The year 2025 is set to conclude as the second hottest year on record, surpassed only by 2024. This trend of exceptional warming continues to raise concerns among scientists as the past three years have recorded unprecedented temperature increases. According to the Copernicus Climate Change Service, each of these years has measured more than 1.5 degrees Celsius warmer than preindustrial levels, indicating a temporary breach of international climate goals aimed at limiting global warming.
Understanding the Drivers of Increased Temperatures
The recent surge in global temperatures, which has exceeded climate model predictions, has left experts searching for answers. Among the factors investigated, climate scientist Zeke Hausfather assessed four key drivers in a recent analysis published in Carbon Brief.
The first factor is the 2022 eruption of Hunga Tonga–Hunga Ha‘apai, an underwater volcano in the South Pacific. This event released a substantial plume of heat-trapping water vapor into the atmosphere. The second contributing factor is a recent increase in solar output. While the timing of this rise aligns with the warming trends, Hausfather concluded that these two elements together can only account for less than half of the temperature increase.
Another critical factor is the formation of a powerful El Niño event in late 2023. El Niño is characterized by the pooling of warm waters in the eastern Pacific, leading to increased global temperatures. However, while this phenomenon might explain the exceptional warmth observed in 2024, it does not account for the early 2023 temperature spike.
The fourth factor involves a significant reduction in sulfur dioxide emissions, primarily from coal-fired power plants. Sulfur dioxide acts as a pollutant that blocks sunlight and cools the planet. Over the past 18 years, emissions have decreased by 40 percent, largely due to pollution control measures in countries like China. In 2020, new international regulations aimed at reducing sulfur dioxide from cargo ships further contributed to this decline, resulting in a notable increase in temperatures.
Implications of Recent Findings
While various studies have suggested that reductions in shipping pollution have only had a modest impact on overall temperatures, research conducted by James Hansen, former chief climate scientist at NASA, indicates that this drop could explain nearly all of the recent surge in warming.
Hausfather emphasizes that while the interplay of these four factors may shed light on the current warming trend, significant questions remain. Specifically, scientists are left wondering whether this surge in temperatures is a temporary anomaly or indicative of a broader trend towards accelerated warming.
As 2025 draws to a close, the implications of these findings highlight the urgent need for continued research and action in addressing climate change. The global community faces a critical juncture in determining both the immediate and long-term responses to this escalating crisis.
