For instructors including a module on climate geoengineering, an interesting reading choice would be an article by Klaus Lackner at The Earth Institute of Columbia University, K.S. Lackner, Capture of Carbon Dioxide from Ambient Air, 176 European Physical Journal Special Topics 93-106 (2009) (subscription required). Lackner’s piece focuses on a carbon dioxide removal (CDR) geoengineering scheme that hasn’t been discussed in this blog yet, air capture of carbon dioxide. Air capture schemes are viewed by proponents as one of the potentially most desirable forms of climate geoengineering because they might avoid some of the most serious possible side effects of other schemes, e.g. alteration of precipitation patterns or depletion of the ozone layer (potential side effects of stratospheric sulfur dioxide injection) or potentially serious ocean ecosystem impacts in the case of ocean iron fertilization. The article is pretty technical, however, so probably not appropriate for undergraduate students or law students.

Among the key take-aways of the piece:

1. Sorbent-based air capture would use a sorbent, a material used to capture gas or liquids, to capture carbon dioxide from the air; given the dilution of carbon dioxide in air, this is the only practical air capture scheme. The system would consist of a large filter standing in an airflow covered with carbon dioxide-selective sorbents;
2. The primary cost consideration in a carbon dioxide air capture system will be sorbent recycling;
3. The study concluded that a successful sorbent candidate could be a resin material similar to Marathon A, produced by Dow Chemical. It’s anticipated that future research will improve the efficiency of such systems;
4. Ten million units of the nature discussed in the study (most likely deployed in large “capture parks”) would collect 3.6 Gt/yr of CO2 if the unit size stays constant. With potential increased collection capacity, ten million units could remove 10 to 20Gt of CO2 on an annual basis. Annual carbon dioxide emissions are currently about 29 Gt annually;
   • An alternative to deploying so many units would be to scale up the size of the units;
   • Some air capture could also be effectuated by portable collector units that could be deployed in areas of high emissions. However, the optimal approach is effectuate air capture where the carbon dioxide might be used (e.g. for enhanced oil recovery, the author suggests) or stored;
5. While the first generation air capture units might cost $200 per ton of carbon captured, this could drop to $30 per ton through further advances in technology, adding 7 cents to a liter of gasoline;
6. Air capture could also foster the development of large-scale renewable energy.  H2O and CO2 can be used feedstock to produce synthetic hydrocarbon fuels like methanol, dimethyl-ether or long chained alkanes like gasoline or diesel

Many commentators believe that Lackner’s estimates for the cost of air capture are wildly optimistic, even assuming the effectiveness of the approach, so this could lead to an interesting discussion about the opportunity costs of pursuing research and deployment of this technology. Moreover, many of the questions associated with carbon capture and sequestration (potential danger of accidental releases of sequestered carbon dioxide, the need for a very large transportation network, and NIMBY issues associated with finding venues for storage) apply in this context also.

Global Warming May Kill Off Fifth of Global Lizard Species

by Celia Cole, Guardian

One–fifth of lizard species globally will become extinct by 2080 due to global warming, according to a study using data from more than 1,200 populations worldwide.

The research found that more than a 10th of Mexico’s Sceloporus lizard populations have been driven to extinction in the last 35 years, with the figure projected to increase to almost 40% by 2080. The scientists projected their findings globally using data from other lizard populations around the world.

The findings come in the wake of immense criticism over the failure of world leaders to live up to a commitment to reduce biodiversity loss by 2010. Professor Barry Sinervo at the University of California, Santa Cruz, who led the study, said he believes “we have now entered the era of climate change extinctions”.

Although we may not be accustomed to considering lizards as important players within our ecosystems in the UK, he warns that the reptiles occupy diverse ecological roles in ecosystems across the globe and their reduced numbers will have important implications for ecosystems and maintaining species diversity. “Their loss could cause a collapse at higher levels of the food webs,” he said.

