Glaciers naturally flow but thinning is alarming
From an Article by Brett Wilkins, The Guardian UK, 4/28/21
Researchers warn of the need for urgent climate action as a study published Wednesday revealed that the world’s mountain glaciers are melting at an unprecedented pace, with glacial thinning rates outside Antarctica and Greenland doubling this century. “A doubling of the thinning rates in 20 years for glaciers outside Greenland and Antarctica tells us we need to change the way we live,” the study’s lead author said.
For the first time ever, researchers analyzed three-dimensional satellite measurements of the world’s approximately 220,000 glaciers, except for those on the Antarctic and Greenland ice sheets. The results, published in Nature, show that the planet’s glaciers lost 267 billion tonnes of ice each year from 2000 to 2019, the equivalent of 21% of sea level rise. The study’s authors said that is enough water to flood all of Switzerland under six feet of water every year.
The paper notes that “thinning rates of glaciers outside ice sheet peripheries doubled over the past two decades.” The study’s authors found that, on average, glaciers lost 4% of their volume during the two decades studied. They determined that the fastest-melting glaciers are in Alaska and the Alps. Alaska alone accounted for one-quarter of the world’s glacial melt, with the Columbia Glacier in Prince William Sound retreating by around 115 feet annually.
“A doubling of the thinning rates in 20 years for glaciers outside Greenland and Antarctica tells us we need to change the way we live,” Romain Hugonnet of the University of Toulouse in France, the study’s lead author, told The Guardian.
“It can be difficult to get the public to understand why glaciers are important because they seem so remote,” he added, “but they affect many things in the global water cycle including regional hydrology, and by changing too rapidly, can lead to the alteration or collapse of downstream ecosystems.”
Hugonnet said he was particularly concerned about glacier loss in high Asian mountain ranges, which are the sources of rivers upon which more than 1.5 billion people rely for water. “India and China are depleting underground sources and relying on river water, which substantially originates from glaciers during times of drought,” he told The Guardian.
“This will be fine for a few decades because glaciers will keep melting and provide more river runoff, which acts as a buffer to protect populations from water stress,” said Hugonnet. “But after these decades, the situation could go downhill. If we do not plan ahead, there could be a crisis for water and food, affecting the most vulnerable.”
Mark Serreze, director of the Colorado-based National Snow and Ice Data Center, told the Associated Press that sea level rise—which is exacerbated by glacier melt—”is going to be a bigger and bigger problem as we move through the 21st century.” Serreze did not contribute to the new paper.
The new study’s authors implore policymakers to devise adaptive measures for the estimated billion people threatened with water and food insecurity before 2050. “We need to act now,” stressed Hugonnet.
Samuel Nussbaumer of the World Glacier Monitoring Service, which did not take part in the study, said that “the new paper will have a big impact.”
“This is the most global, complete study. The gain in new information is huge,” Nussbaumer told The Guardian. “The rapid change we see now is really interesting from a scientific point of view. Never before in history has change happened this fast.”
The new study follows research published last week showing shifts in the Earth’s rotational axis—which have accelerated over the past three decades—are caused by melting glaciers.
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“If we do not plan ahead, there could be a crisis for water and food, affecting the most vulnerable.” —Romain Hugonnet, University of Toulouse
“Never before in history has change happened this fast.” —Samuel Nussbaumer, World Glacier Monitoring Service
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See also: Global Ice Loss on Pace to Drive Worst-Case Sea Level Rise, Bob Berwyn, Inside Climate News, January 25, 2021
A new study combines ice melt data from all sources to reaffirm one of the most serious climate change threats.
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Dissecting ‘Unsettled,’ a Skeptical Physicist’s Book About Climate Science — Five statements author Steven Koonin makes that do not comport with the evidence.
From an Article by Marianne Lavelle, Inside Climate News, May 4, 2021
Physicist Steven Koonin, a former BP chief scientist and Obama administration energy official, seeks to downplay climate change risk in his new book, “Unsettled: What Climate Science Tells Us, What it Doesn’t and Why it Matters.”
