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Friday, March 04, 2011

Climate Science Roundup

Cross posted on Climate Central.

Welcome to Climate Central's weekly science round up. Among last week’s noteworthy research papers were an investigation of over-estimating improved energy efficiency, a look at how the allergy season is growing longer, and a study of the history—and future—of drought in the American southwest. Also published last week were a pair of studies on heavy rain (over North America and Hawaii) and a review of California's changing temperature trends.

These studies, and a number of others, published between February 22nd and 28th are summarized here:

Paper Title: Modifying the rebound: It depends! Explaining mobility behavior on the basis of the German socio-economic panel
Journal: Energy Policy
Authors: Wenzel Matiaskea, Roland Mengesb, and Martin Spiessc

The Gist: This paper investigates the “rebound effect" — the idea that if consumers replace old products with more energy efficient ones, they won’t save as much energy as expected because they will actually use some of their extra savings to buy more energy. For instance, the rebound effect says if lighting is more efficient (and thus cheaper) consumers might end up using more lighting in their homes. People would probably still use less electricity than they did originally, but they wouldn’t have “saved” as much energy as anticipated by simple calculations. This new study concludes that in Germany (where the research was done), consumers who purchase more efficient cars drive more miles, but only up to a point. In this case, the rebound effect is strongest for users switching from low-efficiency cars to medium-efficiency cars, but it disappears with cars that get about 30 miles to the gallon. More generally, the “rebound effect” has recently been discussed by The New Yorker, The Breakthrough Institute, and Rocky Mountain Institute.

Paper Title: Climate change and evolutionary adaptation
Journal: Nature
Authors: Ary A. Hoffmann and Carla M. Sgro

The Gist: Some plant and animal species — especially those with short life spans and large populations — will adapt to climate change through natural selection and evolution. In fact, some species, such as mosquitoes, which have short life spans and can thus adapt quickly, have already “evolved” due to climate change. Scientists have shown that warmer temperatures have caused the genetics of some mosquito populations to change. This particular study suggests improved ways to model how different species will adapt to global warming, taking into account their ability to evolve relatively quickly.

Paper Title: Extended megadroughts in the southwestern United States during Pleistocene interglacials
Journal: Nature
Authors: Peter J. Fawcett and 18 others

The Gist: By studying sediments in New Mexico, these researchers estimated precipitation and temperature in the region for the period between about 370,000 and 550,000 years ago. Why is does this past climate matter? The researchers found that during the warmest times of that period — which might have been slightly warmer than today — the region experienced extreme drought. Most climate models predict that the U.S. southwest will experience severe drought as the planet warms. This new study shows this type of “permanent dust bowl” could develop in the future because it happened in the past. The New York Times offered a nice summary of this research earlier in the week. And in the journal PNAS this week, another study examined how a drier Southwest could increase wind erosion as the vegetation changes in response to drought.

Paper Title: The identification of distinct patterns in California temperature trends
Journal: Climatic Change
Authors: Eugene C. Cordero. Wittaya Kessomkiat, John Abatzoglou, Steven A. Mauge

The Gist: Analyzing 80 years worth of climate data in California, this study finds some interesting results: the average daily low temperature warmed more than twice as much as the average daily high (a warming of 1.36°C versus 0.56°C over 80 years). The researchers did not study why these trends have evolved differently over time but they say the discrepancy is a sign that there are probably many different factors influencing how temperatures are changing in the region.

Paper Title: Influence of hurricane-related activity on North American extreme precipitation
Journal: Geophysical Research Letters
Author: Mathew Barlow

The Gist: Last week we reported on a series of papers that provide evidence climate change has probably already increased the amount of rain falling in big storms. This week, a new paper looks at heavy rainstorms specifically in North America, finding that for locations along the Atlantic and Gulf coasts, hurricanes account for a disproportionate number of the storms with heavy rainfall. How hurricanes respond to climate change — which is still uncertain — will determine the future of heavy rainstorms in these areas and this topic is now being heavily researched.

Paper Title: Projection of changes in the frequency of heavy rain events over Hawaii based on leading Pacific climate modes
Journal: Journal of Geophysical Research
Authors: O. Elison Timm, H. F. Diaz, T. W. Giambelluca, M. Takahashi

The Gist: Climate change is expected to increase heavy rainfall, on average, across the globe. But will every place experience stronger storms? Because there are so many factors that influence regional rainfall, including temperature, humidity and larger climate oscillations like El Niño, more localized studies can offer more insight to this question. This study examines projections for rainfall in Hawaii and finds that climate models don’t show a major change in number of days with heavy rain. This estimate, though, is highly uncertain because currently climate models don’t agree on how rainfall will change in that region.

Paper Title: Recent warming by latitude associated with increased length of ragweed pollen season in central North America
Journal: PNAS
Authors: Lewis Ziskaa and 19 others

The Gist: Global warming is lengthening the ragweed pollen season, and this trend is especially evident in northern areas. Within the northern U.S. (northward of Oregon, South Dakota and Vermont, for example) the pollen season has increased between 13 and 27 days since 1995. Last week, Climate Central provided a more in depth summary of this article.

Paper Title: Climate change risks for African agriculture
Journal: PNAS
Authors: Christoph Müllera, Wolfgang Cramera, William L. Harea, and Hermann Lotze-Campena

The Gist: This paper surveys recent studies of how climate change could affect agriculture in Africa and finds there is wide disagreement. Some research says crop yields will generally increase across the African continent but others say yields will decrease. The range is broad because not only are modelers trying to predict how greenhouse gases will warm the planet and how plants will respond, but they are also trying to predict how farmers and markets will respond. Combining these natural environmental factors with socioeconomic influences is still particularly difficult task. Nonetheless, this new review paper concludes that Africa’s agriculture faces significant risk from warming temperatures.

Paper Title: Greenhouse Gas Emission Reductions from Domestic Anaerobic Digesters Linked with Sustainable Sanitation in Rural China
Journal: Environmental Science & Technology
Authors: Radhika Dhingra, Erick R. Christensen, Yang Liu, Bo Zhong, Chang-Fu Wu, Michael G. Yost, and Justin V. Remais

The Gist: Last year China set a goal of powering 27 million homes with biogas — gas from fermented human and animal waste (yes, that can include animal feces). The biogas is produced by putting waste in airtight containers where anaerobic microbes turn it into methane gas. The methane can then be burned for heat, allowing people to heat their homes without using fossil fuels. Methane, however, is also a potent greenhouse gas; if large quantities of the gas escape into the atmosphere before being burned, it could potentially cause more warming than the carbon dioxide produced by burning fossil fuels. This study analyzed methane leaks at the gas production sites and people’s houses and determined that even somewhat leaky systems emitted much less gas to the atmosphere than houses that used coal or natural gas.

That’s all for this week. If you have a question about one of these papers, feel free to ask in the comments below.

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