Archives par mot-clé : Arctic

Claim: Sea level rise from ice sheets track worst-case climate change scenario

by University of Leeds, September 1, 2020 in WUWT/Nature


Ice sheets in Greenland and Antarctica whose melting rates are rapidly increasing have raised the global sea level by 1.8cm since the 1990s, and are matching the Intergovernmental Panel on Climate Change’s worst-case climate warming scenarios.

So far, global sea levels have increased in the most part through a mechanism called thermal expansion, which means that volume of seawater expands as it gets warmer. But in the last five years, ice melt from the ice sheets and mountain glaciers has overtaken global warming as the main cause of rising sea levels.

Dr Ruth Mottram, study co-author and climate researcher at the Danish Meteorological Institute, said: “It is not only Antarctica and Greenland that are causing the water to rise. In recent years, thousands of smaller glaciers have begun to melt or disappear altogether, as we saw with the glacier Ok in Iceland, which was declared “dead” in 2014. This means that melting of ice has now taken over as the main contributor of sea level rise. “

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Further information

The study, “Ice-sheet losses track high-end sea-level rise projections,” is published today (31 August) in Nature Climate Change.

View towards Icefjord in Ilulissat. Easy hiking route to the famous Kangia glacier in Greenland. The Ilulissat Icefjord seen from the viewpoint. Declared a UNESCO World Heritage Site in 2004. Photo taken in Greenland.

Claim: Past evidence supports complete loss of Arctic sea-ice by 2035

by BRITISH ANTARCTIC SURVEY, August 3, 2020 in WUWT/Ch. Rotter


A new study, published this week in the journal Nature Climate Change, supports predictions that the Arctic could be free of sea ice by 2035.

BRITISH ANTARCTIC SURVEY

A new study, published this week in the journal Nature Climate Change, supports predictions that the Arctic could be free of sea ice by 2035.

High temperatures in the Arctic during the last interglacial – the warm period around 127,000 years ago – have puzzled scientists for decades. Now the UK Met Office’s Hadley Centre climate model has enabled an international team of researchers to compare Arctic sea ice conditions during the last interglacial with present day. Their findings are important for improving predictions of future sea ice change.

During spring and early summer, shallow pools of water form on the surface of Arctic sea-ice. These ‘melt ponds’ are important for how much sunlight is absorbed by the ice and how much is reflected back into space. The new Hadley Centre model is the UK’s most advanced physical representation of the Earth’s climate and a critical tool for climate research and incorporates sea-ice and melt ponds.

Using the model to look at Arctic sea ice during the last interglacial, the team concludes that the impact of intense springtime sunshine created many melt ponds, which played a crucial role in sea-ice melt. A simulation of the future using the same model indicates that the Arctic may become sea ice-free by 2035.

Joint lead author Dr Maria Vittoria Guarino, Earth System Modeller at British Antarctic Survey (BAS), says:

“High temperatures in the Arctic have puzzled scientists for decades. …

NASA “CLIMATE PROPHET” JAMES HANSEN SAID THE ARCTIC WOULD BE “FREE OF SUMMER ICE” BY 2018

by Cap Allon, August 2, 2020 in Electroverse


Bolstered by the sycophantic-praise he received following his 1988 Congressional testimony on man-made global warming, NASA climate scientist/activist James Edward Hansen continued his prophesies well into the 2000s–despite his ever-growing list of climate fails.

“The greenhouse effect is here,” pronounced doomsayer Hansen back on June 23, 1988.

“We’re [still] toast,” he repeated with a straight face 20 years later, in 2008.

in preparation for his 1988 Congressional testimony, scientists/activist Hansen produced three potential scenarios regarding the future trend for global average temperatures:

A) “Business As Usual” — if human’s did nothing regarding rising CO2 levels.

B) If we “moderately” reduced CO2 emissions.

C) If atmospheric carbon dioxide was reduced to year 2000 levels.

 

Real-world observations reveal Hansen’s projections were way off. Scenarios A and Bsignificantly over-predict the warming trend. And digging into the data, A overstates CO2 and other greenhouse gas growth and rejects against the observations; Scenario B slightly understates CO2 growth, overstates methane and CFCs and zeroes-out other greenhouse gas growth, and it too significantly overstates the warming.

