Technology for Azimuth (Part 1)

A bunch of us want to set up a wiki associated to Azimuth, so we can more effectively gather and distribute scientific knowledge related to the overarching theme of “how to save the planet”.

It may also good to have a “discussion forum” associated to that wiki, in addition to the blog here, where I — and other people, once I find some good co-bloggers — hold forth. A blog is a good place for a few people to lead discussions. A different sort of discussion forum, more like the nForum, would be a more democratic environment, good for developing a wiki.

But what exactly should we do?

Let’s discuss that question here… I’m going to copy or move some comments from the welcome page to here, to get things going.

Climate Stabilization Targets

I thank Walter Blackstock at the Institute of Molecular & Cell Biology here in Singapore for pointing this out:

The most distinguished group of scientists in the United States has released an important report on climate change. You can get the whole thing for free, here:

• National Research Council, National Academy of Science, Climate Stabilization Targets: Emissions, Concentrations, and Impacts over Decades to Millennia, 2010.

But here’s the executive summary, for you executives too busy to read the whole thing. It’s clearly written, short, and earth-shakingly important. I’ve put a few key passages in boldface.

EXECUTIVE SUMMARY

Emissions of carbon dioxide from the burning of fossil fuels have ushered in a new epoch where human activities will largely determine the evolution of Earth’s climate. Because carbon dioxide in the atmosphere is long lived, it can effectively lock the Earth and future generations into a range of impacts, some of which could become very severe. Therefore, emissions reductions choices made today matter in determining impacts experienced not just over the next few decades, but in the coming centuries and millennia. Policy choices can be informed by recent advances in climate science that quantify the relationships between increases in carbon dioxide and global warming, related climate changes, and resulting impacts, such as changes in streamflow, wildfires, crop productivity, extreme hot summers, and sea level rise.

Since the beginning of the industrial revolution, concentrations of greenhouse gases from human activities have risen substantially. Evidence now shows that the increases in these gases very likely (>90 percent chance) account for most of the Earth’s warming over the past 50 years. Carbon dioxide is the greenhouse gas produced in the largest quantities, accounting for more than half of the current impact on Earth’s climate. Its atmospheric concentration has risen about 35% since 1750 and is now at about 390 parts per million by volume, the highest level in at least 800,000 years. Depending on emissions rates, carbon dioxide concentrations could double or nearly triple from today’s level by the end of the century, greatly amplifying future human impacts on climate.

Society is beginning to make important choices regarding future greenhouse gas emissions. One way to inform these choices is to consider the projected climate changes and impacts that would occur if greenhouse gases in the atmosphere were stabilized at a particular concentration level. The information needed to understand such targets is multifaceted: how do emissions affect global atmospheric concentrations and in turn global warming and its impacts?

This report quantifies, insofar as possible, the outcomes of different stabilization targets for greenhouse gas concentrations using analyses and information drawn from the scientific literature. It does not recommend or justify any particular stabilization target. It does provide important scientific insights about the relationships among emissions, greenhouse gas concentrations, temperatures, and impacts.

CLIMATE CHANGE DUE TO CARBON DIOXIDE WILL PERSIST MANY CENTURIES

Carbon dioxide flows into and out of the ocean and biosphere in the natural breathing of the planet, but the uptake of added human emissions depends on the net change between flows, occurring over decades to millennia. This means that climate changes caused by carbon dioxide are expected to persist for many centuries even if emissions were to be halted at any point in time.

Such extreme persistence is unique to carbon dioxide among major agents that warm the planet. Choices regarding emissions of other warming agents, such as methane, black carbon on ice/snow, and aerosols, can affect global warming over coming decades but have little effect on longer-term warming of the Earth over centuries and millennia. Thus, long-term effects are primarily controlled by carbon dioxide.

The report concludes that the world is entering a new geologic epoch, sometimes called the Anthropocene, in which human activities will largely control the evolution of Earth’s environment. Carbon emissions during this century will essentially determine the magnitude of eventual impacts and whether the Anthropocene is a short-term, relatively minor change from the current climate or an extreme deviation that lasts thousands of years. The higher the total, or cumulative, carbon dioxide emitted and the resulting atmospheric concentration, the higher the peak warming that will be experienced and the longer the duration of that warming. Duration is critical; longer warming periods allow more time for key, but slow, components of the Earth system to act as amplifiers of impacts, for example, warming of the deep ocean that releases carbon stored in deep-sea sediments. Warming sustained over thousands of years could lead to even bigger impacts.

