In recent years, global temperatures have soared beyond predictions, igniting intense discussions among climate scientists. There is widespread agreement that **global warming** is accelerating. However, opinions diverge; some experts argue it’s accelerating more than current climate models forecast, while others posit the surge is just a natural variation that will soon subside.

The implications of this debate are critical: if the acceleration is robust, the timeline to mitigate or adapt to catastrophic climate impacts may be shorter than expected.

“Ultimately, this is a question of how severe climate change will become,” states Zeke Hausfather, a researcher from Berkeley Earth, a nonprofit organization in California.

The Earth used to warm at a stable rate of approximately 0.18°C per decade until the 2010s, but recent data indicates a slight uptick in this rate.

2023 has recorded the highest temperatures yet, surpassing expectations by 0.17°C, fueled by alarming climate events—catastrophic floods in Libya, record-breaking cyclones in Mozambique and Mexico, and unprecedented wildfires in Canada, Chile, Greece, and Hawaii.

Notably, in 1988, James Hansen from Columbia University presented a groundbreaking paper to Congress highlighting that human activity, rather than natural fluctuations, was the primary driver of climate change. His colleagues claim that since 2010, the warming rate has escalated to about 0.32 degrees Celsius per decade.

This acceleration, they argue, is largely due to a “Faustian bargain” between humans and aerosol pollution. While sulfur aerosols counteract warming by reflecting sunlight, this temporary reprieve masks the true impact of carbon dioxide emissions.

As global sulfur emissions are being curbed, this hidden warming is emerging, intensifying climate change implications. China, for example, initiated a “war on pollution” around the 2008 Beijing Olympics, leading to a significant reduction in sulfur aerosol emissions by at least 75%.

Simultaneously, the International Maritime Organization has imposed strict regulations on sulfur emissions from shipping. With reduced aerosols at sea resulting in fewer reflective clouds, the trend is further contributing to warming.

Consequently, global sulfur dioxide emissions have declined by 40% since the mid-2000s. “With cleaner air, more solar radiation is penetrating our atmosphere,” explains Samantha Burgess at the European Union’s Copernicus Climate Change Agency.

This trend escalated in 2024, a year that was even hotter than 2023, surpassing the alarming threshold of 1.5°C above pre-industrial levels. Strikingly, such temperatures threaten the global goals outlined in the Paris Agreement.

Interestingly, despite most scientists agreeing on the acceleration of global warming due to reduced aerosol emissions, perspectives diverge on the extent. Hansen and his team estimate a rate of 0.32°C per decade—a figure that exceeds the United Nations Intergovernmental Panel on Climate Change’s estimate of 0.24°C and the latest climate models’ average of 0.29°C.

Natural fluctuations also significantly influence Earth’s temperature. For instance, in 2020, an exceptional solar maximum occurred within the 11-year solar cycle, resulting in increased sunlight reaching Earth.

In 2022, a massive undersea volcano erupted near Tonga, releasing 146 million tons of water vapor—a greenhouse gas—into the stratosphere while simultaneously emitting sulfur aerosols that temporarily cooled the atmosphere.

Subsequently, a strong El Niño developed in 2023 and 2024. El Niño is a natural climate phenomenon characterized by weakened trade winds, leading to warmer waters in the Pacific Ocean and heightening global temperatures.

To accurately assess the acceleration of global warming, scientists must disentangle natural variability from long-term trends in observed temperatures, building models that reflect emerging patterns. The lesser the impact of natural variability, the more pronounced the acceleration becomes.

Recently, a statistical analysis conducted by Stefan Rahmstorf from Germany’s Potsdam University and statistician Grant Foster found that global warming has intensified by approximately 0.36°C per decade since 2014.

However, Michael Mann from the University of Pennsylvania argues that Rahmstorf and colleagues might overstate aerosol impacts and underestimate natural variability, asserting that minimal acceleration has occurred since the 1990s.

“The recent warmth aligns with standard climate model simulations shaped by the 2023-2024 El Niño event, without necessitating extraordinary explanations,” Mann stated.

Unexpected climate feedback loops may also be factoring into recent temperature rises. One of the most significant uncertainties lies in the behavior of clouds, which can’t be accurately captured in climate models due to their small scale and scattered nature.

A study by Helge Goessling at the Alfred Wegener Institute indicates that approximately 0.2°C of the 1.5°C warming in 2023 can be attributed to a reduction in low-level clouds. Some of this cloud reduction stems from decreased sulfur pollution, while other factors may involve “new low cloud feedback,” according to researchers.

Typically, a temperature inversion creates a situation where cold, moist air resides over subtropical oceans, separated from warm, dry air above. However, as climate change elevates the temperature of this cold air, the inversion layer may collapse, potentially reducing cloud cover, Goessling explains.

If the acceleration of warming primarily arises from sulfur reduction, climate change might taper off in future decades once sulfur pollution reaches negligible levels. Conversely, unleashed climate feedback loops could propel temperatures even higher.

This suggests potential underestimations regarding climate sensitivity—the degree of warming linked to increases in atmospheric CO2.

“The worst-case scenario involves unexpected cloud feedback mechanisms not envisioned by models, indicating that our climate may be more sensitive than previously predicted,” warns Brian Soden from the University of Miami, Florida.

Current climate policies suggest the world may experience a rise of 2.7°C this century. However, there is potential variability in these predictions, with a possible increase of up to 3.7°C. Without significant reductions in carbon emissions, catastrophic impacts could become more frequent.

“A rise of 3.7 degrees Celsius could render certain areas uninhabitable,” said Hausfather. “While 2.7°C presents its own challenges, some regions may still adapt to this change.”

Ultimately, fossil fuel emissions are on the rise, and reversing this trend is essential for mitigating adverse effects, Burgess emphasizes.

“Global warming is progressing faster, and we’re losing time to implement ambitious measures aimed at decarbonizing society,” she concluded.