Sunday 27th of September 2020

polar bears to go...

warmingwarming

Polar bears will be wiped out by the end of the century unless more is done to tackle climate change, a study predicts.

Scientists say some populations have already reached their survival limits as the Arctic sea ice shrinks.

The carnivores rely on the sea ice of the Arctic Ocean to hunt for seals.

As the ice breaks up, the animals are forced to roam for long distances or on to shore, where they struggle to find food and feed their cubs. 

The bear has become the "poster child of climate change", said Dr Peter Molnar of the University of Toronto in Ontario, Canada.

"Polar bears are already sitting at the top of the world; if the ice goes, they have no place to go," he said.

Polar bears are listed as vulnerable to extinction by the International Union for Conservation of Nature (IUCN), with climate change a key factor in their decline.

 

 

Read more:

https://www.bbc.com/news/science-environment-53474445

humans, displaced...

Monsoon floods in India, Nepal displace 4 million


Floods and mudslides triggered by heavy monsoon rains have displaced millions in India, Nepal and Bangladesh. Nearly 200 people are reported to be dead and many are still missing.


About 4 million people have been displaced in South Asia due to flooding caused by heavy monsoon rains

At least 189 people have died and dozens are missing in India, Nepal and Bangladesh, officials said. 

In the northeastern Indian state of Assam, over 2.75 million people have been displaced by three waves of floods since May, according to a state government official. 

"The flood situation remains critical with most of the rivers flowing menacingly above the danger mark," Assam water resources Minister Keshab Mahanta told Reuters. Some 79 people have died in the state. 

Read more: Climate change poses dire challenges for Bangladesh

Authorities said the floods have also killed more than 100 animals in Assam's Kaziranga National Park, home to an estimated 2,500 rare one-horned rhinos.

 

 

Read more:

https://www.dw.com/en/monsoon-floods-in-india-nepal-displace-4-million/a...

methane in antarctica...

For the first time, scientists have confirmed the discovery of an active leak of methane from the seafloor in Antarctica.

The findings were published on Tuesday in the Proceedings of the Royal Society B journal. According to the report, the methane leak in the Ross Sea was first spotted in 2011. Five years after that, the microorganisms that usually consume the greenhouse gas had only developed in small quantities at the site. 

“In 2011, an expansive (70 m × 1 m) microbial mat formed at 10 m water depth in the Ross Sea, Antarctica which we identify here to be a high latitude hydrogen sulfide and methane seep,” the study’s abstract explains.

Microbes typically consume methane from such leaks before it gets to the atmosphere. However, according to the researchers, methane is still escaping from the sea floor in the Ross Sea, despite the fact that microbes are present at the site.

“The delay [in methane consumption] is the most important finding,” Andrew Thurber of Oregon State University told the Guardian. “It is not good news. It took more than five years for the microbes to begin to show up and even then there was still methane rapidly escaping from the sea floor,” he added, also noting that "it may be five to 10 years before a [microbial] community becomes fully adapted and starts consuming methane." 

Despite the fact that there is a methane leak, the area where it was found in the Ross Sea has not warmed significantly in recent years.

Researchers are generally concerned about the release of methane from frozen, underwater stores and from permafrost regions, as it could accelerate climate change. 

In 2018, NASA warned that the Arctic landscape stores “one of the largest natural reservoirs of organic carbon in the world in its frozen soils.”

“But once thawed, soil microbes in the permafrost can turn that carbon into the greenhouse gases carbon dioxide and methane, which then enter into the atmosphere and contribute to climate warming,” NASA explained.

 

Read more:

https://sputniknews.com/environment/202007221079957378-scientists-discover-first-active-leak-of-methane-from-antarctic-seabed/

 

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how hot? When?...

It seems like such a simple question: How hot is Earth going to get? Yet for 40 years, climate scientists have repeated the same unsatisfying answer: If humans double atmospheric carbon dioxide (CO2) from preindustrial levels, the planet will eventually warm between 1.5°C and 4.5°C—a temperature range that encompasses everything from a merely troubling rise to a catastrophic one.

Now, in a landmark effort, a team of 25 scientists has significantly narrowed the bounds on this critical factor, known as climate sensitivity. The assessment, conducted under the World Climate Research Programme (WCRP) and published this week in Reviews of Geophysics, relies on three strands of evidence: trends indicated by contemporary warming, the latest understanding of the feedback effects that can slow or accelerate climate change, and lessons from ancient climates. They support a likely warming range of between 2.6°C and 3.9°C, says Steven Sherwood, one of the study's lead authors and a climate scientist at the University of New South Wales. “This is the number that really controls how bad global warming is going to be.”

The new study is the payoff of decades of advances in climate science, says James Hansen, the famed retired NASA climate scientist who helped craft the first sensitivity range in 1979. “It is an impressive, comprehensive study, and I am not just saying that because I agree with the result. Whoever shepherded this deserves our gratitude.”

