**Summary of BBC Article: Record-Breaking North Pacific Marine Heatwave and Its Global Impacts**
**Introduction: An Unprecedented Marine Heatwave**
In the summer of 2025, the northern Pacific Ocean experienced its warmest sea surface temperatures on record. This extraordinary heatwave, sometimes called the “warm blob,” has baffled climate scientists and raised pressing questions about its causes and potential consequences for weather far beyond the Pacific itself, including the likelihood of a colder winter in the UK and Europe. The phenomenon is notable not only for its intensity but also for the vast area affected—encompassing a region ten times larger than the Mediterranean Sea.
**Analysis of the Data: A Striking Temperature Spike**
The BBC conducted an in-depth analysis of temperature data from the European Copernicus Climate Service, focusing on the period from July to September. The findings were striking: sea surface temperatures in the north Pacific soared to more than 0.25°C above the previous record set in 2022. This sharp increase is significant, especially considering the sheer size of the region, which stretches from the east coast of Asia to the west coast of North America. Not only has this part of the ocean been warming steadily over the past couple of decades, but the recent jump in 2025 stands out as extraordinary.
Climate scientist Zeke Hausfather of Berkeley Earth described the event as “quite remarkable,” emphasizing that such a vast and rapid temperature increase is highly unusual. Statistical analysis further underscores the rarity: Berkeley Earth’s review of climate models suggests that the likelihood of such high temperatures occurring in any single year is less than 1%.
**Climate Change and Marine Heatwaves**
It is well-established that global warming, driven by human emissions of carbon dioxide and other greenhouse gases, has intensified marine heatwaves worldwide. Oceans have seen a tripling in the number of days with extreme heat over recent decades, according to recent research. However, what is particularly puzzling about the current north Pacific heatwave is that observed temperatures have surpassed even the most pessimistic projections produced by climate models that account for human-induced climate change.
This discrepancy has left scientists searching for additional explanations beyond the steady march of global warming. While natural weather patterns and variability play a role, especially in influencing wind patterns and ocean mixing, these alone do not fully account for the extraordinary warmth observed this year.
**Natural Variability and Weather Patterns**
One factor believed to contribute to the heatwave is weaker-than-usual winds over the north Pacific during the summer. Typically, winds help mix the warmer surface waters with cooler, deeper water, moderating surface temperatures. This year, reduced wind strength allowed more heat from the sun to accumulate at the surface, accentuating the warming effect.
But as Dr. Hausfather notes, natural variability can only explain so much. “It certainly is not just natural variability,” he explains. “There’s something else going on here as well.”
**The Role of Human Activity: Shipping Emissions and Aerosols**
A leading hypothesis among researchers involves recent changes in global shipping fuel regulations. Before 2020, most ships burned heavy fuel oil that produced significant amounts of sulphur dioxide. While this pollutant is harmful to human health, it also leads to the formation of aerosols—tiny particles in the atmosphere that reflect sunlight and have a local cooling effect.
In 2020, new international regulations drastically reduced the amount of sulphur allowed in ship fuels. This change has inadvertently reduced the amount of sunlight-reflecting aerosols over the busy shipping lanes of the north Pacific. The resulting decrease in this “artificial shade” may have allowed the true extent of human-caused warming to become more apparent, particularly in regions frequented by large numbers of ships.
Dr. Hausfather suggests that this reduction in sulphur emissions is a “primary candidate” for the recent spike in temperatures. Similar effects may be in play due to efforts to reduce air pollution in Chinese cities, which would also have decreased the number of sunlight-reflecting particles over the ocean.
**Immediate Impacts: Weather Extremes in the Pacific Region**
The marine heatwave is already having observable impacts on weather patterns around the Pacific Rim. Both Japan and South Korea experienced unusually high summer temperatures, while the western United States, particularly California, saw a spike in storms and thunderstorms.
Amanda Maycock, a professor in climate dynamics at the University of Leeds, explains how warm ocean waters can “supercharge” weather events. Warm seas increase evaporation