Climate Matters: After the hottest year on record, it will likely keep warming
Temperatures were officially the warmest in recorded history across the globe and in the United States last year. The previous record was set just the year before in 2023, and trends for the future will likely continue to warm.
Missouri experienced its second warmest year on record in 2024, with 2012 still holding strong on top. 5 of Missouri's top 10 warmest years have now occurred since 2012. Nationally, the 8 warmest years on record have occurred since then.
2024 especially stands out from the rest. It was the first year to breach 1.5 degrees Celsius above preindustrial averages, a threshold popularly referenced in the 2015 Paris agreement. This international treaty on climate change strives to keep global warming below the 1.5-degree mark, but this is averaged over 30 years. While 2024 is just the first, trends suggest these goals may soon become unattainable.
Missouri State Climatologist Zachary Leasor says it was no surprise to see the hotter temperatures last year due to prevailing weather patterns. "We started off 2024 with a pretty strong El Nino in place, and so that meant Pacific sea surface temperatures were very warm," Leasor says. These warm ocean waters are infamous for bringing record heat during and after the event.
El Nino was a large driver of the heat for both 2023 and 2024, but it finally subsided as the year wore on. "It took a long time for this El Nino event to fade. It wasn't until very recently in January, that we've entered La Nina officially now," says Leasor, and this isn't expected to last.
La Nina is marked by cooler-than-normal temperatures along the equator in the Pacific Ocean, which has brought notable changes to the weather patterns over the United States as it developed in recent months. January will likely end up colder than average after several winter storms brought waves of arctic air to much of the country, not an uncommon setup during a La Nina winter.
Leasor is still cautious of too much of a good thing. "If we are hanging on to this weak La Nina event, with the atmospheric impacts in early summer, we could actually see some dryness. That's a signal we see during La Nina summers in Missouri." Leasor says. A better possibility would be to transition to neutral conditions keeping heat and moisture near normal in the summer.
Regardless of the evolution of La Nina and El Nino, the world is trending toward a warmer future. 2023 and 2024 featured dramatic jumps above preindustrial norms, and climate change thresholds are now in jeopardy. As this warming disproportionately affects communities that contribute some of the least emissions, it will be on larger global figures to work to mitigate climate change's impacts.