8/23/2013

JOURNAL REVIEW July 31 – Aug 5 (Nature, Science, PNAS, ...)


NATURE

1. An age difference of two billion years between a metal-rich and a metal-poor globular cluster
B. M. S. Hansen, J. S. Kalirai, J. Anderson, A. Dotter, H. B. Richer, R. M. Rich, M. M. Shara, G. G. Fahlman, J. R. Hurley, I. R. King, D. Reitzel & P. B. Stetson
Nature 500, 51–53 (01 August 2013) doi:10.1038/nature12334

An absolute age of about ten billion years is determined for the globular cluster 47 Tucanae, which is about two billion years younger than the cluster NGC 6397 is thought to be, suggesting that metal-rich clusters like 47 Tucanae formed later than metal-poor clusters like NGC 6397.

2. Seasonal sea surface cooling in the equatorial Pacific cold tongue controlled by ocean mixing
James N. Moum, Alexander Perlin, Jonathan D. Nash & Michael J. McPhaden
Nature 500, 64–67 (01 August 2013) doi:10.1038/nature12363

In the tropics, a strong seasonal cycle in sea surface temperature exists despite comparatively constant radiation inputs; turbulent mixing from below is now shown to control the cooling phase of the seasonal cycle in the equatorial Pacific ‘cold tongue’ at 140° W.

3. Feeding andesitic eruptions with a high-speed connection from the mantle
Philipp Ruprecht & Terry Plank
Nature 500, 68–72 (01 August 2013) doi:10.1038/nature12342

Diffusion modelling of nickel in mantle melts beneath a volcano reveals the short timescales of magma movement from the base of the crust to the surface in the months to years before an eruption.

4. Reward research outreach in Japan
Amane Koizumi, Yuko Morita & Shishin Kawamoto
Nature 500, 29 (01 August 2013) doi:10.1038/500029a

Only 64% of almost 9,000 surveyed Japanese scientists communicate results outside the scientific community. This is because researcher performance in Japan is evaluated solely on the number of journal publications, so time and effort spent on science communication will not help scientists to secure funding, promotion or employment. Since 2010, the government has urged the researchers it funds to improve communication with the tax-paying public.

5. The milk revolution
Andrew Curry
Nature 500, 20–22 (01 August 2013) doi:10.1038/500020a

When a single genetic mutation first let ancient Europeans drink milk, it set the stage for a continental upheaval.

6. Pilot projects bury carbon dioxide in basalt
Jeff Tollefson
Nature 500, 18 (01 August 2013) doi:10.1038/500018a

Two experiments test viability of sequestering emissions in porous layers of hard rock.
SCIENCE SPECIAL ISSUE ON CLIMATE CHANGE

7. How a Fickle Climate Made Us Human
Ann Gibbons
Science 2 August 2013:
Vol. 341 no. 6145 pp. 474-479, DOI: 10.1126/science.341.6145.474

Many researchers agree that shifts in climate and environment shaped human evolution, but there has been little direct evidence about exactly how. Now researchers are drilling cores to gather geological data in the African landscapes where human ancestors once lived. Such localized data may help test ideas such as the savanna hypothesis, which proposes that the rise of grasses accompanied the birth of hominins.

8. Out of the Kenyan Mud, an Ancient Climate Record
Elizabeth Pennisi
Science 2 August 2013:
Vol. 341 no. 6145 pp. 476-479, DOI: 10.1126/science.341.6145.476

Scientists gather for a first look at a fresh sediment core, hoping that it will offer hard data linking environmental change to human evolution.

9. Can Coastal Marshes Rise Above It All?
Eli Kintisch
Science 2 August 2013:
Vol. 341 no. 6145 pp. 480-481, DOI: 10.1126/science.341.6145.480

There's wide agreement that salt marshes are among the ecosystems most vulnerable to rapid sea-level rise. But few researchers are ready to predict the fate of specific marshes; there's still too much to learn, they say. Now, wetlands scientists are mobilizing to reduce the uncertainty and hope to identify practical steps to protect marshes.

