Science – Page 93 – a sibilant intake of breath

Garnaut Review interim report

The Stern Review – released in October 2006 by the British Government – is generally considered the most authoritative source on the economics of climate change. Among other things, it concludes that the cost of reducing global emissions is significantly less than the probable costs associated with letting climate change continue on its present course. Now, Australia has released a similar assessment, in the form of the Garnaut Climate Change Review.

Only the interim report is available so far, but it’s likely to make interesting reading for Canadians concerned about climate change. In many ways, the Canadian economy is more similar to that of Australia than it is to that of England. As such, this report may offer some especially useful insights.

P.S. I have some notes from a lecture Stern gave in Oxford.

Recovering encryption keys from RAM

Most successful attacks against strong, well-designed encryption take the form of ‘side channel’ attacks: ones that aren’t based on breaking the strong cryptographic algorithm, but which are based or circumventing it or subverting it somehow. Common varieties include timing attacks, which examine the precise amounts of time cryptographic equipment or software takes to perform operations, and power monitoring attacks, which examine which parts of a piece of equipment are using energy when.

Researchers at Princeton have recently uncovered a potentially significant side-channel attack against whole-disk encryption systems like BitLocker (built into Windows Vista), FileVault (same for Mac OS X), and Truecrypt. The attack is based on analyzing the random access memory (RAM) of a computer system once it has been turned off. Despite the common perception that this clears the contents of the RAM, they have demonstrated that it is possible to use simple techniques and equipment to get a copy of what is inside: including the cryptographic keys upon which these programs depend:

We found that information in most computers’ RAMs will persist from several seconds to a minute even at room temperature. We also found a cheap and widely available product — “canned air” spray dusters — can be used to produce temperatures cold enough to make RAM contents last for a long time even when the memory chips are physically removed from the computer. The other components of our attack are easy to automate and require nothing more unusual than a laptop and an Ethernet cable, or a USB Flash drive. With only these supplies, someone could carry out our attacks against a target computer in a matter of minutes.

This is bad news for anyone relying on encryption to protect the contents of their laptop: whether they are a banker, a spy, a human rights campaigner in China, or a criminal. Other technologies exist to help foil whole-disk encryption systems when the attackers are lucky enough to find a computer that is turned on and logged in.

Researchers in the same organization have done some good work on electronic voting machines.

Stirling engines in space

During the course of several past discussions on energy efficiency, the issue of Stirling engines has arisen. These machines convert temperature gradients into usable kinetic energy which can be used to drive machinery or generate electricity. According to an article in this month’s Scientific American, they have found a new use. NASA is phasing out the radioisotope thermoelectric generators (RTGs) that have been used to power some space missions in favour of the older and non-radioactive technology.

RTGs work by using plutonium 238 decay to heat a thermocouple, which then produces usable current. The Stirling based system still uses plutonium decay for energy, but uses the heat more efficiently. The plutonium-Stirling combination is about 25% efficient at converting heat to electricity, compared to 6-7% for a conventional RTG. A prototype constructed by Lockheed Martin uses two Stirling engines to drive a generator and produce 100 watts of power. The unit that does so is about 1m long and 30cm wide, weighing 20kg – half as much as an RTG.

Extrapolating from space technology to more mundane uses is generally hazardous – for instance, satellites have solar panels with 35% efficiency, but they cost millions of dollars. That said, the technology does demonstrate that Stirling engines have a role to play in increasing efficiency in some circumstances.

Colour-shifting cephalopods

As discussed in comments previously, one of the coolest thing about octopodes and cuttlefish is their ability to camouflage themselves and otherwise control the pigmentation of their skin. An article from today’s New York Times discusses the phenomenon. The creatures certainly have some neat tricks:

Dr. Hanlon has watched octopuses perform what he calls the Moving Rock Trick. They assume the shape of a rock and move in plain sight across the sea floor. But they move no faster than the ripples of light around them, so they never seem to move.

The article also describes forms of visual deception used against other cuttlefish. Apparently, there are situations where a male cuttlefish “disguises its skin to look female, he can sneak up to the guarded female and mate. The sneaky male’s disguise may be so good that the other male may try to guard him as part of his harem.” An impressive and cunning trick, for any species.

Crystals for improved CO2 separation

One should always be cautious about noisy announcements regarding climate related technologies. The mainstream media is all-too-willing to repeat them without much investigation or consideration. That said, there is every likelihood that concern about climate change (and increasingly stringent regulations) will produce dramatic breakthroughs in climate relevant technologies. One area in which that could occur is in relation to carbon capture and storage. At present, this is quite an energy intensive process, largely because of the difficulty of separating CO2 from the other flue gasses being produced by a power plant or factory. Some new research suggests that zeolitic imidazolate frameworks could do this much more efficiently than the amine scrubbers currently being tested.

