Recently in Climate Category
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.
A couple of weeks ago I flew into LAX from the east coast and got another perspective on water use there. My first glimpse of the basin was the smog lapping up against the rim of the San Gabriel Mountains. I managed to snap a quick photo after we had flown over the ridge (the smog is on the lower left, though the contrast was more impressive when we were looking from the east side).
Even in May it looks a little dry 'round those parts.
A few minutes later, I noticed large green patches covering the sides (usually the west side) of hills. This continued all the way to downtown LA, and we were high enough for most of that time that I couldn't figure out why the locals were spending so much of their precious water keeping the sunset sides of hills green. Then, finally, we passed over one low enough that the purpose jumped out at me.
Even in death, Los Angelinos maintain their homage to William Mulholland by keeping him eternally damp. And in death, Los Angelinos continue to contribute to the smog shown above -- the grass covering the land of the dead is trimmed quite short. Many, many square miles of it. A cushy life, have those dead people. And to be fair to Los Angeles (which, admittedly, is hard for me), Seattle, too, uses a great deal of water and hydrocarbons to keep our decaying ancestors covered with a trim layer of green. It happens everywhere here. Welcome to America.
Even the way the US irrigates land to feed the living represents a profligate use of water. According to the USDA, 80% of the water consumed in this country goes to agriculture. (Note that "use" and "consumption" are often confused. Agriculture and thermoelectric power generation both "use" about 40% of the nation's freshwater, but while almost 100% of the water used for power generation is returned to where it was taken from -- albeit somewhat warmer than when it was taken -- much of the of water put on crops is does not reach the roots or is evaporated and lost to the atmosphere.) Notice that I did not use the word "waste", because some of the leakage winds up back in groundwater, or otherwise finds its way into the environment in a way that might be classified as "beneficial".
And pondering water use here in the US, and the impact on our economy, my thoughts turn to water use in Asia. Much ado was made in the last couple of years about the IPCC report of anomalous melting of Asian glaciers, followed by the discovery that there was no actual data behind the assertion.
A recent paper in Science adds some much needed analysis to the story. Walter Immerzeel and colleagues set out to understand the relative importance of meltwater and rainwater to river flows in Asia. It is interesting to me that this sort of analysis wasn't done before now: "Earlier studies have addressed the importance of glacial and snow melt and the potential effects of climate change on downstream hydrology, but these are mostly qualitative or local in nature."
For five large river basins the authors used a combination of precipitation data, snow melt models, and evaporation rates, to calculate the Normalized Melt Index (NMI). The NMI is the ratio of snow and glacier discharge to downstream discharge. If all the water in a river downstream is from melting, then this ratio is obviously one; if the ratio is less than one, rainfall contributes more than meltwater, and if it larger than one, more water is lost through evaporation or other processes (like agriculture) and meltwater is more important for total flow.
Here are the results. For each of the rivers, the authors calculated the percentage of the total discharge generated by snow and glacial melt:
In other words, water supplies in the Indus river valley are largely dependent on meltwater, whereas the large river systems in China appear to be less dependent on meltwater. That is a very interesting result, because the story told by lots of people (including myself) about the future of water in China is that they are in big trouble due to glacial melting in the Himalayas. Assuming this result holds up, China may be better off in a warmer world that I had anticipated.
The authors also used various projections of snow and rainfall to estimate what water supplies would look like in these rivers in 2050. As you might expect, a warmer world leads to less snowfall, more melting, and lower river flows. But as the warmer world brings increased rainfall, the impact is smaller than has been widely assumed. I am not going to bother putting any of the numbers in here, because, as the authors note, "Results should be treated with caution, because most climate models have difficulty simulating mean monsoon and the interannual precipitation variation, despite recent progress in improving the resolution of anticipated spatial and temporal changes in precipitation."
But they went one step further and tried to estimate the effects of potential decreased water supply on local food supplies. Couched in terms of crop yields, etc., Immerzeel et al estimate that the Brahmaputra will support about 35 million fewer people, the Indus will support about 26 million fewer people -- that's food for 60 million fewer people in India and Pakistan, if you are counting -- and the Yellow about 3 million more people. Finishing up, they write:
We conclude that Asia's water towers are threatened by climate change, but that the effects of climate change on water availability and food security in Asia differ substantially among basins and cannot be generalized. The effects in the Indus and Brahmaputra basins are likely to be severe owing to the large population and the high dependence on irrigated agriculture and meltwater. In the Yellow River, climate change may even yield a positive effect as the dependence on meltwater is low and a projected increased upstream precipitation, when retained in reservoirs, would enhance water availability for irrigated agriculture and food security.I am perplexed by the take on these results over at Nature News by Richard Lovett. His piece carries the title, "Global warming's impact on Asia's rivers overblown". I'll give Lovett the out that he may not have written the actual headline (Editors!), but nonetheless he sets up the Immerzeel paper as a big blow to some unnamed group of doomsayers. Perhaps he imagines that Immerzeel completely undermines the IPCC report? This is hardly the case. As I wrote last January, sorting out the mistake over Himalayan melting rates is an example of science working through a blunder. Instead overturning some sort of vague conspiracy, as best I can tell Immerzeel is simply the first real effort to make quantitative assessments of something to which much more attention should have been paid, much earlier than it was.
