Month: March 2016

From The New York Times

By Justin Gillis

For half a century, climate scientists have seen the West Antarctic ice sheet, a remnant of the last ice age, as a sword of Damocles hanging over human civilization.

The great ice sheet, larger than Mexico, is thought to be potentially vulnerable to disintegration from a relatively small amount of global warming, and capable of raising the sea level by 12 feet or more should it break up. But researchers long assumed the worst effects would take hundreds — if not thousands — of years to occur.

Now, new research suggests the disaster scenario could play out much sooner.

Continued high emissions of heat-trapping gases could launch a disintegration of the ice sheet within decades, according to a study published Wednesday, heaving enough water into the ocean to raise the sea level as much as three feet by the end of this century.

With ice melting in other regions, too, the total rise of the sea could reach five or six feet by 2100, the researchers found. That is roughly twice the increase reported as a plausible worst-case scenario by a United Nations panel just three years ago, and so high it would likely provoke a profound crisis within the lifetimes of children being born today.

The situation would grow far worse beyond 2100, the researchers found, with the rise of the sea exceeding a pace of a foot per decade by the middle of the 22nd century. Scientists had documented such rates of increase in the geologic past, when far larger ice sheets were collapsing, but most of them had long assumed it would be impossible to reach rates so extreme with the smaller ice sheets of today.

From The New York TImes

The nations of the world agreed years ago to try to limit global warming to a level they hoped would prove somewhat tolerable. But a group of leading climate scientists warned on Tuesday that permitting a warming of that magnitude would actually be highly dangerous.

The likely consequences would include killer storms stronger than any in modern times, the disintegration of large parts of the polar ice sheets, and a rise of the sea sufficient to begin drowning the world’s coastal cities before the end of this century, the scientists declared.

“We’re in danger of handing young people a situation that’s out of their control,” said James E. Hansen, the retired NASA climate scientist who led the new research. The findings were released Tuesday morning by a European science journal, Atmospheric Chemistry and Physics.

A draft version of the paper had been released last year, and it provoked a roiling debate among climate scientists. The main conclusions have not changed, however, and a replay of that debate seems likely in the coming weeks.

Virtually all climate scientists agree with Dr. Hansen and his co-authors that society is not moving fast enough to reduce emissions of greenhouse gases, posing grave risks. The basic claim of the paper is that by burning fossil fuels at a prodigious pace and pouring heat-trapping gases into the atmosphere, humanity is about to provoke an abrupt climate shift.

That claim has intrigued some experts who say the paper may help explain puzzling episodes in the Earth’s past when geological evidence suggests the climate underwent sudden, drastic shifts.

Yet many of the experts remain unconvinced by some of the specific assertions that were made in the draft paper, and they have not all been persuaded by the final version.

“Some of the claims in this paper are indeed extraordinary,” said Michael E. Mann, a climate scientist at Pennsylvania State University. “They conflict with the mainstream understanding of climate change to the point where the standard of proof is quite high.”

Among Dr. Hansen’s colleagues, some of the discomfiture about the new paper stems from his dual roles as a publishing climate scientist and, in recent years, as a political activist. He has been arrested at rallies, and he has joined with a group of young people who sued the federal government over what they said was its failure to limit global warming.

Dr. Hansen argues that society is in such grave peril that he feels morally compelled to go beyond the normal role played by a scientist and to sound a clear warning. That stance has made him a hero to college students fighting climate change, but some fellow scientists say they believe he has opened himself to the charge that he is skewing his scientific research for political purposes.

The nations of the world agreed to try to limit the warming to 3.6 degrees Fahrenheit, or 2 degrees Celsius, above the preindustrial level, though they have yet to agree on any program remotely ambitious enough to achieve that goal. The Earth has already warmed by about half that amount, with the consequence that virtually all land ice on the planet has started to melt and that the oceans are rising at an accelerating pace.

The paper by Dr. Hansen and 18 co-authors dwells on the last time the Earth warmed naturally, about 120,000 years ago, when the temperature reached a level estimated to have been only slightly higher than today. Much of the polar ice disintegrated then, and scientists have established that the sea level rose 20 to 30 feet.

Climate scientists agree that humanity is about to cause an equal or greater rise in sea level, but they have tended to assume that such a large increase would take centuries. The new paper argues that it could happen far more rapidly, with the worst case being several feet of sea-level rise over the next 50 years, followed by increases so precipitous that they would force humanity to beat a hasty retreat from today’s coastlines.

Read the full article at The New York Times

GLOBAL CHANGE CHEAT SHEET: What is climate change?

[hr]

By Maryn McKenna at National Geographic

Concerns about climate change have caused researchers to warn that rising global temperatures will reduce crop yields and create food insecurity, the inability to get enough calories to survive. Now, scholars from the United Kingdom and the United States have revealed another possible result: an increase in deaths not just from hunger, but from chronic diseases that would be made worse as diets change.

Writing in the medical journal The Lancet, the researchers from Oxford University and the International Food Policy Research Institute in Washington, D.C. predict that by 2050, more than a half-million people will die not just because not enough food will be available, but because the composition of their diets will change, losing nutrient-dense foods such as fruits and vegetables, and meats. But taking international action to reduce climate change, they say, could eliminate up to three-fourths of those deaths.

“The traditional interest in the interaction between climate change and agriculture has really been on calorie availability,” explains Marco Springmann, PhD, the paper’s first author, who is a research fellow at the Oxford Martin Programme on the Future of Food. “That is what most people understand when you say food security. But if you look at the health inpacts of food consumption, then you see that it is the composition of diets that leads to the most health impacts. Most deaths and also most disability-adjusted life years are already attributed to imbalanced diets; that is what kills people in most areas of the world. We wanted to shine a light on those implications.” (For more, see Why Micronutrient Deficiency Is a Macro-Problem.)

The researchers used a long-standing computer model of agricultural productivity, the International Model for Policy Analysis of Agricultural Commodities and Trade, along with other models that predict changes in temperature and precipitation for different climate-change scenarios, to estimate possible effects on the crops and foods that end up on our plates.

Without climate change, they say, existing trends would improve global food access and level out inequality: By 2050, people would have access to an average 289 more calories per day, and to an average 36 grams of fruits and vegetables and four grams more meat daily. But climate change would reverse that trend, taking away available food and especially nutritious food.

Read the full story at National Geographic

[hr]