The authors suggest that these crystals could be and inexpensive and durable way to isolate CO2 for sequestration. Their central conclusions about the materials sound promising:

Members of a selection of these ZIFs (termed ZIF-68, ZIF-69, and ZIF-70) have high thermal stability (up to 390°C) and chemical stability in refluxing organic and aqueous media. Their frameworks have high porosity (with surface areas up to 1970 square meters per gram), and they exhibit unusual selectivity for CO2 capture from CO2/CO mixtures and extraordinary capacity for storing CO2: 1 liter of ZIF-69 can hold ~83 liters of CO2 at 273 kelvin under ambient pressure.

If so, they could help reduce the costs associated with installing and operating CCS equipment – a particular boon given the likelihood that coal use will remain a feature of many economies and some processes – like concrete manufacture – are extremely hard to decarbonize.

Technological options for mitigation

Black circles indicate a definite ‘yes,’ whereas hollow ones denote a partial ‘yes.’ For instance, it isn’t entirely clear whether nuclear fission can ever be economically viable in the absence of government subsidies. Empty squares denote a probable ‘no’ while question marks indicate situations too uncertain to render any judgment upon.

A few of these technologies are so speculative that it is hard to make a decision. That said, this is probably a relatively good summary of the state of the debate at the moment.

GHG stocks, flows, and climate change

[Update: 22 January 2009] Some of the information in the post below is inaccurate. Namely, it implies that some level of continuous emissions is compatible with climate stabilization. In fact, stabilizing climate required humanity to have zero net emissions in the long term. For more about this, see this post.

On this blog, I have frequently cited a figure of about 750kg of carbon dioxide per person per year as sustainable. This is just what you get when you divide the approximate level of sustainable emissions (about 5,000 megatonnes) by the number of people alive on Earth. If each person emitted that much, the net radiative forcing effect of anthropogenic emissions would be approximately zero. That means the sum of the concentrations of all greenhouse gasses, multiplied by their global warming potential, would be in balance with the capacity of the planet to absorb those gasses.

Of course, suddenly achieving the transition to 750kg each would be extremely painful. Thankfully, achieving it instantly is not necessary. Right now, the atmospheric concentration of carbon dioxide (the most important greenhouse gas) is about 383 ppm. That compares with 280 ppm at the time of the Industrial Revolution. Scientists disagree about how much that concentration can rise before extremely harmful effects start to manifest themselves. The highest number generally suggested by reasonable people is 550 ppm, a more mainstream figure is 450 ppm, and some people even argue that we have already emitted enough that very harmful effects are inevitable, once lags in the climate system are overcome. At present, unsustainable global emissions are increasing the global concentration of carbon dioxide by about 2 ppm a year.

Acknowledging the uncertainty, let’s take 450 ppm as a best guess. That means we have about 67 ppm of shoulder room left. It is vital to note that this isn’t shoulder room for total emissions to rise; in the long run, they absolutely must fall dramatically. It is shoulder room in which we can keep emitting above unsustainable levels without wrecking the planet. The situation is akin to being in a lifeboat in a hot, dry climate with a barrel of water and a solar still that produces a small amount of water per day. The 750kg each is the output from the still. The 67 ppm is approximately how much we have left in the barrel. The question now becomes how to divide it. Here are some possibilities:

Continued unsustainable emissions in the developed world
Continued and increasing unsustainable emissions in the developing world
Additional security against abrupt or runaway change

We also have a choice about how to divide the use of barrel water across time. We might decide to drink lots of it in the early days, leaving less for later on. We might decide to save as much as we can. Of course, our capacity to do the latter is somewhat limited by the tragedy of the commons. It’s like there are a whole bunch of strangers in the lifeboat and any one can drink from the barrel without the others being able to stop them. You might end up with everyone trying to grab all they can early, even if saving most of the water for later would produce the best outcome for everyone.

Will we be able to find a way to moderate how much each person takes from the barrel? How much should we be willing to suffer in able to conserve some water for the future, or as a hedge against the possibility that 450 ppm is actually too high? These are among the toughest and most pressing questions in global climate change policymaking.

The norovirus – way more common than you probably think

When people say that they are sick with ‘the flu,’ they often mean they have gastroenteritis. Influenza is caused by viruses in the family Orthomyxoviridae and is the stuff of flu vaccines and avian flu worries. Influenza usually often presents with fever, sore throat, muscle pains, severe headache, coughing, weakness and general discomfort. Gastroenteritis is defined as inflammation of the gastrointestinal tract, involving both the stomach and the small intestine. While it can be caused by bacteria including salmonella and E. Coli, gastroenteritis is usually caused by norovirus or rotavirus. In North America, only the common cold (usually caused by a picornavirus or coronavirus) is a more frequently occurring illness.

