Climate scientists anticipate 2023 to be the warmest year on record, with the fourth monthly global temperature record in a row recently set in September. June, July, and August of 2023 all saw previous high temperature records broken too.
Why were summer temperatures in the northern hemisphere so high?
The Copernicus Climate Change Service reported that the global average surface air temperature for September 2023 was 16.38°C. This is 0.93°C above the 1991-2020 average for September, 0.5°C above the temperature of the previous warmest September in 2020, and 1.75°C above pre-industrial levels.
While it may not seem like a large increase in temperature, last month’s temperature record is significantly higher than previous records.
“It’s huge,” says Professor Ed Hawkins, climate scientist at the National Centre for Atmospheric Science and the University of Reading. He adds: “We shouldn’t be breaking records by this amount”.
As with the other record-breaking temperatures seen this year, September’s record is thought to be driven primarily by human-caused climate change. Scientists are also investigating the role of regional climate and weather, ocean circulation, and El Niño.
El Niño is an irregular climate pattern occurring every 2-7 years, which causes warming of surface and subsurface waters in the eastern and central tropical Pacific Ocean. In turn this warming affects atmospheric circulation and influences global climate, meaning El Niño can warm the planet significantly (up to about 0.2°C averaged over a given year).
Climate change means the background temperature of the planet is warmer, meaning periods of hot weather are likely to be more frequent and more intense – leading to unparalleled temperature being recorded.
Professor Ed Hawkins explains:
“Month after month of record heat is not necessarily a sign the climate crisis is accelerating, but a taste of the future under continued global warming.”
“What we’re seeing this year is a bump in temperature on top of the current level of global warming,” says Professor Ed Hawkins, which could be “due to other factors such as El Niño or other global weather patterns”.
He explains: “The largest component by far is the fact that we have added so much carbon dioxide into the atmosphere from burning fossil fuels and deforestation.”
Professor Colin Jones, a climate scientist at the National Centre for Atmospheric Science based at the Met Office, expands the point further:
“It is anticipated in the future that there will continue to be temporary accelerations, as seen in 2023, and slowing down of global warming at the Earth’s surface. This is linked with the periodic El Niño and La Niña oscillations. During El Niño events surface warming is increased in the tropical Pacific and globally, whereas during a La Niña, excess heat is mixed deeper into the ocean, below the surface, and the rate of surface warming slows down until this heat reappears at the surface some time in the future. As a result, global warming tends to occur in a step-like fashion rather than just increasing at the same rate every year.”
Could 2023 be the warmest year on record?
Earth is warming at a rate that is unprecedented in the history of human civilisation. The average temperature at the Earth’s surface has risen by 1.2°C since the pre-industrial period, and 19 of the top 20 warmest years on record have occurred after 2000.
Professor Rowan Sutton from the National Centre for Atmospheric Science and University of Reading emphasises:
“Rapid warming means we must expect records to be broken – not just by small margins but quite often by very large ones.”
2023 is anticipated to be the warmest year on record after numerous temperature records have been broken over recent months. Global temperatures may increase even further above average as El Niño continues to grow before peaking during December to January.
This year alone has seen numerous extreme weather events, record-breaking sea surface temperatures, and a record low Antarctic sea ice extent. As climate change continues, these events are expected to become more extreme or occur much more frequently.
Dr Till Kuhlbrodt, a climate scientist at the National Centre for Atmospheric Science and University of Reading, describes the scale of the change:
“Since April 2023 the sea-surface temperature in the North Atlantic has been considerably higher than in any of the 40 previous years, including in the seas around the UK. In the Southern Hemisphere, since May and throughout the winter season, the sea-ice extent around Antarctica has been substantially smaller than in any of the 40 previous years.”
What does this mean for the Paris Agreement?
Every additional 0.1°C of warming makes climate change worse. In pursuit of curbing dangerous levels of temperature rise, the Paris Agreement has set a goal of holding the increase in global average temperature to well below 2°C above pre-industrial levels – and to aim for 1.5°C.
According to the Copernicus Climate Change Service, the months of July, August, and September in 2023 have all been more than 1.5°C warmer than pre-industrial the reference period.
This starkly illustrates the global temperature extremes in 2023, but should not be misinterpreted to mean the Paris Agreement has been breached.
Breaking the 1.5°C – 2°C global warming threshold refers to long-term annual average global surface temperatures, not individual months.
Assuming that no drastic greenhouse gas emission reductions are implemented in the coming years, the planet is expected to overshoot 1.5°C global warming in the mid-2030s – in around 12 years from now.
It is widely anticipated by climate scientists and the United Nations’ Intergovernmental Panel on Climate Change that breaching the 1.5°C threshold will mean much more severe climate and weather extremes and large-scale damaging impacts.