Uncertain sea levels
Michael Le Page rightly highlights the need to know how far and how quickly sea level will rise (25 May, p 26). However, I would like to counter the assertion that predictions based on research body ice2sea’s models are “dangerously misleading”.
Those who make use of such predictions do not do so naively. For example, the Environment Agency’s Thames Estuary 2100 flood prevention project assumes that predicted water level extremes will have intrinsic, unquantifiable residual uncertainties.
A route-map approach is taken, identifying adaptation measures to span the plausible range of extreme water levels and creating timetables for investment and implementation, based on the best science available at the time. The ice2sea results have improved the toolkit and knowledge to support such decisions.
From David Vaughan, ice2sea coordinator, British Antarctic Survey
Le Page’s article was thoughtful and thought-provoking, and highlights issues that ice2sea has grappled with for years.
The methods for producing best estimates of sea-level rise are computer simulations of the type developed by ice2sea. Clearly, they cannot take account of all the “unknown unknowns” that could be significant, especially when trying to capture unlikely possibilities that might concern those planning defences for heavily populated areas. So ice2sea has presented a best estimate, derived from two emissions scenarios. We also used input from experts to attempt to picture low-likelihood outcomes.
We hope our complex simulations will soon take account of a wider range of emissions scenarios, but even without this it is clear that overall uncertainty has reduced.
The very high projections of sea-level rise published since the last report by the Intergovernmental Panel on Climate Change, some suggesting more than 1.5 metres by 2100, now look pretty implausible.
Dam downsides
Optimism about building a giant dam on the river Congo is unwarranted (23 May). The “bad news” is not only that “few Congolese will get any electricity”, as Fred Pearce reports, but that the costs are likely to be so high that the project is unviable.
Research at the University of Oxford, based on data from 245 big dams, finds they often come in over budget and late. On average, they cost 90 per cent more than expected.
The proposed $9-billion first phase of the Congo dam is likely to cost double that, and even more if the effects of inflation and debt servicing are taken into account. A repeat of the Democratic Republic of Congo’s debt crisis of recent years is possible.
Costs aside, mega-dams take a long time to build. Even if work begins in 2015, it will most likely take eight to 10 years to complete 鈥� too late to solve today’s pressing energy needs. Smaller projects that can be more easily adapted to social and environmental concerns are preferable.
Space buttocks
If ever there was an idea that showed that physicists need to do more experiments and devise fewer theories, it is Boltzmann brains (25 May, p 12). No matter when in time, the spontaneous formation of simple structures must happen more often than complicated ones.
So Boltzmann brains will be far outnumbered by Boltzmann BMWs and Boltzmann buttocks.
The philosophers who fear the universal dominance of Boltzmann brains in the far future of an eternal universe have forgotten one thing: simpler entities such as, say, the “red-haired proto Boltzmann brain chaser” would also appear to hunt them down. And because of their simplicity, they would be present in far greater numbers than Boltzmann brains.
So, luckily, logic dictates a universe without Boltzmann brains, even until eternity.
Burning issues
Jochen Flasbarth, head of Germany’s environment agency, mentions the successful expansion of renewable energy and the rundown of nuclear (18 May, p 24). However, he does not mention that the country’s energy future seems to involve a lot of coal and lignite.
Great play is made of the environmental impact of nuclear power, but not that of coal. German energy choices seem to be driven by a distaste for nuclear, rather than a genuine environmental concern.
From Geoff Russell
Flasbarth has ignored the biggest risk associated with renewable energy, namely that it is glacially slow to roll out and our window for preventing gross climate destabilisation is vanishing fast.
Adelaide, South Australia
From Andrew Fogg
In his response to Flasbarth’s article, Lucian McLellan asserts that “fusion and renewables have always made the most sense” (1 June, p 31). In principle, I’d agree. However, renewables alone can’t provide enough energy, and sadly we can’t do fusion yet.
In the UK, in the short term, we need fission to reduce carbon emissions. But can we please use thorium as fuel, to remove the potential use for weapons?
Sandy, Bedfordshire, UK
Approach or flee?
Clare Wilson explores possible evolutionary advantages of consciousness (18 May, p 38). There is a well-founded model for the evolutionary trajectory, as described by me and others().
Briefly, nervous systems have always dealt with the conflict between approach (to obtain advantages) and avoidance (to escape danger). Feelings appeared as a “common currency” allowing the organism to weigh positive or negative outcomes. But making this a viable strategy required an awareness of how sad or happy a decision would leave you. This evolved into the consciousness we see in humans today.
Independently coming up with the hard problem of consciousness strikes me as good evidence of consciousness.
For example, we would know if computers, aliens or even dolphins had consciousness if they started to discuss the hard problem without having been introduced to it by us.
Mini Feynman
In his letter, Bruce Harris describes his 8-year-old niece’s solution to keeping track of two entangled photons on different trajectories: paint one red and the other blue (11 May, p 31).
Of course, Felicity meant that one photon should be given a left-hand and the other a right-hand spin before sending them off, so that their emissions would shift to either end of the spectrum and thus differentiate them.
I suspect that rather than confusing her uncle, a mere adult, with complex explanations involving Doppler shifts, Felicity termed it painting them. It seems that she is destined to become a great teacher of quantum physics.
Climate solution
I was struck by the links between the article about large-scale seawater greenhouses to green desert areas (25 May, p 44), the letter in the same issue by Steve Phillips about adding salt to oceans to protect the Gulf Stream (p 30), Michael Le Page’s dire predictions about rising sea levels (p 26) and the interview with Ralph Keeling on measurements of increasing atmospheric carbon dioxide (p 27).
Maybe adding the salt by-product from the desert greenhouses back into the seawater made less saline by ice melt, along with the carbon dioxide take-up by the plants grown could work?
All this would have the added benefit of providing food and employment for many.
No bad publicity
Feedback rightly rubbishes New Age nonsense called “Double Helix Water” that promises “Quantum Health” (1 June), but then marvels that the promotional guff was sent to 快猫短视频 by the promoters themselves, asking: “What were they thinking?”.
Well, perhaps they were thinking that they might be able to add the phrase “as featured in 快猫短视频” to their publicity. Now, of course, they can.
Gravity first
Let me see if I have got this right. We do not understand how gravity works and yet, because some distant galaxies refuse to behave according to our gravitational expectations, we invent “dark energy” in order to get them to behave according to our expectations (11 May, p 32).
Should we not first be concentrating our efforts on understanding exactly how gravity works?
Warmer crust
Iain Climie writes that even if net greenhouse gas emissions became neutral, climate change would still occur because there is a “time lag of decades between changes in gas levels and temperature changes” (25 May, p 31). It’s worth noting that the atmosphere only takes a couple of months to heat up or cool down in response to changes in atmospheric carbon dioxide.
However, Earth’s crust and oceans would continue to warm 鈥� not just for decades but for centuries. This would have an effect on sea level, but not much effect on air temperatures.
For the record
鈥� Oh hell! Our story on the formation of a hot Venus-like planet (1 June, p 17) should have said water vapour, rather than the entire atmosphere, would be stripped by the solar wind.
鈥� In our US edition’s look at cancer research careers (1 June) we should have said Anna Giuliano of the Moffitt Cancer Center in Tampa, Florida, was part of a team that conducted clinical trials of a human papillomavirus vaccine, rather than developing it.
鈥� Using ant behaviour as a model to study building evacuation in emergencies (1 June, p 16), the most effective exit layouts reduced human reaction times in a simulation by 61 per cent, from 30.52 seconds to 11.77 seconds. The 160 per cent figure we gave would of course have equated to going back in time.