10. a) Worth a Thousand Words
Elizabeth Pennisi
Science 2 August 2013:
Vol. 341 no. 6145 p. 482, DOI: 10.1126/science.341.6145.482-a

By comparing historic images with modern photos snapped at the very same spots, researchers are documenting biological change that might be otherwise invisible in Ethiopia, China, Sweden, and the Arctic. Photo comparisons have yielded numerous insights and a few surprises. In this article, Science takes a look at a few projects that use photos to go back in time.

10. b) Advancing Seasons in China
Elizabeth Pennisi
Science 2 August 2013:
Vol. 341 no. 6145 pp. 482-483, DOI: 10.1126/science.341.6145.482-b
  
10. c) Tundra in Turmoil
Elizabeth Pennisi
Science 2 August 2013:
Vol. 341 no. 6145 pp. 483-484, DOI: 10.1126/science.341.6145.483

10. d) Tree Line Shifts
Elizabeth Pennisi
Science 2 August 2013:
Vol. 341 no. 6145 p. 484, DOI: 10.1126/science.341.6145.484

10. e) Humans Greening a Landscape
Elizabeth Pennisi
Science 2 August 2013:
Vol. 341 no. 6145 p. 485, DOI: 10.1126/science.341.6145.485

Reviews:

11. Changes in Ecologically Critical Terrestrial Climate Conditions
Noah S. Diffenbaugh, Christopher B. Field
Science 2 August 2013
Vol. 341 no. 6145 pp. 486-492, DOI: 10.1126/science.1237123

Terrestrial ecosystems have encountered substantial warming over the past century, with temperatures increasing about twice as rapidly over land as over the oceans. Here, we review the likelihood of continued changes in terrestrial climate.

12. Marine Ecosystem Responses to Cenozoic Global Change
Science 2 August 2013:
Vol. 341 no. 6145 pp. 492-498, DOI: 10.1126/science.1240543

The future impacts of anthropogenic global change on marine ecosystems are highly uncertain, but insights can be gained from past intervals of high atmospheric carbon dioxide partial pressure. The long-term geological record reveals an early Cenozoic warm climate that supported smaller polar ecosystems, few coral-algal reefs, expanded shallow-water platforms, longer food chains with less energy for top predators, and a less oxygenated ocean than today.

13. Climate Change and the Past, Present, and Future of Biotic Interactions
Science 2 August 2013:
Vol. 341 no. 6145 pp. 499-504, DOI: 10.1126/science.1237184

Biotic interactions drive key ecological and evolutionary processes and mediate ecosystem responses to climate change. We highlight episodes of climate change that have disrupted ecosystems and trophic interactions and identify knowledge gaps and fruitful areas for research that will further our understanding of the effects of climate change on ecosystems.

14. The Future of Species Under Climate Change: Resilience or Decline?
Science 2 August 2013:
Vol. 341 no. 6145 pp. 504-508, DOI: 10.1126/science.1237190

As climates change across already stressed ecosystems, there is no doubt that species will be affected, but to what extent and which will be most vulnerable remain uncertain. The fossil record suggests that most species persisted through past climate change, whereas forecasts of future impacts predict large-scale range reduction and extinction.



15. Climate Change Impacts on Global Food Security
Science 2 August 2013:
Vol. 341 no. 6145 pp. 508-513, DOI: 10.1126/science.1239402

Climate change could potentially interrupt progress toward a world without hunger. The evidence supports the need for considerable investment in adaptation and mitigation actions toward a “climate-smart food system” that is more resilient to climate change influences on food security.

16. Climate Change and Infectious Diseases: From Evidence to a Predictive Framework
Science 2 August 2013:
Vol. 341 no. 6145 pp. 514-519, DOI: 10.1126/science.1239401

Climate change has already increased the occurrence of diseases in some natural and agricultural systems. We highlight research progress and gaps that have emerged during the past decade and develop a predictive framework that integrates knowledge from ecophysiology and community ecology with modeling approaches.

