A couple of weeks ago I spoke at an event run by the UPMC Center for Biosecurity, Preserving National Security: The Growing Role of the Life Sciences. Here is the video of my presentation, followed by Roger Breeze, with an introduction by Gigi Gronvall. There is a short panel discussion at the end of the clip. Video of the rest of the meeting is also online, along with a conference report (PDF).
March 2011 Archives
This month's Geophysical Research Letters brings more ice sheet melting data to be concerned about. A paper by Eric Rignot and colleagues at JPL, Caltech, UC Irvine, and Utrecht University demonstrates the "Acceleration of the contribution of the Greenland and Antarctic ice sheets to sea level rise". Here is a nice summary at ScienceDaily that goes into some broader implications for sea level rise. In addition to putting a bunch of nice data and analysis on the table, Rignot et al will contribute substantially to a broader understanding of the overall ice/water system near the poles.
The paper describes work integrating a variety of methods to build up a two decade-long picture of ice mass loss in Antarctica and Greenland. The numbers by themselves are pretty impressive: the ice sheet loss rate was ~478 Gigatons/year in 2006, with an acceleration of ~36 Gigatons/year^2. Note that this means the acceleration is 7.5% of the rate -- in other words, ice sheet mass loss is speeding up at a remarkable clip for a process that is ongoing at continental length-scales. Notably, the authors report a very small uncertainty in the acceleration (about 5%), which means that we can be quite certain there is a large non-linear contribution that is reducing ice sheet mass (one that is proportional to time^2).
Here are a few tidbits that are not in the paper or associated press stories. I wrote to Dr. Rignot to satisfy my curiosity about a couple of points, and he graciously responded and gave me permission to quote the emails here.
First, after staring at the ice loss rate and acceleration data for a little while, I got to wondering why the authors extracted a linear change in the rate of ice loss, which results in a constant acceleration. Given the data, you might wonder whether the acceleration was actually increasing rather than being a constant. In our brief email exchange, Dr. Rignot said that while the linear fit was the simplest fit, it appears that, in fact, the acceleration is increasing in Antarctica (no word from Dr. Rignot about Greenland). The team is going to wait for a few more years worth of data -- to increase their certainty and better constrain the statistical significance -- before they talk more about it.
This is pretty important. We are talking about adding a highly non-linear term to models of the total ice sheet mass, one that is proportional to (time^3). Depending on the size of the change in acceleration, this could radically change estimates of sea level rise from melting.
The present paper already demonstrates that ice sheet loss will account for substantially more sea level rise than is included in the IPCC models. In addition, the authors observe that increased mass loss is likely to lead to a substantial increase in the speed at which glaciers deliver ice to nearby water, something that is not adequately addressed (or is simply not included, if you are following that story) in IPCC forecasts.
Perhaps it is time to revisit investing in water wings.
The paper describes work integrating a variety of methods to build up a two decade-long picture of ice mass loss in Antarctica and Greenland. The numbers by themselves are pretty impressive: the ice sheet loss rate was ~478 Gigatons/year in 2006, with an acceleration of ~36 Gigatons/year^2. Note that this means the acceleration is 7.5% of the rate -- in other words, ice sheet mass loss is speeding up at a remarkable clip for a process that is ongoing at continental length-scales. Notably, the authors report a very small uncertainty in the acceleration (about 5%), which means that we can be quite certain there is a large non-linear contribution that is reducing ice sheet mass (one that is proportional to time^2).
Here are a few tidbits that are not in the paper or associated press stories. I wrote to Dr. Rignot to satisfy my curiosity about a couple of points, and he graciously responded and gave me permission to quote the emails here.
First, after staring at the ice loss rate and acceleration data for a little while, I got to wondering why the authors extracted a linear change in the rate of ice loss, which results in a constant acceleration. Given the data, you might wonder whether the acceleration was actually increasing rather than being a constant. In our brief email exchange, Dr. Rignot said that while the linear fit was the simplest fit, it appears that, in fact, the acceleration is increasing in Antarctica (no word from Dr. Rignot about Greenland). The team is going to wait for a few more years worth of data -- to increase their certainty and better constrain the statistical significance -- before they talk more about it.
