2025 is set to conclude as the second hottest year on record, following only 2024. The data reveals a concerning continuation of exceptional and unexplained warming trends. According to the Copernicus Climate Change Service, the last three years have been the hottest ever documented, each measuring over 1.5 degrees C warmer than preindustrial levels. This situation places the world in temporary violation of international climate goals aimed at limiting warming below this threshold.
The recent surge in temperatures has surpassed the expectations of climate models, leaving scientists perplexed. A range of potential contributors has been examined, including the aftermath of a significant volcanic eruption in the South Pacific and a decrease in sunlight-blocking pollution. Climate scientist Zeke Hausfather explored four primary factors driving this warming trend in an analysis published by Carbon Brief.
Exploring the Factors Behind the Warming Surge
One of the key contributors identified was the 2022 eruption of the Hunga Tonga–Hunga Ha‘apai volcano. This underwater volcano released a massive plume of heat-trapping water vapor into the upper atmosphere, which could significantly influence global temperatures.
Additionally, there has been a recent increase in solar output. While the timing of this uptick coincides with the recent rise in temperatures, Hausfather notes that these factors only account for less than half of the observed temperature increase.
Another significant factor is the development of a powerful El Niño event in late 2023. This phenomenon, characterized by warm waters accumulating in the eastern Pacific, typically drives global temperatures higher. However, while El Niño might explain the exceptional temperatures in 2024, it does not account for the warming observed in early 2023.
A further contributing element is the recent and dramatic reduction in emissions of sulfur dioxide. This pollutant, primarily produced by coal power plants, has a cooling effect on the planet by blocking sunlight. In the past 18 years, global sulfur dioxide emissions have decreased by 40 percent, largely due to pollution control efforts in countries like China. A new international regulation established in 2020 further curtailed sulfur dioxide emissions from cargo ships, leading to a notable decline in shipping-related pollution.
Shipping Pollution and Its Impact on Global Temperatures
While prior research indicated that reductions in shipping pollution had only a modest impact on global temperatures, a study conducted by James Hansen, the former chief climate scientist at NASA, suggests that this decline could account for nearly all of the recent exceptional warming.
Combining the four identified factors may provide a comprehensive explanation for the current temperature surge. Yet, questions linger regarding the permanence of this warming trend. Is the surge merely a temporary phenomenon, or does it signal an acceleration in global warming?
The findings underscore the urgency for continued research and action in addressing climate change. As the world grapples with these unprecedented temperature records, the implications for ecosystems, weather patterns, and global health remain profound. Understanding the nuances behind this warming trend is crucial for informing future climate policy and global cooperation in mitigating the impacts of climate change.
