Volume 3 Issue 1, January 2010

Self-censorship of private scientific e-mail-exchanges cannot be the solution to the threat from hackers.

Nearly an eighth of the population in Bangladesh relies on arsenic-contaminated drinking water. Arsenic-removal filters could help to reduce exposure, but their price is high for the poor and their maintenance is cumbersome.

Arsenic occurs naturally in the groundwater of southern Asia. Analyses of an agricultural site in Bangladesh suggest that human activities, including widespread farming practices, can dictate where elevated arsenic is found.

Most climate models consider only short-term processes such as cloud and sea-ice formation when assessing Earth's sensitivity to greenhouse-gas forcing. Mounting evidence indicates that the response could be stronger if boundary conditions change drastically.

The effect of rising greenhouse-gas emissions on climate is not uniform across the globe. An analysis of the mechanisms behind model-projected changes in ocean temperature gives greater confidence in the pattern of tropical warming and its potential impacts.

Where the Pacific and Australian tectonic plates collide under the South Island of New Zealand large quantities of aqueous fluid are produced. But how does this happen? Geophysical and petrological data indicate that it may not be as we thought.

Spatially extensive evidence for nitrogen-induced stimulation of forest growth has been lacking. Analysis of forest inventory data from the northeastern and north-central US collected during the 1980s and 1990s indicates that nitrogen deposition enhanced above-ground carbon storage by 61 kg per kg of nitrogen deposited.

The concentration of chemicals that absorb low-frequency sound in the ocean has declined as a result of anthropogenic increases in ocean acidity. Model simulations predict large reductions in sound absorption in the high latitudes and areas of deep-water formation over the twenty-first century.

Antarctic Intermediate Water is an oxygen-rich water mass that spreads throughout the Southern Hemisphere oceans. Marine sediment chemistry indicates that the water mass was produced at higher rates and had higher oxygen concentrations during the Last Glacial Maximum.

Earth-system climate sensitivity includes the effects of long-term feedbacks such as changes in continental ice-sheet extent and terrestrial ecosystems. A reconstruction of atmospheric carbon dioxide levels 4.5 million years ago suggests that Earth-system climate sensitivity is significantly higher than that estimated from global climate models, which includes only fast feedback mechanisms such as changes in clouds and sea ice.

The generation of fluids as mountain belts form is thought to be related to the heating that accompanies rock burial. Mineral-equilibria modelling suggests that the exhumation of greywacke — a common rock type in mountain-forming regions — following heating also generates new fluid.

The movement of tectonic plates before the Cretaceous period is poorly understood. A global mantle tomography model suggests that the longitude of oceanic subduction zones up to 300 million years ago was offset by up to 18^∘ compared with tectonic reconstructions for the same period.

The collision history of asteroids in the early Solar System is difficult to reconstruct. A study of plagioclase breakdown using X-ray diffraction measurements under increasing pressures and temperatures suggests that peak pressures in collisions that formed shocked meteorites have been overestimated.

Microbially mediated oxidation of organic carbon is thought to drive the release of arsenic into groundwater. Hydrological and geochemical analyses suggest that pond water is the source of organic carbon in groundwater in Bangladesh.

Bangladesh relies heavily on groundwater for the irrigation of dry-season rice. Analysis of soil porewater and floodwater in rice paddy fields during the monsoon season in Bangladesh suggests that flooding removes a significant amount of arsenic from the soils.

The equilibrium response of global temperatures to an increase in atmospheric carbon dioxide concentrations is difficult to quantify. Simulations and proxy data of the mid-Pliocene warm climate suggest that the response is 30 to 50% higher than traditionally calculated when slowly adjusting components of the Earth system, such as ice sheets and vegetation, are included in the estimate.

Arsenic-contaminated groundwater endangers the health of millions of people in southern Asia. In this focus issue we gather together articles on the origin and fate of arsenic in groundwater, together with opinion pieces outlining options for dealing with the problem, and backstories detailing some of the challenges faced by the researchers.