The scenario that best-matches the observations is C — the one where Hansen has CO2 topping-out at 368 ppm in 2000 but then sees it fixed at that level thereafter–something that obviously didn’t happen. It’s this drastic “halt the industrial revolution” scenario that ended up with a warming trend most like the real-world observations.

Here is one thought, proposed by climate scientist John Christy:

Suppose Hansen had offered a Scenario D, in which greenhouse gases continue to rise, but after the 1990s they have very little effect on the climate. That would play out similarly in his modeled Scenario C, and it would match the data — this hypothetical Scenario D is the reality we’re living today.

James Edward Hansen is still considered a “climate prophet” by many, but his 1988 scenarios simply DO NOT FIT THE DATA–speaking of which, let’s look at his Arctic sea ice predictions.

 

A snapshot of melting Arctic sea ice during the summer of 2018

by C. Rotter, July 30, 2020 in WUWT


 

IMAGE: THIS FIGURE SHOWS THE SEA ICE CONCENTRATION AND THICKNESS IN THE ARCTIC ON SEPTEMBER 23RD 2018. view more CREDIT: JUHI YADAV

As sea ice in the Arctic retreats further and melts faster every decade, scientists are racing to understand the vulnerabilities of one of the world’s most remote and unforgiving places. A study appearing July 29 in the journal Heliyon details the changes that occurred in the Arctic in September of 2018, a year when nearly 10 million kilometers of sea ice were lost over the course of the summer. Their findings give an overview at different timescales of how sea ice has receded over the 40 years of the satellite era and show how the summer’s extensive decline is linked to global atmospheric processes as far south as the tropics.

At the peak of its melting season, in July 2018, the Arctic was losing sea ice at a rate of 105,500 square kilometers per day–an area bigger than Iceland or the state of Kentucky. “On the ground, I am sure it would have looked like an excellent summer month in the Arctic, in general, but over the past four decades, September sea-ice loss has accelerated to a rate of 12.8% per decade and 82,300 square kilometers per year,” says co-author Avinash Kumar, a senior scientist at the National Centre for Polar and Ocean Research (NCPOR) in India.

NCEP Analysis: Northern Hemisphere Surface Temperature Falls 1°C Since February

by P. Gosselin, July 18, 2020 in NoTricksZone


Also the Danish Meteorological Institute (DMI) projects a sturdy Arctic sea ice extent for this July, meaning no falling summer ice extent trend since 2007! The climate alarms are being muffled. 

Snowfan here gives us the latest on global mean temperature and Arctic sea ice.

After the year’s low in June 2020, with an anomaly of +0.48°C from the 1981-2010 WMO climate mean, the global 2-meter temperatures (black line) depicted below shows the July 16, 2020 analysis and forecast up to July 23.

Source: here

 

Source: DMI

A surprising DMI forecast was issued on July 14, 2020 which projects strong growth of Arctic sea ice areas for July 2020. If this expert forecast is correct, it would mean there’s been a strongly positive summer trend since 2007 – instead of the ridiculous Al Gore complete meltdown.

Arctic Ocean changes driven by sub-Arctic seas

by University of Alaska Fairbank, July 12, 2020 in WUWT


New research explores how lower-latitude oceans drive complex changes in the Arctic Ocean, pushing the region into a new reality distinct from the 20th-century norm.

The University of Alaska Fairbanks and Finnish Meteorological Institute led the international effort, which included researchers from six countries. The first of several related papers was published this month in Frontiers in Marine Science.

Climate change is most pronounced in the Arctic. The Arctic Ocean, which covers less than 3% of the Earth’s surface, appears to be quite sensitive to abnormal conditions in lower-latitude oceans.

“With this in mind, the goal of our research was to illustrate the part of Arctic climate change driven by anomalous [different from the norm] influxes of oceanic water from the Atlantic Ocean and the Pacific Ocean, a process which we refer to as borealization,” said lead author Igor Polyakov, an oceanographer at UAF’s International Arctic Research Center and FMI.

