This week’s Published Research Synopsis focuses on the impact global warming will have on the availability of water across the globe. This paper is part Review Paper, part original research. This means, essentially, that the authors have published important new results by synthesizing the results of many other researchers.
I’ve selected this week’s paper for two reasons: 1) the results are extremely important and immediately relevant, and 2) the results and “data” do not possess large uncertainties typically present in forecasts of water supply changes, but more on that later!
Citation: (view online at CiteULike.org)
T. P. Barnett1, J. C. Adam2, and D. P. Lettenmaier3. Potential impacts of a warming climate on water availability in snow-dominated regions. Nature, 438(7066):303–309.
1Climate Research Division, Scripps Institution of Oceanography. 2Department of Civil and Environmental Engineering. 3Department of Civil and Environmental Engineering, University of Washington.
Synopsis:
Even small increases in mean annual temperature lead to earlier snow melt, and thus earlier arrival of the big pulses of spring stream flow in regions that depend on snow melt. The authors develop a simple model to plot, globally, the relative influence of melting snow on seasonal stream flow, and present the figure shown below. The region outlined in red, containing 1/6th of the world’s population, is dependent on the current timing of the annual snow melt for its water supplies, and is most likely to be immediately impacted by even relatively small increases in annual temperature. They then review the climate change literature in order to highlight the need for governments to redesign water storage reservoirs and alter their management practices. If not, the vast majority of the water released in earlier snow melt will be lost to the oceans before it can enter the water supply, reducing supplies for the remainder of the year.
They go on to examine the potential impacts of warming on the most sensitive regions in the world, those that depend on glacial melt water for water supplies. Lest we think such areas isolated or unimportant, much of Southern Central Asia depends on Himalayan glaciers melting during the dry season for its water. The glaciers there, and in the much of the Andes, are melting rapidly, and when they are gone so will be a primary source of water for those regions.
Finally the authors address the two largest uncertainties in their study: the effects of warming on evaporation and plant transpiration, as well as the effect of pollutant aerosols on precipitation. They conclude that, as best as can be determined, the effects of both evaporation/transpiration and aerosols will not change their conclusions: that much of the globe will see earlier snow melt and lower summer/dry-season stream flows.
Context:
Climate change models are notoriously incapable of agreeing on how precipitation will change seasonally as global warming progresses. Researchers examining the effects of warming on the hydrologic cycle and water resources have focused on these models, but have been hampered by their uncertainties. By focusing instead on the effect that temperature change (about which the models agree to a reasonable degree) will have on water supplies, this study seems likely to have a greater impact than those previously.
General Explanations:
Global climate change models have emerged in a bewildering variety. The gold-standard, the General Circulation Model, really refers to a computer model that keeps track of the energy and water that flow in an out of each of the millions of tiny cells that represent the world’s atmosphere. These models, though similar in name, can produce drastically different results depending on how the model parameters are set. These model parameters are the focus of active research, but still contain a good deal of uncertainty. The biggest of these models require the massive computational resources of the world’s largest supercomputers, and can run literally for months on end. Thus it can be very difficult to understand exactly how these parameters then affect model outcomes.
An interesting approach, to connect some “high level” observables that are not buried so deeply in a complex climate model and lead to important results that are (I hope) hard to deny. Thanks for pointing out the article and “translating” it.
With the huge flood of technical literature in the world, it may be Quixotic to say “I will choose one peer-reviewed article each week and summarize it for my readers to put them in closer touch with the scientific process and with some important and minimally filtered results.” But I think it is worthwhile, in part as an example of the possibility and value of doing this.
-Bruce
Bruce,
I agree totally with calling it Quixotic, in fact I think that adjective applies to much that I do! I’m not yet sure of the real value of doing these weekly Synopses, but it’s something I’ve wanted to do for a long time, so I think it’s worthwhile. Part of my purpose in writing this blog is to aid my own abilities in communicating science to non-scientists. So, if this does nothing else except to share a few interesting papers and make me a better communicator in the process, then perhaps it’s been successful.
There is a bit of an agenda here, too. I’ve recognized the fact that the Intelligent Design people having “peer-reviewed journal articles” is an important card for them to play. This is something that lends credibility to their cause disproportionately in the eyes of the general public. I’m hoping to demistify the whole peer-review process to reveal the more human side of it as well. Perhaps I will choose a few papers whos results have either been discredited or are suspect in order to make this point more forcefully.