Nature: In contrast, West Antarctic temperature changes in recent decades remain uncertain. West Antarctica has probably warmed since the 1950s, but there is disagreement regarding the magnitude, seasonality and spatial extent of this warming.

This is primarily because long-term near-surface temperature observations are restricted to Byrd Station in central West Antarctica, a data set with substantial gaps. Here, we present a complete temperature record for Byrd Station, in which observations have been corrected, and gaps have been filled using global reanalysis data and spatial interpolation.

The record reveals a linear increase in annual temperature between 1958 and 2010 by 2.4±1.2 °C, establishing central West Antarctica as one of the fastest-warming regions globally. We confirm previous reports of West Antarctic warming, in annual average and in austral spring and winter, but find substantially larger temperature increases.

In contrast to previous studies, we report statistically significant warming during austral summer, particularly in December–January, the peak of the melting season. A continued rise in summer temperatures could lead to more frequent and extensive episodes of surface melting of the West Antarctic Ice Sheet. These results argue for a robust long-term meteorological observation network in the region. 

SEA LEVEL RISE (SLR)

Scientific American: If the number reaches 560 ppm, a doubling of preindustrial values, sea level globally could rise 25 meters, according to Eelco Rohling, professor of ocean and climate change at University of Southampton in the U.K., who presented data at the AGU meeting with Hansen. Many large cities worldwide lie at that elevation or lower. The two scientists agreed that if nations continue to emit CO2 at current rates, the world could reach 560 ppm by 2100.

The paleoclimate record also shows that 560 ppm would be enough to melt all the ice in the Arctic, and later the Antarctic. Rohling said that once the Antarctic melts, sea levels would rise by 60 to 70 meters. “If governments keep going the way they are going,” Hansen added, “the planet will reach an ice-free state.”

NON LINEAR PROBLEMS FROM ALBEDO FLIP EFFECT

The amplifying feedback mechanism of polar ice melt is the so-called albedo-flip effect, where loss of reflection by melted ice is compounded by infrared absorption by open water, a process currently taking place in the Arctic Sea, as reported by Hansen et al.: “… amplifying feedbacks make ice sheet disintegration necessarily highly non-linear.

In a non-linear problem, the most relevant number for projecting sea level rise is the doubling time for the rate of mass loss. Hansen (2007) suggested that a 10-year doubling time was plausible, pointing out that such a doubling time from a base of 1 mm per year ice sheet contribution to sea level in the decade 2005-2015 would lead to a cumulative 5 m sea level rise by 2095.” http://www.countercurrents.org/glikson050411.pdf

BBC Interview with James Lovelock: “Just the melting of all the floating ice in the arctic ocean, will add as much heat to the earth, as all the Co-2 we put in the atmosphere to date.” Prof. James Lovelock

Estimating the Global Radiative Impact of the Sea-Ice-Albedo Feedback in the Arctic a more realistic ice-free-summer scenario (no ice for one month, decreased ice at all other times of the year) results in a forcing of about 0.3 W m−2, similar to present-day anthropogenic forcing caused by halocarbons.

Related

• RealClimate: The heat is on in West Antarctica
• Scientists Report Faster Warming in Antarctica
• West Antarctic Ice Sheet warming twice earlier estimate
• Nature: Antarctica Is Melting From Below, Which ‘May Already Have Triggered A Period of Unstable Glacier Retreat’