17. Ecological Consequences of Sea-Ice Decline
Science 2 August 2013:
Vol. 341 no. 6145 pp. 519-524, DOI: 10.1126/science.1235225

After a decade with nine of the lowest arctic sea-ice minima on record, including the historically low minimum in 2012, we synthesize recent developments in the study of ecological responses to sea-ice decline.


SCIENCE

18. Study Links Climate Change and Violence, Battle Ensues
Science 2 August 2013:
Vol. 341 no. 6145 pp. 444-445
DOI: 10.1126/science.341.6145.444

In many cities, violence spikes with the temperature. Some social scientists say that the same could be true globally, proposing that climate change could lead to escalating violence. Now, a study published online this week in Science tries to quantify the increase.

19. Efficient Generation of H2 by Splitting Water with an Isothermal Redox Cycle
Science 2 August 2013:
Vol. 341 no. 6145 pp. 540-542
DOI: 10.1126/science.1239454

Solar thermal water-splitting (STWS) cycles have long been recognized as a desirable means of generating hydrogen gas (H2) from water and s unlight. Two-step, metal oxide–based STWS cycles generate H2 by sequential high-temperature reduction and water reoxidation of a metal oxide. We show that these temperature swings are unnecessary.

20. Is There Social RNA?
Science 2 August 2013:
Vol. 341 no. 6145 pp. 467-468, DOI: 10.1126/science.1243175

Our understanding of the forms, functions, and movement of RNA continues to expand. Not only can RNA control gene expression by multiple mechanisms within a cell, it appears to travel outside the cell within an organism as well. This raises the interesting question of whether the RNA world extends beyond the boundaries of the organism. Can RNA traffic integrate an organism into its environment—is there “social RNA”? Examining the mechanism of RNA interference (RNAi) may be a good route for seeking the answer.


PNAS

21. Rapid accumulation of committed sea-level rise from global warming
Benjamin H. Strauss
PNAS 2013 ; published ahead of print July 29, 2013, doi:10.1073/pnas.1312464110

22. Dynamic model constraints on oxygen-17 depletion in atmospheric O2 after a snowball Earth
Xiaobin Cao and Huiming Bao
PNAS 2013 ; published ahead of print July 29, 2013, doi:10.1073/pnas.1302972110

A large perturbation in atmospheric CO2 and O2 or bioproductivity will result in a drastic pulse of 17O change in atmospheric O2, as seen in the Marinoan Oxygen-17 Depletion (MOSD) event in the immediate aftermath of a global deglaciation 635 Mya. A snowball Earth is a precondition for the observed MOSD event.

23. Mass support for global climate agreements depends on institutional design
Michael M. Bechtel and Kenneth F. Scheve
PNAS 2013 ; published ahead of print July 25, 2013, doi:10.1073/pnas.1306374110

Effective climate mitigation requires international cooperation, and these global efforts need broad public support to be sustainable over the long run. We provide estimates of public support for different types of climate agreements in France, Germany, the United Kingdom, and the United States.

24. Variations in atmospheric CO2 growth rates coupled with tropical temperature
Weile Wang, Philippe Ciais, Ramakrishna R. Nemani, Josep G. Canadell, Shilong Piao, Stephen Sitch, Michael A. White, Hirofumi Hashimoto, Cristina Milesi, and Ranga B. Myneni
PNAS 2013 ; published ahead of print July 24, 2013, doi:10.1073/pnas.1219683110

Previous studies have highlighted the occurrence and intensity of El Niño–Southern Oscillation as important drivers of the interannual variability of the atmospheric CO2 growth rate, but the underlying biogeophysical mechanisms governing such connections remain unclear. Here we show a strong and persistent coupling (r2 ≈ 0.50) between interannual variations of the CO2 growth rate and tropical land–surface air temperature during 1959 to 2011.


NATURE GEOSCIENCE

25. Troubling milestone for CO2
Nicola Jones
Nature Geoscience 6, 589 (2013) doi:10.1038/ngeo1900
Published online 30 July 2013

On 9 May 2013, the daily average concentration of CO2 in our planet's atmosphere, measured at the famous Mauna Loa Observatory in Hawaii, crept above 400 parts per million for the first time since humans walked the Earth.