Although the Arctic is often viewed as a single system that is impacted by climate change uniformly, the research stressed that the Arctic’s Amerasian Basin (influenced by Pacific waters) and its Eurasian Basin (influenced by Atlantic waters) tend to differ in their responses to climate change.

Since the first temperature and salinity measurements taken in the late 1800s, scientists have known that cold and relatively fresh water, which is lighter than salty water, floats at the surface of the Arctic Ocean. This fresh layer blocks the warmth of the deeper water from melting sea ice.

IMAGE: A MAP OF THE ARCTIC OCEAN SHOWS THE LOCATION OF THE AMERASIAN AND EURASIAN BASINS. ARROWS SHOW THE PATH OF WARM, FRESH PACIFIC WATER AND WARM, SALTY ATLANTIC WATER INTO… view more CREDIT: GRAPHIC ADAPTED FROM POLYAKOV ET AL. 2020, FRONTIERS IN MARINE SCIENCE PAPER.

10 fallacies about Arctic sea ice & polar bear survival refute misleading ‘facts’

by S. Crockford, July 8, 2020 in WUWT


This updated blog post of mine from last year is as pertinent now as it was then: it’s a fully-referenced rebuttal to the misleading ‘facts’ so often presented this time of year to support the notion that polar bears are being harmed due to lack of summer sea ice. Polar Bears International developed ‘Arctic Sea Ice Day’ (15 July) to promote their skewed interpretation of polar bear science at the height of the Arctic melt season. This year I’ve add a ‘Polar Bears and the Arctic Food Chain‘ graphic, which readers are free to download and share. For further information, see “The Polar Bear Catastrophe That Never Happened“.

Remember when we were told: “The Arctic Is On Fire, and We Should all Be Terrified”? It’s SNOWING there now.

by Anthony Watts, July 7, 2020 in WUWT


From the “weather is not climate”, you идиот department comes this about face by climate change nature.

Remember just a couple of weeks ago we were lectured to about the dangers of climate change turning towns around the Arctic circle into easy-bake ovens?

Well, I pointed out how absurd this all was, especially since it also happened 100 years ago, before the climate change was even a glimmer in leftists eyes. And, because with 24 hour sunlight at the peak of the summer solstice, the area is bound to get hot, because there’s no “night” to cool off. Of course, that didn’t stop opportunistic trough-feeding scientists like Mark “the Arctic is screaming” Serreze from taking advantage of the situation, claiming it was all part of a disturbing pattern.

Naturally, the visual that was produced on Twitter to scare people was pretty convincing to the non-thinking media types that pounced on the story.

DESPITE THE LIES, THE SPIN, AND THE PROPAGANDA, ANTARCTIC SEA ICE IS GROWING — BOTH EXTENT AND CONCENTRATION GREATER NOW THAN IN 1980

by Cap Allon, July 6, 2020 in Electroverse


The UN and their scraggly little offshoot, the IPCC, are at it again — obfuscating data in order to push their fraudulent catastrophic global warming agenda.

According to the IPCC, and picked up the usual AGW propaganda rags such as the Guardian: “the South pole is warming three times faster than rest of the world.”

The Guardian articledated June 30, 2020 continues in predictably befogging fashion: “Dramatic change in Antarctica’s interior in past three decades a result of effects from tropical variability working together with increasing greenhouse gases.”

But, 1) the MSM have a habit of claiming everywhere is warming faster than everywhere else:

And 2), the actual data reveals quite the opposite re Antarctica.

As @Harry_Hardrada recently pointed out on Twitter, there was a larger extent and concentration of Antarctic Sea Ice in June 2020 than back in June 1980:

Robert Felix over at iceagenow.com dives into the data, adding that sea ice extent today stands at 700,000 sq km (270,272 sq miles) greater than in 1980.

And in case you’re having a hard time reading the numbers, Felix breaks them down for you:

Sea ice extent in June 2020 = 13.2 million sq km
Sea ice extent in June 1980 = 12.5 million sq km

Sea ice concentration in June 2020 = 10.6 million sq km
Sea ice concentration in June 1980 = 9.6 million sq km

Fact-checked!

That’s enough extra ice to entirely cover Maryland, Delaware, West Virginia, South Carolina, Virginia, Indiana, Ohio and all six New England states. Oh, and throw in Washington, D.C. for good measure. (Which might be a good idea.)

