Our glaciers are more at risk than researchers think

There are more than 215,000 people in the mountains of our beautiful Earth glaciersglaciers. Glaciers also suffering from global warming. A study a few months ago confirmed this. Glaciers are melting all over the world. Not only are they melting, but now they are melting faster than ever. Today, an international team of researchers is going one step further. Their work shows that even under the most optimistic climate scenarios, our glaciers will lose more massmass more than previously estimated.

The researchers draw this conclusion from new datasets from which they have developed global projections of all the world’s glaciers. Especially considering the processes accurately for the first time physicalphysical switches that control their mass loss. What to overcome the limitations of existing forecasts.

Effects on sea level

According to the researchers, the world’s glaciers are expected to lose 26-41% of their total mass under scenarios where temperatures rise 1.5-4°C above the pre-industrial average. With a situation that gets worse or better for every tenth of a degree of more or less warming. Even in the targeted +1.5°C scenario, up to half of the Earth’s glaciers will be lost by 2100. If the world follows the trajectory of commitments made at COP26 — enough to contain +2.7°C warming — our planet will likely experience complete deglaciation of all regions latitudeslatitudes average indicators. Including in Europe.

Thus, sea levels must rise more than previously thought. More globally, Earth will experience changes in hydrology and freshwater availability.ecologyecology and natural hazards. But the researchers note that any effort to limit the rise in global average temperatures will have a direct impact on reducing the number of glaciers that will be lost. And according to these results…

Climate emergency: The world’s glaciers are melting faster than ever

Glaciers around the world are also melting as a result Global WarmingGlobal Warming anthropogenic. But it remained to clarify the scale of the phenomenon. Today, researchers believe that they lose about 300 billion tons of ice every year. And that’s the rhythm of it meltingmelting has accelerated significantly in the last two decades. It contributes significantly to sea level rise.

article Nathalie MayerNathalie Mayer Published on 02/05/2021

For the first time, CNRS researchers, with the support of the National Space Research Center (Cnes), have succeeded in accurately measuring changes in the thickness of all the world’s glaciers – or rather, a very precise 97% of them. And their conclusions are not encouraging. Almost everywhere on the planet, glaciers are melting today at a record rate and speed. Under the influence 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 about 227 billion tons 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, in 2019 they lost exactly 69 centimeters. Greenland is more than an ice cap or an ice sheetAntarcticAntarctic. And this is enough to pour 50 centimeters of water over the entire mainland of France.

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

Melting glaciers raise sea levels

For glaciologists around the world, this work is literally a game-changer. Because currently only a few hundred glaciers are observed in place. These new data should allow researchers to better constrain their models. to better appreciate the interaction between weatherweather and glaciers. Thus, they already note that if decadal precipitation changes provide some explanation anomaliesanomalies Global acceleration of glacier mass loss observed regionally — for example in Scandinavia — clearly reflects global warming of the atmosphere.

Researchers also hope to better predict how glaciers contribute to sea-level rise.A phenomenon often attributed to the melting of ice in Greenland and Antarctica does indeed appear to be related to melting glaciers.

Did you know?

Glaciers are rivers of ice formed by the accumulation of snow over the years. Now about 10% of the surface of our planet is covered by glaciers. They hold 70% of fresh water.

If all the ice that has melted since 2000 reached the ocean, the researchers calculate that it would have contributed to a rise in excess water levels of 0.74 millimeters per year. They also estimate 6-19% of sea-level acceleration in 21e century due to mass loss from glaciers. However, 21% of this height will come from the melting waters of these glaciers. According to the study authors, “Further scientifically rigorous evidence of the urgency of rapid and collective action to reduce greenhouse gas emissions”.

Melting of glaciers is the main cause of rising oceans

The melting of the Earth’s glaciers will play a major role in the rise of the ocean levels. EnlargementEnlargement thermal water or the melting ice of Greenland and Antarctica. Between 1902 and 2009, the increase in water caused by this phenomenon is estimated at 11 cm. This figure may increase by another 15 cm by 2100.

Article posted by Quentin Mauguit on 19/11/2012

Average ocean levels have been rising steadily since the beginning of the 20th century.e century Its total rise for this period is currently estimated at 20 cm. Two factors related to the warming of our planet allow us to explain this. On the one hand, an increase in temperature causes the thermal expansion of water and, therefore, its increase volumevolume. On the other hand, heatheat melts ice regardless of its origin. The presence of Arctic sea ice made headlines last summer, but let’s not forget that glaciers also contain large amounts of fresh water.

Ben Marzeion and colleaguesUniversity of Innsbruck (Austria) determined the contribution to the average sea level rise in the last century. They modeled about 300,000 glaciers the doorthe door Our planet except for Greenland and Antarctica. Their evolution over time was then followed by taking into account carefully recorded rainfall and temperature over many years. The results of the simulations were later confirmed by thousands of field measurements.

Thus, the melting of the glaciers from 1902 to 2009 would have caused an average rise in seas of 114 ± 5 ​​mm, or about 11 cm. Therefore, this would be the main reason for the rise in water levels even before the melting of the Antarctic and Greenland ice sheets and thermal expansion! This result was published in the journal Cryosphere.

Half of the ice in the Alps in 2040

The rate of global melting in the 20th century is astonishinge century would be relatively stable despite temperature fluctuations. Indeed, during cold periods, glaciers expand, descend in altitude, and stop in warmer places, where they… melt. Moreover, a much colder turn of the century would have been marked by two relatively warm periods in the Arctic (1930s and 1950s). They then caused significant melting of Canada’s glaciers.

Projections were also made to determine the impact of melting glaciers on mean sea levels by 2040, 2100 and 2300. 15 climate models for this Integrated Inter-Model Comparison Project phase 5 (CMIP5) was used to estimate the likely development of temperature and precipitation in future centuries. For each of them, four possible scenarios of the technical, economic and social evolution of our society were launched (CPRCPR 2.6, 4.5, 6.0 and 8.5). In particular, they allow us to calculate the amount of greenhouse gases we will emit over time.

The Alps, like all regions with small glaciers, could thus lose half of their ice by 2040, but with no major consequences for the world’s oceans (an increase of 0.2 mm). The situation is completely different for countries with large frozen water bodies. So Canada will hold 70% of the Arctic ice cap volume by 2100, but the melted portions will cause sea levels to rise by 2 cm in that time!

Global mean sea level may rise from 148 ± 35 mm (RCP 2.6) to 217 ± 47 mm (RCP 8.5) by the end of the century. In 2300, the increase should be at least 248 ± 66 mm (RCP 2.6), with a maximum limit of 424 ± 46 mm (RCP 8.5). Of course, all these figures, which do not take into account the melting of the Greenland and Antarctic ice sheets and the thermal expansion of water, are subject to many uncertainties. FYI, RCP 2.6 corresponds to a very optimistic scenario where humans can quickly stop producing CO2.2 then swallow.

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