DATE: April 20, 2018
SNIP: Aerosols, tiny particles that are suspended in the atmosphere, contribute significantly towards climate change.
The scientists’ observations also reveal an enormous difference between today’s polluted atmosphere and that of pre-industrial times. Aerosol concentrations in the pristine pre-industrial atmosphere resemble their Amazonian findings: high Upper Troposphere (UT) and low Lower Troposphere (LT) aerosol levels. However, in polluted continental regions, aerosol concentrations are generally much higher at ground level than in the UT. In an era where humans are the dominant influence on climate and the environment, the aerosol concentration profile has “been turned upside down,” say the journal paper authors. The consequences for Earth’s climate are significant. “By their radiative and microphysical effects on convection dynamics, aerosols are also able to increase upper tropospheric humidity, which plays an important role in the Earth’s radiation budget and may also affect the potential for aerosol nucleation in the UT, thus providing an additional feedback,” the authors conclude.
SOURCE: Inside Climate News
DATE: April 19, 2018
SNIP: [T]emperatures are rising in the Arctic at about twice the global average. That causes melting around the edges of the ice sheet each year and reaches across more of the surface during summer heat waves.
In areas near the edge of the ice sheet, things get even more interesting: a carpet of microbes and algae mixed with dust and soot, a short-lived climate pollutant, is darkening the ice sheet, absorbing the sun’s rays and accelerating the melting of the ice.
New research shows this dark zone is growing.
The new research, published in the journal Nature Communications, describes a geological feedback loop on the ice that’s expanding the dark zone: Warming melts the western edge of the ice sheet, releasing mineral dust from rock crushed by the ice sheet thousands of years ago. That dust blows to the surface of the ice, nurturing the microbes and algae living there. Those organisms produce colored pigments as sunscreen, which contribute to the darkening of the surface, reducing reflectivity and increasing melting.
“Just the little bit of extra heat from a tiny soot particle can start transforming feathery and highly reflective snow crystals into darker, rounded grains that absorb more heat,” said climate researcher Jason Box.
DATE: April 18, 2018
SNIP: Sea level rise could be happening at a faster rate than previously thought, as scientists have identified a new source of melting ice in Antarctica.
Melting glaciers can create a positive feedback loop in which the more they melt, the more they drive further melting, according to the Australian team.
They predict that the processes they identified could be playing a role in accelerating both sea level rise and climate change.
As glaciers melt, they produce fresh water. When this meltwater enters the ocean surrounding the glacier it makes the surface layer less salty and therefore more buoyant.
This leads to a layer of water floating on the surface, and prevents the natural mixing of the ocean.
The lack of mixing becomes a problem during winter, as it prevents warm water at greater depths from mixing with cooler water above.
With a pool of warm water underneath them, the melting of the bottom side of the glaciers accelerates.
SOURCE: The Sydney Morning Herald
DATE: April 18, 2018
SNIP: Corals in the Great Barrier Reef have a lower tolerance to heat stress than expected, contributing to a permanent transformation of the mix of species in some of most pristine regions, a team of international researchers has found.
The scientists examined the impact of the 2016 marine heatwave that alone caused the death of about one-third of the Great Barrier Reef corals, mostly centered on the northern third section.
They studied how much abnormal heat triggers bleaching, the additional heat that killed the corals, and the accumulation needed to cause “an ecological collapse in the transformation of species”, said Terry Hughes, Director of the ARC Centre of Excellence for Coral Reef Studies at James Cook University, and the lead of author of the paper published Thursday in Nature.
The thresholds “are lower than we thought they would be“, Professor Hughes told Fairfax Media.
Just as coral species responded differently to the heat stress, so too have fish species that depend on them.
Butterfly fish, for instance, feed on only a couple of coral species. “If their diet disappears, so do they,” Professor Hughes said.
SOURCE: The Guardian
DATE: April 11, 2018
SNIP: The warm Atlantic current linked to severe and abrupt changes in the climate in the past is now at its weakest in at least 1,600 years, new research shows. The findings, based on multiple lines of scientific evidence, throw into question previous predictions that a catastrophic collapse of the Gulf Stream would take centuries to occur.
Such a collapse would see western Europe suffer far more extreme winters, sea levels rise fast on the eastern seaboard of the US and would disrupt vital tropical rains. The new research shows the current is now 15% weaker than around 400AD, an exceptionally large deviation, and that human-caused global warming is responsible for at least a significant part of the weakening.
Scientists know that the Atlantic Meridional Overturning Circulation (AMOC) has slowed since 2004, when instruments were deployed at sea to measure it. But now two new studies have provided comprehensive ocean-based evidence that the weakening is unprecedented in at least 1,600 years, which is as far back as the new research stretches.
