Physics, like everything else, has an energy problem. Big science – from huge particle accelerators to massive ground-based telescopes – not only costs big money, but also needs lots of energy to run. CERN’s Large Hadron Collider, for example, has an energy bill comparable to that of all the households in the region around Geneva – estimated at about €10m per year. Telescopes with huge air-conditioned domes churn out terabytes of data that are analysed on thousands of desktop computers worldwide and compared with simulations run on supercomputers housed in air-conditioned centres. As facilities get ever larger they will need more and more energy to run.

The issue of large facilities' power needs is set to be tackled this month when researchers meet in Lund, Sweden, to discuss "energy for sustainable science". The meeting's goal is to identify ways to do large-scale physics research with a reliable, affordable and sustainable energy supply that is "carbon neutral". Indeed, big science does not have to be a big polluter. Those building the European Spallation Source in Lund, for example, will be able to claim that theirs will be the first carbon-neutral big-science facility when it is completed towards the end of the decade. All of its electricity will come from renewable sources, built as part of the project, and more than half of the heat it generates will be recycled and fed back into the local heating system.

Facilities such as the ESS are becoming more carbon conscious – but what about individual scientists? Are their personal footprints relevant? In 2009, together with colleagues across the US, I carried out an approximate energy audit of US astrophysics for the US 2010 decadal survey (see arXiv:0903.3384). The study reached a surprising conclusion: in astronomy it is not the big facilities that are the most polluting, but the astronomers themselves, as they fly all over the world to observatories, conferences and meetings. We estimated that astronomers were averaging some 23,000 air miles per year during the course of their work, which at 1.8 kWh per mile added up (in our simple model) to about 85% of the professional energy consumption of astrophysics. For comparison, the average US citizen uses about 250 kWh per day on transport, heating, lighting, food, consumer goods and so on; US astronomers use an additional 130 kWh per day doing astronomy.

Fortunately, there are only a few thousand astronomers in the US, so the actual impact of astronomy is very small, accounting for a tiny fraction – about 1000th of a per cent – of total US energy use. But astronomy's consumption per astronomer is high, about the same as that of a high-flying businessperson – and because it is carbon footprint per capita that needs to be decreased, we have an opportunity to lead the way. Individual physicists can help to solve the energy problem, and not just the ones whose research is in new technologies; we can all contribute by setting the right example.

In it together

Well-established climate science summarized by, among others, the Intergovernmental Panel on Climate Change, has shown that the Earth is getting warmer, and predicts severe consequences for humanity if our greenhouse-gas emissions are not significantly reduced. Fortunately, many countries have pledged to take action, with the UK, for example, passing the 2008 Climate Change Act, which commits it to reducing its emissions by at least 80% by 2050 (compared with 1990 levels). Achieving this, in the UK and across the world, will require mass action, because the bulk of the consumption is done by the bulk of the consumers.

Yet many still seem disengaged with the problem. A recent survey by the information provider Nielsen shows that more than half of Americans are not concerned about climate change. For many people climate change seems distant in either or both of its causes and effects, while some are sceptical about the scientific evidence that links human activity to increasingly high global mean temperatures and extreme weather events.

Physicists need to talk about climate change, and can play a small but important role by putting evidence and numbers in such conversations. Indeed, trusted voices are at a premium at the moment: it matters what physicists say. It matters even more what they do. The staff at the Gemini Observatory South in Chile, for example, are reducing their environmental impact in all areas with their "green initiative". Calculating and logging the facility's energy consumption every month, in 2009 alone they reduced their overall number of observatory air miles by 23%.

Many physicists are doing remarkable work tackling climate change, and the least the rest of us can do is to champion their work in support

Significant energy savings such as these are actually not too difficult to make. Some travel is very high value, with some workshops and conferences exponentially increasing research productivity – but some is not, and could be replaced by video conferences without much loss in outcome. The gain in time not wasted sitting in planes may tip the balance: push for video meetings, make them happen and often there will be a net gain in research output.

My experience from attending all-night workshops across the Atlantic by video is that the main thing required to make them work is the will to make them work; the technology is already good enough, and increasingly widespread. Informal discussion is indeed important, but there is no reason why it cannot happen in the presence of a videoscreen – it is not difficult to imagine "teleschmoozing" in meeting breaks.

Everyone is used to cheap travel, but it turns out that its true cost – the environmental one – is high. Currently, one carbon permit in the European Union Emissions Trading Scheme (worth one tonne of emitted carbon dioxide) costs about £20. Just how high this price will need to rise in the future is an active area of research, but the results so far are eye-opening.

The price is right

Last year I attended a seminar at Stanford University by management scientist John Weyant about modelling the world's ecosystems and economies in various climate-change scenarios. The models, fitted to data and then cautiously extrapolated over the next century, were being used to explore various mechanisms for achieving one future history over another. In the discussion afterwards someone queried the estimated level of the carbon tax in 2050: was Weyant’s value of $2000 per tonne of emitted carbon dioxide an overestimate or would $1000 per tonne be sufficient? As a physicist in the audience, I took away the following message: while the uncertainty in the global modelling was a factor of two, these scientists were discussing a required increase in the price of carbon emissions over today's value by one to two orders of magnitude. They were talking about a very different world – and one that may take quite a bit of getting used to. Will ships and airships make a comeback, making travel cheap in carbon but expensive in time? Will governments heavily subsidize jet fuel for airlines to allow poorer people to travel? Will research budgets increase to match the rising cost of carbon? Low-carbon research methods seem like a very good investment for the future.

Many physicists are doing remarkable work tackling climate change, which may be the greatest challenge humanity has ever faced. The least the rest of us can do in return is support them by championing their work. We can also act on the ecologists' warnings by reducing our own carbon footprint, while encouraging those around us to do likewise, and keeping up the pressure on our governments to make and honour global commitments. Some may object to scientists being advocates for action – but anyone who understands the science can see the need for it. As Nobel laureate Sherwood Rowland from the University of California, Irvine, put it: "What's the use of having developed a science well enough to make predictions, if all we're willing to do is stand around and wait for them to come true?"