IMPACTS CAN BE LINKED TO GLOBAL MEAN TEMPERATURES

To date, climate stabilization goals have been most often discussed in terms of stabilizing atmospheric concentrations of carbon dioxide (e.g., 350 ppmv, 450 ppmv, etc.). This report concludes that, for a variety of conceptual and practical reasons, it is more effective to assess climate stabilization goals by using global mean temperature change as the primary metric. Global temperature change can in turn be linked both to concentrations of atmospheric carbon dioxide and to accumulated carbon emissions.

An important reason for using warming as a reference is that scientific research suggests many key impacts can be quantified for given temperature increases. This is done by scaling local to global warming and by “coupled linkages” that show how other climate changes, such as alterations in the water cycle, scale with temperature. There is now increased confidence in how global warming levels of 1°C, 2°C, 3°C etc. would relate to certain future impacts. This report lists some of these effects per degree (°C) of global warming, including:

• 5-10 percent changes in precipitation in a number of regions

• 3-10 percent increases in heavy rainfall

• 5-15 percent yield reductions of a number of crops

• 5-10 percent changes in streamflow in many river basins worldwide

• About 15 percent and 25 percent decreases in the extent of annually averaged and September Arctic sea ice, respectively

For warming of 2°C to 3°C, summers that are among the warmest recorded or the warmest experienced in people’s lifetimes, would become frequent. For warming levels of 1°C to 2°C, the area burned by wildfire in parts of western North America is expected to increase by 2 to 4 times for each degree (°C) of global warming. Many other important impacts of climate change are difficult to quantify for a given change in global average temperature, in part because temperature is not the only driver of change for some impacts; multiple environmental and other human factors come into play. It is clear from scientific studies, however, that a number of projected impacts scale approximately with temperature. Examples include shifts in the range and abundance of some terrestrial and marine species, increased risk of heat-related human health impacts, and loss of infrastructure in the coastal regions and the Arctic.

STABILIZATION REQUIRES DEEP EMISSIONS REDUCTIONS

The report demonstrates that stabilizing atmospheric carbon dioxide concentrations will require deep reductions in the amount of carbon dioxide emitted. Because human carbon dioxide emissions exceed removal rates through natural carbon “sinks,” keeping emission rates the same will not lead to stabilization of carbon dioxide. Emissions reductions larger than about 80 percent, relative to whatever peak global emissions rate may be reached, are required to approximately stabilize carbon concentrations for a century or so at any chosen target level.

But stabilizing atmospheric concentrations does not mean that temperatures will stabilize immediately. Because of time-lags inherent in the Earth’s climate, warming that occurs in response to a given increase in the concentration of carbon dioxide (“transient climate change”) reflects only about half the eventual total warming (“equilibrium climate change”) that would occur for stabilization at the same concentration. For example, if concentrations reached 550 ppmv, transient warming would be about 1.6°C, but holding concentrations at 550 ppmv would mean that warming would continue over the next several centuries, reaching a best estimate of an equilibrium warming of about 3°C. Estimates of warming are based on models that incorporate ‘climate sensitivities’—the amount of warming expected at different atmospheric concentrations of carbon dioxide. Because there are many factors that shape climate, uncertainty in the climate sensitivity is large; the possibility of greater warming, implying additional risk, cannot be ruled out, and smaller warmings are also possible. In the example given above, choosing a concentration target of 550 ppmv could produce a likely global warming at equilibrium as low as 2.1°C, but warming could be as high as 4.3°C, increasing the severity of impacts. Thus, choices about stabilization targets will depend upon value judgments regarding the degree of acceptable risk.

CONCLUSION

This report provides a scientific evaluation of the implications of various climate stabilization targets. The report concludes that certain levels of warming associated with carbon dioxide emissions could lock the Earth and many future generations of humans into very large impacts; similarly, some targets could avoid such changes. It makes clear the importance of 21st century choices regarding long-term climate stabilization.

Bose Statistics and Classical Fields

Right now Kazimierz Rzążewski from the Center for Theoretical Physics at the Polish Academy of Sciences is giving a talk on “Bose statistics and classical fields”.

Abstract: Statistical properties of quantum systems are the heart of quantum statistical physics. Probability distributions of Bose-Einstein condensate are well understood for an ideal gas. In the presence of interactions only crude approximations are available. In this talk I will argue that now we have a powerful computational tool to study the statistics of weakly interacting Bose gas which is based on the so-called classical field approximation.

