Global warming

Greenhouse Gases Hit Record High in 2011

Yahoo,

21 November, 2012

The concentration of greenhouse gases in the atmosphere hit a record high in 2011, the United Nations' World Meteorological Organization (WMO) reported Tuesday (Nov. 20).

Chief among these heat-trapping gases is carbon dioxide (CO2), the biggest culprit behind global warming. Carbon dioxide levels reached about 390.9 parts per million last year, which is 140 percent of the pre-industrial level of 280 parts per million and nearly 2 parts per million higher than the 2010 carbon dioxide level, according to the WMO report.

The international body estimates that about 413 billion tons (375 billion metric tons) of carbon have been released into the atmosphere since 1750, primarily from fossil fuel combustion. About half of this atmospheric carbon dioxide remains in the atmosphere, and much of it will linger for centuries, causing the planet to warm further, WMO Secretary-General Michel Jarraud warned.

Historically, the Earth's oceans and forests have helped balance the atmosphere's carbon equation by sucking up large amounts of the greenhouse gas. But Jarraud said natural carbon sinks might not be able to mitigate the problem as effectively in the future.

"Until now, carbon sinks have absorbed nearly half of the carbon dioxide humans emitted in the atmosphere, but this will not necessarily continue in the future," Jarraud said in a statement. "We have already seen that the oceans are becoming more acidic as a result of the carbon dioxide uptake, with potential repercussions for the underwater food chain and coral reefs. There are many additional interactions between greenhouse gases, Earth's biosphere and oceans, and we need to boost our monitoring capability and scientific knowledge in order to better understand these."

Greenhouse cases trap heat within the Earth's atmosphere and create a warming effect on the climate known as radiative forcing. From 1990 to 2011, radiative forcing by greenhouse gases shot up 30 percent, with carbon dioxide blamed for about 80 percent of this increase, according to the National Oceanic and Atmospheric Administration (NOAA).

Besides carbon dioxide, methane (CH4) and nitrous oxide (N2O) are also implicated in the greenhouse effect. In 2011, the level of methane in the atmosphere reached a new high of about 1,813 parts per billion, or 259 percent of the pre-industrial level, due to increased emissions from human activities, such as cattle breeding, rice farming and fossil fuel use. The atmospheric concentration of nitrous oxide, meanwhile, hit about 324.2 parts per billion last year, or 120 percent of the pre-industrial level and 1 part per billion above the 2010 level.

Antarctic Glacier Primed to Form Iceberg

Yahoo,

21 November, 2012

With its protective sea ice barrier melted away, Antarctica's Pine Island Glacier grows ever closer to finally dropping its New York City-sized iceberg into the ocean, according to NASA.

The giant crack in Pine Island Glacier was first spotted by scientists with NASA's IceBridge mission in 2011 as they surveyed the massive ice shelf in their specially equipped DC-8 plane. A second rift also formed and joined the northern side of the crack in May 2012, as captured on satellite images that track the incipient iceberg.

When IceBridge scientists returned this month, they discovered the original rift now has only about half a mile (less than 1 kilometer) to go before the 300-square-mile (770 square kilometers) berg forms.

The calving front of Pine Island Glacier is also free of sea ice, as shown in an Oct. 26 image from the Landsat 7 satellite. Warm spring temperatures are melting the sea ice that rings the continent during the winter, and winds help push the remaining ice out to sea. Sea ice acts as a buttress against waves, protecting the front of the glacier from calving, Kelly Brunt, a cryosphere scientist at NASA Goddard Space Flight Center, said in a NASA video about the Pine Island Glacier rift.

"So the fact that there's no sea ice in front of the Pine Island Glacier right now implies that it might be in a state that's sort of primed to calve," she said.

Pine Island Glacier is one of the West Antarctic Ice Sheet's fastest-changing ice shelves, simultaneously thinning and flowing faster out to sea. Melting ice from the region represents the largest input to sea level rise from an Antarctic source, Brunt said. Once the glacier calves, the calving front will be further upstream from any calving front seen in the last 40 years, she added.