The Hottest Year Ever Has Just Broken a New Type of Record

It’s official: June 2023 through June 2024 was the hottest 12-month stretch since modern global temperature record-keeping began in the 1800’s. Not only did this last year of heat set a new overall record, but it also temporarily pushed Earth past a key climate benchmark, according to a July 4 report from the European Commission’s Copernicus.

Our planet has now gone a full year where each month was more than 1.5 degrees Celsius (2.7 degrees Fahrenheit) hotter than the estimated pre-industrial average, per the EU data. In total, this past year’s annual temperature was 1.64C above that 1850-1900 mean, captured before humans had released enough greenhouse gasses to fundamentally alter the composition of the atmosphere. Other climate analyses may come to slightly different conclusions based on variation between datasets and statistical methods, but the Copernicus findings are notable on their own.

If 1.5C sounds familiar, that’s because it’s an oft-cited warming threshold. The number was enshrined in the pivotal Paris Agreement. In 2015, 196 countries signed on to a legally binding international treaty to mitigate climate change. Parties agreed to limit warming to “well below 2 degrees Celsius” and to try to prevent warming beyond 1.5C, relative to the baseline of the pre-industrial estimate.

Our planet has now gone a full year where each month was more than 1.5 degrees Celsius (2.7 degrees Fahrenheit) hotter than the estimated pre-industrial average.

Staying below 1.5C of warming was chosen as the goal because the scientists that make up the United Nations International Panel on Climate Change (UN IPCC) determined that, past 1.5, the consequences of human-caused climate change would become much more severe and the planet would be at significant risk of passing critical tipping points.

So what happens now that we’ve lived a full year over that line?

First, it’s important to know that a year of weather over 1.5C doesn’t mean Earth’s average temperature has permanently warmed to that point, nor that the Paris Agreement signatories have definitively broken their promises (though both seem more and more unavoidable every passing day). In fact, this isn’t the first time Earth has blown past 1.5C, just the longest documented stretch. In 2016, shortly after the Paris Agreement was signed, January through February also surpassed the threshold, according to reporting from Inside Climate News.

Climate averages of the kind used by the UN IPCC are calculated on a 20 to 30-year basis, and we have not yet sustained this level of heating over multiple years. On a multi-year basis, it’s well-accepted that we’ve reached about 1.2C of warming above pre-industrial times — still quite a lot for the global climate, but not yet 1.5C.

Climatologists generally agree that this year’s scorching temperatures are due, in part, to El Niño, the atmospherically warmer side of the global ENSO climate pattern. Sea surface temperatures have fallen in the past few weeks, signaling that El Niño is over. We’re now in ENSO “neutral” conditions, and forecasted to enter La Niña by fall. As a result, global temperatures are likely to trend closer to historic averages over the next few months.

Yet El Niño’s influence does not account for all of this year’s record-setting heat and experts remain alarmed by what they’re seeing. “This is more than a statistical oddity and it highlights a large and continuing shift in our climate,” Carlo Buontempo, director of the Copernicus Climate Change Service, said in a statement. “Even if this specific streak of extremes ends at some point, we are bound to see new records being broken as the climate continues to warm. This is inevitable, unless we stop adding GHG into the atmosphere and the oceans,” he added.

Climate change is not an all or nothing proposition. There is no temperature past which we should give up, and no threshold beyond which we can’t continue trying to hold off even more warming.

The message: every record, whether it pushes us permanently past a Paris Agreement threshold or not, should be a renewed call to action. Though we might not have exceeded 1.5C by UN standards, already humans have warmed the planet by enough to cause serious problems: More extreme storms and fires, sea level rise, flooding, crop failures, and disease. If and when we reach the point where the IPCC is ready to declare we’ve passed 1.5 C permanently, we will have already locked ourselves into centuries of climate chaos, far more intense than what the past decade has looked like. On our current trajectory, most climate scientists believe we’re on track for about 2.5 to 3 degrees Celsius of warming by 2100, according to a survey conducted by The Guardian, meaning world leaders and the general public alike need to do more.

Climate change is not an all or nothing proposition. There is no temperature past which we should give up, and no threshold beyond which we can’t continue trying to hold off even more warming. Unless and until we reach human extinction, doing everything we can to mitigate our climate impact, namely ending our reliance on fossil fuels, will always be critical for preventing additional, future harm.