This is pretty important. We are talking about adding a highly non-linear term to models of the total ice sheet mass, one that is proportional to (time^3). Depending on the size of the change in acceleration, this could radically change estimates of sea level rise from melting.
The present paper already demonstrates that ice sheet loss will account for substantially more sea level rise than is included in the IPCC models. In addition, the authors observe that increased mass loss is likely to lead to a substantial increase in the speed at which glaciers deliver ice to nearby water, something that is not adequately addressed (or is simply not included, if you are following that story) in IPCC forecasts.
Perhaps it is time to revisit investing in water wings.
This morning, Tom Murray at The Hastings Center pointed me to a new paper from James Liao's lab at UCLA demonstrating the first engineered bug that produces isobutanol from cellulose. Wendy Higashide, et al, ported the artificial butanol synthesis pathway from the group's earlier work in E. coli (see this previous post) into Clostridium cellulolyticum. Here is the article.
Recall that butanol is a much better biofuel than is ethanol. Butanol is also not hygoscopic (doesn't suck up water), which means it can be blended at any point in the distribution chain, whereas ethanol must be trucked/barged/piped in dedicated infrastructure until just upstream of a gas station in order to avoid pulling contaminating water into the fuel stream. Butanol has a long history of use as a transportation fuel, and has been demonstrated to be a drop in replacement for gasoline in existing engines. See, for example, the work of the 2007 iGEM team from Alberta, and my earlier post "A Step Toward Distributed Biofuel Production?" One advantage of making butanol instead of ethanol is that butanol spontaneously phase separates from water (i.e., it floats to the top of the tank) at concentrations above about 7.5% by volume, which substantially reduces the energy required to separate the molecule for use as a fuel.
The press release accompanying the Higashide paper describes the work as a "proof of concept". The team attempted to insert the butanol synthesis pathway into a Clostridum strain isolated from decaying grass -- a strain that naturally consumes cellulose. Unfortunately, this Clostridium strain is not as well characterized as your average lab strain of coli, nor does it have anywhere near the same number of bells, knobs, and whistles for controlling the inserted metabolic genes. The short summary of the paper is that the team managed to produce 660 mg of butanol per liter of culture. This is only about 0.07% by volume, or ~100 times below the concentration at which butanol phase separates from water. The team lays out a number of potential routes to improving this yield, including better characterization of the host organism, or simply moving to a better characterized organism.
So, a nice proof of principle. This is exactly the sort of technological transformation I discuss in my book. But this proof of concept is not anywhere near being economically useful or viable. Nonetheless, this progress demonstrates the opportunities ahead in relying on biology for more of our industrial production.
Recall that butanol is a much better biofuel than is ethanol. Butanol is also not hygoscopic (doesn't suck up water), which means it can be blended at any point in the distribution chain, whereas ethanol must be trucked/barged/piped in dedicated infrastructure until just upstream of a gas station in order to avoid pulling contaminating water into the fuel stream. Butanol has a long history of use as a transportation fuel, and has been demonstrated to be a drop in replacement for gasoline in existing engines. See, for example, the work of the 2007 iGEM team from Alberta, and my earlier post "A Step Toward Distributed Biofuel Production?" One advantage of making butanol instead of ethanol is that butanol spontaneously phase separates from water (i.e., it floats to the top of the tank) at concentrations above about 7.5% by volume, which substantially reduces the energy required to separate the molecule for use as a fuel.
The press release accompanying the Higashide paper describes the work as a "proof of concept". The team attempted to insert the butanol synthesis pathway into a Clostridum strain isolated from decaying grass -- a strain that naturally consumes cellulose. Unfortunately, this Clostridium strain is not as well characterized as your average lab strain of coli, nor does it have anywhere near the same number of bells, knobs, and whistles for controlling the inserted metabolic genes. The short summary of the paper is that the team managed to produce 660 mg of butanol per liter of culture. This is only about 0.07% by volume, or ~100 times below the concentration at which butanol phase separates from water. The team lays out a number of potential routes to improving this yield, including better characterization of the host organism, or simply moving to a better characterized organism.
So, a nice proof of principle. This is exactly the sort of technological transformation I discuss in my book. But this proof of concept is not anywhere near being economically useful or viable. Nonetheless, this progress demonstrates the opportunities ahead in relying on biology for more of our industrial production.
