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Our glaciers are in more danger than researchers thought

Our Earth is heating up. And the ice melts. Not only on the side of the poles. Pretty much everywhere in the world. The glaciers are disappearing. Faster and faster. But also more massively than researchers thought so far. Again, every tenth of a degree counts…

In the mountains of our beautiful Earth, there are more than 215,000glaciersglaciers. Glaciers which are also suffering from global warming. A few months ago, a study confirmed it. All over the world, glaciers are melting. Not only do they melt, they now melt faster than ever. Today a international team of researchers adds. Their work shows that even under the most optimistic climate scenarios, our glaciers will lose far more massemasse than previously estimated.

This conclusion, the researchers draw it from new sets of data thanks to which they produced global projections of all the glaciers of the world. Taking account, in particular, for the first time in a precise manner of the processes physiquesphysiques keys controlling their mass loss. What to overcome the limitations of existing projections.

Effects on sea level

What the researchers predict is that under scenarios of temperature increases of 1.5-4°C above pre-industrial averages, the world’s glaciers are expected to lose 26-41% of their total mass. . With a situation that worsens — or improves — for each tenth of a degree of warming more — or less. Even in the target scenario of +1.5°C, up to half of the Earth’s glaciers will be lost by 2100. If the world follows the trajectory of the commitments made at COP26 — enough to hold a warming of +2.7°C — our Planet will probably experience complete deglaciation of entire regions at latitudeslatitudes averages. Including, in Europe.

It is thus the sea level which should rise more significantly than that envisaged until now. More globally, the Earth will be exposed to changes in hydrology and the availability of fresh water, theecologyecology and natural hazards. But the researchers note that any effort to limit the increase in global average temperature will have a direct effect on reducing the number of glaciers that will be lost. And on these consequences…


Climate emergency: Glaciers are melting faster than ever around the world

All over the world, glaciers are melting under the effect of global warmingglobal warming anthropogenic. But the extent of the phenomenon remained to be clarified. Today, researchers assure that they lose almost 300 billion tons of ice every year. And that the rhythm of this sourcesource has accelerated significantly over the past twenty years. Contributing substantially to sea level rise.

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Article of Nathalie MayerNathalie Mayer published on 02/05/2021

For the first time, CNRS researchers, with the support of the National Center for Space Studies (Cnes), have managed to accurately measure the changes in thickness of all the glaciers in the world – or let’s say very exactly 97% of them. And their conclusions are not encouraging. Almost everywhere on the planet, glaciers are melting today at a record and accelerating rate. Under the effect of anthropogenic global warming.

What is the role of glaciers for the climate and the planet?

Between 2000 and 2004, the world’s glaciers lost some 227 billion tonnes each year. Between 2015 and 2019, they melted about 298 billion tons of ice each year. In other words, while in 2000, the glaciers thinned by 36 centimeters, they lost no less than 69 centimeters in 2019. Their global mass has, for its part, fallen by an average of 267 billion tons per year. year since 2000. This is more than the Greenland ice cap or that of theAntarcticAntarctic. And that’s enough to dump 50 centimeters of water over the whole of mainland France.

These values, the researchers hold them from the analysis of half a million images taken by the Terra satellite of nearly 220,000 glaciers. Using two cameras, since 2000 it has regularly acquired pairs of images of the Earth’s surface. And these images have allowed scientists to create digital modelsdigital models of glacier elevation with unrivaled spatial and temporal precision.

Melting glaciers are raising sea levels

For glaciologists around the world, this work is literally a game-changer. Because only a few hundred glaciers are currently monitored on site. These new data should allow researchers to better constrain their models. To better assess the interaction between the weatherweather and glaciers. They thus already note that if ten-year changes in precipitation patterns explain certain anomaliesanomalies Observed regionally — in Scandinavia, for example — the global acceleration of glacier mass loss clearly reflects the global warming of the atmosphere.

The researchers also expect to better predict, in particular, what will be the contribution of glaciers to sea level rise. The phenomenon, often attributed to the melting of the ice in Greenland and Antarctica, indeed also seems linked to the melting of glaciers.

