Climate

climate

Comment: How long have humans been altering Earth's climate?

The early anthropogenic hypothesis holds that greenhouse gas emissions from agriculture, as early as 7,000 years ago, kept the Holocene climate warmer than it otherwise would have been.

08 Apr 2016

Crippling heat stress projected by midcentury in densely populated regions

Extreme heat is the world’s top weather-related killer. Exposure to extreme heat caused more than 7,800 fatalities in the U.S. from 1999 to 2009, according to a 2013 report by the U.S. Centers for Disease Control and Prevention. And a single heat wave last summer killed at least 2,300 people in India, according to NOAA.

05 Apr 2016

North Sea uplift caused Jurassic cooling event

The climate of the Jurassic, long envisioned as ubiquitously warm from the equator to the poles, was actually more dynamic, sometimes cooling dramatically, according to a new study. The research joined isotopic and sedimentological data to suggest that an abrupt cooling event occurred in the midlatitudes early in the Middle Jurassic as a result of changing ocean currents associated with a feature known as the North Sea Dome.

31 Mar 2016

Atmosphere, more than ocean, might drive Atlantic climate variation

Atmospheric, not oceanic, circulation may be the main driver of climate variations over the North Atlantic Ocean, potentially complicating future hurricane and drought predictions, according to the authors of a new study.
 
01 Feb 2016

Lake sediments suggest mild volcanic winter after massive Toba eruption

Roughly 74,000 years ago, the largest volcanic eruption of at least the last 2.5 million years — and possibly the last 27 million years — spewed as much as 5,000 cubic kilometers of magma and ash, the latter of which spread far and wide from the source. This catastrophic eruption of the Toba supervolcano on the Indonesian island of Sumatra has long been suggested as a trigger for a precipitous period of global cooling known as a “volcanic winter” that in turn might have driven early humans to the brink of extinction. In a new study, researchers dispute these notions, concluding from an analysis of climate-sensitive microfossils preserved in lake sediments in East Africa — the ancestral home of early humans — that the region experienced little or no cooling following the massive eruption. 
 
10 Jan 2016

No laughing matter: Ocean nitrous oxide emissions greater than thought

Nitrous oxide is a potent greenhouse gas and, since the banning of chlorofluorocarbons in 1987, it has become the main driver of ozone loss from the stratosphere. Most atmospheric nitrous oxide is emitted from agricultural land and soils, but roughly a third is thought to come from the ocean. However, marine sources and sinks of the gas are not well understood. 
 
27 Nov 2015

Solar flare calibration reveals past patterns of volcanism and cooling

When Mount Pinatubo erupted in the Philippines in 1991, it sent a cloud of ash and sulfuric acid into the atmosphere that blocked incoming solar radiation and caused global temperatures to drop 0.5 degrees Celsius for three years. Quantifying such effects of prehistoric volcanic eruptions on climate, however, has long proved difficult due to inconsistencies in the proxies used to reconstruct atmospheric and temperature fluctuations. In a new study, scientists have used markers left by an unusual solar flare event to align ice-core and tree-ring records, enabling a more accurate accounting of the effects of volcanic eruptions in recent millennia.
 
25 Nov 2015

Deforestation hangs climate out to dry

Across the tropics, vast swaths of forest have been cleared to make room for crops and livestock. Beyond releasing vast stores of carbon trapped in soil and biomass, tropical deforestation has the potential to alter hydrological cycles in ways that could affect temperature and precipitation patterns around the planet, according to a new report in Nature Climate Change.
 
13 Jul 2015

Shrinking snowpack projected in western U.S. as rain-snow boundary climbs higher

Gauging the impacts of climate change on future precipitation is challenging, especially in the western U.S., a region with highly variable temperatures, precipitation patterns and terrain. But understanding such impacts in the West — and, in particular, how much precipitation will fall as snow versus rain in the future — is important given the region’s dependence on wintertime snowfall as a freshwater resource. Now, a new study forecasts a broad shift from snow to rain for much of the West — a projection that will require attention from land and water resource managers planning for the future.

24 Apr 2015

Wedge approach proposed to lower water stress

Roughly 30 percent of the global population — or about 2.2 billion people — lives in water-stressed parts of the world, where high freshwater withdrawals endanger ecosystems, agriculture and drinking-water supplies. If current population and water usage trends persist, this fraction could rise to about one-half by the century’s end. In a recent study, researchers — taking a page from the climate-change mitigation literature — have proposed a “wedge” approach to address global water stress, laying out how various tactics could ease the growing problem.

22 Apr 2015

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