The cover of the Bulletin of the Atomic Scientists ¨C founded in 1945 by Manhattan Project physicists troubled by the consequences of their work ¨C depicts a clock. The closeness of its hands to midnight indicates the editorial board¡¯s view of the degree of peril the world is in. Recently, those hands have been creeping forward, and stand now at two and a half minutes to midnight.

That trend partly reflects the growing risk of localised nuclear conflict. But it¡¯s mainly for other reasons. Nuclear bombs are 20th-century science. But the Promethean power of 21st-century science confronts us with new threats and ethical conundrums.

Advances in technology, hugely beneficial though they are, render us vulnerable in new ways. For instance, our interconnected world depends on elaborate networks, from power transmission and international finance to air traffic control and just-in-time delivery. Unless these are highly resilient, their manifest benefits could be outweighed by catastrophic (albeit rare) breakdowns cascading through the system. Pandemics could spread at the speed of jet aircraft, causing maximal havoc in the burgeoning megacities of the developing world. Social media could spread psychic contagion ¨C rumours and panic ¨C literally at the speed of light.

Malign or foolhardy individuals and small groups have far more leverage than in the past. Concern about cyber-attacks, by criminals or by hostile nations, is rising sharply. Advances in biotech, likewise, offer huge potential for medicine and agriculture, but amplify the risk of bioerror or bioterror.

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In the 1970s, in the early days of recombinant DNA, a famous conference at Asilomar, California proposed guidelines for researchers to ensure responsible innovation. These were followed. But today, in the era of ¡°gain of function¡± experiments and CRISPR gene editing, the research community is far more global and competitive ¨C and there¡¯s commercial pressure too. So I worry that even if regulations are imposed, they can¡¯t be enforced worldwide, any more than drug laws, or tax laws, can be. Anything that can be done will be done somewhere, by someone, whatever the regulations say.

Some experts have longer-term concerns about robotics and artificial intelligence. The smartphone would have seemed magic 20 years ago. So looking ahead to 2050 and beyond, we should keep our minds open, or at least ajar, to what may now seem science fiction ¨C artificial intelligence getting a ¡°mind of its own¡±, for instance.

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Another key global issue is our rising collective footprint on the non-human environment. We are running up against so-called planetary boundaries. The resultant ecological shocks, aggravated by climate change, could irreversibly impoverish our biosphere. We¡¯re destroying the book of life before we¡¯ve read it.

Can nations sustain effective but non-repressive governance in the face of threats from small groups with high-tech expertise? And ¨C above all ¨C can our institutions prioritise projects that are long-term in political perspectives, even if they are but a mere instant in the history of our planet?

There are habitual grumbles that it¡¯s hard for governmental scientific advisers to gain sufficient traction ¨C especially on long-term global issues. This isn¡¯t surprising. For politicians, the focus is on the urgent, the local and on getting re-elected. Issues that attract their attention are those that get headlines in the media and fill their in-boxes. So scientists might have more leverage on politicians indirectly: by campaigning, so that the public and the media amplify their voices on science issues.

Transitioning to low-carbon energy and coping with potential shortages of food, water and resources can¡¯t be solved by each nation separately. Nor can threat reduction. For instance, whether or not a pandemic gets a global grip may hinge on how quickly a Vietnamese poultry farmer can report any strange sickness.

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Science is a universal culture, spanning all nations and faiths. So scientists confront fewer impediments to straddling political divides.

I think we should all be prepared to divert some of our energies towards public policy, and to engage with individuals from government, business and non-governmental organisations. This can be done through blogging and journalism, as well as directly. But there is a case for setting up more formal structures. In the US, for instance, there is one distinctive format for such engagement that has no real parallel in the UK. This is the JASON group, founded in the 1960s with support from the Pentagon to advise the government on science related to national security. It involves top-ranked academic scientists: in the early days they were mainly physicists, but the group now embraces other fields. The JASONs spend about six weeks together in the summer, with other meetings during the year. It¡¯s a serious commitment ¨C very different from (and more productive than) sitting around a committee table for a day.

We should try to replicate the sociology and ¡°chemistry¡± of such groups in the UK, not for the military but in civilian areas. The challenge is to assemble a group of really top-ranked scientists who enjoy cross-disciplinary discourse. It won¡¯t take off unless they dedicate substantial time to it ¨C and unless the agenda addresses problems that play to their strengths.

Universities are highly international institutions. We should use their convening power to gather experts together to address these problems. That¡¯s why some of us in Cambridge (with international advisers) have set up the Centre for the Study of Existential Risks, to study some of the more extreme ¡°low probability/high consequence¡± threats that might confront us ¨C to decide which are just science fiction and which are sufficiently credible that they should be on our risk register.

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Even if we reduced these risks by only a tiny percentage, the stakes are so high that we¡¯ll have earned our keep. A wise mantra is that the unfamiliar is not the same as the improbable.

Martin Rees is astronomer royal at the Institute of Astronomy, University of Cambridge. He will give a lecture on ¡°The World in 2050 and Beyond¡± at the Institute for Policy Research at the University of Bath on 9 February.

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