Humanity has already emitted enough CO2 to be halfway to the doubling point of 560 parts per million, and many emissions scenarios have the planet reaching that threshold by 2060. The report underscores the risks of that course: It rules out the milder levels of warming sometimes invoked by those who would avoid emissions cuts. “For folks hoping for something better, those hopes are less grounded in reality,” says David Victor, a climate policy researcher at the University of California, San Diego, who was not part of the study.

The WCRP sensitivity estimate is designed to be used by the United Nations's Intergovernmental Panel on Climate Change (IPCC) when it publishes its next major report in 2021 or 2022. The estimate will also inform projections for sea-level rise, economic damage, and much else. A clearer picture of those consequences could do much to spur local governments to cut emissions and adapt to warming, says Diana Reckien, a climate planning expert at the University of Twente. “The decreasing uncertainty could potentially motivate more jurisdictions to act.”

The study dispels uncertainty introduced by the latest climate models. Models have historically been used to estimate sensitivity, beginning in 1979, with the world's first comprehensive assessment of CO2-driven climate change. That summer, at a meeting in Woods Hole, Massachusetts, led by Jule Charney, scientists produced a paper, known ever since as the Charney report, that predicted between 1.5°C and 4.5°C warming for a CO2 doubling. Those numbers—based in part on a model Hansen had developed—stuck around far longer than anyone imagined: The latest IPCC report, from 2013, gave the same range.

Recent models suggest the range might even go higher. They run hot, some predicting warming of more than 5°C for a CO2 doubling (Science, 19 April 2019, p. 222), apparently because of the way they render clouds, especially over the Southern Ocean. Yet these high-end models struggle to accurately re-create the climate of the 20th century, undermining their credibility. Such models play only a supporting role in the new assessment, says Robert Kopp, a climate scientist at Rutgers University, New Brunswick, who was not involved in the effort. “We now have enough independent lines of evidence that we don't need to use the climate models as their own line.”

The WCRP study arose out of a 2015 workshop at Schloss Ringberg, a castle in the Bavarian Alps. Many participants were dissatisfied with the IPCC process and wanted to look at how physical mechanisms might set the boundaries of the sensitivity range. “Work on the ends, rather than on the middle,” says Bjorn Stevens, a cloud scientist at the Max Planck Institute for Meteorology, who edited the WCRP report with Sandrine Bony of the Pierre Simon Laplace Institute. Sherwood and Mark Webb, a climate scientist at the United Kingdom's Met Office, agreed to lead the effort.

The first line of evidence they considered was modern-day warming. Since record keeping began in the 1800s, average surface temperatures have risen by 1.1°C. Continuing that trend into the future would lead to warming on the lower end of the range. But recent observations have shown the planet is not warming uniformly; in particular, warming has barely touched parts of the eastern Pacific Ocean and Southern Ocean, where cold, deep waters well up and absorb heat. Eventually, models and paleoclimate records suggest, these waters will warm—not only eliminating a heat sink, but also spurring the formation of clouds above them that will trap more heat. Adjusting the temperature projections for this fact rules out low-sensitivity estimates, says Kate Marvel, a climate scientist at NASA's Goddard Institute for Space Studies.

Second, the team probed individual climate feedbacks. Some of these, like the warming effect of water vapor, are well known. But clouds, which can cool or warm the planet depending on how they reflect sunlight and trap heat, have long been a wild card. In particular, climate scientists want to understand the decks of stratocumulus clouds that form off coastlines. If they grow more extensive in response to warming, as some suspect, they could have a cooling effect.

Several years ago, a suite of high-resolution cloud models identified two feedbacks that would have the opposite effect, thinning clouds and making warming worse. In the models, higher temperatures allowed more dry air to penetrate thin clouds from above, preventing them from thickening. At the same time, higher CO2 levels trapped heat near the clouds' tops, subduing turbulence that drives the formation of more clouds. Satellites have since observed these dynamics in warmer-than-average parts of the atmosphere. “There's a growing consensus that the [cloud] feedback is positive, but not super-large,” says Thorsten Mauritsen, a climate scientist at Stockholm University.

Finally, the team looked at records from two past climates—20,000 years ago, at the peak of the last ice age, and a warm period 3 million years ago, the last time atmospheric CO2 levels were similar to today's. Recent work suggests climate sensitivity is not a fixed property of the planet, but changes over time. During warm periods, for instance, the absence of ice sheets probably raised sensitivity. Records of ancient temperatures and CO2 levels enabled the team to pin down sensitivities of 2.5°C and 3.2°C for the cold and warm periods, respectively. “It's really comprehensive,” says Jessica Tierney, a paleoclimatologist at the University of Arizona, who was not part of the report. Even for the coldest climate state, she says, the possibility of a sensitivity below 2°C seems negligible.

Assembling the three lines of evidence was a huge task. But wiring them together for a unified prediction was even tougher, Marvel says. The team used Bayesian statistics to churn through its assembled data, which allowed the researchers to test how their assumptions influence the results. “The real advantage” of Bayesian statistics, Tierney says, is how it allows uncertainties at each stage to feed into a final result. Co-authors often butted heads, Marvel says. “It was such a long and painful process.” The final range represents a 66% confidence interval, matching IPCC's traditional “likely” range. The WCRP team also calculated a 90% confidence interval, which ranges from 2.3°C to 4.7°C, leaving a slight chance of a warming above 5°C.

