Explanatory-What is the difference between global warming between 1.5 ° C and 2 ° C? By Reuters

Author: Kate Abnett

GLASGOW (Reuters) – At a United Nations climate summit in Glasgow, world leaders repeatedly stressed the need to limit global warming to 1.5 degrees Celsius.

The 2015 Paris Agreement commits countries to limit the rise in global average temperature to much less than 2 ° C above pre-industrial levels and to 1.5 ° C.

Scientists say exceeding the 1.5 ° C threshold risks releasing much more serious effects of climate change on people, wildlife and ecosystems.

To prevent this, it calls for a halving of CO2 emissions by 2030 from the 2010 level and a zero reduction by 2050 – an ambitious task being discussed by COP26 scientists, funders, negotiators and activists on how to achieve and pay for them.

But what is the difference between 1.5 ° C and 2 ° C heating? We asked several scientists to explain:

WHERE ARE WE NOW?

Already, the world has warmed to around 1.1 ° C above pre-industrial levels. Each of the last four decades has been hotter than any decade since the 1850s.

“In a few decades we have never had such global warming,” said climate scientist Daniela Jacob at the German Climate Service Center. “Half a degree means much more extreme weather, and it can be more frequent, more intense, or longer lasting.”

Earlier this year, rains flooded China and Western Europe, killing hundreds of people. Hundreds more died when temperatures in the Pacific Northwest were at record highs. Greenland had major melting events, forest fires destroyed the Mediterranean and Siberia, and a record drought hit parts of Brazil.

“Climate change is already affecting all regions around the world,” said climate scientist Rachel Warren of the University of East Anglia.

HEAT, RAIN, LEORTEA

Heating above 1.5 ° C will exacerbate such impacts.

“For every increase in global warming, the changes in extremes are greater,” said climate scientist Sonia Seneviratne ETH Zurich.

For example, heat waves would be more frequent and severe.

An extreme heat event that occurs once a decade in a human-free climate would occur 4.1 times a decade when heated to 1.5 ° C, and 5.6 times at 2 ° C, according to the UN Panel on Climate Science (IPCC).

Allow the spiral heating to 4 ° C, and such an event could occur 9.4 times a decade.

A warmer environment can contain more moisture, which can result in extreme rainfall that increases the risk of flooding. It also increases evaporation, causing more intense droughts.

ICE (NYSE :), SEAS, CORAL REEFS

The difference between 1.5 ° C and 2 ° C is crucial for the Earth’s oceans and frozen regions.

“At 1.5 ° C, there’s a good chance that most of the ice sheets in western Greenland and Antarctica won’t fall,” said climate scientist Michael Mann of Pennsylvania State University.

This would help limit sea level rise to a few feet by the end of the century; it is still a big change that will erode the coasts and overwhelm some small island states and coastal cities.

But it could rise above 2 ºC and collapse the ice sheets, Mann said, as sea levels rise to 10 meters (30 feet), although it is doubtful how quickly that could happen.

Heating to 1.5 ° C would destroy at least 70% of coral reefs, but lose more than 99% at 2 ° C. This would destroy fish habitats and communities based on reefs for food and livelihoods.

FOOD, FORESTS, DISEASE

Heating to 2 ° C, compared to 1.5 ° C, would also increase the impact on food production.

“If at the same time you have crop failures in a couple of loaves of bread in the world, then you can see rising food prices and hunger and famine in large areas of the world,” said climate scientist Simon Lewis of University College London.

A warmer world could see mosquitoes carrying diseases like malaria and dengue fever spread over a wider area. But 2 ° C would also lose a larger share of insects and animals to most of its habitat area, compared to 1.5 ° C, and would increase the risk of forest fires, another risk to wildlife.

‘TIPPING POINTS’

As the world warms, the risk increases for the planet to reach “point to point” where the Earth’s systems exceed the threshold that causes irreversible impacts or cascading impacts. It is not certain exactly when these points were reached.

Droughts, reduced rainfall and continued destruction through the destruction of the Amazon (NASDAQ :), for example, can see the collapse of the forest system, releasing CO2 into the atmosphere instead of storing it. Or warming Arctic permafrost can cause the decomposition of long-frozen frozen biomass, releasing a large amount of carbon emissions.

“That’s why it’s so dangerous to continue emitting fossil fuels … because we’re increasing the likelihood of overcoming one of those extremes,” Lewis said.

2 ° C I DO

To date, the climate commitments presented by countries in the United Nations Register of Commitments have put the world on the path to global warming of 2.7 ° C. The International Energy Agency said on Thursday that https://www.reuters.com/business/cop/net-zero-methane-pledges-push-world-near-paris-climate-goal-iea-2021-11-04 are new promises What was announced at the COP26 summit – if implemented – could keep warming below 1.8 ° C, although some experts have questioned that calculation. It remains to be seen whether these promises will become real-world action.

Heating to 2.7 ° C would provide “unbearable heat” in tropical and subtropical areas in some parts of the year. Biodiversity would be severely depleted, food security would decline, and extreme weather would exceed the capacity of most urban infrastructures to cope, scientists said.

“If we keep warming below 3 ° C we will probably remain within our adaptive capacity as a civilization, but we would experience great difficulties in warming up to 2.7 ° C,” Mann said.