- By Matt McGrath
- Correspondence in nature
Our overheating world is likely to breach a significant temperature limit for the first time in the next few years, scientists predict.
Researchers say there is a 66% chance we will pass the 1.5C global warming threshold between now and 2027.
The chances are increased due to emissions from human activities and the El Niño weather event expected this summer.
If the world exceeds the limit, scientists emphasize that the breach, while worrying, is likely to be temporary.
Hitting the threshold means the world will be 1.5C warmer than in the second half of the 19th Century, before fossil fuel emissions from industrialization began to rise.
The 1.5C figure has become a symbol of global climate change negotiations. Countries agreed to “continue efforts” to limit the rise in global temperatures to 1.5C under the 2015 Paris agreement.
An increase of 1.5C per year over a decade or two would see greater warming effects, such as longer heat waves, stronger storms and wildfires.
But passing level one in the next few years does not mean that the Paris limit has been broken. Scientists say there is still time to stop global warming by cutting emissions.
Since 2020 the World Meteorological Organization has provided an estimate of the world’s chance of exceeding the 1.5C threshold in any one year.
They previously predicted a less than 20% chance of exceeding 1.5C in the next five years.
Last year it increased to 50%, and now it has jumped to 66%, which scientists say means it is “more likely than not.”
What does over 1.5C mean?
The number is not a direct measure of global temperature but an indication of how much or how little the Earth is warming or cooling compared to the long-term global average.
Scientists use average temperature data from the period between 1850-1900 as a measure of how hot the world was before our modern reliance on coal, oil and gas.
For decades they believed that if the world warmed by around 2C that would be the threshold of dangerous effects – but in 2018 they revised this estimate, indicating that a drop of 1.5C would be devastating to the world.
Over the past few decades our overheating world has raised the mercury so that in 2016, the hottest on record, global temperatures were 1.28C above pre-industrial figures.
And in the years between now and then they believe there is a strong chance that the 1.5C limit will be breached for the first time.
“We are now actually in a temporary excess of 1.5C for the annual average temperature, and that is the first time in human history that we have come close,” said Prof Adam Scaife, head of the tag- as forecasts by the Met Office, which compiles data from weather and climate agencies around the world.
“I think that’s probably the clearest and clearest and simplest statistic we have in the report,” he said at a news conference.
The researchers stressed that the temperature must remain at or above 1.5C for 20 years to be able to say that the threshold of the Paris agreement has been passed.
But breaking the limit for even just one year is a worrying sign that warming is accelerating and not slowing down.
“This report does not mean that we will permanently exceed the 1.5C level set by the Paris Agreement which aims at long-term warming for many years,” said WMO Secretary-General Prof. Petteri Tallas
“However, the WMO is sounding the alarm that we will exceed the 1.5C level on a temporary basis with increasing frequency,” he said.
What is the difference between El Niño?
There are two key elements – the first is the continued high level of carbon emissions from human activities that despite falling during the pandemic still continues.
The second, critical feature is the likely appearance of El Niño, a weather phenomenon with global implications.
In the last three years the world has experienced a La Niña event that has slowed climate warming to some extent.
But the extra heat that El Niño will bring over the Pacific will likely push global temperatures to new highs next year.
However, there is uncertainty in the onset and scale of the event.
“It’s worth noting that many of our forecasts made today for El Niño that we think is developing this winter, show relatively large amplitude,” Prof Scaife told reporters.
“But to actually predict the magnitude, or the next event within a five-year period, we can’t give exact dates beyond this one year ahead, so it could be three or four years. from now on we will come to a two. and a half degree El Niño and that’s probably what made it.”
What are the likely effects in the UK and elsewhere?
The Arctic will experience warming at a higher level than many regions, with the temperature anomaly expected to be three times greater than the global figure in the next five northern winters.
Northern Europe including the UK is likely to experience more rainfall for the May to September period over the next five years, the report said.