World's hottest year: 2024 first to pass 1.5C warming limit

New data reveals that the risk of the Earth warming beyond 1.5 degrees Celsius has significantly increased, despite world leaders' promises a decade ago to avoid it. The European Copernicus climate service, a major global data provider, stated on Friday that 2024 is the first calendar year to breach this symbolic threshold and also the hottest year on record globally.

This does not mean that the 1.5-degree Celsius target set by the international community has been breached, as that target refers to a long-term average over decades. However, as fossil fuel emissions continue to exacerbate atmospheric warming, we are getting closer to breaching that target. UN Secretary-General Antonio Guterres described the recent series of temperature records as a "climate breakdown" last week. In his New Year's address, he called on countries to drastically cut emissions of global warming gases in 2025, stating, "We must get off this path to destruction—and we don’t have time to waste."

According to Copernicus data, the global average temperature in 2024 was about 1.6 degrees Celsius higher than the pre-industrial period (before humans began burning large amounts of fossil fuels). This breaks the record set in 2023 by more than 0.1 degrees Celsius, meaning the past decade has been the hottest on record. The UK Met Office, NASA, and other climate organizations will also release their data later on Friday. It is expected that all agencies will agree that 2024 was the hottest year on record, although the specific numbers may vary slightly.

Last year's high temperatures were mainly attributed to human emissions of global warming gases such as carbon dioxide, which remain at historic highs. Natural weather patterns such as El Niño, which is the abnormal warming of surface waters in the tropical eastern Pacific, played a smaller role. Samantha Burgess, deputy director of the Copernicus Climate Change Service, said in an interview with the BBC, "By far, the biggest factor impacting our climate is the concentration of greenhouse gases in the atmosphere."

Since the agreement reached in Paris in 2015, the 1.5-degree Celsius target has become an important symbol in international climate negotiations, with many of the most vulnerable countries seeing it as a matter of survival. According to a key UN report in 2018, the risks from climate change, such as intense heat waves, sea-level rise, and loss of wildlife, would be far greater at 2 degrees Celsius of warming than at 1.5 degrees Celsius. However, the world is getting closer to breaching the 1.5-degree Celsius threshold.

Myles Allen, a physicist at Oxford University and author of the UN report, said, "It's hard to predict when we will breach the long-term 1.5-degree Celsius threshold, but we are clearly very close." Current trends suggest that the globe may breach the long-term 1.5-degree Celsius warming in the early 2030s. This will have significant political implications, but it does not mean the end of climate action. Zeke Hausfather, a climate scientist at Berkeley Earth, explained, "It's not like 1.49 degrees Celsius is fine and 1.51 degrees Celsius is the end of the world – every tenth of a degree matters, and climate impacts get progressively worse as warming increases."

Even a fraction of a degree increase in global warming can lead to more frequent and intense extreme weather events, such as heat waves and heavy rainfall. In 2024, West Africa experienced scorching heat, parts of South America experienced prolonged droughts, Central Europe experienced heavy rainfall, and North America and South Asia suffered some particularly intense tropical storms. The World Weather Attribution organization stated that these events are just some examples of climate change exacerbation last year. Just as the new data was released, Los Angeles was also experiencing devastating wildfires this week due to high winds and insufficient rainfall.

While there are many contributing factors to this week's events, experts say that California is more prone to fire conditions in a warming climate. Not only did 2024 see record high temperatures, but global sea surface temperatures also reached new daily records, and total atmospheric humidity also reached record levels. The world breaking new records is not surprising: due to the effects of El Niño, which ended around April last year, and human-caused global warming, 2024 was expected to be hot.

However, the magnitude of the breaches of multiple records in recent years has been unexpected, and some scientists are concerned that this may represent an acceleration of warming. Dr. Hausfather said, "I think it's safe to say that the temperatures in both 2023 and 2024 have surprised most climate scientists – we didn't expect to see a year above 1.5 degrees Celsius this early." Helge Gößling, a climate physicist at the Alfred Wegener Institute in Germany, also stated, "Since 2023, we have seen about 0.2 degrees Celsius of extra warming, which is beyond what we expected from climate change and El Niño, and we can't fully explain it."

Various theories have been proposed to explain this "extra" warming, such as a seemingly reduced low-level cloud cover that often cools the Earth, and the continued high ocean temperatures after El Niño ended. "The question is whether this acceleration is related to human activities, leading to more severe warming in the future, or is part of natural variability," Dr. Gößling added. "It's hard to say at the moment."

Despite this uncertainty, scientists emphasize that humans can still control the future climate, and drastically reducing emissions can mitigate the consequences of warming. Dr. Hausfather said, "Even if the 1.5-degree Celsius target is no longer achievable, we still have the possibility of limiting warming to 1.6 degrees Celsius, 1.7 degrees Celsius, or 1.8 degrees Celsius this century. If we continue to burn coal, oil, and gas unchecked, and end up with 3 degrees Celsius or 4 degrees Celsius of warming, the situation will be much worse—it is still very important."