Earth & Environment

Clouds intensify soot’s Arctic heating
Reining in soot production could dramatically slow Arctic warming, Mark Jacobson of Stanford University reported August 31 in Denver at the American Chemical Society’s national meeting. Soot’s presence in water droplets heats clouds much more than it does the black carbon particles between cloud droplets, new computer analyses show — which Jacobson says “helps to explain the burning off of clouds in polluted regions.” Once clouds disappear, more sunlight reaches the surface to melt sea ice and warm Arctic waters. But curbing all soot that now wafts into the Arctic could within 15 years eliminate 15 to 20 percent of the total warming contribution to the region, which could reduce the net temperature rise by 50 percent, his computer projections indicate. —Janet Raloff

Bedrock can help the climate
Researchers from the University of California, Davis offer data that could overturn the conventional wisdom about where new nitrogen in land-based ecosystems comes from. It’s supposed to come from the atmosphere. But forests and local soils underlain with nitrogen-rich sedimentary rock contain 50 percent more nitrogen, a fertilizer, than do those atop nitrogen-poor rock, the scientists report in the Sept. 1 Nature. These researchers fingerprinted the bonus nitrogen to the weathering of bedrock below. Forests and soils over nitrogen-releasing rock also contained substantially more carbon than in nitrogen-poor areas, the scientists found, demonstrating that bedrock can dramatically boost the carbon-sequestering climate benefits of some forests. —Janet Raloff

Clean-smelling clothes dirty the air
Fragrance chemicals in detergents and dryer sheets can release toxic chemicals — none listed on product labels — especially into the air vented from a dryer. Anne Steinemann of the University of Washington in Seattle and her colleagues did laundry using no products, scented detergents, and detergents plus dryer sheets. The researchers report online August 19 in Air Quality, Atmosphere & Health finding substantial quantities of airborne organics including seven chemicals considered hazardous, two of which are potential carcinogens: acetaldehyde and benzene. Acetaldehyde measurements, if extrapolated to all users of the top five detergent brands throughout the county, could equal 6 percent of that toxic chemical’s releases from area cars if all the detergents produce the same levels the test detergent did, the researchers calculate. —Janet Raloff

Triggering earthquakes
Injecting carbon dioxide deep underground to keep it from entering the atmosphere can trigger earthquakes on local faults, a new study suggests. Scientists from the Lawrence Berkeley National Laboratory in California and the C´te d’Azur Observatory in France simulated what would happen if carbon dioxide entered an underground reservoir with a common kind of fault nearby. Depending on how and when the injection was done, an earthquake of up to magnitude 4.5 could occur, the team reports in a paper to appear in Geophysical Research Letters. Oil exploration, geothermal and other companies want to understand the conditions under which injections cause earthquakes. —Alexandra Witze

Supercontinent of the future
Continental drift, combined with heat from deep within Earth, could push North America, Eurasia, Australia and Africa together to form a new supercontinent in the Northern Hemisphere within the next 250 million years. Although scientists know about past supercontinents such as Pangaea, speculating about future landmasses has been something of a guessing game. Now, scientists in Japan have modeled heat welling up from Earth’s mantle and suggested exactly how that could drive today’s continents together. Antarctica and South America never join the future supercontinent, the team reports online August 17 in Terra Nova. —Alexandra Witze