In its latest global climate report, the National Oceanic and Atmospheric Administration confirmed that July was the 14th straight month of record-breaking heat. That, in and of itself, is a new record.
In the last 175 years, there has been only one other hot streak that comes close in terms of longevity. According to NOAA, the second longest hot streak on record spanned the 12 months from May 2015 to May 2016 (SN: 1/20/16; SN: 1/14/21). Then things drop off: The third and fourth longest recorded streaks were six months each, and subsequent stints are shorter still.
Many of these streaks occurred during an El Niño, a natural phenomenon in which warm surface waters spread across the tropical Pacific Ocean, temporarily elevating the global average temperature (SN: 8/21/19). Its cyclical counterpart, La Niña, involves those warm surface waters receding to the western side of the Pacific, causing a transient global cooling effect.
Since the most recent El Niño ended in May, the tropical Pacific has inhabited a neutral state — neither El Niño nor La Niña is occurring.
But human-caused climate change is steadily turning up the heat (SN: 7/13/23). “There’s some year-to-year variability, but overall we do see a climbing of temperatures since the mid-1970s,” says climatologist Karin Gleason of NOAA’s National Centers for Environmental Information in Asheville, N.C. We’re sort of riding an escalator up: When El Niño arrives, we jump up a few steps; when La Niña comes, we step back down a few — but we’re still higher than when we hopped on.
Amid all this persistent heat, Science News spoke with Gleason to learn more about the ongoing global heat streak. The following conversation has been edited for length and clarity.
SN: When will this current hot streak end?
Gleason: A La Niña is forecasted for this fall, so we’re flipping. We’re going from the warming to the cooling signal. Depending on how quickly and intensely that happens, we expect the streak to end sometime during this year, probably sometime in the next several months. July 2024 was only three-hundredths of a degree Celsius warmer than last July. You could almost call that a photo finish. Knowing that that margin was so close, we don’t know what’s going to happen in August at this point.
SN: El Niño ended in May, so why has the hot streak continued?
Gleason: There’s some lag time between things starting to cool down and the response of our planet.
SN: Aside from its longevity, what sets the ongoing hot streak apart from others in the past?
Gleason: Talking with other folks in the climate science community, I think there were a couple takeaways. It was surprising how quickly the warmth amplified at the end of last summer, going into fall. And I don’t think anyone anticipated the persistence and extent of the record warm Atlantic Ocean waters (SN: 6/15/23).
SN: When might the next hot streak emerge?
Gleason: Assuming that the temperature trend will continue upward, the next time we have a strong El Niño [the timing of which is hard to predict], it is highly likely that we could go back into having multiple consecutive months that are in record territory for the globe. Whether or not it will exceed this streak, whenever it ends, that remains to be seen.
SN: Here’s a question from Science News reader Dorothy Hunt about climate change: Have we passed the point of no return?
Gleason: I don’t know if there is necessarily a magic temperature that we have to stay below. I think the take-home message is that … everything everyone does collectively can make an impact. The higher we go, the harder it is to unravel, so every little bit now counts and will help in the future.
Please keep sending in your questions about Earth’s extreme heat and shifting climate — we’ll look for ones to answer in upcoming Extreme Climate Update columns.
Source: Heart - www.sciencenews.org
