Havniveau stigninger - hvad mener forskningen?

Afsmeltningen var på sit højeste i 2012

Studiet er lavet af det verdensomspændende samarbejde IMBIE, der støttes af rumagenturerne NASA og ESA.

Forskere verden over har bidraget med data om Indlandsisen, som stammer fra blandt andet lasermålinger fra satellitter og satellitfotos over en årrække på næsten 30 år.

En anden af de forskere, der har bidraget, er Shfaqat Abbas Khan, der er professor på DTU Space i Kongens Lyngby nord for København.

Han fortæller, at afsmeltningen af Indlandsisen steg støt fra 1992 og frem, men nåede sit højeste i sommeren 2012. Dengang troede forskerne, at udviklingen ville fortsætte, men:

»Det toppede i 2012. Det var et rekordvarmt år, men det tyder på, at det vejrmæssigt var meget unikt, når man kigger på en længere periode. Når vi måler med satellitter år efter år kan vi se, om det er en tendens, der ser ud til at fortsætte, eller om det heldigvis er en usædvanlig vejrmæssig variation,« siger han.

Vi er stadig på vej mod oversvømmelser

Selvom der er sket en lille nedbremsning i forhold til de vådeste år for Indlandsisen, smelter den stadig hurtigt, og det er alvorligt, fastslår forskerne.

»Studiet dokumenterer en stigning i havniveauet på 1 centimeter over 30 år. Men hvis det fortsætter i nuværende tempo kommer vi til at se en stigning på yderligere 20 centimeter i år 2100,« siger William Colgan.

I alt lyder IPCC's beregninger på, at cirka 400 millioner mennesker vil være udsatte for voldsomme årlige oversvømmelser frem mod 2100, når alle vandstandsstigninger, udover dem fra Grønland, medregnes.

»Jeg håber, at moralen i den her historie er en god motivation for at gribe til handling. Hvis vi vil mindske klimaændringerne, så er vi nødt til at reducere udledningen af drivhusgasser i atmosfæren,« slutter William Colgan.

yaknudsen skrev:
Interessant, men både foruroligende og uvidenskabeligt at Peter Villadsen vælger at fremhæve hvad "ihvertfald medierne er enige om", og synes det er "dejligt".

Men - det med videnskabelig nuancering ER jo også svært når man som Peter Villadsen tilsyneladende gør, vælger at fastholde et ensidigt ukritisk fokus på mainstream mediernes storsælgende apokalypse-fortællinger.

Begge artikler var enige om, at undersøgelsen fandt frem til 400 millioner mennesker år 2100, der påvirkes af øget havstigning.

Peter Villadsen skrev:
[quote]yaknudsen skrev:
Interessant, men både foruroligende og uvidenskabeligt at Peter Villadsen vælger at fremhæve hvad "ihvertfald medierne er enige om", og synes det er "dejligt".

Men - det med videnskabelig nuancering ER jo også svært når man som Peter Villadsen tilsyneladende gør, vælger at fastholde et ensidigt ukritisk fokus på mainstream mediernes storsælgende apokalypse-fortællinger.

Sludder og vrøvl.
Det var sådan set dig, der så det alarmistiske spøgelse, men ikke læste artiklerne ordentligt.

Begge artikler var enige om, at undersøgelsen fandt frem til 400 millioner mennesker år 2100, der påvirkes af øget havstigning.

Det er for egen regning at kalde videnskab for storsælgende apokalypse-fortællinger.

...Din argumentation og din debatform er efter min opfattelse useriøs, ukritisk og unuanceret mainstream media ekkokammer-eftersnakkeri uden nævneværdig selvstændig tankevirksomhed

yakknudsen : Jeg kalder ikke videnskab for storsælgende apokalypse-fortællinger, det er en stråmand du fabrikerer - muligvis fordi du ikke er i stand til at læse og forstå en simpel tekst. Stakkels dig!

Jeg argumenterer derimod for, at den udlægning som mainstream mediernene præsenterer, ofte er storsælgende apokalypse-fortællinger med en ideologisk slagside der ukritisk tages for gode varer af ideologisk forblindede mennesker.

Ideologisk forblindede mennesker der som dig forveksler ren og uforfalsket videnskab, med det unuancerede vrøvl der alt for ofte bliver resultatet, når videnskaben har været igennem mainstream medias forsimplende vrøvlemaskine.

