Earth/Environment

Hard rain falling
Human-produced greenhouse gases could be to blame for the increase in heavy rains seen across two-thirds of Northern Hemisphere lands in recent decades. Climate simulations that include the gases’ effects more closely match observations of extreme precipitation between 1951 and 1999 that leave them out, scientists have found. A team led by Seung-Ki Min of Environment Canada in Toronto reports the finding in the Feb. 17 Nature. —Alexandra Witze

Grow those pores
Plants must adapt as atmospheric carbon dioxide levels rise; a new study suggests how they might have done so before. Researchers led by Emmy Lammertsma of Utrecht University in the Netherlands studied leaf fragments and herbarium specimens of nine Florida plant species. Over the past 150 years, all responded to higher carbon dioxide by reducing the amount of water lost through leaf pores, generally by shifting to fewer and larger pores. Modern plants do this when exposed to carbon dioxide, but this work, to appear in the Proceedings of the National Academy of Sciences, is the first to show how plants have adapted over the long term. —Alexandra Witze

Volcano off the hook
One of the worst historic eruptions may not have been the cause of a winter so cold that the Mississippi River froze at New Orleans. In June 1783, the Icelandic volcano Laki began erupting, spewing sun-blocking particles that scientists blamed for a harsh winter that year. But a team led by Rosanne D’Arrigo, of the Lamont-Doherty Earth Observatory in Palisades, N.Y., fingers a different phenomenon. Tree rings reveal that two climate patterns — the North Atlantic Oscillation and the El Ni±o Southern Oscillation — were at play in 1783–84, just as in the 2009–2010 winter that brought bitter cold to Europe and North America. The study will appear in Geophysical Research Letters. —Alexandra Witze

No tipping point for sea ice
On average, more of the Arctic Ocean’s frozen sea-ice cover melts away with each passing summer. Some scientists have worried the ice might reach a catastrophic “tipping point,” in which the relatively dark open ocean absorbs so much heat one summer that the ice cannot refreeze that winter. New simulations from the Max Planck Institute for Meteorology in Hamburg, Germany, suggest this won’t happen. Instead, the scientists report in Geophysical Research Letters, sea ice should recover from an ice-free state every July, even as late as 2060. The long-term decline continues, however. —Alexandra Witze

Two pesticides linked with Parkinson’s
Farmers and others who for years regularly applied either of two pesticides face a greatly elevated risk of Parkinson’s disease, an international team of researchers finds. Previous animal data had shown these pesticides — the broad-spectrum insecticide rotenone and the herbicide paraquat — cause brain abnormalities similar to the human disease. The pesticides work by damaging the particular cells that underlie Parkinson’s, but until now human studies have had difficulty linking those chemicals to Parkinson’s disease, a devastating and incurable neurological disorder characterized by problems controlling muscle movements. The study was published online January 26 in Environmental Health Perspectives. —Janet Raloff