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Antarctic ice melting – sea level rise by 2100

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New research reveals how much melting ice in Antarctica will help raise sea levels. After pessimistic forecasts from 2016, good news is now arriving, but only if the obligations from the Paris Agreement are met.

Human greenhouse gas emissions are causing global warming and consequent melting of ice, increasing the volume of the oceans and seas.

Finally the concentration of greenhouse gases Today’s sea level is 10-30 meters above sea level, and it is estimated that the sea level will rise to 70 meters if all the ice on the planet melts. It threatens many coastal cities and small island nations, and scientists spend a lot of time and effort trying to understand the processes that cause ice to melt and the speed at which our planet loses its ice cover in the future.

Over the past decade, great progress has been made in this area, followed by interesting scientific discussions between teams that have reached different results in research. The ultimate goal of these studies is to design the best response to the new conditions that people face due to climate change, as well as to reach international agreements on significantly reducing greenhouse gas emissions and limiting average global warming growth. Paris Agreement).

2016 Warning

The 2016 weather forecast, which warns that we can minimize the danger of ice melting from Antarctica, has shaken not only the scientific community but also the general public. The study was conducted by American scientists Decon and Pollard. It is estimated that by 2100 the melting of Antarctic ice will add a whole meter to the average level in the world, which certainly resonated in many media.

This paper deals primarily with previously unexplained phenomena of the instability of ice sheets and rock formations, which, due to various factors, decompose from the land and end up in the sea. Only by incorporating these phenomena into existing models have scientists been able to reconstruct the last interglacial (period between 130,000-115,000 years ago, two great ice ages) in the Pliocene (three million years ago). To understand how much the melting of Antarctic ice in today’s climate will help raise world sea levels, compare it to the Pliocene period. At that time, the concentration of carbon dioxide in the atmosphere was 400 ppm, which is the current level (419 ppm), while sea level is estimated to be 10-30 meters higher than it is today.

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The results of this study were questioned in 2019 by British scientist Tomson Edwards at King’s College London, who used their statistics to significantly increase the number of weather model simulations developed by Deccan and Pollard. Ice. With this method, it has been concluded that Antarctica’s contribution to world sea levels will be 45 cm by 2100 – far less than it actually is – in a high-emission situation (RCP 8.5) where little has been done about climate change – studies reported in 2016

Five years after the publication of the pessimistic predictions of Deacon and Pollard, their latest research was published in the journal Nature on May 5, 2021, at about the same time as the latest results of a team of 84 researchers from Thomson Edward and 62 researchers from various institutions. Although they differ in their approach to the uncertainty and calibration of climate models, the predictions of both papers are much more optimistic than in 2016.

What causes sea level rise?

Glaciers and glaciers are currently melting, causing world sea levels to rise by half. An important reason is the warming of the ocean, which leads to its expansion, and therefore contains a large amount of the same amount of water (because hot water has a lower density). The reason for these studies to deal only with land ice is very simple – sea ice does not cause sea level rise because it already exists.

Both groups of scientists included different warming conditions in their studies, forcing two papers, including the current global eruption, followed by the 2-degree Paris Agreement target and the more desirable 1.5-degree target.

Edwards et al (2021): There is room for optimism if we strive to achieve the greatest goal of the Paris Agreement.

The advantage of the statistical model is that the so-called ’emulator’ used by Edward and his associates combines many imitations from various previous models. This conclusion gives hope: if countries achieve their current goal of reducing pollution, the melting of land ice will raise world sea levels by 25 centimeters by the end of this century; However, if the international community respects the Paris Agreement and raises the average annual temperature to 1.5 degrees Celsius compared to pre-industrial standards, Edward and his team predict a doubling of sea level – 13s.

The study concludes that if the 1.5 degree target is reached, the contribution of the Greenland ice sheet will be reduced by 70 percent and the contribution of land glaciers will be doubled. It should be noted that the study also includes data on the melting of 220,000 glaciers, which contribute up to 20 percent of sea level rise, and represent only 1 percent of the world’s ice.

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On the other hand, the contribution of descent to Antarctica varies considerably, and represents the greatest unknown in the equation at sea level. Various factors, such as the magnitude of the new ice attack and the rate at which the edges of the ice sheets are melting, greatly influence the uncertainty in the study of this phenomenon.

Part of the work is devoted to pessimism, but physically possible predictions. Based on these calculations, the contribution of land ice to sea level rise (including Antarctica) would be 42 cm based on current emission reduction policies or 30 cm (so-called SAA1-19 if fully complied with the Paris Agreement).

Deconto et al (2021): Given current emissions, it is impossible to change the intensity of heating by 2060

In contrast to the previous one, the model of this paper has been calibrated in relation to changes in sea level in the past, but it does not examine such broad uncertainties.

The conclusion is that limiting the average annual Earth’s temperature to two degrees above pre-industrial levels will not change the melting rate of Antarctic ice much more than it currently does. Robert Decont’s team predicts that by 2060 we will have reached a turning point if greenhouse gas emissions continue at current levels – that is, it is impossible to change the heating intensity and melting point of ice after this period, and the world community decides to implement mass geoengineering projects.

According to the current policies and laws of the various countries analyzed by Climate Action Tracker, the average annual temperature on the planet will rise to about 2.9 by C by the end of the century, however, if fully committed to the treaty aimed at countries committed to Paris, the average temperature will be 2.4 higher C by 2100. The latest Climate Action Tracker report takes into account the optimism that the recently announced aspirations to achieve net zero emissions by 2050 will be successfully fulfilled. If so, the planet will heat up to 2 degrees Celsius by the end of the century.

That is why the results of Deacon’s research are now calling for more desirable action to limit the melting of ice in Antarctica.

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What is the significance of these studies at the local level?

In short, they tell us the magnitude of the potential values ​​of future sea levels and the potential of many situations, which means that current adaptations must be very flexible, while forcing greenhouse gas emissions to drastically reduce (mitigation).

On the one hand, if decision makers rely on more optimistic circumstances, even if the sea level is low and the obligations under the Paris Agreement are not met, the adjustment procedures may not be adequate, resulting in material damage and loss of life. On the other hand, if they decide to prepare for more unfavorable circumstances, a very high amount of unnecessary investment may occur, which can also lead to significant financial consequences.

Floods covering large coastal areas do not depend on ice melting alone – factors such as local consumption and tectonic plate shifting are also important, as they can cause entire cities to sink (Jakarta, the capital of Indonesia). The American National Oceanic and Atmospheric Administration has developed the Sea Level Rise Viewer, a tool that brings scientific data closer to us, to present the average elevation above sea level at a given altitude.

Edwards vs.. Deconto: Which model is better?

There is no climate model that can accurately predict future sea level rise. Since the contribution of most factors is highly uncertain, information from a variety of sources, i.e. members of the scientific community with different attention and approaches, can be said to be a combination of these models and information on sea level rise (as the latest IPCC Special Report on the Oceans and the Cryosphere did).

As statistician George Box put it: “All models are wrong, but some are useful.” Therefore, it is important to note that despite the disagreement of scientists on some issues of model design, their contributions to further research and decision making remain immeasurable. It must be remembered that the ambitious goals of the Paris Agreement can only be achieved through the collaboration of science and smart policies.

As can be seen from the works mentioned, the scientific community is mainly based on the goals achieved internationally for weather forecasting. It remains to be seen at the next UN Climate Summit (COP26) in Scotland in November whether decision makers will take scientific research into account.

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