Anyone who has watched global average temperature records land every month since June probably doesn’t need to be told that 2023 was the hottest year ever, but just in case, the world’s major scientific weather monitoring bodies delivered the hard data this week. According to the European Union’s Copernicus Climate Change Service (CCCS), the United Nations World Meteorological Organization (WMO), and the United States’ National Oceanic and Atmospheric Association (NOAA), last year didn’t just break 2016’s heat record, it shattered it by a wide margin.
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According to CCCS and WMO calculations, 2023 was 1.48°C warmer than the pre-industrial period, perilously close to the 1.5°C threshold that nations agreed to respect in the 2015 Paris climate accords, with 2.0°C not to be crossed. Breaching this limit, say scientists, risks more storms, droughts, extreme heat, and flooding than humanity can safely handle.
Back in 2015, scientists thought it would be decades before we reached 1.5°C. Yet, according to CCCS data, every single day of 2023 the global average temperature was at least 1°C warmer than pre-industrial averages; half were above 1.5°C, and two days in November surpassed 2°C. NOAA’s data, which tends to be more conservative, put the 2023 average at 1.35°C above pre-industrial levels, but warned that 2024 had a one-in-three chance of hitting even higher temperatures, and a 99% chance that it would rank among the top five warmest years in human history.
Last year’s record-high temperature average sparked heat waves, floods, and wildfires around the world, with 28 billion-dollar-or-more climate disasters in the U.S. alone. Climate analyses by attribution scientists showed that many of those extreme events would have been virtually impossible had it not been for global warming caused by rising carbon emissions.
One day of 1.5°C above pre-industrial levels, or even a year for that matter, does not spell certain doom—the 1.5 goal of the Paris agreement actually refers to an average temperature over several years. But scientists are now trying to figure out whether 2023’s unusually high temperatures mark an acceleration in climate change, or if it was just an anomaly sparked by the return of the planet-warming El Niño climate phenomenon. (2016, the previous record-holder was also an El Niño year). CCCS and the United Kingdom’s Met Office are already predicting a temperature average at or in excess of 1.5°C next year, largely because El Niño is expected to extend well into the northern hemisphere spring or even summer. Former NASA scientist James Hansen, who first alerted the world to the risks of a changing climate back in the ‘80s, warned last week in his newsletter bulletin that temperatures could rise as much as 1.7°C before next May. “We are now in the process of moving into the 1.5°C world,” he told the Guardian. “You can bet $100 to a donut on this and be sure of getting a free donut, if you can find a sucker willing to take the bet.”
A similarly solid bet would say that the weather disasters of 2023 are not yet behind us. “2023 was a mere preview of the catastrophic future that awaits if we don’t act now,” U.N. Secretary-General António Guterres said in a statement accompanying the release of the WMO data. “Humanity’s actions are scorching the earth. We must respond to record-breaking temperature rises with path-breaking action.”
Read more: Where We’ll End Up Living as the Planet Burns
Just because we neared 1.5°C this year, and may yet surpass it next year, does not mean that we should give up the fight to reduce climate-warming emissions. The United Nations scientific panel on climate change shows we are destined for 3°C of warming by 2100 at current emissions levels, at which point weather extremes may prove insurmountable for large swaths of the global population. Which means that every fraction of a degree we manage to claw back from current trajectories will make a huge difference across the planet.
“Climate change is the biggest challenge that humanity faces,” says WMO Secretary-General Celeste Saulo. “We cannot afford to wait any longer. We are already taking action but we have to do more and we have to do it quickly. We have to make drastic reductions in greenhouse gas emissions and accelerate the transition to renewable energy sources.” By how fast, and by how much? Climate and atmospheric scientists Chris Smith at the University of Leeds and Robin Lamboll at Imperial College London calculated the stakes in a new paper published in November in Nature Climate Change. They found that if humanity wants to have a 50-50 chance of limiting global warming to 1.5°C, that means maximum emissions of another 250 billion metric tons of CO2, effectively giving the world just over six more years of business-as-usual before it must hit net-zero emissions.
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