What is the difference between an increase in the temperature of the planet by 1.5 degrees and an increase of two degrees? .. The world’s scientists answer

At the United Nations Climate Summit in Glasgow, COP26, world leaders have been emphasizing, one by one, that the increase in global temperature should be limited to 1.5 degrees Celsius.

is required”Paris Agreement(The Paris Agreement) – concluded in 2015 – states to work to keep the average increase in the planet’s temperature below two degrees Celsius above pre-industrial levels, and target the increase to 1.5 degrees Celsius. Scientists have said that exceeding 1.5 degrees represents the risk of launching The most severe implications of climate change for humans, wildlife and ecosystems.

Preventing this requires reducing carbon dioxide emissions into the atmosphere by almost half by 2030 from their level in 2010 and reducing them to net zero by 2050, an ambitious task that scientists, owners of the financing sector, negotiators and activists discuss at the COP26 climate summit on how to achieve and finance it.

But what is the difference between 1.5 degrees and two degrees? A number of scholars were asked about the interpretation of the difference, and the following is what they answered:

Heavy rains swamped China and western Europe, killing hundreds (Getty Images)

where are we now?

The planet is already about 1.1 degrees Celsius warmer than it was before the industrial revolution. The temperature has increased in each of the last four decades than in any decade since 1850.

“We haven’t seen such a rise in global temperature in a few decades,” said Daniela Jakob, a climate expert at Germany’s climate center DKRZ. “And half a degree means much more extreme weather events that can be more frequent, intense and longer-lasting. “.

This year, heavy rains inundated China and western Europe, causing hundreds of deaths. Hundreds more were killed when temperatures in the Pacific Northwest reached record levels. Greenland has seen massive glaciers melt, wildfires have caused huge losses in the Mediterranean and Siberia, and an unprecedented drought has affected parts of Brazil.

“Climate change is already affecting all populated areas around the globe,” said Rachel Warren, a climate scientist at the University of East Anglia.

DroughtRising temperature increases risks of water evaporation leading to more extreme droughts (Getty Images)

Heat, rain and drought

A rise in the difference to 1.5 degrees Celsius would worsen these repercussions. “For every increase in temperature, the changes in extreme events increase in magnitude,” said Sonia Seneviratne, a climate expert at ETH University in Zurich. She added that heat waves, for example, will recur at a faster pace and will be more severe.

The United Nations body on climate change (IPCC) says that the extreme heat wave, which used to occur once every decade in a climate with no human influence, will recur 4.1 times per decade when the increase in temperature reaches 1.5 degrees Celsius, and 5 6 times as the increase amounted to two degrees. And if the increase jumps to 4 degrees Celsius, this wave will repeat 9.4 times during the decade.

Also, the increase in the temperature of the atmosphere can lead to an increase in the humidity in the atmosphere; This leads to more intense rains and increases the risk of floods and torrential rains. It also increases the risks of water evaporation leading to more extreme droughts.

Coral reefsA 1.5°C increase in temperature would destroy at least 70% of coral reefs (Getty Images)

Ice, seas and coral reefs

The difference between 1.5 degrees and 2 degrees Celsius is extremely important for Earth’s oceans and ice areas. “At 1.5 degrees, there is a good chance that we can prevent the collapse of the Greenland and West Antarctic ice sheets,” said climate scientist Michael Mann at Penn State University.

This contributes to limiting sea level rise to a few feet by the end of this century, although this represents a major change that will lead to the erosion of coastal areas and the inundation of some small countries based on coastal islands and cities.

But Mann said that exceeding 2 degrees Celsius would cause the ice sheet to collapse and sea levels to rise by up to 10 metres, although the pace at which this might happen is uncertain.

Also, an increase in temperature of 1.5 degrees Celsius would destroy at least 70% of coral reefs, but an increase of two degrees Celsius would lead to the loss of more than 99% of them. This would eliminate fish growth environments and human societies that depend on reefs for their food and livelihoods.

Global warming may lead to the spread of mosquitoes that transmit diseases such as malaria and dengue fever (Getty Images)

Food, forests and diseases

A temperature increase of 2 degrees compared to 1.5 degrees Celsius will have greater implications for food production. “If there are crop losses in some of the areas that are the world’s food baskets all at once, you will see extreme increases in food prices and starvation and famine in large parts of the world,” said Simon Lewis, a climate scientist at University College London.

In addition, global warming may lead to the spread of mosquitoes that transmit diseases such as malaria and dengue fever to wider areas. However, an increase in temperature of two degrees Celsius will lead to a greater percentage of insects and animals losing most of their natural habitats, compared to an increase of only 1.5 degrees. It would also lead to an increased risk of wildfires, with the risk to wildlife that this entails.

Forest fires have caused great losses in different regions of the world (Getty Images)

The turning point

As the world warms, the risks of reaching a “tipping point” at which Earth’s systems cross a threshold at which cascading or irreversible repercussions will be triggered increases. The exact timing of reaching these points is uncertain.

Droughts, less rain, and continued destruction of the Amazon through desertification, for example, can lead to the collapse of the rainforest system and release carbon dioxide into the atmosphere instead of being absorbed and stored.

Or that the warming of the ice in the Arctic Circle will cause the decomposition of long-frozen biomass and release a huge amount of carbon emissions.
“That’s why it’s so dangerous to continue emitting fossil fuels because we increase the likelihood that we will reach one of these tipping points,” Lewis said.

Exceeding 2 degrees Celsius will cause the ice sheet to collapse and sea levels to rise by up to 10 metres (Getty Images)

more than two degrees

So far, the climate pledges made by countries from the UN pledge register would push the world to a 2.7°C increase.

The International Energy Agency (IEA) said last Thursday that the new promises made at the “Cop26” summit could limit the increase if implemented to below 1.8 degrees Celsius, although some experts questioned the validity of these the accounts. It remains a mystery whether these promises will turn into actions on the ground.

Scientists said that a global warming of 2.7 degrees Celsius would lead to unbearable heat at some times of the year across the tropics and subtropics. They said biodiversity would be massively depleted, food security would decline, and extreme weather events would overwhelm most of the infrastructure needed to accommodate it in urban areas.

“If we can keep the temperature increase below 3 degrees Celsius we will probably remain within our adaptive capabilities as a civilization, but at 2.7 degrees Celsius we will see huge hardships,” Mann said.

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