One of the interesting things that the Lindau Meeting made clear is that (if you'll excuse a gross generalization), the physics community is splitting in two. A large chunk of it, from theoreticians to cosmologists, is focused on CERN's Large Hadron Collider, waiting to see whether dark matter and supersymmetric particles come out of its collisions (We'll have much more on that in the near future, as our Lindau trip included a detour to CERN). A good chunk of the rest of it, including CERN's former Director General Carlo Rubbia and fellow Nobel Laureate Steven Chu, have decided to focus on something with the potential for a more immediate payback: energy.

Energy and climate issues were major topics at Lindau, featuring in the thoughts of and talks from various Laureates. The events wrapped up with a panel discussion of energy issues that included Rubbia and Yuan Tseh Lee, as well as a physicist-turned-climate expert, the Potsdam Institute's Hans Schellenhuber. They were joined by a German politician, Georg Schütte, who spoke on some of the policy challenges.

Energy issues were presented as just one aspect of a larger sustainability challenge. As Lee pointed out, if everyone on the planet lived the lifestyle of a typical American, we'd need over five Earths to accommodate that level of consumption—he joked that countries should be categorized as "overdeveloped" or "not yet overdeveloped" while noting that even some of the developing world, like his native Taiwan, has already reached the overdeveloped state.

Because some of the things we now rely on, like hydrocarbons and helium, are present in deposits that will only be refreshed on geological time scales, Lee said that humanity is simply living beyond its means. Rubbia echoed this point, suggesting that we're living in the fossil age now, but the younger audience members would see it come to an end, replaced by advanced versions of solar and nuclear power, which would be relatively sustainable—the caveats being that accessible nuclear fuel supplies are finite.

If the implications of Rubbia's expectations weren't clear, Schellenhuber spelled them out: to limit the risk of pushing the climate into a new equilibrium state, we'd have to decarbonize and move to sustainable energy sources within the next 40 years, after which we can focus on sustainability, which he termed "perpetual progress within boundaries." Unfortunately, population trends are going to add to that challenge; he noted that estimates are that the global population will hit 9 billion by 40 years from now, before declining to something similar to today's levels by the end of the century.

Lots of those people will be in the developing world, which has its good and bad points. As Schütte, the government minister, noted, societies simply don't develop an environmental awareness until they have a sufficient standard of living. But Lee noted that if we take the amount of carbon we can afford to put in the atmosphere and divide it on a per-capita basis, then the citizens of places like Bangladesh are so far below the final figure that it provides them with an incredible development opportunity.

Solutions are in energy, not the atmosphere

With the rough issues outlined, the panel then fielded questions about some of the technologies that might play a role in a sustainable energy economy. There was a clear consensus among the panel that the key tech would be emissions limiting, rather than something that would help us continue burning fossil fuels near current rates.

Nearly everyone thought carbon capture and storage (CCS) technology was terrible, but we should research it anyway. Rubbia argued that removing 20 Gigatonnes a year would never be trivial, and we'd never have confidence that the storage locations would contain things for the sorts of time scales we'd need. He'd rather see the CO 2 pulled out of the atmosphere via biofuels. Schellenhuber said that, at the moment, CCS was only being used as cover for building more coal plants, but he feared we'd probably overshoot our emissions targets, and needed to make sure we had the technology to pull some carbon back out of the atmosphere.

Similar things applied to geoengineering—it should only be used if we fail to get emissions down. Most geoengineering solutions only fix part of the problem, since they do nothing about ocean acidification, which Schellenhuber termed "a big, big sleeping giant that will really come to get us."

When it comes to generating power, there was a general sense that most of it would come from advanced versions of existing technologies like solar and wind. Throughout the entire conference, there was a general pessimism about fusion, in part from a technological and physics standpoint, and because of the funding crisis being faced by the ITER fusion reactor. About the only new technology that had anyone excited was nuclear fission of thorium, which is cleaner and more abundant than uranium—Rubbia is a big fan.

The panel was also asked a bit about transport issues, and largely echoed Robert Laughlin's talk. Physics seems to dictate that batteries will never get the same energy density as hydrocarbons, and their production relies on materials that also can't be extracted sustainably. Hydrogen simply has too many storage and transport issues. Rubbia is partial to methanol-based biofuels, while Schellenhuber thinks it might be time to rethink the car model entirely—he joked that we don't expect ownership and autonomous control of elevators, even if we live in a high-rise.

Getting society onboard

So, if most of the technology we'd need for sustainability is evolutionary, and sustainability is an issue we'll have to deal with in one way or another, why isn't more of the public committed to doing something about the challenges? Here, the panel generally thought it was a problem with communications—one mentioned a job candidate that was recently rejected at his institution because people thought he spent too much time doing outreach to the public.

There was some thought that matters were better in the US, but that may simply be a product of none of the participants working here. Even if things are better in terms of communications, recent public polling suggests that the public acceptance of climate science has, at best, been stable, and there's certainly been little in the way of political action.

The panel suggested that there are two problems here. The first, pointed out by Lee, is simply that the public doesn't get the significance of global mean temperatures, in part because the daily changes in temperature are much larger. Put another way, would we really notice a 2°C shift when the daily temperature range is 20°C? Schellenhuber suggested the right metaphor might be body temperature. When that rises by 2°C, we know there's something wrong; if we let it rise by 5°C for a significant length of time, we're dead.

The second is that the public has become completely confused about what areas of the science are well understood. Schellenhuber said that attribution—assigning the recent temperature rise to anthropogenic CO 2 —is on strong footing. Paleoclimatology shows that greenhouse gasses can "force" the climate (that is, give the climate a shove), while the signature of greenhouse warming is apparent in data showing large temperature deviations after the sun sets and the atmosphere warming from the bottom up.

Modeling, he said, is useful, but isn't at the same level of sophistication. It's possible to make better models, but doing so involves large costs in terms of computing power and code, and we already know enough that the money is probably better spent on doing something about what we already know.

Overall, the value of the panel didn't seem to come from any new information they provided; anyone who follows energy issues has heard all of this before. Instead, it provided a glimpse into how some of the smarter people around view the huge array of potential solutions that have been offered. There are definitely people out there excited by geoengineering and CSS, but they certainly didn't have fans on the panel, and nobody from the audience (which included dozens of other Nobel Laureates) leapt to defend them, or to promote fusion as being viable any time soon.

And the sorts of people who were on the panel, since they run major institutions and have a large voice in policy decisions, are likely to have a lot of say in where things actually go within the next 40 years, as the push to get the carbon out of our energy system intensifies.