The North Pacific Ocean experienced its warmest summer on record between July and September this year, driven by a perplexing marine heatwave that has climate scientists searching for answers. Sea surface temperatures in the affected region, often referred to as the "warm blob," were more than 0.25 degrees Celsius above the previous high recorded in 2022. This significant increase spans an area approximately ten times the size of the Mediterranean Sea, according to an analysis by the BBC of data from the European Copernicus climate service.

While the broader influence of climate change is known to heighten the likelihood of marine heatwaves, researchers are struggling to fully explain the prolonged and intense warming observed in the North Pacific. Zeke Hausfather, a climate scientist at Berkeley Earth, a US-based research group, described the jump in temperatures across such a vast region as "quite remarkable."

Historical and Political Context

Marine heatwaves are periods of unusually high ocean temperatures that can persist for days to months. The phenomenon of the "warm blob" first gained prominence between 2013 and 2015, with subsequent iterations in 2019 and the current event, officially named NEP25A, which began in early May this year. These events have become a recurring feature in the Northeast Pacific since the early 2010s. The current heatwave has expanded to cover an area roughly the size of the contiguous United States, stretching from the waters off Japan to North America's west coast.

The increasing frequency and intensity of marine heatwaves are largely attributed to global warming, driven by human emissions of carbon dioxide and other greenhouse gases. Research indicates that global warming has already tripled the number of days of extreme heat in oceans worldwide. However, the current temperatures in the North Pacific have exceeded predictions from most climate models, suggesting additional contributing factors.

Laws/Policy and Governance

Kenya, like many nations, is highly vulnerable to the impacts of climate change, including extreme weather events such as droughts, floods, and rising temperatures. The country's socio-economic development is significantly exposed to climate variability, with key sectors like agriculture and tourism being particularly sensitive. In recognition of these challenges, Kenya has integrated climate resilience into its Bottom-up Economic Transformation Agenda.

The Kenya Meteorological Department (KMD) plays a crucial role in providing weather and climate information services to support sustainable development and disaster risk reduction. KMD issues daily near-shore forecasts for coastal counties such as Kwale, Mombasa, Kilifi, and Lamu, and provides timely warnings on hazardous marine conditions like high waves and strong winds. The department has also advocated for the introduction of early warning systems to mitigate the effects of adverse weather.

Stakeholders and Testimonies

The impacts of climate change extend beyond environmental and economic spheres, affecting human well-being. In rural Kenyan farming communities, extreme heat, erratic rainfall, and unpredictable seasons are taking a significant psychological toll, particularly on women. Research by Jasmit Shah, a data scientist at The Aga Khan University's Brain and Mind Institute, indicates a correlation between droughts and heatwaves and higher levels of suicidal thoughts among women in areas like Kaloleni, Kilifi County. Zul Merali, also from The Aga Khan University, highlighted the immense pressure on women to ensure their families are fed amidst crop failures, leading to psychological distress and mental health conditions such as depression.

Evidence/Data

• Sea surface temperatures in the North Pacific between July and September 2025 were over 0.25°C above the previous record set in 2022.
• The "warm blob" currently spans an area roughly ten times the size of the Mediterranean Sea.
• Kenya's temperature has increased by 1.0°C since 1960, with projections of up to 2.5°C by 2050.
• The economic cost of climate impacts in Kenya is projected to reach 2.6% of GDP by 2030.
• Agriculture, which employs over 40% of Kenya's workforce, is highly vulnerable to climatic variations.

Risks/Implications

The North Pacific marine heatwave has significant implications for marine ecosystems, leading to shifts in marine life, harmful algal blooms, and disruptions to food webs. Past "warm blob" events have resulted in mass mortality of seabirds and sea lions, collapse of kelp forests, and altered fish populations. For instance, the 2014-2016 marine heatwave caused an unprecedented harmful algal bloom that led to the closure of the Dungeness crab fishery for an entire season.

While the direct impact on Kenya's climate from a North Pacific heatwave is complex and not fully understood, global ocean-atmosphere interactions mean such events can influence weather patterns worldwide. For instance, some researchers believe the extra heat in the North Pacific could lead to a colder start to winter in the UK. For Kenya, climate change is already manifesting in more frequent and prolonged droughts, increased rainfall leading to flooding in other areas, and sea-level rise threatening coastal cities like Mombasa. These changes exacerbate existing challenges with food and water security, damage infrastructure, and pose risks to public health through increased heat stress and waterborne diseases.

Unknowns and Controversies

A key uncertainty remains the precise mechanisms driving the exceptional and prolonged warming in the North Pacific. While climate change is a fundamental factor, scientists are investigating other potential contributors. One intriguing hypothesis suggests that a recent change in shipping fuels, specifically the reduction of sulphur dioxide emissions, might be playing a role. Sulphur aerosols previously had a cooling effect by reflecting sunlight, and their reduction could be revealing the full extent of human-caused warming. Natural weather variability, such as weaker-than-usual winds, which allow more solar heat to remain in the sea surface, is also considered a contributing factor, though it alone cannot explain the magnitude of the current heatwave.

Timeline and Next Steps

The current North Pacific marine heatwave, officially NEP25A, began forming in early May 2025. Sea surface temperatures reached record highs between July and September 2025. NOAA's latest forecasts predict that marine heatwave conditions near the US West Coast may ease as winter approaches, but are likely to persist further offshore.

What to Watch

Monitoring the evolution of the North Pacific "warm blob" and its potential teleconnections to global weather patterns will be crucial. For Kenya, continued vigilance and investment in climate adaptation and mitigation strategies are paramount. The Kenya Meteorological Department's efforts to enhance early warning systems and provide accurate forecasts will be vital for communities to prepare for and respond to extreme weather events. Further research into the specific impacts of distant marine heatwaves on East African weather patterns would also be beneficial.