Did you know ?

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Glaciers are rivers of ice that form by accumulating snow over years. About 10% of the surface of our planet is now covered by glaciers. They store 70% of fresh water.

If all the ice melted since 2000 has reached the ocean, the researchers calculate that it has already contributed to raising the water level by 0.74 millimeters per year. They also estimate that between 6 and 19% of the acceleration in sea level rise in the 21e century is due to the loss of mass from the glaciers. While 21% of this elevation would come from these glacial meltwaters. According to the study authors, “additional scientifically rigorous proof of the urgency of rapid and collective action to reduce our greenhouse gas emissions”.


The melting of glaciers, the main cause of the rise of the oceans

The melting of the globe’s glaciers would play a major role in the rise in the level of the oceans, much more than the dilatationdilatation thermal water or the melting ice of Greenland and the Antarctic. The rise in water caused by this phenomenon between 1902 and 2009 has been estimated at 11 cm. This figure could increase by another 15 cm by 2100.

Article by Quentin Mauguit published on 19/11/2012

The mean sea level continues to rise since the beginning of the XXe century. Its total rise for this period is currently estimated at 20 cm. Two factors linked to the warming of our planet make it possible to explain this. On the one hand, the increase in temperature causes a thermal expansion water and therefore an increase in its volumevolume. On the other hand, the heatheat melts ice, whatever its origin. The case of the arctic pack ice made the news last summer, but let’s not forget that large quantities of fresh water are also trapped within glaciers.

Ben Marzeion and his colleagues from theUniversity of Innsbruck (Austria) have determined their involvement in the average rise in the level of oceans during the last century. They modeled the approximately 300,000 glaciers that porteporteour planet, excluding Greenland and Antarctica. Their evolution over time was then retraced taking into account precipitation and temperatures carefully recorded for many years. The results provided by the simulations were then validated by thousands of measurements taken in the field.

Thus, from 1902 to 2009, the melting of the glaciers would have caused an average sea level rise of 114 ± 5 ​​mm, or about 11 cm. This would therefore be the main cause explaining the rise in water levels, even before the melting of the ice of Antarctica and Greenland and thermal expansion! This result was published in the journalThe Cryosphere.

Half the ice in the Alps in 2040

Surprisingly, the global rate of melting during the XXe century would have been relatively constant, despite changes in temperature. Indeed, in cold periods, the glaciers expand, descend in altitude and stop in the warmer zones where… they melt. Moreover, the beginning of the century, which was considerably colder than today, would have been marked by two relatively warm periods in Arctic (in the 1930s and 1950s). They then caused a significant melting of Canadian glaciers.

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Projections were also made to determine the impact of melting glaciers on mean sea levels by 2040, 2100 and 2300. To do this, 15 climate models belonging toCoupled Model Intercomparison Project phase 5 (CMIP5) were used to estimate the likely development of temperature and rainfall in the coming centuries. For each of them, four possible scenarios of technical, economic and social evolutions of our society were launched (RCPRCP 2.6, 4.5, 6.0 and 8.5). In particular, they make it possible to estimate over time the quantities of greenhouse gas that we will issue.

The Alpeslike all regions with small glaciers, could thus lose half of their ice by 2040, but without major consequences for the oceans of the globe (elevation of 0.2 mm). The situation is quite different for countries with large bodies of frozen water. Thus, Canada will retain 70% of the volume of its Arctic glaciers by 2100, but the melted parts will have caused a 2 cm rise in sea level in the meantime!

Globally, mean sea level could rise from 148 ± 35 mm (RCP 2.6) to 217 ± 47 mm (RCP 8.5) by the end of the century. In 2300, the rise should be at least 248 ± 66 mm (RCP 2.6), the maximum limit being fixed at 424 ± 46 mm (RCP 8.5). Of course, all these figures, which do not take into account the Greenland ice meltand Antarctica and the thermal expansion of water, remain subject to many uncertainties. For information, RCP 2.6 corresponds to a very optimistic scenario where humans would quickly be able to stop the production de CO2 then to absorber.

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