His critics say he often draws general conclusions from specific slices of data or uncertainties (sometimes signaled by key words or phrases.) As a result, they say, his statements are frequently misleading, and often leave the reader with the incorrect impression climate scientists are hiding the truth.
“Identifying, quantifying, and reducing uncertainties in models and observations is an integral part of climate science,” said atmospheric scientist Benjamin Santer of Lawrence Livermore National Laboratory. “The climate science community discusses uncertainties in an open and transparent way, and has done so for decades. It is simply untrue that Prof. Koonin is confronting climate scientists with unpleasant facts they have ignored or failed to understand.”
Scientists who have been engaged in recent climate research also believe Koonin’s critique seems out of step with what has been happening in the field. He relies on the latest statements of the consensus science, but the most recent reports of the United Nations Intergovernmental Panel on Climate Change came out in 2013 and 2014. The IPCC’s updated assessment reports due out later this year and next year will almost certainly include recent studies that undercut Koonin’s conclusions.
Here are five statements Koonin makes in “Unsettled” that mainstream climate scientists say are misleading, incorrect or undercut by current research:
1. “The warmest temperatures in the US have not risen in the past fifty years.”
The average annual temperature in the contiguous U.S. has increased from 0.7 degrees to 1.0 degrees Celsius (1.2 to 1.8 degrees Fahrenheit) since the start of the 20th century. The year 2020 was the fifth-warmest year in the 126-year record for the contiguous U.S. And the five warmest years on record have occurred since 2012, NOAA reports.
There is a more marked increase in nighttime lows than in daytime highs (the “warmest” temperatures) because of factors like the cooling effect of daytime aerosol pollution and soil moisture evaporation.
2. “Most types of extreme weather events don’t show any significant change—and some such events have actually become less common or severe—even as human influences on the climate grow.”
There have been statistically significant trends in the number of heavy precipitation events in some regions. Some regions have experienced more intense and longer droughts, while in other places, droughts have become less frequent, less intense, or shorter. Marine heatwaves, periods of extremely high ocean temperatures in specific regions, have become more than 20 times more frequent over the last 40 years due to human activity and the burning of greenhouse gases, according to a 2020 study that relied on satellite measurements of sea surface temperatures.
3. “Humans have had no detectable impact on hurricanes over the past century.”
In 2020, scientists detected a trend of increasing hurricane intensity since 1979 that is consistent with what models have projected would result from human-driven global warming. Rapid intensification of hurricanes has increased in the Atlantic basin since the 1980s, which federal researchers showed in 2019 is attributable to warming. A 2018 study showed that Hurricane Harvey, which hit Houston the prior year, could not have produced so much rain without human-induced climate change. That same year, a separate study showed that increased stalling of tropical cyclones is a global trend.
4. “Greenland’s ice sheet isn’t shrinking any more rapidly today than it was eighty years ago.”
Scientific findings indicate with high confidence that the Greenland ice sheet, the world’s second-largest land-based ice reservoir, has lost ice, contributing to sea level rise over the last two decades. And Greenland is on track to lose more ice this century than at any other time in the 12,000-year Holocene, the epoch encompassing human history, scientists reported in 2020.
The rate of ice melt in Greenland has varied widely over the decades, and there is evidence of a period of rapid melting in the 1930s that exceeded the rate of today. But the 1930s-era melt affected fewer glaciers, mostly those located entirely on land. Today’s melting involves more glaciers, most of them connected to the sea, with average ice loss more than double that of the earlier period.
5. “The net economic impact of human-induced climate change will be minimal through at least the end of this century.
Global warming is very likely to have exacerbated global economic inequality, with the disparities between poor and wealthy countries 25 percent greater than in a world without warming, researchers concluded in 2019.
Only a limited number of studies have calculated the aggregate economic impact of climate change, not enough to place confidence in numeric results. But the data indicates with high confidence that climate change will aggravate other stressors, like inadequate housing, food or water supplies, with negative outcomes especially for the poor.