And even Lovett appears to acknowledge that reducing the human carrying capacity of the Brahmaputra and Indus river valleys by 60 million people is something to be concerned about. From Lovett:
The findings are important for policy-makers, says Jeffrey Kargel, a glaciologist at the University of Arizona in Tucson. "This paper adds to mounting evidence that the Indus Basin [between India and Pakistan] is particularly vulnerable to climate change," says Kargel. "This is a matter that obviously concerns India and Pakistan very much."Indeed. As they should concern us all.
First up, a paper from this week's PNAS by Breeker et al at UT Austin, "Atmospheric CO2 concentrations during ancient greenhouse climates were similar to those predicted for A.D. 2100". Already from the title you can see where this is going.
The problem Breeker and colleagues address is the following: how do you correlate the carbon content of fossil soils with prevailing atmospheric carbon dioxide concentrations? Well established methods exist for measuring the carbon content of compounds in fossil soil, but less certain were conditions under which chemical reactions produce those particular compounds. It turns out that model used to infer atmospheric CO2 contained an error. Breeker determined that the primary compound assayed when determining soil carbon content forms at much lower atmospheric CO2 concentrations than had been assumed.
Prior attempts to correlate soil carbon (and by proxy atmospheric CO2) with greenhouse periods in Earth's climate had concluded that warm periods experienced CO2 concentrations of much greater than ~1000 parts per million (ppm). Therefore, one might conclude that only when average atmospheric CO2 spiked above this level would we be in danger of experiencing greenhouse gas warming that threatened glaciers. The correction supplied by Breeker substantially lowers estimates of the average CO2 concentration that is correlated with continental glacial melting. Eyeballing the main figure in the paper, it looks to me like we could be in real trouble above 450 ppm -- today we are at just shy of 390 ppm and there is no sign we will be slowing down anytime soon, particularly if India and China keep up their pace of development and emissions.
Looking forward to 2100, things get a touch squiffy because Breeker relies on an estimate of CO2 concentrations that come out of model of global economic activity. So the title of the paper might be a tad alarmist, simply because 2100 is a long way out for any model to be taken too seriously. But the correction of the paleodata is a big story because at minimum it reduces the uncertainty of atmospheric CO2 levels, and it appears to clarify the connection between CO2 levels and continental glaciation. More work is needed on the later point, obviously, or this paper would have been on the cover of Science or Nature.
Now on to a serious screw-up at the IPCC. Elisabeth Rosenthal at the NYT is reporting that "A much-publicized estimate from a United Nations panel about the rapid melting of Himalayan glaciers from climate change is coming under fire as a gross exaggeration." Here is Andrew Revkin's take on DotEarth, and anyone interested in this story should read through his post. The comments are worth perusing because some of the contributors actually seem to have additional useful knowledge, though, of course, nut jobs aplenty show up from both sides of the debate over climate change.
In a nutshell, the issue is that the most recent IPCC chapter on glaciers contained a conclusion, advertised as real analysis, that was in fact a speculation by one scientist promulgated through the popular press. The authors of that section of the IPCC report may have been warned about the unsubstantiated claim. Contradictory data and analysis seems to have been ignored.
So, to be frank, this is a giant, inexcusable fuck-up. The IPCC is composed of so many factions and interest groups that this may be a case of simple blundering or of blatant politicization of science. But here is the beautiful thing about science -- it is self-correcting. It may take a while, but science always wins. (See also my post of a couple of years ago, Dispelling a Climate Change Skeptic's "Deception".) Every newspaper story I have seen about this particular IPCC screw-up notes that it was brought to light by...wait for it...a climate scientist. It is an excellent public airing of dirty laundry by the community of science. So while this episode demonstrates that the last official IPCC report on glacial melting in the Himalayas should not be used for any sort of scientific policy recommendation or economic forecast, you can bet that the next report will do a damn fine job on this topic.
Finally, whether or not the IPCC gets its act together, there are plenty of good data out there on the state of the planet. Eventually, Science -- with a capital S -- will get the right answer. The same methodical process that has resulted in computers, airplanes, and non-stick fry pans will inevitably explain what is really going on with our climate. And if you use computers, fly on airplanes, or eat scrambled eggs then you are implicitly acknowledging, whatever your political or religious persuasion, that you believe in science. And you better, 'cause science always wins.
A few other tidbits from the article: sugar beets now supply about half the US sugar demand, and it seems that GM sugar beets account for about 95% of the US crop (I cannot find any data on the USDA site to support the latter claim). A spokesman for the nation's largest sugar beet processor claims that food companies, and consumers, have completely accepted sugar from the modified beets -- as they should, because it's the same old sugar molecule.
