vote, let alone be in that audience of experts, mainly white men.

A woman from Glaxo-Smith-Klein referred to JS’s call for a coalescence round shared goals. How would the economics of it work in practice, apart from commandeering the American military budget?

Tony Waite (C of E clergyman, best known as hostage in Lebanon for c. 5 years) – he returned to Christopher Meyer’s point – what is the basis of JS’s belief that human beings can make the right choices? He doesn’t find convincing the empirical evidence JS offered for his faith in human nature.

JS replied that he spends his time with people who are dying. 20 years ago we said the debts of the poorest countries should be cancelled – and eventually they were. He can’t give up. In fact that is why he began as he did – giving up because you don’t think you can change anything is "a dangerous, defeatist belief. We have to believe we can make the right choices if we understand what is involved in them. No part of the whole planet has done more to change the course of history than the Royal Society. Life expectancy figures demonstrate how things can change – years ago, in the rich world it was 25 years – now it’s 80 years; and 70 years in middle-income countries.

Antoine de Caritat, Marquis de Condorcet (1743-1794; mathematician, economist, philosopher), months before he died in the French Revolution, said reason could be harnessed to grow more crops and increase life expectancy. What right did he have to be optimistic? But he got it exactly right. What right do we have to be so pessimistic and white when people are dying on our watch?