26. Acidification and acclimation
Anna Armstrong
Nature Geoscience 6, 590 (2013) doi:10.1038/ngeo1913

Continued acidification of the global ocean as a result of rising concentrations of atmospheric carbon dioxide reduces the formation of calcium carbonate in the oceans and could therefore impair the growth of carbonate coral skeletons. Corals that occur in naturally acidic waters near the Yucatan Peninsula show decreased levels of calcification, according to a morphological analysis of corals in the region.

27. Miocene melt-down
Alicia Newton
Nature Geoscience 6, 590 (2013) doi:10.1038/ngeo1915
Published online 30 July 2013

About 23 million years ago, ice sheets on Antarctica temporarily expanded to near-modern volumes. An analysis of marine sediments suggests that this expansion was accompanied by cooling of deep waters and increased burial of organic carbon.

28. Extinction promoted fire
Beverly Johnson
Nature Geoscience 6, 595–596 (2013) doi:10.1038/ngeo1907
Published online 30 July 2013

The extinction of megafauna in Australia roughly coincided with shifts in vegetation and fire regimes. Sediment geochemistry shows that the vegetation shift followed the extinction, indicating that the loss of browsers promoted fire and altered plant composition.

29. Imprint of Southern Ocean eddies on winds, clouds and rainfall
I. Frenger, N. Gruber, R. Knutti & M. Münnich
Nature Geoscience 6, 608–612 (2013) doi:10.1038/ngeo1863

Owing to the turbulent nature of the ocean, mesoscale eddies are omnipresent. An analysis of atmospheric conditions associated with several hundred thousand eddies in the Southern Ocean suggests that the transitory sea surface temperature fronts associated with these eddies alter near-surface winds, clouds and rainfall. 

30. Limits in detecting acceleration of ice sheet mass loss due to climate variability
Nature Geoscience 6, 613–616 (2013) doi:10.1038/ngeo1874
Received 26 July 2012 Accepted 05 June 2013 Published online 14 July 2013

The Greenland and Antarctic ice sheets have been reported to be losing mass at accelerating rates. Comparison of mass loss trends over the past decade with reconstructions of past mass loss indicates that the existing satellite record is too short to separate long-term mass loss trends from natural variability.

31. Variable North Pacific influence on drought in southwestern North America since AD 854
Staryl McCabe-Glynn, Kathleen R. Johnson, Courtenay Strong, Max Berkelhammer, Ashish Sinha, Hai Cheng & R. Lawrence Edwards
Nature Geoscience 6, 617–621 (2013) doi:10.1038/ngeo1862
Received 19 December 2012 Accepted 29 May 2013 Published online 07 July 2013

Over the twentieth century, droughts in southwestern North America have been linked to sea surface temperature variability in the North Pacific Ocean. Speleothem data from southern California suggest that links between the North Pacific and drought were less pronounced during the past millennium.

32. Transient stratification as the cause of the North Pacific productivity spike during deglaciation
Phoebe J. Lam, Laura F. Robinson, Jerzy Blusztajn, Camille Li, Mea S. Cook, Jerry F. McManus & Lloyd D. Keigwin
Nature Geoscience 6, 622–626 (2013) doi:10.1038/ngeo1873
Received 15 March 2013 Accepted 04 June 2013 Published online 14 July 2013

During the last deglaciation, the North Pacific Ocean was characterized by a spike in primary productivity, which has been attributed to iron input. Marine sediment analyses suggest that, instead, the productivity may have been fuelled by deep convection and subsequent stratification.

33. Abrupt vegetation change after the Late Quaternary megafaunal extinction in southeastern Australia
Raquel A. Lopes dos Santos, Patrick De Deckker, Ellen C. Hopmans, John W. Magee, Anchelique Mets, Jaap S. Sinninghe Damsté & Stefan Schouten
Nature Geoscience 6, 627–631 (2013) doi:10.1038/ngeo1856

The extinction of megafauna in Australia about 43,000 years ago has been linked to both human arrival and vegetation change. Marine sediment analyses from the east coast of Australia suggest that vegetation change was a result, rather than cause, of the extinction.

