In the hot, dry Middle East, where populations are growing rapidly and all major rivers cross political borders, water has become a focal point for escalating violence.

From the foothills of the Taurus Mountains in Turkey that feed the Tigris and Euphrates rivers to the desert wadis on the southern tip of Yemen, the history of water conflicts provides a cautionary tale: When water and politics mix, and when cooperation gives way to conflict, freshwater becomes an issue of human and national security and a tool of violence. Read more

A new test for assessing the quality of drinking water is faster, and possibly cheaper, than the current method. While current tests take a couple of days, the new test can tell whether water is contaminated in only eight minutes.

Felipe Lombo and his BIONUC research team from the University of Oviedo in Spain exploited a naturally occurring bacteria-binding protein, colicin S4, fused to green fluorescent protein. This fluorescent sensor produces a light signal when exposed to UV, making it a great tool for detecting bacterial contamination in drinking water.

Colicin S4 is produced by some bacteria to kill rival bacteria and specifically detects Escherichia coli, a bacterium that is an indicator of faecal water contamination. While colicin S4 provides specificity, green fluorescent protein emits a light signal that allows detection. The fusion of the two parts results in a sensor that can bind E. coli in contaminated water and produce light signals. Using a filter that retains the bacteria, unbound sensor molecules are washed away. If bacteria were present in the water sample, a light signal will occur in response to UV light. If no bacteria were present, all sensor molecules are washed away and no light signal is observed. Read more

Since the time of Aristotle, some scientists have claimed that hot water freezes faster than cold. Philip Ball looks at current attempts to shed light on this puzzling phenomenon.

Intuitively we think that cold water should take less time to freeze than hot water, but Aristotle and others since have found this not to be the case.

It sounds like the kind of question you would be dismayed to hear schoolchildren getting wrong: which takes less time to freeze, cold or hot water? Common sense and the laws of thermodynamics appear to insist that cold water must freeze first. For example, Newton’s law of cooling states that the rate at which a body cools is proportional to the temperature difference between the object and its surroundings. But, in fact, it does seem as though hot water sometimes “overtakes” cold as it cools.

Indeed, Aristotle, Francis Bacon and René Descartes all claimed that hot water does freeze more quickly. Erasto Mpemba, a secondary-school student in Tanzania, may have been unaware of their claims, but it was something he also observed in 1963. To make ice cream for a school project, he was told to boil milk and then let it cool before putting it in the refrigerator. But, fearful of losing his place, Mpemba put his mixture in the fridge while it was still hot. He found that it froze before the other, cooled mixtures. Read more

In a 2002 paper, what is frequently referred to as “Munk’s enigma”, Scripps Institution of Oceanography’s senior researcher bemoaned the fact researchers could not fully account for the causes of sea level rise.

He lamented, “the historic rise started too early, has too linear a trend, and is too large.” Early IPCC analyses noted about 25% of estimated sea level rise was unaccounted for. Accordingly, in 2012, an international team of prominent sea level researchers published, Twentieth-Century Global-Mean Sea Level Rise: Is the Whole Greater than the Sum of the Parts? (henceforth Gregory 2012).

They hoped to balance struggling sea level budgets by re-analyzing and adjusting estimates of the contributions from melting glaciers and ice caps, thermal expansion, and the effects of dam building and groundwater extraction. However, a natural contribution from any imbalance in groundwater re-charge vs discharge was never considered. Yet the volume of freshwater stored as groundwater, is second only to Antarctica’s frozen supply, and 3 to 8 times greater than Greenland’s. Read more