A study published in Nature finds that Antarctic ice-sheet collapse driven by greenhouse gas emissions could double the sea-level rise predicted for this century -- from 3.2 feet according to a three-year-old United Nations estimate to upward of 6.5 feet by 2100. The research builds on the work of other recent studies pointing to an irreversible melting of the West Antarctic Ice Sheet as a result of human-caused climate change, but it suggests that sea-level rise could shift into high gear, becoming an existential problem for low-lying coastal cities within the lifespan of current generations of people absent rapid emissions cuts to contain warming to within 2 degrees Celsius above pre-industrial levels.
The study findings are based on new computer simulations showing that warming of the atmosphere and the oceans makes the ice sheet vulnerable from above and below. By the 2050s, according to the simulations, the ice sheet would begin disintegrating, and parts of the higher, colder ice sheet of the East Antarctica would also eventually fall apart.
The climate model developed by the study authors accounts for ice loss through complex processes, including "hydro fracturing," a process whereby meltwater on ice shelves causes huge chunks of ice to fall into the water. By reflecting these processes, the researchers were able to simulate past geological periods in which sea levels were higher than today but carbon dioxide levels were about the same or even much lower. They projected sea-level rise using versions of their model that best simulated these periods--the first model to do so.
Why is reconstruction of past rises in sea level important? High sea levels during warm intervals, such as the Pliocene and Eemian eras, imply that the Antarctic Ice Sheet is highly sensitive to climate warming.
"In the past, when global average temperatures were only slightly warmer than today, sea levels were much higher," said study co-author Rob DeConto, a geoscientist at the University of Massachusetts Amherst. "At the high end, the worst-case scenarios, with sort of business as usual greenhouse gas emissions ... we will literally be remapping coastlines. North America is kind of a bull's eye for impacts of sea level rise if it's the west Antarctic part of Antarctica that loses the ice first. That's the place that we're worried about losing ice first."
Study: Health Impacts of Climate Change Significant
The public health impacts of climate change on people in the United States will be significant and wide ranging, according to a study by the U.S. Global Change Research Program. The study reflects data and analysis from eight agencies, led by the U.S. Environmental Protection Agency (EPA), the Department of Health and Human Services, and the National Oceanic and Atmospheric Administration, which said that "Nearly all of the health threats, from increases in our exposure to excessive heat to more frequent, severe or longer-lasting extreme weather events to degraded air quality to diseases transmitted through food, water, and vectors (such as ticks and mosquitoes) -- even stresses to our mental health -- are expected to worsen."
Without rapid efforts to combat climate change, extreme heat alone will cause more than 11,000 additional deaths in the summer of 2030, the study suggests. Other risks include worsening allergy and asthma conditions and increased exposure of food to certain pathogens and toxins. But climate change will not just exacerbate existing risks -- it will give rise to unprecedented health problems such as the spread of Lyme disease in new locations.
"Every American is vulnerable to the health impacts associated with climate change," said White House Science Adviser John Holdren, adding that "Some are more vulnerable than others."
These groups include pregnant women, children, the elderly, low-income people, communities of color and those with disabilities or pre-existing medical conditions.
Release of the findings coincided with the Obama administration's announcement of several new initiatives to address those impacts, such as expanding the scope of a presidential task force on childhood risks to include climate change (subscription). Other actions include creating climate change and health curricula for schools and establishing a Climate-Ready Tribes and Territories Initiative, which will provide funding for prevention of climate-change-related health problems.
Paris Deal: Largest Polluters Agree to Sign
"Our cooperation and our joint statements were critical in arriving at the Paris agreement, and our two countries have agreed that we will not only sign the agreement on the first day possible, but we're committing to formally join it as soon as possible this year," said President Obama. "And we urge other countries to do the same."
Brian Deese, senior adviser to President Obama, said swift approval of the agreement would keep emissions reductions efforts on track. Noting congressional action last year to extend tax credits for wind and solar energy and asserting firm legal ground for the Clean Power Plan, Deese said that the United States has both "the capacity and the tools" to meet its international commitments.
United Nations Secretary-General Ban Ki-moon has said that he expects at least 120 countries will sign the agreement at the April 22 ceremony at the U.N.'s New York headquarters. To enter into force, that agreement needs at least 55 countries representing at least 55 percent of global emissions to formally accede to it. So far, three Pacific island nations have ratified the deal.
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.