The heatwaves and balmy oceans set the stage and now it is official: 2023 is the warmest year on record, with the global temperature increase on track to exceed a 1.5 degree Celsius threshold meant to limit the most severe impacts of climate change.

Unprecedented global temperatures from this past June onward resulted in 2023 overtaking the previous warmest year, 2016, by a large margin, Copernicus Climate Change Service said in a Jan. 9 press release. And it’s likely that a 12-month period ending in January or February 2024 will exceed 1.5 C above the pre-industrial level, the group said, reflecting record-setting temperatures on land and seas around the world.

Copernicus, a component of the European Union’s space program that focuses on climate data, cited a string of heat-related milestones over the past year, including above-average temperatures in Europe for 11 months during 2023.

“2023 was an exceptional year with climate records tumbling like dominoes,” Copernicus deputy director Samantha Burgess said in the statement.

“Not only is 2023 the warmest year on record, it is also the first year with all days over 1 C warmer than the pre-industrial period,” she said, adding that temperatures in 2023 likely exceed those of any period in at least the past 100,000 years.

The 1.5 degree threshold has been part of the climate change dialogue since at least 2015, when nearly 200 countries, including Canada, signed the Paris Agreement. That treaty, which came into force in 2016, was based on scientific research that concluded human activities are releasing greenhouse gases that are warming the planet.

The pact is designed to limit the global average temperature rise to below 2 degrees Celcius above pre-industrial levels, while focusing on holding the increase to 1.5 degrees Celcius, based on research that indicates going over the 1.5 C threshold increases the risk of more severe climate change impacts, including more frequent and severe droughts, heatwaves and rainfall. (The term ‘pre-industrial’ in climate science usually refers to the period between 1850-1900 – the earliest period for which there are near global temperature records available.)

To limit global warming to 1.5 C, greenhouse gas emissions must peak before 2025 at the latest and decline by 43 per cent by 2030, according to a United Nations summary of the agreement.

But global greenhouse gas emissions have increased since 2015 and hit a new high in 2022, according to the 2023 edition of the United Nations Emissions Gap Report, an annual report that tracks the gap between actual global emissions and where they should be to limit warming to 1.5.

Annual average air temperatures were the warmest on record, or close to the warmest, over sizable parts of all ocean basins and all continents except Australia, Copernicus said.

Global average sea surface temperatures were “persistently and unusually high” in 2023, driving marine heatwaves around the globe, the agency said. Last year also saw the Earth shift into an El Niño year, a global climate pattern that typically brings higher temperatures to some parts of the world. But the transition to El Niño does not explain the widespread increases in ocean surface temperatures in 2023, Copernicus said, noting that high sea temperatures extended beyond the equatorial Pacific region most affected by El Niño.

The one-year record does not mean that the world has surpassed the limits set by the Paris Agreement because those limits are based on long-term warming, over periods of at least 20 years, but sets a dire precedent, Copernicus said in its release.

The Globe and Mail, January 9, 2024