Din argumentation og din debatform er efter min opfattelse useriøs, ukritisk og unuanceret mainstream media ekkokammer-eftersnakkeri uden nævneværdig selvstændig tankevirksomhed.

Greenland is losing ice seven times faster than in the 1990s and is tracking the Intergovernmental Panel on Climate Change's high-end climate warming scenario, which would see 400 million more people exposed to coastal flooding by 2100.

A team of 96 polar scientists from 50 international organisations have produced the most complete picture of Greenland ice loss to date. The Ice Sheet Mass Balance Inter-comparison Exercise (IMBIE) Team combined 26 separate surveys to compute changes in the mass of Greenland's ice sheet between 1992 and 2018. Altogether, data from 11 different satellite missions were used, including measurements of the ice sheet's changing volume, flow and gravity.

The findings, published today in Nature today, show that Greenland has lost 3.8 trillion tonnes of ice since 1992—enough to push global sea levels up by 10.6 millimetres. The rate of ice loss has risen from 33 billion tonnes per year in the 1990s to 254 billion tonnes per year in the last decade—a seven-fold increase within three decades.

The assessment, led by Professor Andrew Shepherd at the University of Leeds and Dr. Erik Ivins at NASA's Jet Propulsion Laboratory in California, was supported by the European Space Agency (ESA) and the US National Aeronautics and Space Administration (NASA).

n 2013, the Intergovernmental Panel on Climate Change (IPCC) predicted that global sea levels will rise by 60 centimetres by 2100, putting 360 million people at risk of annual coastal flooding. But this new study shows that Greenland's ice losses are rising faster than expected and are instead tracking the IPCC's high-end climate warming scenario, which predicts 7 centimetres more.

Professor Shepherd said: "As a rule of thumb, for every centimetre rise in global sea level another six million people are exposed to coastal flooding around the planet."

"On current trends, Greenland ice melting will cause 100 million people to be flooded each year by the end of the century, so 400 million in total due to all sea level rise."

"These are not unlikely events or small impacts; they are happening and will be devastating for coastal communities."

The team also used regional climate models to show that half of the ice losses were due to surface melting as air temperatures have risen. The other half has been due to increased glacier flow, triggered by rising ocean temperatures.

Ice losses peaked at 335 billion tonnes per year in 2011—ten times the rate of the 1990s—during a period of intense surface melting. Although the rate of ice loss dropped to an average 238 billion tonnes per year since then, this remains seven times higher and does not include all of 2019, which could set a new high due to widespread summer melting.

Dr. Ivins said: "Satellite observations of polar ice are essential for monitoring and predicting how climate change could affect ice losses and sea level rise".

"While computer simulation allows us to make projections from climate change scenarios, the satellite measurements provide prima facie, rather irrefutable, evidence."

"Our project is a great example of the importance of international collaboration to tackle problems that are global in scale."

Guðfinna Aðalgeirsdóttir, Professor of Glaciology at the University of Iceland and lead author of the Intergovernmental Panel on Climate Change's sixth assessment report, who was not involved in the study, said:

"The IMBIE Team's reconciled estimate of Greenland ice loss is timely for the IPCC. Their satellite observations show that both melting and ice discharge from Greenland have increased since observations started."

"The ice caps in Iceland had similar reduction in ice loss in the last two years of their record, but this last summer was very warm here and resulted in higher loss. I would expect a similar increase in Greenland mass loss for 2019."

"It is very important to keep monitoring the big ice sheets to know how much they raise sea level every year."

yakknudsen: Jeg argumenterer derimod for, at den udlægning som mainstream mediernene præsenterer, ofte er storsælgende apokalypse-fortællinger med en ideologisk slagside der ukritisk tages for gode varer af ideologisk forblindede mennesker.

"The findings, published today in Nature today, show that Greenland has lost 3.8 trillion tonnes of ice since 1992—enough to push global sea levels up by 10.6 millimetres. The rate of ice loss has risen from 33 billion tonnes per year in the 1990s to 254 billion tonnes per year in the last decade—a seven-fold increase within three decades."

Peter Villadsen skrev:
Jeg bringer her hele indholdet af artiklen og jeg skal bede dig - yakknudsen - at udpege hvad det er, der er alarmistisk?

