Changes in drinking water quality in the 21st Century are coming from a myriad of circumstances, and not all are for the best. Top contenders for why water-drinking quality might become suspect to the average consumer include California's drought conditions, the technology of fracking, and the nationwide aging infrastructure of rusty, degrading pipes.

Citing these and other relatively recent scenarios, Andrea Dietrich, professor of civil and environmental engineering at Virginia Tech, and her colleague Gary A. Burlingame of the Philadelphia Water Department, are calling for a critical review and rethinking of the U.S. Environmental Protection Agency's (EPA) secondary standards for maintaining consumers' confidence in tap water as well as in its sensory quality.

The greatest concentrations of the world's soil carbon have been pinpointed by researchers - and much of it is a dangerously flammable addition to climate change concerns. An international scientific survey of peat bogs has calculated that they contain more carbon than all the world's forests, heaths and grasslands together - and perhaps as much as the planet's atmosphere. Since peat can smoulder underground for years, it is another potential factor in global warming calculations.

The “warming hiatus” that has occurred over the last 15 years has been caused in part by small volcanic eruptions. Scientists have long known that volcanoes cool the atmosphere because of the sulfur dioxide that is expelled during eruptions. Droplets of sulfuric acid that form when the gas combines with oxygen in the upper atmosphere can persist for many months, reflecting sunlight away from Earth and lowering temperatures at the surface and in the lower atmosphere. Previous research suggested that early 21st-century eruptions might explain up to a third of the recent warming hiatus.

Despite record heat and drought Australia's emissions and coal exports are soaring, says a new report, and both are increasing as a matter of government policy. But a homegrown climate action movement is putting a spanner in the works - and just stopped its first coal train.

Australia's response to climate change is headed completely backwards. If we can stop this new coal mine we set a precedent for the rest of Australia to stand up.

There are consequences of the successful efforts worldwide to save beavers from extinction. Along with the strong increase in their population over the past 100 years, these furry aquatic rodents have built many more ponds, establishing vital aquatic habitat. In doing so, however, they have created conditions for climate changing methane gas to be generated in this shallow standing water, and the gas is subsequently released into the atmosphere. In fact, 200 times more of this greenhouse gas is released from beaver ponds today than was the case around the year 1900, estimates Colin J. Whitfield of the University of Saskatchewan in Canada. He led a study in Springer's journal AMBIO² about the effect that the growth in beaver numbers in Eurasia and the Americas could be having on methane emissions.

The fur trade of the sixteenth to nineteenth centuries nearly led to the extinction of beaver populations worldwide. After trapping was limited and conservation efforts led to the re-introduction of these animals into their natural ranges, the number of North American (Castor canadensis) and Eurasian (Castor fiber) beavers grew. The North American beaver has also been introduced to Eurasia and South America (specifically the archipelago of Tierra del Fuego); establishment of these populations has, in effect, created an anthropogenic greenhouse gas source in these landscapes.

Average chloride concentrations often exceed toxic levels in many northern United States streams due to the use of salt to deice winter pavement, and the frequency of these occurrences nearly doubled in two decades. Chloride levels increased substantially in 84 percent of urban streams analyzed, according to a U.S. Geological Survey study that began as early as 1960 at some sites and ended as late as 2011. Levels were highest during the winter, but increased during all seasons over time at the northern sites, including near Milwaukee, Wisconsin; Chicago, Illinois; Denver, Colorado; and other metropolitan areas. The report was published today in the journal Science of the Total Environment.

Princeton University researchers have uncovered a previously unknown, and possibly substantial, source of the greenhouse gas methane to the Earth's atmosphere. After testing a sample of abandoned oil and natural gas wells in northwestern Pennsylvania, the researchers found that many of the old wells leaked substantial quantities of methane. 

Natural gas power plants produce substantial amounts of gases that lead to global warming. Replacing old coal-fired power plants with new natural gas plants could cause climate damage to increase over the next decades, unless their methane leakage rates are very low and the new power plants are very efficient.

These are the principal findings of new research from Carnegie’s Ken Caldeira and Xiaochun Zhang, and Nathan Myhrvold of Intellectual Ventures that compares the temperature increases caused by different kinds of coal and natural gas power plants. Their work is published in Environmental Research Letters.

The climate warming caused by a single carbon emission takes only about 10 years to reach its maximum effect. This is important because it refutes the common misconception that today’s emissions won’t be felt for decades and that they are a problem for future generations. For the first time, a study conducted by Carnegie's Katharine Ricke and Ken Caldeira has evaluated how long it takes to feel the maximum warming effect caused by a single carbon emission. Their work is published in Environmental Research Letters.

Scientists have presented the most comprehensive evidence to date that climate extremes such as droughts and record temperatures are failing to change people’s minds about global warming. Instead, political orientation is the most influential factor in shaping perceptions about climate change, both in the short-term and long-term, said Sandra Marquart-Pyatt, a Michigan State University sociologist and lead investigator on the study.