I got lured into spending most of my day on this because I noticed that the Sierra Club was one of the plaintiffs. This surprised me, because the Sierra Club is less of a noisemaker on biotech crops than some of the co-plaintiffs, and usually focuses more on climate issues. Though there is as yet no press release, digging around the Sierra Club site suggests that the organization wants all GM crops to be tested and evaluated with an impact statement before approval. But my surprise also comes in part because the best review I can find of GM crops suggests that their growing use is coincident with a substantial reduction in soil loss, carbon emissions, energy use, water use, and overall climate impact -- precisely the sort of technological improvement you might expect the Sierra Club to support. The reductions in environmental impact -- which range from 20% to 70%, depending on the crop -- come from "From Field to Market" (PDF) published earlier this year by the Keystone Alliance, a diverse collection of environmental groups and companies. Recall that according to USDA data GM crops now account for about 90% of cotton, soy, and corn. While the Keystone report does not directly attribute the reduction in climate impacts to genetic modification, a VP at Monsanto recently made the connection explicit (PDF of Kevin Eblen's slides at the 2009 International Farm Management Congress). Here is some additional reporting/commentary.
So I find myself being pulled into exploring the cost/benefit analysis of biotech crops sooner than I had wanted. I dealt with this issue in Biology is Technology by punting in the afterword:
Obviously we will all be talking about biotech crops for years to come. I don't see how we are going to address the combination of 1) the need for more biomass for fuel and materials, 2) the mandatory increase in crop yields necessary to feed human populations, and 3) the need to reduce our climatic impacts, without deploying biotech crops at even larger scales than we have so far. But I am also very aware that nobody, but nobody, truly understands how a GM organism will behave when released into the wild.
The broader message in this book is that biological technologies are beginning to change both our economy and our interaction with nature in new ways. The global acreage of genetically modified (GM) crops continues to grow at a very steady rate, and those crops are put to new uses in the economy every day. One critical question I avoided in the discussion of these crops is the extent to which GM provides an advantage over unmodified plants. With more than ten years of field and market experience with these crops in Asia and North and South America, the answer would appear to be yes. Farmers who have the choice to plant GM crops often do so, and presumably they make that choice because it provides them a benefit. But public debate remains highly polarized. The Union of Concerned Scientists recently released a review of published studies of GM crop yields in which the author claimed to "debunk" the idea that genetic modification will "play a significant role in increasing food production" The Biotechnology Industry Organization responded with a press release claiming to "debunk" the original debunking. The debate continues.
We do live in interesting times.
Craig Venter makes an appearance arguing that the best long-term bet is to build photosynthetic bugs that use atomspheric CO2 to directly produce fuel. Maybe. This would require containment facilities for culturing engineered bugs, where those facilities also must capture sunlight and CO2 to feed the bugs. The costs for this infrastructure are not insignificant, and this is exactly what is presently standing in the way of large scale algal biodiesel production.
Here is the question I keep asking in these circles: why not just grow naturally occurring algae, which can be grown at extremely high yield in a wide variety of conditions, as food for bugs hacked to eat cellulose? If there is no algae to be had, just throw in another source of cellulose or other biomass. There would be minimal concern over growing modified organisms that might escape into the wild. The processing of biomass into fuel under would also be under conditions that are easier to optimize and control.
I'm not suggesting this is the only answer, but rather that it appears to balance 1) the costs of infrastructure, 2) concerns over enviromental release of genetically modified organisms, and 3) provide an efficient processing infrastructure that could use a wide variety of feedstocks.
The new results follow on James Hansen's earlier work based on data, rather than models, suggesting that both warming and sea level rise are likely happen faster than the IPCC consensus estimates (see "It's time to Invest in Water Wings"), because the IPCC models explicitly exclude the effect of ice sheet movement and landlocked ice melting.
It gets even better. Reduced sea ice coverage is also now strongly affecting the thermal balance of the poles:
As sea ice melts, the Arctic waters absorb more heat in the summer, having lost the reflective powers of vast packs of ice. That absorbed heat is released into the air in the autumn. That has led to autumn temperatures in the last several years that are 6 degrees Fahrenheit to 10 degrees (3.5 degrees to 6 degrees) warmer than they were in the 1980s.Warming of the land and sea are coupled: "The loss of sea ice warms the water, which warms the permafrost on nearby land in Alaska, thus producing methane," itself a potent greenhouse gas, according to Julienne Stroeve, a research scientist at the National Snow and Ice Data Center in Boulder, Colorado. (See my previous posts: "Methane Time Bomb" and "Update".)
With respect to the anomolously high Arctic temperatures, The Independent's Steve Connor wonders "Has the Arctic melt passed the point of no return?":
The phenomenon, known as Arctic amplification, was not expected to be seen for at least another 10 or 15 years and the findings will further raise concerns that the Arctic has already passed the climatic tipping-point towards ice-free summers, beyond which it may not recover.The coupling of land and sea warming constitute a feedback mechanism that threatens to create runaway warming and increased methane emissions, which will only make things worse. Only more data will help resolve any remaining uncertainty. While we gather that data, our time to fiddle is running out.