 See also THE ARCTIC IS ON FIRE, AND WE SHOULD ALL BE TERRIFIED” — FACT CHECK: IT’S CURRENTLY SNOWING IN VERKHOYANSK

CLAIM: 100 degrees in Siberia? 5 ways the extreme Arctic heat wave follows a disturbing pattern

by C. Rotter, June 28, 2020 in WUWT


This essay from director of NSIDC, Mark Serreze, is provided for reference. You may remember Serreze who once said “the Arctic is screaming” while botching and then backpedaling on claims of “ice free summers” on the near horizon for the Arctic that never happened. Give it all the consideration it is due. For some perspective, see my article on a previous 100 degree event above the Arctic circle over 100 years ago. By the way, with 24 hours daylight above the Arctic circle, and near 24 hour daylight in Siberia this time of year, (the first day of summer aka  the summer solstice) is it any surprise it would get warm?

This Arctic heat wave has been unusually long-lived. The darkest reds on this map of the Arctic are areas that were more than 14 degrees Fahrenheit warmer in the spring of 2020 compared to the recent 15-year average. Joshua Stevens/NASA Earth Observatory

Scientists Panic, Because Arctic Is 0.4F Warmer Than In 1915!

by P. Homewood, June 21, 2020 in NotaLotofPeopleKnowThat


The Arctic is thought to have recorded its hottest ever temperature of 100.4F (38C) in Siberia, an astonishing 32F (18C) above the normal level for this time of year.

The mercury shot up to the unprecedented level in Verkhoyansk, 3,000 miles east of Moscow, as the region endures a summer heatwave.

Scientists had predicted the Arctic wouldn’t reach these levels until 2100, meaning it is warming 80 years faster than previously thought.

If the record is confirmed it will represent a new high. The current record for hottest temperature in the Arctic is held by Prospect Creek, Alaska, which recorded 100F (38C) in 1915.

Weatherman for CBS, Jeff Beradelli, said on Twitter yesterday: ‘Likely the hottest temperature ever recorded in the Arctic happened today.

‘What’s happening in Siberia this year is nothing short of remarkable. For perspective, Miami has only reached 100F (38C) once on record.’

https://www.dailymail.co.uk/news/article-8444319/Arctic-records-hottest-temperature-mercury-hits-100F-town-Verkhoyansk-Siberia.html?login#readerCommentsCommand-message-field

 

Even the babies who write for the Mail could surely spot the fly in the ointment – that this new record is only 0.4F higher than the previous one set in 1915! Hardly the apocalypse they are trying to present.

As for Verkhoyansk itself, temperatures there reached 37.3C (99.1F) in 1988 during a succession of 30C+ days, so again there is nothing remarkable about the latest weather at all :

A HISTORY OF THE ADVANCE AND RETREAT OF ALPINE GLACIERS

by Cap Allon, June 23, 2020 in Electroverse


It should be obvious after watching that glacial advances and retreats have always occurred and that they must therefore be the result of natural forcings.

On the back of decades of historically high solar activity, modern human’s witnessed a gradual glacial melt. But now, the Sun is once again shutting down, and the evidence for a return to glacial advance is ever-building:

The Greenland Ice Sheet continues to gain record amounts of snow & ice:

 

What Happened To Greenland’s Tipping Point?

by P. Homewood, June 22, 2020 in NotaLotofPeopleKnowThat


Ten years ago, the Guardian warned us that Greenland would have passed a tipping point by now, with the whole ice sheet due to disappear by the end of the century:

How did that work out then?

The article was written in 2010, which was the warmest on record. Since then, however, Greenland’s temperatures have returned to normal, and are no higher than they were in the 1930s.

Far from being the start of a new trend, 2010 was simply an outlier:

 

ASTONISHING, RECORD-BREAKING GAINS CONTINUE ACROSS THE GREENLAND ICE SHEET — MSM SILENT

by Cap Allon, June 11, 2020 in Electroverse


The month of June is breaking records across the Greenland ice sheet, and not records for warmth and melt –as the mainstream media have trained you to expect– but new benchmarks for COLD and GAINS.

