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- Written by Mark Pointing
- BBC News climate correspondent
image source, Getty Images
According to the EU Climate Office, global warming exceeded 1.5 degrees Celsius for the first time in a year.
World leaders pledged in 2015 to try to limit long-term temperature rise to 1.5 degrees Celsius, which is considered critical to avoiding the most harmful effects.
This first year of violations will not break the landmark Paris Agreement, but it will bring the world closer to it in the long run.
Scientists say urgent action to reduce carbon emissions can also slow warming.
“To overcome [1.5C of warming] That’s a significant amount on average per year,” says Professor Liz Bentley, chief executive of the Royal Meteorological Society.
“This is another step in the wrong direction. But we know what we have to do.”
Limiting long-term warming to 1.5 degrees Celsius above “pre-industrial” levels, before humans started burning massive amounts of fossil fuels, has become an important symbol of international efforts to tackle climate change. There is.
A landmark 2018 United Nations report found that the risks from climate change, such as severe heatwaves, rising sea levels and declines in wildlife, are much higher if temperatures rise by 2 degrees Celsius than by 1.5 degrees Celsius. It says that it will become.
But temperatures continue to rise at an alarming pace, according to data from the EU’s Copernicus Climate Change Agency over the past year, as shown in the graph below. The period from February 2023 to January 2024 reached a warming of 1.52 degrees Celsius.
This year-long breach is not a big surprise. January was the warmest on record for the eighth year in a row.
In fact, one scientific organization, Berkeley Earth, says that calendar year 2023 was more than 1.5 degrees warmer than pre-industrial levels. Other scientific agencies such as NASA estimate that the temperature increase over the past 12 months was just under 1.5 degrees.
These small differences are primarily due to the way global temperatures were estimated in the late 1800s, when measurements were more sparse.
But all major datasets agree on the recent warming trajectory and that the world is in the warmest period since modern records began, and perhaps much longer. .
And the average global sea surface temperature has also reached an all-time high, another sign of the widespread nature of the climate record. This phenomenon is especially noteworthy considering that it typically takes about another month for ocean temperatures to reach their peak, as the graph below shows.
Why has the temperature exceeded 1.5℃ in the past year?
The long-term warming trend is undoubtedly driven by human activity, primarily through the combustion of fossil fuels, which release global warming gases such as carbon dioxide. This is also responsible for much of the warmth over the past year.
In recent months, a natural climate warming phenomenon known as El Niño has also caused temperatures to rise further, although they typically only rise by about 0.2 degrees Celsius.
Starting in late 2023, when the El Niño phenomenon began, global average temperatures began to exceed 1.5 degrees of warming almost every day, and this continues until 2024. This is indicated by the red line above the dashed line in the diagram. Graph below.
El Niño is expected to end within a few months, allowing global temperatures to temporarily stabilize and then drop slightly, possibly below the 1.5 degree threshold.
But human activities will ultimately keep temperatures rising for decades to come unless urgent action is taken.
“Rapidly reducing greenhouse gas emissions is the only way to stop global temperatures from rising,” concludes Copernicus Deputy Director Samantha Burgess.
Is it still possible to curb global warming?
At current emissions rates, the Paris goal of limiting global warming to 1.5°C over the long term, rather than in single years, could be achieved within the next 10 years.
While this would be a highly symbolic milestone, researchers say it does not signal a climate cliff edge.
“This is not a threshold beyond which climate change will go out of control,” said Professor Miles Allen of Gresham College, University of Oxford.
Professor Allen added: “Every tenth of warming causes more harm than the last.”
An extra 0.5 degrees of global warming, the difference between 1.5 degrees Celsius and 2 degrees Celsius, also significantly increases the risk of passing a “tipping point.”
These are thresholds within the climate system that, if exceeded, can cause rapid and irreversible changes.
For example, if the Greenland and West Antarctic ice sheets cross a tipping point, potentially runaway ice sheets would cause a “catastrophic” rise in global sea levels for centuries to come, Bentley said. says the professor.
But the researchers want to emphasize that humans can still make a difference in the global warming trajectory.
This means that some of the worst-case scenarios of more than 4 degrees of warming this century, which were considered possible a decade ago, are now more likely than not, based on current policies and commitments. This means that it is considered to be considerably lower.
And perhaps most encouragingly, it is still believed that the world will more or less stop warming once net-zero carbon emissions are achieved. Effectively halving emissions over this decade is considered particularly important.
“That means we can ultimately control how much the world warms based on the choices we make as a society and as a planet,” said Zeke House, a climate scientist at the US group Berkeley Earth. Father says.
“Doom is not inevitable.”
Graphics by Erwan Rivault.
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