Norovirus is of particular interest, since it causes about 50% of all food-related cases of gastroenteritis. In total, it causes about 90% of non-bacterial gastroenteritis worldwide. Norovirus is transmitted either directly from person-to-person or through the faecal contamination of food or water. It is highly susceptible to bleach, though more resistant to alcohol and soap. Susceptibility to the virus is genetically linked. About 29% of the population have two recessive copies of the (1,2)fucosyltransferase gene, which means they don’t form a ligand required by the virus to bond. Lucky people. People with at least one dominant copy of the gene only get a brief period of partial immunity after the fight off the virus. Your best bet is to wash your hands often, avoid salads and shellfish cooked in places with poor hygienic standards, and avoid exposing yourself to people who are already infected.

Hydroelectricity and bare winter mountaintops

Hydroelectricity is a crucial energy source for Canada: providing 59% of the national electricity supply (and 97% in Quebec), as well as energy for things like the Kitimat Aluminium Smelter. As such, there is good reason to be concerned about changes in mountain glaciers and snowpack arising from climate change. Ideally, you want snow and ice to accumulate in the mountains during the winter. That somewhat reduces the flow of water into reservoirs, which helps prevent the need to release large quantities because the dam is at capacity. Then, during the spring and summer, you want the ice to melt, helping to keep the water level in the reservoir relatively steady and allowing the continuous production of energy without threatening riverflow-dependent wildlife or downstream water usage.

Climate change is upsetting this dynamic in several ways. Warmer winters involve less snowfall, overwhelming dams during the wet season and failing to build up frozen reserves. Hot summers increase evaporation from reservoirs and water usage by industry and individuals. Some scientific evidence also suggests that climate change is exacerbating both the intensity of rainy and dry periods: further worsening the stability of water levels and the ability of dams to produce baseload energy reliably.

Mike Demuth, a glaciologist working for Natural Resources Canada, predicts the disappearance of all small to mid-sized glaciers in the Rockies within the next 50 to 100 years. The Athabasca and 29 other glaciers feed the Columbia River, which in turn provides 60% of the electricity used in the western United States (generated by the Grand Coulee Dam, Chief Joseph Dam, and others). The low cost of energy in the area has even led companies like Google to locate their server farms in the region. Not only is the loss of our mountain cryosphere likely to cause domestic problems, it is highly likely to eventually provoke a pretty serious international conflict.

Will technology save us?

All sensible commentators acknowledge that asking people to make big voluntary sacrifices to fight climate change is a strategy unlikely to succeed. People will fight to keep the benefits they have acquired, as well as their capacity to acquire yet more in the future. They will turf out or overthrow leaders who demand heavy sacrifices from them – especially if people in other places are not making the same ones.

If we accept that contention, we are left with a number of possible outcomes:

Painless technological triumph: technological advances allow us to stabilize greenhouse gas concentrations without big sacrifices in current or future standard of living.
Disaster provoked changed priorities: a big and undeniably climate related cataclysm convinces people to buckle down for the sake of their own safety.
Inaction with fairly benign climate change: people do little or nothing, and it turns out that climate change is not as harmful as predicted.
Unmitigated disaster: people do nothing or act too late and slowly, causing global disaster.

Intermediate outcomes are clearly also possible. The differences between several of these have to do with unknown facts about the climate system. Will it throw up a few big and undeniable disasters before a slippery slope is reached? What is the actual sensitivity of the climate to greenhouse gas concentration increases, once feedback and adaptive effects are included?

The first option is certainly the one most popular among politicians. Virtually everyone likes technology and progress: it creates jobs and economic growth while increasing the welfare of those already alive. What big technologies are people hoping might make the difference?

Renewables: sound in theory and partially demonstrated in practice. New transmission capacity and incremental improvements in efficiency required. Potentially high land use.
Biofuels: politically popular but increasingly scientifically discredited. There may be hope for cellulosic fuels.
Nuclear fission: works in practice, with big non-climatic risks.
Nuclear fusion: promising in theory, but nobody has made it work.
More efficient machines: highly likely to occur, unlikely to be sufficient, may not cut total energy use.
Carbon capture and storage: theoretically viable, undemonstrated in practice. May divert attention from technologies with longer-term potential.
Geoengineering: desperate last ditch option, unlikely to work as predicted.

The question of whether climate change can be tackled without a substantial reduction in standard of living remains open. So does the question of whether climate change mitigation can be compatible with the elevation of billions in the developing world to a higher level of affluence. Given the above-stated unwillingness of anyone to undergo avoidable sacrifice, we should be hoping that technology does a lot better than expected, or some potent force changes the balance of risks and opportunities in the perception of most people.