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Greenland’s largest glaciers nearing rates of melt expected in ‘worst-case scenario’
Greenland’s largest glaciers nearing rates of melt expected in ‘worst-case scenario’
Greenland’s three biggest glaciers added the equivalent of around 8mm to global sea levels from 1880 to 2012, study says
Using a combination of aerial photographs and field data, the study found that current rates of mass loss from Greenland’s three largest glaciers are higher than once thought.
The melting of these three glaciers added the equivalent of around 8mm to global sea levels from 1880 to 2012, according to the research.
Previous had estimated that the same three glaciers would contribute 9-15mm to global sea levels by 2100 under a “worst-case scenario”.
The Greenland ice sheet is a mass of frozen freshwater sitting on the island of Greenland that is around 1.7m square kilometres in size. This is about three times the size of Texas.
As a result of climbing air and ocean temperatures, the ice sheet is losing mass each year. The loss of mass from Greenland’s glaciers is, in turn, causing sea levels to rise.
The research, published in , focuses on the “big three” glaciers in Greenland: Jakobshavn Isbræ, Kangerlussuaq Glacier and Helheim Glacier. These glaciers together hold enough ice to raise sea levels by around 1.3 metres, if they melted completely.
It found that the amount of sea level rise from the melting of these three glaciers is already nearing rates previously expected under a future “worst-case” scenario.
This suggests that, if the world were to see extremely high emissions in the coming decades, ice loss from Greenland’s glaciers would be considerably higher than previously projected, explains study author Prof Jonathan Bamber, a glaciologist at the University of Bristol.
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More than half the world could see ‘record-setting heat’ every year by 2100
More than half the world could see ‘record-setting heat’ every year by 2100
More than half of the world could see new temperature records set in every single year by the end of the century if global warming is not curbed, a study finds.
And new heat records could be set in two-thirds of the world’s least developed countries each year by 2100 under the same scenario, the research adds.
Limiting global warming to below 2C above pre-industrial levels could reduce the extent of land seeing record-setting heat by almost three quarters, the lead author tells Carbon Brief.
The research “nicely illustrates the pace of change”, another scientist tells Carbon Brief. However, it is worth noting that there are limitations to using climate models to project future temperature extremes, he adds.
Heating up
Climate change is causing unprecedented heat extremes worldwide. The past four yearshave been the warmest on record – with 2016 being the hottest year ever recorded.
In 2016, temperatures at the Mitribah weather station in Kuwait reached 53.9C – the highest ever seen in Asia, according to a recent study.
Glossary RCP2.6: The RCPs (Representative Concentration Pathways) are scenarios of future concentrations of greenhouse gases and other forcings. RCP2.6 (also sometimes referred to as “RCP3-PD”) is a “peak and decline” scenario where stringent mitigation… Read More
During last summer’s northern-hemisphere heatwave, temperature records were broken in cities across the world, including Belfast, Montreal, Denver and Kumagaya in Japan. The world also saw its highest ever “minimum” temperature, when a city in Omanexperienced a 24-hour period where temperatures did not drop below 42.6C.
The new study, published in Nature Climate Change, explores how often new temperature records are likely to be set in the future across every world region. Lead author Dr Scott Power, head of climate research at the Australian government’s Bureau of Meteorology, explains to Carbon Brief:
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Sea level rise due to Antarctic ice melt has ‘tripled over past five years’
The study, published in Nature, finds that ice loss from Antarctica has caused sea levels to rise by 7.6mm from 1992-2017, with two fifths of this increase occurring since 2012.
At a press conference held in London, scientists said the results suggest that Antarctica has become “one of the largest contributors to sea level rise”.
A glaciologist not involved in the paper tells Carbon Brief that the findings show “there now should be no doubt that Antarctica is losing ice due to regional climate change, likely linked to global warming”.
Melting continent
The new research was carried out by a team of scientists from the Ice Sheet Mass Balance Inter-comparison Exercise (IMBIE). The international group was established in 2011 with the aim of creating a comprehensive view of how melting in world’s polar regions could be contributing to sea level rise.
In its last assessment report, released in 2012, it found that ice melt in Antarctica was causing global sea levels to rise by 0.2mm a year. (Over the past two decades, global sea levels have risen around 3.2mm a year in total.)
However, the new analysis finds that Antarctic ice melt is now driving sea level rise of 0.6mm a year – suggesting that the rate of melting has increased three-fold in just five years.
The results show that Antarctic ice melt has become “one of the largest contributors to sea level rise”, says Prof Andrew Shepherd, co-leader of IMBIE and director of the Natural Environment Research Council (NERC) Centre for Polar Observation and Modelling based at the University of Leeds.