For a 3d ideal gas of bosonic atoms trapped in a 3d harmonic oscillator potential, the fraction of atoms in the ground state goes like

for T below a certain critical value, and 0 above that.

The grand canonical ensemble, where we assume the number of particles in our gas and its total energy are both variable, is a dubious method for Bose-Einstein condensates, because there’s no contact with a particle reservoir. The canonical ensemble is also fishy, where we assume the particle number is fixed both the total energy is variable, is also fishy. Why? Because there’s not contact with a heat reservoir, either. The microcanonical ensemble, where the energy and number of particles are both fixed, is closest to experimental reality.

We see this when we compute the fluctuations of the number of particles in the ground state. For the grand canonical ensemble, the standard deviation of the number of particles in the ground state becomes infinite at temperature below a certain value!

The fun starts when we move from the ideal gas to a weakly interacting gas. Most papers here consider particles trapped in a box, not in a harmonic oscillator — and they use the Bogoliubov approximation, which is exactly soluble for a box. This approximation involves a quadratic Hamiltonian that’s a sum of terms, one for each mode in the box. To set up this equation we need to use the Bogoliubov-deGennes equations.

As the temperature goes up, the Bogoliubov approximation breaks down… so we need a new approach.

Here is Rzążewski’s approach. A gas of bosons is described by a quantum field. But we can approximate the long-wavelength part of this quantum field by a classical field. Of course the basic idea here is not new. In our study of electromagnetism — this is what lets us approximate the quantum electromagnetic field by a classical field obeying the classical Maxwell equations. But the new part is setting up a theory that keeps some of the virtues of the quantum description, while approximating it with a classical one at low frequencies (i.e., large distance scales).

So: for modes below the cutoff we describe the system using annihilation and creation operators; for each mode above the cutoff we have 2d classical phase space. But: how to put in a nice ‘cutoff’ where we make the transition from the quantum field to the classical field?

Testing this problem on an exactly soluble model is a good idea: for example, the 1-dimensional ideal gas!

It turns out that by choosing the cutoff in an optimal way, the approximation is very good — not just for the 1d ideal gas, but also the 3d case, in both a harmonic potential and in a box. There is an analytic form for this optimal cutoff.

But more significant is the nonideal gas, where the particles repel each other. Here it’s easiest to start with the 1d case of a gas trapped in a harmonic oscillator potential. Now it’s more complicated. But we can simulate it numerically using the Metropolis algorithm!

We can also study ‘quasicondensates‘, where the coherence length is shorter than the size of the box, or the size of the cloud of atoms. (For example, in 2 dimensions, at temperatures above the Berezinskii-Kosterlitz-Thouless transition, there are lots of vortices in the gas, so the phase of the gas is nearly uniform only in small patches.)

Some papers:

• E. Witkowska, M. Gajda, and K. Rzążewski,
Bose statistics and classical fields, Phys. Rev. A 79 (2009), 033631.

• E. Witkowska, M. Gajda, and K. Rzążewski,
Monte Carlo method, classical fields and Bose statistics,
Opt. Comm. 283 (2010), 671-675.

• Z. Idziaszek, L. Zawitkowski, M. Gajda, and K. Rzążewski, Fluctuations of weakly interacting Bose-Einstein condensate, Europhysics Lett. 86 (2009), 10002.

As usual, I’d love it if an expert came along and explained anything more about these ideas. For example, I’m pretty vague about how exactly the Metropolis algorithm is used here.

Turning Renewable Energy into Fuels

Terry Bollinger wrote a comment that deserves to be a post of its own, because it could start an interesting discussion. Here it is:

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The theme of “what scientists can do to help save the planet” is a good one.

I’d like to introduce a topic that concerns me greatly these days: Well-intended efforts to produce cellulosic biofuels that, if applied in non-tropical climates (read “not in Brazil”), could end up taking over huge percentages of land and water resources without necessarily truly solving the problem of replacing fossil fuels.

At present, and quite ironically, it’s not even possible to produce biofuels without using a lot of petroleum in the process. Even more ominously, there have already been cases where people who didn’t have much to begin with are going without food because biofuels have run up the prices and taken over land that should have been used to feed them. That is a very scary trend, especially this early in the biofuels game. And if people who can at least express their need are going hungry, what does that leave as the most likely fate for forests and the animals that live in them? Again, a scary trend.

So here’s the scientific part of my query: Are there other options that would make more sense for fueling the mobile part of our global infrastructure? Good rechargeable batteries obviously are part of the answer, but surely there are more possibilities.

