Climate

Earth’s landmasses are holding onto a lot less water than they used to — and this loss is not just due to melting ice sheets. Terrestrial water storage, which includes water in underground aquifers, lakes, rivers and the tiny pore spaces within soil, declined by trillions of metric tons in the early 21st century, researchers report in the March 28 Science.

This sharp decrease in freshwater stores is driven by rising temperatures on land and in the oceans, which in turn are linked to an increased global incidence of drought. And given the projected warming of the planet, this trend isn’t likely to change any time soon, say geophysicist Ki-Weon Seo of Seoul National University and colleagues. More

Beneath the great, white expanse of the Antarctic Ice Sheet, a mysterious realm of streams and lakes lies out of sight. Much about this hidden water world remains poorly understood. But a new study suggests that if scientists continue to overlook it, they might greatly underestimate global sea level rise.

Factoring this subglacial water into computer simulations could boost projections of sea level rise over the next two centuries by about two meters, researchers report April 7 in Nature Communications. For context, scientists estimate that climate warming has raised sea levels by about 0.2 meters over the last century. More

The Arabian Desert, today the largest expanse of windswept sand dunes on Earth, experienced recurring periods of humidity millions of years ago, researchers report April 9 in Nature. The study may explain how mammals at that time survived the trek across what is now a vast and barren landscape.

The findings come from mineral formations deep inside caves beneath the Arabian Peninsula. These speleothems — stalagmites and stalactites, formed by dripping rainwater — provide evidence that the region underwent repeated humid periods stretching back nearly 8 million years. The scientists used uranium dating to precisely determine the ages of speleothem samples, offering one of the oldest climate records for the region. More

Earth’s average temperature is continuing to tick inexorably upward as the world’s nations stall at reducing their atmosphere-warming emissions. In the face of that grim future, strategies to try to turn down the planet’s thermostat are gaining traction. One strategy in particular — solar geoengineering, which aims to cool the planet by reflecting solar radiation back into space — may be having a moment in the sun.

Depending on whom you ask, it’s potentially highly dangerous, highly promising or highly uncertain. There aren’t any real guidelines. But, with the future of emissions restrictions also highly uncertain, some researchers say solar geoengineering needs to be on the table. More

A new cement-making process could shift production from being a carbon source to a carbon sink, creating a carbon-negative version of the building material, researchers report March 18 in Advanced Sustainable Systems. This process might also be adaptable to producing a variety of carbon-stashing products such as paint, plaster and concrete.

Cement production is a huge contributor to global carbon dioxide emissions, responsible for about 8 percent of total CO2 emissions, making it the fourth-largest emitter in the world. Much of that carbon comes from mining for the raw materials for concrete in mountains, riverbeds and the ocean floor. More

Ecologist Akhil Javad felt the thrill of fieldwork quickly fade when he was faced with the prospect of scaling trees over five times his height. But for some of the trees he was studying in India’s Western Ghat mountains, that was the only way to take their temperature.

So, Javad got climbing. Sensors that he placed on leaves in the upper canopy are providing unprecedented insights into how tropical forests are weathering global warming. The findings suggest that the trees may be in better shape than scientists thought, he and colleagues report in the February Global Change Biology.

Ecologist Akhil Javad (shown) and colleagues found that tropical trees’ ability to photosynthesize may be more resilient to rising global temperatures than previously thought.Akhil Javad

In the summer, which lasts from March through June in the region, daily high temperatures in the mountains can cross 37° Celsius and are projected to rise by about 4 degrees Celsius in the next 60 years. That could be a problem for trees, since leaves can get much hotter than the surrounding air.

As the temperature of a leaf rises, its ability to harness sunlight to make sugar and oxygen becomes less efficient. On average, when leaves surpass 46.7° C, their photosynthetic machinery shuts down, lab studies have shown. When that happens, trees don’t get the energy they need. Many trees in the tropics are already experiencing temperatures beyond that average limit. More

Cloud forests are strange and ghostly places — akin to coral reefs hidden high on tropical mountains. Stunted trees loom in the mist, gnarled trunks and branches crusted in moss, lichens, orchids, ferns, bromeliads and even climbing cactus vines. Arboreal frogs and salamanders spawn in fog-fed bromeliad pools, and spider monkeys pause to sip drinks.

But these enigmatic forests are being squeezed by warming and deforestation.

Hundreds of tree and plant species that make up Mesoamerican cloud forests are being chased uphill by rising temperatures, at an average rate of 1.8 to 2.7 meters per year, researchers report in the March 7 Science. From 1979 to 2010, these forests retreated 84 meters uphill. At the same time, cattle grazing and deforestation higher on the mountains is pushing the forests downward 6.3 meters per year — squishing these ecosystems into ever narrower bands of territory. More

Rural communities in arid regions have harvested tiny droplets of fog for years as a source of fresh drinking water. Now, researchers say that fog water can be a practical supplement to stave off water stress for larger desert cities.

A yearlong assessment of the potential volume of harvested fog water near a city in northern Chile’s Atacama Desert found that it’s possible to collect as much as 5 liters per square meter each day, scientists report Feb. 20 in Frontiers in Environmental Science. More