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World can limit global warming to 1.5C by ‘improving energy efficiency’
It is possible to limit global warming to 1.5C and achieve many of the sustainable development goals without “negative emissions technologies”, a new study finds.
The research suggests that improving energy efficiency – chiefly by saving on everyday energy use – could play a major role in restricting warming to 1.5C above pre-industrial levels, which is the aspirational target of the Paris Agreement.
Emerging technologies, such as multipurpose smartphones and electric autonomous cars, could be key to improving energy efficiency both in the developed world and the global south, the lead author tells Carbon Brief.
The “landmark” study provides policymakers with tools to implement strategies to rapidly increase energy efficiency, another scientist tells Carbon Brief.
Negative emissions
Under the Paris Agreement, countries agreed that warming should be limited to “well below” 2C above pre-industrial levels, with efforts to keep it below 1.5C. Since then, researchers have developed a range of scenarios to explore how this could be achieved.
Until recently, scenarios limiting warming to 1.5C have typically relied on the rapid and widespread deployment of negative emissions technologies (NETs).
NETs are a group of methods – many still in development – that would limit global warming by removing CO2 from the air and storing it on land, underground or in the oceans.
In particular, most 1.5C scenarios assume that the world will develop large-scale bioenergy with carbon capture and storage (BECCS). Put simply, BECCS involves burning biomass – such as trees and crops – to generate energy and then capturing the resulting CO2 emissions.
The assumption that BECCS will be needed to reach 1.5C has proved controversialamong some groups. This is because BECCS has yet to be demonstrated at a commercial scale and research suggests that deployment would take up large amounts of land, which could threaten food production and wildlife.
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Acidification could leave oceans ‘uninhabitable’ for cold-water corals
Ocean acidification, which occurs as seawater takes up CO2 from the atmosphere, could threaten around 70% of cold-water coral living below 1,500 metres in the North Atlantic Ocean by 2050, the research finds.
Acidified waters that accumulate in the North Atlantic could then be circulated to the global seas via a system of ocean currents, the lead author tells Carbon Brief, which could have consequences for reefs across the world.
The findings reiterate how many coral reefs could “dissolve” and “crumble” as the world continues to warm, another scientist tells Carbon Brief.
Cool corals
Cold-water corals are found in deep, dark parts of the world’s oceans in both the northern and southern hemisphere. They can thrive at depths of up to 2,000 metres and in water temperatures as low as 4C.
Unlike tropical corals, cold-water corals do not rely on colourful algae for their food. Instead, cold-water coral feed on floating plankton.
This means they are unaffected by coral bleaching, a process which is heightened by climate change and poses a great threat to the survival of tropical reefs, such as the Great Barrier Reef.
However, both tropical and cold-water coral species are threatened by a process known as “ocean acidification”, which occurs as seawater absorbs CO2 from the atmosphere.
The oceans have absorbed around 30% (pdf) of the CO2 released by human activity since the industrial revolution. This has caused oceans, which are alkaline, to become more acidic over time. The overall pH of seawater has fallen from around 8.2 to 8.1from pre-industrial times to the present day.
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Long-term climate variability ‘could fall’ as the world warms
Long-term climate variability is the range of temperatures and weather patterns experienced by the Earth over a scale of thousands of years. New research suggests it could fall as the world warms.
A study using data taken from fossils and ice cores finds that long-term temperature variability decreased four-fold from the Last Glacial Maximum (LGM) around 21,000 years ago to the start of the Holocene around 11,500 years ago. Within this period, natural processes caused the planet to warm by around 3-8C.
If future global emissions are not curbed, human-driven global warming could cause further large declines in long-term temperature variability, the lead author tells Carbon Brief, which may have far-reaching effects on the world’s seasons and weather.
However, it is still unclear how a decline in long-term variability could affect the frequency of extreme weather events, she adds. This is because the chances of an extreme event happening could be influenced by both short- and long-term climate variability, as well as global temperature rise.
Digging up the past
The new study, published in Nature, is the first to make a global assessment of how long-term temperature variability changed from the LGM to the Holocene.
During the LGM, the world’s last major ice age, snow covered much of Asia, Europe and North America. Yet, within a few thousand years, global temperatures rose by around 3-8C, causing the ice to thaw and the world to enter its current geological period, the Holocene.
The cause of this temperature rise is still disputed by scientists, but research suggests the natural release of large stores of CO2 from the world’s oceans may have played a role.
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