For the first time, annual warming reaches the 1.5°C mark, and what that means – 02/10/2024 – Environment

For the first time, annual warming reaches the 1.5°C mark, and what that means – 02/10/2024 – Environment

For the first time, global temperature rise exceeded 1.5°C over an entire year, according to the European Union’s climate service.

World leaders pledged in 2015 to try to limit long-term temperature rise to 1.5°C compared to pre-industrial levels, which is seen as key to avoiding the most harmful impacts of global warming on the planet.

This first-year violation does not break what was aligned in the Paris Agreement, but it brings the world closer to that milestone in the long term.

Urgent action to reduce carbon emissions could still slow global warming, scientists say.

“Overcome [1,5°C de aquecimento] on an annual average is significant,” says Professor Liz Bentley, chief executive of the UK’s Royal Meteorological Society.

“It’s another step in the wrong direction. But we know what we have to do.”

Limiting long-term warming to 1.5°C above “pre-industrial” levels — before humans began burning large amounts of fossil fuels — has become a key symbol of international efforts to combat climate change.

A 2018 UN report stated that the risks of climate change — such as intense heat waves, rising sea levels and wildlife deaths — were much higher with warming of 2°C than with 1.5°C. .

But temperatures continued to rise at a worrying pace, as shown by data from the European Union’s Copernicus Climate Change Service from last year, illustrated in the chart below. The period from February 2023 to January 2024 had a warming of 1.52°C.

This year-long breach isn’t a huge surprise. January was the eighth consecutive month with record heat.

A scientific group, Berkeley Earth, claims that the year 2023 will have a temperature of more than 1.5 ºC above pre-industrial levels. Other scientific entities, such as NASA, estimate the last 12 months to be slightly below 1.5°C of warming.

These small differences are mainly due to the way global temperatures are estimated for the late 19th century, when measurements were sparser.

But all the major data sets agree on the recent trajectory of warming, and indicate that the world is in by far the hottest period since modern records began — and probably for much longer in history.

The sea surface also reached the highest average temperature ever recorded — yet another alarming sign in climate records. As the chart below shows, this is particularly notable given that ocean temperatures typically don’t peak for a month or so.

Ocean temperature

Why was the 1.5°C mark broken last year?

The long-term warming trend is unquestionably caused by human activities — mainly the burning of fossil fuels, which release planet-warming gases such as carbon dioxide. This is also responsible for most of last year’s heat.

In recent months, a natural climate-warming phenomenon known as El Niño has also given an extra boost to air temperatures, although its contribution is about 0.2°C.

Global average air temperatures began to exceed 1.5°C of warming almost daily in the second half of 2023, as El Niño began to take effect, and this has continued into 2024. This is shown where the red line is above the dashed in the graph below.

Rising temperatures

An end to El Niño conditions is expected within a few months, which could allow global temperatures to temporarily stabilize and then fall slightly, probably back below the 1.5°C threshold.

But human activities mean temperatures will continue to rise in the coming decades unless urgent action is taken.

“Rapid reductions in greenhouse gas emissions are the only way to halt the rise in global temperatures,” says Samantha Burgess, deputy director of Copernicus.

Can we still stop global warming?

At the current rate of emissions, the Paris Agreement’s goal of limiting warming to 1.5°C as a long-term average — rather than a single year — could be exceeded as early as the next decade.

This would be an extremely symbolic milestone, but researchers say it does not represent a climate catastrophe.

“It is not a threshold beyond which climate change will spiral out of control,” says Professor Myles Allen, of the University of Oxford and Gresham College, and lead author of the 2018 UN report.

However, the impacts of climate change would continue to accelerate — as shown by extreme heat waves, droughts, forest fires and floods over the last 12 months.

“Every tenth of a degree of warming causes more damage than the last,” says Allen.

Half a degree more — the difference between 1.5°C and 2°C of global warming — also enormously increases the risks of exceeding so-called “tipping points”.

These are limits within the climate system that, if exceeded, could lead to rapid and potentially irreversible changes.

For example, if the Greenland and West Antarctic ice sheets passed a tipping point, their potentially uncontrolled collapse would cause “catastrophic” rises in global sea levels over the centuries that followed, Bentley says.

But the researchers are keen to point out that humans can still change the world’s warming trajectory.

The world has made some progress, with green technologies, such as renewable energy and electric vehicles.

This means that some of the worst-case scenarios of warming of 4°C or more this century — considered possible a decade ago — are now considered much less likely, based on current policies and commitments.

And perhaps most encouraging of all, it is still thought that the world will more or less stop warming once net-zero carbon emissions are achieved. Effectively halving emissions this decade is seen as particularly critical.

“This means that we can ultimately control the level of warming the world experiences, based on our choices as a society and as a planet,” says Zeke Hausfather, climate scientist at the US group Berkeley Earth.

“Tragedy is not inevitable.”

Graphics by Erwan Rivault

This text was originally published here.

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