The SMB gains occurring right now across Greenland are truly astonishing.

Data-driven FACTS reveal vast regions to the south have been GAINING RECORD/NEAR-RECORD LEVELS of snow & ice all month.

Never before in June has the Greenland ice sheet grown by more than 4 Gigatons in a single day (since 1981 when DMI records began), but now the past week has gone and delivered two such days — June 3, and now yesterday, June 10.

In fact, yesterday’s gains actually neared 5 Gts — you can see from the chart below how anomalous that gain is for the time of year:

 

Blue line (Gt/day): total daily contribution to the SMB from the entire ice sheet. Grey line: mean value from 1981-2010 (DMI).

New Study: Arctic Waters Were 4°C Warmer Than Today And Nearly Sea-Ice Free Year-Round ~4100 Years Ago

by Brice et al., May 28, 2020 in NoTricksZone


Today, the region north of Svalbard is encrusted with sea ice for all but a few weeks per year and summer sea surface temperatures (SSTs) hover near 0°C.  Scientists (Brice et al., 2020) have determined this same region had sea ice-free conditions last about 10 months per year while SSTs reached 4°C just ~4100 years ago.

In early September, 2019, Arctic explorers once again needed to be rescued from the “disappearing” sea ice that had captured their ship in central Svalbard. This region is presently free of sea ice for only a few weeks per year (late August).

Image Source: electroverse.net

The Yin and Yang of Holocene Polar Regions Andy May / 1 day ago May 27, 2020

by R. Hannon/A. May, May 27, 2020 in WUWT


Introduction

The Arctic and Antarctic regions are different and yet similar in many ways. The Arctic has ocean surrounded by land and the Antarctic is a continent surrounded by water. Both are cold, glaciated and located at Earth’s poles some 11,000 miles apart. While sea ice has been retreating in the Arctic, it has been relatively stable in the Antarctic. This post examines surface temperature trends, solar insolation, and CO2 at the polar Arctic and Antarctic regions during the Holocene interglacial period.

 

 

Continuer la lecture de The Yin and Yang of Holocene Polar Regions Andy May / 1 day ago May 27, 2020

Arctique géologique 1/2

by Préat A. & Van Vliet-Lanoë B., 22 mai 2020 in ScienceClimatEnergie


A la grande différence de l’Antarctique, l’Arctique est un océan entouré de plateaux continentaux (Fig. 2). L’océan ou bassin arctique est actuellement constitué par un double bassin, séparé une crête très importante, la ride Lomonosov : le sous-bassin canadien à croûte continentale amincie (3 600 m)  et le sous-bassin eurasiatique à croûte océanique mince, de loin le plus profond (5000 m entre la crête Lomonosov et la ride océanique active de Gakkel). Il est entouré comme le long de l’Atlantique Nord par une plateforme continentale ennoyée, constituée de croûte continentale.  Le bassin arctique  d’abord marin et connecté au Proto-Atlantique au début du Jurassique (voir plus loin), est isolé depuis le Jurassique moyen et essentiellement de nature lacustre, modifiant le régime thermique océanique, amenant un contexte voisin du Glaciaire au Crétacé inférieur (au Valanginien in Dromart et al. 2003 ; Korte et al. 2015 ; Piskarev et al. 2018). Il ne se ré-ouvrira sur le bassin atlantique qu’à partir de l’Eocène, via l’ouverture du détroit de Fram. D’autre part le pôle  magnétique terrestre (Nord) est resté sur le bassin arctique depuis le début du Jurassique, donc en position de déficit énergétique lié à l’obliquité de l’orbite terrestre.

Fig. 2  Image Gebco Arctique : L’océan ou bassin arctique est actuellement constitué par un double bassin, séparé une crête très importante, la ride Lomonossov (voir texte).

GREENLAND HAS GAINED 27+ GIGATONS OF SNOW AND ICE OVER THE PAST 5 DAYS ALONE — MSM SILENT

by Cap Allon, April, 2020 in Electroverse


Despite decades of doom-and-gloom prophecies, Greenland’s Ice Sheet is currently GAINING monster amounts of “mass” — 27 gigatons over the past 5 days alone (April 14 – 18, 2020).

