A new study published in the journal Nature is drawing attention to the effect of warming water on the world's largest ice mass, Totten Glacier in East Antarctica. Melting of the glacier, which has an ice catchment area bigger than California, could lift oceans at least two meters (6.56 feet). According to researchers who mapped the shape of the ice sheet as well as the thickness of rocks and sediments beneath it to examine the historical characteristic of erosion of Totten's advances and retreats, unabated climate change could cause the glacier to enter an irreversible and rapid retreat within the next century.
"While traditional models haven't suggested this glacier can collapse, more recent models have," said study co-author Alan Aitken of the University of Western Australia. "We confirm that collapse has happened in the past, and is likely to happen again if we pass a tipping point, which would occur if we had between 3 and 6 degrees of warming above present."
Aitken said that the Totten Glacier could ultimately account for nearly 15 percent of Antarctica's total contribution to sea-level rise.
Satellite measurements from a previous study show that the glacier is thinning at a rate of about half a meter per year--a thinning that is most likely due to warm ocean water moving under and melting the glacier's floating front. A retreat of another 100-150 kilometers (62-93 miles) may cause that front to sit on an unstable bed, triggering the Antarctic ice to shrink by 300 kilometers (186 miles).
"The evidence coming together is painting a picture of East Antarctica being much more vulnerable to a warming environment than we thought," said study co-author Martin Siegert of Imperial College London. "This is something we should worry about."
Index Suggests Increase, Acceleration of Carbon Dioxide Levels
The latest Annual Greenhouse Gas Index released by the National Oceanic and Atmospheric Administration (NOAA) shows that carbon dioxide levels in the atmosphere are not just rising but accelerating and that the level of methane, another potent greenhouse gas, rose sharply last year. The index, which compares global greenhouse gas emissions to pre-industrial revolution levels, suggests that warming capacity has increased 37 percent since 1990.
"We're dialing up Earth's thermostat in a way that will lock more heat into the ocean and atmosphere for thousands of years," said Jim Butler, director of NOAA's Global Monitoring Division.
According to the latest index, the global average carbon dioxide concentration for 2015 reached 399 parts per million (ppm), far above the 278 ppm just prior to the Industrial Revolution and a record increase of 3 ppm compared to the year previous.
Following on the heels of that news, NOAA and the National Aeronautics and Space Administration (NASA) reported that last month was the hottest April on record. According to the World Meteorological Organization, April marked the 12th consecutive month of global temperature records, the longest such streak since global record-taking began in 1880.
EPA Proposes Rise in Biofuel Targets
The U.S. Environmental Protection Agency (EPA) proposed an increase in the amount of corn-based ethanol and biofuels that must be blended into the nation's fuel supply in 2017. The new targets call for 18.8 billion gallons of biofuels, up 4 percent from 2016 but far less than the 24 billion-gallon biofuel target that lawmakers established in a 2007 statute.
The reason for the lower-than-mandated target, EPA says, is lack of infrastructure to blend ethanol into gasoline as well as the cellulosic biofuel industry's slow development and marketplace constraints, such as lower gasoline and diesel demand than Congress envisioned in 2007.
Nevertheless, acting assistant administrator for EPA's Office of Air and Radiation Janet McCabe said that the Obama administration is "committed to keeping the [biofuels mandate] on track, spurring continued growth in biofuel production and use, and achieving the climate and energy independence benefits that Congress envisioned from this program."
Under the renewable fuel standard (RFS), the proposed rule sets the 2017 renewable volume obligations (RVOs) for cellulosic biofuel at 312 million gallons and the advanced biofuel RVO at 4 billion, and it sets the 2018 RVO for biomass-based diesel at 2.1 billion gallons.
The proposed volumes would represent growth over historic levels. Between 2016 and 2017, total renewable fuel volumes are expected to increase by nearly 700 million gallons and advanced renewable fuels, which require 50 percent reductions in life-cycle carbon emission, by nearly 400 million gallons.
The proposed volumes are subject to public comment through July 11, and a public hearing is scheduled June 9. The EPA has until Nov. 30 to finalize the 2017 quotas.
The Climate Post offers a rundown of the week in climate and energy news. It is produced each Thursday by Duke University's Nicholas Institute for Environmental Policy Solutions.