A wild example: Is there any way a fully chemical process (versus a land-using plant base one) could use concentrated, e.g. electrical, energy from renewable sources (or perhaps nuclear, sigh) to replicate what plants do using sunlight? That is, pull CO₂ from the air, add water, and generate high-energy-density hydrocarbon or carbohydrate fuels?

The point of such a wild idea would be to achieve the goal of biofuels — less use of fossil fuels — but in a way that avoids the awful environmental consequences of, in effect, using huge areas of land or water area as a very costly and inefficient way to collect renewable solar energy [1].

In short: Why not separate the energy collection component from the fuel-from-CO₂ part, then optimize both to achieve minimal global environmental impact?

I know the answer: Because it’s really hard to do. But that doesn’t necessarily mean it’s impossible.

Cheers,
Terry Bollinger

[1] Plants themselves are of course highly efficient at photosynthesis, especially some grasses. However, that’s the wrong metric; it’s like picking a gold nugget out of a ton of dross and then pretending the entire ton of dross has the value of gold. For biofuels, a realistic net cost metric would need to include how much land is used, the type of land used, what other uses of that land are being displaced (there is often a significant energy penalty when that is factored in correctly), and the average usable solar energy for the particular plants used. Under that kind of a full-cost metric, even the best cellulosic plant options amount to a very poor (and for some northern regions a potentially negative net benefit) way to collect solar energy.

Record High Temperatures

One swallow does not a summer make, nor does a hot day mean that global warming is underway… but since climate change deniers in the US made a big deal of the snowstorms this winter, despite the fact that global warming should increase the chance of such storms, I can’t resist pointing out this item from the blog of meteorologist Jeff Masters:

June 2010 features an unprecedented heat wave in Asia and North Africa

A withering heat wave of unprecedented intensity brought the hottest temperatures in recorded history to six nations in Asia and Africa, plus the Asian portion of Russia, in June 2010. At least two other Middle East nations came within a degree of their hottest temperatures ever in June.

The heat was the most intense in Kuwait, which recorded its hottest temperature in history on June 15 in Abdaly, according to the Kuwait Met office. The mercury hit 52.6°C (126.7°F). Kuwait’s previous all-time hottest temperature was 51.9°C (125.4°F), on July 27,2007, at Abdaly. Temperatures reached 51°C (123.8°F) in the capital of Kuwait City on June 15, 2010.

Iraq had its hottest day in history on June 14, 2010, when the mercury hit 52.0°C (125.6°F) in Basra. Iraq’s previous record was 51.7°C (125.1°F) set August 8, 1937, in Ash Shu’aybah.

Saudi Arabia had its hottest temperature ever on June 22, 2010, with a reading of 52.0°C (125.6°F) in Jeddah, the second largest city in Saudi Arabia. The previous record was 51.7°C (125.1°F), at Abqaiq, date unknown. The record heat was accompanied by a sandstorm, which caused eight power plants to go offline, resulting in blackouts to several Saudi cities.

In Africa, Chad had its hottest day in history on June 22, 2010, when the temperature reached 47.6°C (117.7°F) at Faya. The previous record was 47.4°C (117.3°F) at Faya on June 3 and June 9, 1961.

Niger tied its record for hottest day in history on June 22, 2010, when the temperature reached 47.1°C (116.8°F) at Bilma. That record stood for just one day, as Bilma broke the record again on June 23, when the mercury topped out at 48.2°C (118.8°F). The previous record was 47.1°C on May 24, 1998, also at Bilma.

Sudan recorded its hottest temperature in its history on June 25 when the mercury rose to 49.6°C (121.3°F) at Dongola. The previous record was 49.5°C (121.1°F) set in July 1987 in Aba Hamed.

The Asian portion of Russia recorded its highest temperature in history on June 25, when the mercury hit 42.3°C (108.1°F) at Belogorsk, near the Amur River border with China. The previous record was 41.7°C (107.1°F) at nearby Aksha on July 21, 2004. (The record for European Russia is 43.8°C–110.8°F–set on August 6, 1940, at Alexandrov Gaj near the border with Kazakhstan.

Two other countries came within a degree of their all time hottest temperature on record during the heat wave. Bahrain had its hottest June temperature ever, 46.9°C, on June 20, missing the all-time record of 47.5°C (117.5°F), set July 14, 2000. Temperatures in Quatar reached 48.8°C (119.8°F) on June 20. Quatar’s all-time record hottest temperature was 49.6°C (121.3°F) set on July 9, 2000. All of these records are unofficial, and will need to be verified by the World Meteorological Organization (WMO.) The source for the previous all-time records listed here is the book Extreme Weather by Chris Burt. According to Mr. Burt, the only other time as many as six nations set their all-time highest temperature marks in a single month was during the European heat wave of August 2003.