Crucial to the survival of a glacier is its surface mass balance (SMB)–the difference between accumulation and ablation (sublimation and melting). Changes in mass balance control a glacier’s long-term behavior, and are its most sensitive climate indicators (wikipedia.org).

On the back of substantial SMB gains over the past few years, the Greenland ice sheet looks set to continue that trend in 2019-20. From April 14 through April 18, 2020, the world’s largest island added a monster 27+ gigatons to its ice sheet. According to climate alarmists, this simply shouldn’t be happening in a warming world. In fact, it might as well not be happening as developments like these NEVER receive MSM attention, meaning alarmists are NEVER privy to the full and unalarming picture…

‘Arctic April’ Grips N. America Breaking Hundreds Of Cold Records

by Cap Allon, April 16, 2020 in ClimateChangeDispatch


Record cold and snowfall hit many parts of North America over the Easter weekend, continuing what has so far been a largely Arctic April.

Records were toppled across many U.S. states, with Montana, Iowa, South Dakota, and Colorado seemingly worst hit.

A winter storm system moved through Iowa on Sunday delivering between three inches and a foot to the majority of locations — several northern Iowa towns saw all-time records tumble:

The 3.7 inches that fell at Sioux Gateway Airport broke the record for April 12th; it also made it the second-highest Easter snowfall ever behind the 4.7 inches during Easter 1929.

The town of Ringsted in Emmet County (also Iowa) came in with a record-busting 11 inches.

Robert “Lightning” Petersen was the man to log the accumulation — he uses his back yard measuring equipment to keep track of snow and rainfall. He works in concert with the National Weather Service out of Johnston.

El Nino & Arctic Warming In the 1930s

by P. Homewood, April 5, 2020 in NotaLotofPeopleKnowThat


Just following up on Joe Bastardi’s article yesterday about El Ninos and Arctic warming, it is worth looking at longer term trends.

Below is the chart of the MEI, with red indicating El Ninos and blue La Ninas.:

Extended Multivariate ENSO Index

https://www.esrl.noaa.gov/psd/enso/mei.ext/

As we can see, the period 1925 to 1945 was dominated by powerful El Ninos. This of course was also the time of great warming in the Arctic, known as “The Warming in The North”, when temperatures across much of the Arctic were as high as they are now.

During the 1950s, a much colder climate took over in the Arctic, until it became warmer again in the 90s. This was also a period when La Ninas dominated.

Coincidence?

The climate in the Arctic is also very well correlated with the Atlantic Multidecadal Oscillation (AMO):

Continuer la lecture de El Nino & Arctic Warming In the 1930s

GREENLAND’S SMB GAINED 6 GIGATONS YESTERDAY + NORTHERN HEMISPHERE SNOW MASS SITTING AT 500 GIGAGTONS ABOVE THE NORM

by Cap Allon, March 29, 2020 in Electroverse


Despite decades of doom-and-gloom prophecies, Greenland’s Ice Sheet is currently GAINING monster amounts of “mass”— 6 gigatons yesterday alone (March 28, 2020).

Crucial to the survival of a glacier is its surface mass balance (SMB)–the difference between accumulation and ablation (sublimation and melting). Changes in mass balance control a glacier’s long-term behavior, and are its most sensitive climate indicators (wikipedia.org).

On the back of substantial SMB gains over the past few years, the Greenland ice sheet looks set to continue that trend in 2019-20. On March 28, 2020, the world’s largest island added a monster 6 gigatons to its ice sheet. According to climate alarmists, this simply shouldn’t be happening in a warming world. In fact, it might as well not be happening–developments like this NEVER receive MSM attention, meaning alarmists are NEVER privy to the full and unalarming picture…

polarportal.dk/

In addition, Total Snow Mass for the Northern Hemisphere continues to track WELL-above average with the latest data point (March 27) seeing NH snow at a staggering 500+ gigatons above the norm—another real-world reality we were told should be an impossibility by now: IPCC 2001: “Milder winter temperatures will decrease heavy snowstorms…”

Continuer la lecture de GREENLAND’S SMB GAINED 6 GIGATONS YESTERDAY + NORTHERN HEMISPHERE SNOW MASS SITTING AT 500 GIGAGTONS ABOVE THE NORM