>>> Marianne Lavelle is a reporter for InsideClimate News. She has covered environment, science, law, and business in Washington, D.C. for more than two decades. She has won the Polk Award, the Investigative Editors and Reporters Award, and numerous other honors. Lavelle spent four years as online energy news editor and writer at National Geographic. She spearheaded a project on climate lobbying for the nonprofit journalism organization, the Center for Public Integrity. She also has worked at U.S. News and World Report magazine and The National Law Journal. While there, she led the award-winning 1992 investigation, “Unequal Protection,” on the disparity in environmental law enforcement against polluters in minority and white communities. Lavelle received her master’s degree from Columbia University Graduate School of Journalism, and is a graduate of Villanova University.
https://insideclimatenews.org/news/04052021/dissecting-unsettled-a-skeptical-physicists-book-about-climate-science/
Study Warns of ‘Rapid and Unstoppable’ Sea Level Rise If World Misses Paris Climate Targets
From Jake Johnson, Common Dreams, May 5, 2021
“Once you put enough heat into the climate system, you are going to lose those ice shelves, and once that is set in motion you can’t reverse it.”
A new study published Wednesday in the journal Nature warns that if the world’s governments fail to meet warming targets set by the Paris climate accord, sea level rise from the melting of the Antarctic ice sheet will accelerate at a “rapid and unstoppable” rate in the coming decades.
Authored by researchers at the University of Massachusetts Amherst, the new paper finds that if planetary warming continues at its current rate—which is headed toward 3° Celsius above pre-industrial levels—Antarctic melting will reach a tipping point by 2060, beyond which the consequences would be “irreversible on multi-century timescales.”
“If we did nothing at all to reduce emissions we could get five meters of sea level rise just from Antarctica by 2200, at which point you’d have to remap the world from space. It would be unimaginable.”
—Robert DeConto, University of Massachusetts Amherst
“If the world warms up at a rate dictated by current policies we will see the Antarctic system start to get away from us around 2060,” Robert DeConto, the lead author of the study, told The Guardian. “Once you put enough heat into the climate system, you are going to lose those ice shelves, and once that is set in motion you can’t reverse it.”
“It’s really the next few decades that will determine the sea level rise from Antarctica,” DeConto added. “These ice shelves won’t be able to just grow back.”
The researchers find that if the most optimistic Paris goal of no more than 1.5° Celsius of warming by the end of the century is met, the Antarctic ice sheet would contribute around six centimeters of sea level rise by 2100.
“But if the current course toward 3 degrees is maintained, the model points to a major jump in melting,” the study warns. “Unless ambitious action to rein in warming begins by 2060, no human intervention, including geoengineering, would be able to stop 17 to 21 centimeters of sea-level rise from Antarctic ice melt alone by 2100.”
Under a scenario in which no further action is taken to limit planet-warming greenhouse gas emissions, the research paper finds, Antarctic melting would contribute a “globally catastrophic” 10 meters or more to sea level rise by 2300.
“If we did nothing at all to reduce emissions we could get five meters of sea level rise just from Antarctica by 2200, at which point you’d have to remap the world from space,” said DeConto. “It would be unimaginable.”
The study comes days after U.S. President Joe Biden hosted a climate summit with 40 world leaders to discuss ways to bring the world into line with Paris warming targets. Biden, for his part, pledged to cut U.S. emissions at least 50% below 2005 levels by the end of the decade—a goal climate activists slammed as nowhere near sufficient.
“Science and justice demand that we reduce emissions by 70% from 2005 levels by 2030 on the road to zero emissions by mid-century,” Janet Redman of Greenpeace USA said last month. “The White House can get this done by removing government subsidies to fossil fuel companies, investing in an equitable and sustainable economic recovery, and stopping fishy carbon offset deals.”
https://www.commondreams.org/news/2021/05/05/study-warns-rapid-and-unstoppable-sea-level-rise-if-world-misses-paris-climate/