Alle der kender lidt til denne indlandsis ved, at indlandsisen størrelse og omfang har svinget rigtig meget igennem tiderne

Vi har undersøgt ikke færre end 132 gletsjere på en 600 km lang strækning i Sydøstgrønland. Både dem som har deres udspring på land og dem som 'lever og kælve' i vandet. I den sammenhæng spiller de gamle luftfotos af kyststrækningerne en væsentlig rolle. Ud fra disse luftfotos, andre taget af amerikanerne under krigen, andre igen i 70'erne og 80'erne og satellitfotos eller spionfotos fra 60'erne under Den Kolde Krig har vi kunnet dannet os et klFoto fra 30'erne af gletsjere i Grønland. Foto: Arktisk Institut i København.art billede af, hvordan gletsjerne har udviklet sig over en så relativ kort periode i historisk sammenhæng. Bl.a. var der varme temperaturer i begyndelsen af 20'erne og 30'erne på højde med dem i dag, som påvirkede gletsjernes afsmeltning. Mange gletsjere oplevede dengang en afsmeltning på højde og højere, end hvad vi har set de seneste 10 år. Da det senere blev koldere igen i 50-60'erne stoppede afsmeltningen og for en stor dels vedkommende begyndte gletsjerne rent faktisk at vokse...

yaknudsen skrev:

Peter Villadsen skrev:
Jeg bringer her hele indholdet af artiklen og jeg skal bede dig - yakknudsen - at udpege hvad det er, der er alarmistisk?

Jeg vil lade mine indlæg i denne tråd tale for sig selv og undlade at reagere yderligere på stråmands-argumenter og retoriske afsporings-strategier fra din side.

Jeg står ved hvert eneste ord jeg har skrevet i denne tråd og har ikke mere at tilføje i den sammenhæng - men overlader det til læserne at vurdere relevansen af den manglende nuancering (som jeg efter egen vurdering fokuserer meget tydeligt på, i den første linie af mit første indlæg i denne tråd).

2019 Headlines

Arctic ecosystems and communities are increasingly at risk due to continued warming and declining sea ice

The Arctic marine ecosystem and the communities that depend upon it continue to experience unprecedented changes as a result of warming air temperatures, declining sea ice, and warming waters. Arctic Report Card 2019 draws particular attention to the Bering Sea region, where declining winter sea ice exemplifies the potential for sudden and extreme change. Indigenous Elders from the Bering Sea region offer their experiences of living at the forefront of climate change.

Highlights
The average annual land surface air temperature north of 60° N for October 2018-August 2019 was the second warmest since 1900. The warming air temperatures are driving changes in the Arctic environment that affect ecosystems and communities on a regional and global scale.

On the land

The Greenland Ice Sheet is losing nearly 267 billion metric tons of ice per year and currently contributing to global average sea-level rise at a rate of about 0.7 mm yr-1.
North American Arctic snow cover in May 2019 was the fifth lowest in 53 years of record. June snow cover was the third lowest.
Tundra greening continues to increase in the Arctic, particularly on the North Slope of Alaska, mainland Canada, and the Russian Far East.
Thawing permafrost throughout the Arctic could be releasing an estimated 300-600 million tons of net carbon per year to the atmosphere.

In the oceans

Arctic sea ice extent at the end of summer 2019 was tied with 2007 and 2016 as the second lowest since satellite observations began in 1979. The thickness of the sea ice has also decreased, resulting in an ice cover that is more vulnerable to warming air and ocean temperatures.
August mean sea surface temperatures in 2019 were 1-7°C warmer than the 1982-2010 August mean in the Beaufort and Chukchi Seas, the Laptev Sea, and Baffin Bay.
Satellite estimates showed ocean primary productivity in the Arctic was higher than the long-term average for seven of nine regions, with the Barents Sea and North Atlantic the only regions showing lower than average values.
Wildlife populations are showing signs of stress. For example, the breeding population of the ivory gull in the Canadian Arctic has declined by 70% since the 1980s.

Focus on the Bering Sea

The winter sea ice extent in 2019 narrowly missed surpassing the record low set in 2018, leading to record-breaking warm ocean temperatures in 2019 on the southern shelf. Bottom temperatures on the northern Bering shelf exceeded 4°C for the first time in November 2018.
Bering and Barents Seas fisheries have experienced a northerly shift in the distribution of subarctic and Arctic fish species, linked to the loss of sea ice and changes in bottom water temperature.
Indigenous Elders from Bering Sea communities note that "[i]n a warming Arctic, access to our subsistence foods is shrinking and becoming more hazardous to hunt and fish. At the same time, thawing permafrost and more frequent and higher storm surges increasingly threaten our homes, schools, airports, and utilities."