34. Subduction zone earthquake as potential trigger of submarine hydrocarbon seepage
David Fischer, José M. Mogollón, Michael Strasser, Thomas Pape, Gerhard Bohrmann, Noemi Fekete, Volkhard Spiess & Sabine Kasten
Nature Geoscience 6, 647–651 (2013) doi:10.1038/ngeo1886
Received 31 March 2013 Accepted 12 June 2013 Published online 28 July

Methane is abundant in marine sediments. Analysis of sediment cores and seismic images of marine sediments obtained off the coast of Pakistan show fracturing of gas hydrates and an increase in upward methane flux in the decades following a large earthquake in the Arabian Sea in 1945, suggesting that quakes can trigger hydrocarbon seepage.

35. Low simulated radiation limit for runaway greenhouse climates
Colin Goldblatt, Tyler D. Robinson, Kevin J. Zahnle & David Crisp
Nature Geoscience 6, 661–667 (2013) doi:10.1038/ngeo1892

As a moist atmosphere warms, it will reach a limit after which it is unable to radiate incoming solar radiation back to space, and a runaway greenhouse will occur. Calculations suggest that this limit is lower than previously thought and, for a water-saturated atmosphere, a runaway greenhouse can occur under present-day solar radiation.

36. Lithium isotope evidence for enhanced weathering during Oceanic Anoxic Event 2
Philip A. E. Pogge von Strandmann, Hugh C. Jenkyns & Richard G. Woodfine
Nature Geoscience 6, 668–672 (2013) doi:10.1038/ngeo1875
Received 16 April 2013 Accepted 05 June 2013 Published online 07 July 2013

Ocean Anoxic Event 2 was marked by rapid global warming and loss of O2 from the ocean. Lithium isotope data suggest that the warming was accompanied by enhanced silicate weathering, which stimulated marine productivity and helped stabilize atmospheric CO2 levels.


NATURE COMMUNICATIONS
37. Tertiary structural elements determine the extent and specificity of messenger RNA editing
Leila E. Rieder, Cynthia J. Staber, Barry Hoopengardner & Robert A. Reenan
Nature Communications 4, Article number: 2232 doi:10.1038/ncomms3232

The specificity and extent of RNA editing by ADAR enzymes is determined largely by local primary sequence and secondary structural imperfections in duplex RNA. Our results demonstrate that complex RNA tertiary structures, which may be difficult to predict computationally, form in vivo and can regulate RNA-editing events.

38. Nitrate formation from atmospheric nitrogen and oxygen photocatalysed by nano-sized titanium dioxide
Shi-Jie Yuan, Jie-Jie Chen, Zhi-Qi Lin, Wen-Wei Li, Guo-Ping Sheng & Han-Qing Yu
Nature Communications 4, Article number: 2249 doi:10.1038/ncomms3249

The concentration of nitrate in aquatic systems is rising with the development of modern industry and agriculture, causing a cascade of environmental problems. Given the expanding use of titanium dioxide worldwide, such a titanium dioxide-mediated photocatalysis process may reveal a potentially underestimated source of nitrate in the environment, which on one hand may lead to an increasing environmental pollution concern, and on the other hand may provide an alternative, gentle and cost-effective method for nitrate production.

39. The effects of carbon dioxide and temperature on microRNA expression in Arabidopsis development
Patrick May, Will Liao, Yijin Wu, Bin Shuai, W. Richard McCombie, Michael Q. Zhang & Qiong A. Liu
Nature Communications 4, Article number: 2145 doi:10.1038/ncomms3145

Elevated levels of CO2 and temperature can both affect plant growth and development, but the signalling pathways regulating these processes are still obscure. Here we identify, using the small RNA-sequencing method, microRNAs that change significantly in expression by either doubling the atmospheric CO2 concentration or by increasing temperature 3–6 °C. Notably, nearly all CO2-influenced microRNAs are affected inversely by elevated temperature.