“AMOC is a really important part of the Earth’s climate system and it has played an important part in abrupt climate change in the past,” said Dr David Thornalley, from University College London who led one of the new studies. He said current climate models do not replicate the observed slowdown, suggesting that AMOC is less stable that thought.
SOURCE: Science Daily
DATE: April 10, 2018
SNIP: New ice cores taken from the summit of Mt. Hunter in Denali National Park show summers there are least 1.2-2 degrees Celsius (2.2-3.6 degrees Fahrenheit) warmer than summers were during the 18th, 19th, and early 20th centuries. The warming at Mt. Hunter is about double the amount of warming that has occurred during the summer at areas at sea level in Alaska over the same time period, according to the new research.
The warmer temperatures are melting 60 times more snow from Mt. Hunter today than the amount of snow that melted during the summer before the start of the industrial period 150 years ago, according to the study. More snow now melts on Mt. Hunter than at any time in the past 400 years, said Dominic Winski, a glaciologist at Dartmouth College in Hanover, New Hampshire and lead author of the new study published in the Journal of Geophysical Research: Atmospheres, a journal of the American Geophysical Union.
SOURCE: Science Daily
DATE: April 4, 2018
SNIP: Over the past 10 years, the number of plant species on European mountain tops has increased by five-times more than during the period 1957-66. Data on 302 European peaks covering 145 years shows that the acceleration in the number of mountain-top species is unequivocally linked to global warming.
During the decade from 1957-66, the number of species on each of the 302 mountain tops increased by 1.1 species on average. Since then, the trend has accelerated: From 2007-16, on average 5.5 new species moved up to the 302 summits.
The researchers have only been able to count the plant species that have already responded to the temperature rise and actually have moved upwards. They have not studied the number of species that might be on the way upwards.
SOURCE: The Guardian
DATE: April 2, 2018
SNIP: Hidden underwater melt-off in the Antarctic is doubling every 20 years and could soon overtake Greenland to become the biggest source of sea-level rise, according to the first complete underwater map of the world’s largest body of ice.
Warming waters have caused the base of ice near the ocean floor around the south pole to shrink by 1,463 square kilometres – an area the size of Greater London – between 2010 and 2016.
The research by the UK Centre for Polar Observation and Modelling at the University of Leeds suggests climate change is affecting the Antarctic more than previously believed and is likely to prompt global projections of sea-level rise to be revised upward.
“What’s happening is that Antarctica is being melted away at its base. We can’t see it, because it’s happening below the sea surface,” said Professor Andrew Shepherd, one of the authors of the paper. “The changes mean that very soon the sea-level contribution from Antarctica could outstrip that from Greenland.”
SOURCE: Nature Communications
DATE: March 29, 2018
SNIP: In this study, we investigate how a warming climate has impacted the Lake Hazen watershed from its glacier headwaters, all the way through to the Arctic Char at the top of the aquatic foodweb, using a combination of historical, contemporary, modeled and paleoliminological datasets. We hypothesized that, due to its large size and thermal inertia, Lake Hazen would be more resilient to Arctic warming than smaller aquatic ecosystems, a number of which have already undergone significant regime shifts.
However, we demonstrate that the Lake Hazen watershed was not resilient to even an ~1 °C relative increase in recent summer air temperatures. Accelerated melt in the cryosphere resulted in an ~10 times increase in delivery of glacial meltwaters, sediment, organic carbon and legacy contaminants to Lake Hazen and a reduction in summer lake ice cover. Changes to the physical and chemical components of the watershed caused an ecological reorganization of the algal (diatom) community assemblage and a decline in the physiological condition of Arctic Char.
SOURCE: Inside Climate News
DATE: March 28, 2018
SNIP: As the planet warms, giant icebergs and sea ice that once would have remained trapped in the frozen Arctic are moving southward faster and more frequently, menacing shipping and oil and gas drilling operations.
In the North Atlantic, scientists say the number of icebergs spotted south of 48 degrees latitude—where they start to get into more shipping lanes—is up again this year, following a series of extreme iceberg seasons.
That ice can pose serious risks to ships and offshore oil and gas rigs. Last year, strong storms sent a swarm of icebergs surging into the oil and gas drilling field at the Grand Banks off Newfoundland, marking the fourth extreme iceberg season in a row, according to International Ice Patrol Commander Gabrielle McGrath.
“There were so many in the area that we couldn’t count them all. Our models couldn’t keep up with how quickly they were moving to the south,” she said.
Increased ice mobility is a sign that the Arctic climate system is likely to change in big increments in the next few decades, said University of Manitoba ice researcher Dave Babb, one of scientists who tested the sea ice off Newfoundland last year.
The Arctic Ocean along the northern coast of Alaska is remaining unfrozen for more than two months longer than just 30 years ago, and there’s evidence that storms are getting stronger over the open water, and whipping up bigger waves.
The extreme conditions would make cleaning up an oil spill nearly impossible.