Perhaps more important than these scattered jaw-dropping hot spots are the following facts from the US National Climatic Data Center:

The world land surface temperature June 2010 anomaly of 1.07°C (1.93°F) was the warmest on record, surpassing the previous June record set in 2005 by 0.12°C (0.22°F). The anomalous warm conditions that affected large portions of each inhabited continent also contributed to the warmest June worldwide land and ocean surface temperature since records began in 1880. The previous June record was set in 2005. Separately, the worldwide ocean surface temperatures during June 2010 were 0.54°C (0.97°F) above the 20th century average—the fourth warmest June on record.

In fact, the whole year has been hot…

But even more important are the long-term trends…

Of course, you need to read the paper to understand how this graph was made.

Quantum Steganography

Besides talking about environmental issues, I’d also like to use this blog to talk about my day job at the Centre for Quantum Technologies. I hope this isn’t too distracting…

I’d like to try live-blogging a talk here. Today there’s a talk by Bilal Shaw of the University of Southern California about a paper he wrote with Todd Brun on Quantum Steganography.

“Steganography” is the art of hiding information by embedding it in a seemingly innocent message. In case you’re wondering – and I’ve got the kind of mind that can’t help wondering – the word “steganography” actually is etymologically related to the word “stegosaurus”. They both go back to words meaning “cover” or “roof”. Some other words with the same root are “thatch”, “deck” -and even “detect”, which is like “de-deck”: to take the lid off something!

Steganography is an ancient art, still thriving today. For example, that Russian spy ring they just caught were embedding secret data in publicly visible websites. The advantage of steganography over ordinary cryptography is that if you do it right, it doesn’t draw attention to itself. See this picture?

Remove all but the two least significant bits of each color component and you’ll get a picture that’s almost black. But then make that picture 85 times brighter and here’s what you’ll see:

All this is purely classical, of course. But what fiendish tricks can we play using quantum mechanics? Can we hide Schrödinger’s cat in a seemingly innocent tree?

Bilal’s paper describes a few recipes for quantum steganography. Alas, I’m not good enough at cryptography and live-blogging to beautifully deliver an instant summary of how they work. But roughly, the idea is to fake the effects of mildly “depolarizing” channel, one that introduces some errors into the qubits you’re transmitting, pushing pure states closer to the center of the Bloch sphere, where pure noise lives. You can’t introduce too many errors, since this would make the error rate suspiciously high to someone spying on our transmissions. So, there’s a kind of tradeoff here…

I’d be happy for an expert to give a better description!

News About the Younger Dryas

I don’t want to write anything really interesting here until the technology gets upgraded…

… but I figure I might as well start puttle little comments about ecological issues here, instead of on my diary.

So:

• Chris Colose, Revisiting the Younger Dryas, RealClimate, July 17, 2010.

The Younger Dryas was, among other things, a sudden cooling event in Europe shortly after the end of the last ice age. In only 20 years, the temperature in Europe dropped about 7 Celsius! It stayed cold for about 1,300 years. In Greenland, the temperature went down 15 Celsius. And then, at the end of the Younger Dryas, temperatures in Europe bounced back just as fast.

Sudden climate changes of this magnitude could have a huge impact on human civilization – just imagine glaciers in the Lake District in England. So, it’s worth learning all we can about this episode. Indeed, some people have suggested that freshwater from melting ice was what brought on the Younger Dryas, by disrupting ocean circulation in the northern Atlantic… which raises the specter of a repeat of this incident sometime soon! Luckily, the chances of that now seem very low. But it’s still good to understand this stuff.

If you haven’t learned a bit about Heinrich events (when icebergs drop lots of rocks on to the floor of the northern Altantic), the Bølling-Allerød warm period that came right before the Younger Dryas, the Last Glacial Maximum or LGM around 20,000 year ago, and the Atlantic meridional overturning circulation or AMOC, Chris Colose’s comments may seem a bit dry and jargonesque. But I find them fascinating!

For one thing, I hadn’t known that people were finding evidence of Younger-Dryas-like episodes at the end of earlier glacial periods, suggesting that these events are in some sense routine, rather than something that requires a freak event like a comet impact to explain. (Yes, some people have argued that a comet was to blame.)