“Many people appreciate that climate warming may lead to extinction in the future,” said Prof Raymond Huey an evolutionary physiologist at the University of Washington, who was not directly involved in the study. “But this paper shows that climate-induced extinction has already arrived and that more is coming. What is especially concerning is that lizards – a group of animals that tolerate heat and should be well buffered against warming – are the victims.”

Scientists made the initial discovery by distributing an electronic device across 200 sites in Mexico where the lizards were both thriving and had already gone extinct. They found that rapid warming was causing the animals to spend more time in cooler retreats, preventing them from finding food and reproducing at a level able to maintain a stable population size. The reptiles do no produce their own heat internally and so are dependent on the sun.

When the researchers plotted the thermal biological data from the Sceloporus lizards, and more than 1,200 other populations found worldwide, against projected temperature rises they discovered that global warming will drive 39% of all global lizard populations and one fifth of all lizard species to extinction by 2080.

A drastic cut in CO2 production which limited temperature rise might enable losses to be limited to 6% of species, the study predicts. However, given the time lag required for current levels of CO2 to decline in the atmosphere and the projected rise in temperatures that we have already observed, Sinervo believes it is unlikely that more extinctions could be avoided.

Huey said the paper was a call to arms for scientists and policymakers. “This is a mission critical paper that sends urgent messages to two groups. First, it should prompt government officials to draft regulatory changes that may slow the growth of greenhouse gasses. Second, it sends a strong message to biologists – we need to get busy and start studying extinctions [their extent and causes] rather than just predicting future extinctions.”

(Republished with permission of The Guardian.)

A sobering new study in the Proceedings of the National Academy of Sciences emphasizes the incredibly high risks of a business as usual scenario in terms of fossil fuel use and greenhouse gas emissions, Sherwood & Huber, An Adaptability Limit to Climate Change Due to Heat Stress, PNAS, Early Edition (2010) (subscription required).

Among the findings in the study:

1. While the middle-range estimate of temperature increases associated with a doubling of carbon dioxide is 1.9-4.5 degrees C of warming at equilibrium, a new study concludes that there is a 5% change of exceeding 7.1C. Moreover, because combustion of all available fossil fuel supplies could produce 2.75 doublings of carbon dioxide, temperatures could soar 12 degrees C, even with a 4.5 degrees C sensitivity;
   • If one factors in potential releases of natural stores of methane and carbon dioxide in a warmer climate, temperature increases by 2100 could be between 10-20 degrees C
2. While many studies assessing climatic impacts have focused on ecosystem, social and economic costs, the direct impact on humans and other mammals in the form of heat stress may also be extremely serious. A key consideration is peak heat stress, including humidity. While humans can tolerate, and adapt, a wide range of climates, peak heat stress may reach “intolerable levels;”
   • Humans maintain a core body temperature at 37 degrees C; sustained temperatures above 35 degrees C can cause hyperthermia, reaching lethal values (42-43 degrees C) for skin temperatures of 37-38 degrees C
   • Under future warming scenarios, a large majority of locations reach 30 degrees C at some point during a typical year, with a few regions reaching closer to 50 degrees C, with peak heat stress surprisingly similar across many regions;
   • A global-mean warming of 7 degrees C would create small zones where metabolic heat dissipation would provide “impossible;” at 11-12 degrees C warming, these zones would expand to encompass most human populations. While air conditioning is a potential compensatory response, it would remain cost-prohibitive for billions, and wouldn’t help other species, e.g. livestock.;
   • If warmings of 10 degrees C occurred in three centuries, the area of land that would be habitable would be reduced by half, dwarfing humans affected by rising sea level

Some interesting class discussion could ensue from this piece, including the levels of risk that we’re willing to tolerate as a society (does a 5% risk of extremely high temperatures mandate massive interventions?) and the implications of severe impacts that would no longer be restricted to certain regions (could this mobilize more support for addressing climate change in developed countries?).