 

 

Read more:

Science  24 Jul 2020:

Vol. 369, Issue 6502, pp. 354-355

 

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Gus still holds the possibility of a 6 to 9 degrees Celsius rise by 2150... Presently at 16 degrees Celsius planetary average, another two degrees of warming will see much of the ice disappear... leading to a change in albedo and other natural processes such as major releases of methane from sinks. Beyond this, as mentioned before, most of the warming will be done at the poles (+9) while the temperate regions will experience +6 and the equatorial region around +3... I could be wrong but the major imbalance will become obvious by 2032...

losing ice...

Taking stock of our losses

Earth's ice sheets are melting and sea levels are rising, so it behooves us to understand better which climate processes are responsible for how much of the mass loss. Smith et al. estimated grounded and floating ice mass change for the Greenland and Antarctic ice sheets from 2003 to 2019 using satellite laser altimetry data from NASA's ICESat and ICESat-2 satellites. They show how changing ice flow, melting, and precipitation affect different regions of ice and estimate that grounded-ice loss averaged close to 320 gigatons per year over that period and contributed 14 millimeters to sea level rise.


Abstract

Quantifying changes in Earth’s ice sheets and identifying the climate drivers are central to improving sea level projections. We provide unified estimates of grounded and floating ice mass change from 2003 to 2019 using NASA’s Ice, Cloud and land Elevation Satellite (ICESat) and ICESat-2 satellite laser altimetry. Our data reveal patterns likely linked to competing climate processes: Ice loss from coastal Greenland (increased surface melt), Antarctic ice shelves (increased ocean melting), and Greenland and Antarctic outlet glaciers (dynamic response to ocean melting) was partially compensated by mass gains over ice sheet interiors (increased snow accumulation). Losses outpaced gains, with grounded-ice loss from Greenland (200 billion tonnes per year) and Antarctica (118 billion tonnes per year) contributing 14 millimeters to sea level. Mass lost from West Antarctica’s ice shelves accounted for more than 30% of that region’s total.

...


Some of the highest Greenland ice mass losses are in the northwest and southeast sectors, where strong dynamic changes took place shortly after the start of the ICESat mission (32). The recent acceleration in ice loss from Northeast Greenland (33) appears more limited in extent and magnitude and has less impact on the total mass balance. Despite the record-setting discharge rates of Jakobshavn Isbrae (34), its contribution is only around 10% of the Greenland mass loss between 2003 and 2019, in part because the rapid mass loss due to its acceleration in the late 1990s (35) declined with the slowing and thickening of the lower part of the glacier between 2013 and 2018 (36). Overall, loss of solid ice around the margins outpaced lower rates of snow gain distributed across the interior.


In Antarctica, we see broad-scale patterns that are the fingerprints of two competing climate processes: snow accumulation and ocean melting. These processes occur on different spatial and temporal scales (Fig. 3) and exhibit strong connections between changes in grounded and floating ice in West Antarctica and the Antarctic Peninsula. The “background” pattern is one of subtle thickening along the steep slopes of the Antarctic Peninsula and around the coast to Queen Maud Land, East Antarctica, where gains decrease with distance from the ocean, which is indicative of snow accumulation in excess of that needed to balance flux divergence due to ice flow. This is likely due to enhanced moisture flux from marine air masses, but our measurements only provide an upper bound on the duration over which this may have occurred. Superimposed on this is a pattern of dramatic, ongoing mass loss around the margins, especially in the Amundsen and Bellingshausen regions of West Antarctica, which is likely in response to rapidly shrinking ice shelves. Ice shelf thinning in the Amundsen Sea has been attributed to an increase in atmospheric-driven incursions of modified Circumpolar Deep Water under the ice shelves, enhancing ocean-induced melting of marine-based basins (14, 16). Similar patterns may be emerging for marine-based outlet glaciers of !East Antarctica, such as at Denman Glacier (Fig. 3), where a deep subglacial canyon and a retrograde slope may drive unstable retreat (37). The three large cold-water ice shelves (Ross, Filchner-Ronne, and Amery) have smaller rates of height change, but there are striking internally driven changes where the stagnant Kamb Ice Stream (38) and slowing Whillans Ice Stream (39) starve downstream Ross Ice Shelf of mass input (locations are provided in fig. S8). In contrast to West Antarctic ice shelves, East Antarctic ice shelves gained 106 ± 29 Gt year−1

 

Science  12 Jun 2020:

Vol. 368, Issue 6496, pp. 1239-1242

 

 

See also:

http://yourdemocracy.net.au/drupal/node/26175

 

Here we explain how "rapid" climate change anomalously increases snow falls in Antarctica — the driest continent on earth. Yet the net loss of ice in Antarctica and at the north pole region should ring our alarm bells in regard to the speed of change in climatic patterns and sea level rise...

 

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