Les glaces terrestres, la cryosphère (2/3)

by J.C. Maurin, 27 mars 2020 in ScienceClimatEnergie


Partie 2/3 : Lecture critique du chapitre cryosphère de l’AR5

par J.C. Maurin, Professeur agrégé de physique

Cette deuxième partie de l’article examine la composition du chapitre 4 du 5ème rapport du GIEC (AR5) [1].
Dans ce chapitre, qui concerne les différentes composantes de la cryosphère, les banquises [2] et glaciers [3] sont particulièrement mises en avant par les rédacteurs du GIEC.
A propos de ces 2 composantes mineures (0,65 % du volume de la cryosphère), l’article développe certains éléments d’appréciation que les rédacteurs de l’AR5 n’ont pas mis en exergue.

Continuer la lecture de Les glaces terrestres, la cryosphère (2/3)

Absence of evidence for greenhouse warming over the Arctic Ocean-Mark Serreze 1990

by P. Homewood, March 23, 2020 in NotaLotofPeopleKnowThat


We are familiar with the incessant claims that the Arctic is one of the fastest warming regions on Earth, and that this is due to the polar amplification effect of greenhouse gases.

But scientists back in the 1990s found that this theory did not stack up then:

Abstract

ATMOSPHERIC general circulation models predict enhanced greenhouse warming at high latitudes1owing to positive feedbacks between air temperature, ice extent and surface albedo2–4. Previous analyses of Arctic temperature trends have been restricted to land-based measurements on the periphery of the Arctic Ocean5,6. Here we present temperatures measured in the lower troposphere over the Arctic Ocean during the period 1950–90. We have analysed more than 27,000 temperature profiles, measured by radiosonde at Russian drifting ice stations and by dropsonde from US ‘Ptarmigan’ weather reconnaissance aircraft, for trends as a function of season and altitude. Most of the trends are not statistically significant. In particular, we do not observe the large surface warming trends predicted by models; indeed, we detect significant surface cooling trends over the western Arctic Ocean during winter and autumn. This discrepancy suggests that present climate models do not adequately incorporate the physical processes that affect the polar regions.

https://www.nature.com/articles/361335a0

The cooling between 1950 and 1990 is very evident at a whole range of land sites on the fringes of the Arctic, ranging from Greenland right through to eastern Siberia.

Les glaces terrestres, la cryosphère (1/3)

by J.C. Maurin, 13 mars 2020 in ScienceClimatEnergie


On désigne par cryosphère l’ensemble des glaces terrestres. Son évolution, lors des dernières décennies, est souvent présentée comme préoccupante: il en résulterait une forte hausse des niveaux marins et un changement d’albédo et donc du bilan énergétique de la Terre. Cette première partie de l’article présentera quelques ordres de grandeurs pour les glaces terrestres.
On utilisera principalement les données du chapitre 4 du rapport AR5 WG1 (5th Assessment Report, Working Group 1) qui a été publié en 2013 par l’organisme intergouvernemental GIEC.

 

 

 

 

4. Conclusions

  • La cryosphère c’est en premier lieu les zones proches du pôle Sud : banquises et glaciers ne représentent ensemble que 0,7% du volume de la cryosphère alors que la seule partie Est de l’Antarctique, bien moins connue, représente plus de 75% de la cryosphère, soit 107 fois plus.
  • La simple correction du volume de glace en Antarctique, entre les rapports du GIEC AR4 (2007) et AR5 (2013), est 4 fois plus grande que le volume (Banquises + Glaciers).
  • Les variations actuelles de la cryosphère restent négligeables si on les compare à celles du passé : l’ensemble des glaces terrestres, il y a 20 millénaires, devait avoir un volume au moins double du volume actuel. En effet, la fonte des glaces (entre -18 ka et -8 ka) fait monter le niveau des océans de ≈ 120 m  contre 66 m SLE (Sea Level Equivalent à la Figure 1).

La deuxième partie de l’article (2/3) commentera les choix rédactionnels du GIEC pour le chapitre 4 de l’AR5 et donnera des ordres de grandeurs complémentaires pour les banquises et les glaciers.