Two-and-a-half billion people worldwide have no access to safe, durable sanitation systems. Brian Arbogast, director of the water, sanitation and hygiene programme at the Bill & Melinda Gates Foundation, tells SciDev.Net how innovative toilet technologies and business models could help fix this — and help communities cope with the devastation of climate change.

How does climate change impact sanitation?

With sea levels rising, you have flooding that causes huge health problems. As latrines and septic tanks get flooded and waste goes into the streets and streams, it can carry a lot of disease, including cholera, dysentery and typhoid.

The problem is that the world has only one gold standard for sanitation, which is having flush toilets connected to sewer lines, that are further connected to big and expensive wastewater treatment plants. Growing cities that already have water shortages may not have enough water for everybody to bathe and cook, let alone to flush toilets. So, are these cities going to follow the same path we have taken for the last century in developed cities?

A KPMG study shows that the cost of solar power in India, revealed by public auctions, is barely half a cent above that of cheap local coal , writes Chris Goodall, with generators bids falling well below 5p (UK) / 7¢ (US) per kWh. The idea put about at COP21 that India and other poor but sunny countries need coal to develop their economies is fast running out of steam.

When the accountants have fully loaded the network and other costs PV ends up as very slightly cheaper than using lndian-mined coal. And, of course, this advantage will grow as solar gets cheaper.

Commentators eager to arrest the move towards renewable energy are facing increasing difficulties finding arguments for the continued use of fossil fuel.

Last June, Pope Francis released his much-anticipated encyclical on the environment, Laudato Si’, which received tremendous praise from diverse quarters. The same day, Coral Davenport, writing in the New York Times, noted that the papal encyclical "is as much an indictment of the global economic order as it is an argument for the world to confront climate change." Ms. Davenport quoted me (accurately) as saying that elements of the encyclical were unfortunately "out of step with the thinking and the work of informed policy analysts around the world." In this column, I will elaborate.

First of all, the Pope is to be commended for taking global climate change seriously, and for drawing more world attention to the issue. There is much about the encyclical that is commendable, but where it drifts into matters of public policy, I fear that it is — unfortunately — not helpful.

The long encyclical ignores the causes of global climate change: it is an externality, an unintended negative consequence of otherwise meritorious activity by producers producing the goods and services people want, and consumers using those goods and services. That is why the problem exists in the first place. There may well be ethical dimensions of the problem, but it is much more than a simple consequence of some immoral actions by corrupt capitalists. The document also ignores the global commons nature of the problem, which is why international cooperation is necessary.

As 2015 comes to a close, Mongabay is looking back at the year that was. This year saw President Obama reject the Keystone pipeline as historic droughts and a vicious wildfire season wracked the western US and Canada. The world committed to climate action in Paris as Southeast Asia was choking on the worst Indonesian haze in years, Shell aborted its plans to drill in the Arctic for the “foreseeable” future, and ExxonMobil is being investigated for lying to the public about climate risks. Here, in no certain order, are the top 15 environmental stories of 2015.

The current strong El Niño brewing in the Pacific Ocean shows no signs of waning, as seen in the latest satellite image from the U.S./European Ocean Surface Topography Mission (OSTM)/Jason-2 mission. 

El Niño 2015 has already created weather chaos around the world. Over the next few months, forecasters expect the United States to feel its impacts as well. 

The latest Jason-2 image bears a striking resemblance to one from December 1997, by Jason-2's predecessor, the NASA/Centre National d'Etudes Spatiales (CNES) Topex/Poseidon mission, during the last large El Niño event. Both reflect the classic pattern of a fully developed El Niño.

California's forests are home to the planet's oldest, tallest and most-massive trees. New research from Carnegie's Greg Asner and his team reveals that up to 58 million large trees in California experienced severe canopy water loss between 2011 and today due to the state's historic drought. Their results are published in Proceedings of the National Academy of Sciences.

In addition to the persistently low rainfall, high temperatures and outbreaks of the destructive bark beetle increased forest mortality risk. But gaining a large-scale understanding a forest's responses to the drought, as well as to ongoing changes in climate, required more than just a picture of trees that have already died. 

LSU paleoclimatologist Kristine DeLong contributed to an international research breakthrough that sheds new light on how the tilt of the Earth affects the world's heaviest rainbelt. DeLong analyzed data from the past 282,000 years that shows, for the first time, a connection between the Earth's tilt called obliquity that shifts every 41,000 years, and the movement of a low pressure band of clouds that is the Earth's largest source of heat and moisture -- the Intertropical Convergence Zone, or ITCZ.

"I took the data and put it through a mathematical prism so I could look at the patterns and that's where we see the obliquity cycle, that 41,000-year cycle. From that, we can go in and look at how it compares to other records," said DeLong, who is an associate professor in the LSU Department Geography & Anthropology.

The climatic conditions needed by 285 species of land birds in the United States have moved rapidly between 1950 and 2011 as a result of climate change, according to a recent paper published in Global Change Biology.

Lush greenery rich in Douglas fir and hemlock trees covers the Triangle Lake valley of the Oregon Coast Range. Today, however, geologists across the country are more focused on sediment samples dating back 50,000 years that were dug up by University of Oregon scientists.

The sediment indicates that the mountainous region, which was not covered in glaciers during the last ice age, was a frost-covered grassy landscape that endured erosion rates at least 2.5 higher than today's, an eight-member team reports in a paper in the journal Science Advances.

All over the planet, every day, oceans send plumes of sea spray into the atmosphere. Beyond the poetry of crashing ocean waves, this salt- and carbon-rich spray also has a dramatic effect on cloud formation and duration.

In a new paper published this week in the journal Proceedings of the National Academy of Sciences, Colorado State University atmospheric scientist Paul DeMott finds that sea spray is a unique, underappreciated source of what are called ice nucleating particles. These microscopic bits make their way into clouds and initiate the formation of ice, affecting the clouds' composition.