Berkeley Earth Annual Temperature Report 2025

The Berkeley Earth Annual Temperature Report 2025 highlights global warming trends, record-breaking heat, regional climate anomalies, and their implications for climate policy and sustainability.

Table of Contents

Context

The 2025 Annual Temperature Report released by Berkeley Earth presents a stark assessment of the global climate system.

Key Highlights from the Berkeley Earth Report 2025

Warmest La Niña year on record: Despite La Niña conditions in the Pacific, global average temperatures in 2025 exceeded all previous La Niña years, highlighting the dominance of anthropogenic warming.
770 million people were exposed to extreme heat: even during what is conventionally considered a “cooling phase” of the climate cycle.
Natural variability overwhelmed by human influence: The report underscores that greenhouse gas accumulation has now raised baseline temperatures so high that ENSO-related cooling can no longer offset warming trends.
Extreme heat as a global norm: Heatwaves were observed across multiple continents, indicating that extreme heat is becoming a persistent global condition, not confined to El Niño years.
Disproportionate impacts on the Global South: Regions with high population density, limited adaptive capacity, and dependence on outdoor labour bore the brunt of heat stress, reinforcing climate inequality concerns.
Rising risks to food, health, and labour productivity: Sustained high temperatures increased risks of crop stress, water scarcity, heat-related illnesses, and economic losses, particularly in tropical and subtropical regions.
Implications for climate modelling: The report suggests that assumptions about La Niña years being relatively cooler may no longer hold, requiring updates to climate risk assessments and adaptation planning.
Clear mitigation warning: Berkeley Earth cautions that reliance on natural climate oscillations for temporary relief is no longer viable; only deep and sustained emission reductions can prevent further escalation of heat extremes.

La Niña

- It refers to the periodic cooling of ocean surface temperatures in the central and east-central equatorial Pacific, coupled with changes in the tropical atmospheric circulation, such as winds, pressure and rainfall.
- In La Niña, trade winds strengthen, pushing more warm water toward the western Pacific, making the eastern Pacific cooler than usual.
- Together, La-Nina and El Niño are the cold and warm phases of the ENSO or El Niño Southern Oscillation.
Impact of La Niña:

- Rainfall associated with the summer monsoon in Southeast and South Asia tends to be greater than normal, especially in northwest India and Bangladesh.
- Strong La Niña events are associated with catastrophic floods in northern Australia.
- Rainier-than-normal conditions are over southeastern Africa and northern Brazil.
- Decreased cloud production and rainfall in central and eastern Pacific.
- Drier-than-normal conditions along the west coast of tropical South America, the Gulf Coast of the United States, and the pampas region of southern South America.
- Upwelling brings cold, nutrient-rich waters to the surface, having positive effects on the fishing industry in western South America.

El Niño v/s La Niña
Basis	El Niño	La Niña
Sea surface temperature	Periodic warming of sea-surface temperatures across the east-central equatorial Pacific.	Periodic cooling of sea-surface temperatures across the east-central equatorial Pacific.
Formation	Trade winds weaken. Warm water is pushed back east, toward the west coast of the Americas, resulting in a weaker Walker cell.	Trade winds strengthen, pushing more warm water toward Asia, resulting in a stronger Walker cell.
Period of occurrence	Typically, they occur every 3–5 years and last 9–12 months.	Typically, they occur every 3–5 years and last 1–3 years.
Impacts	Droughts in eastern Australia Flooding in western South America Weak upwelling over the west coast of South America.	Excessive rainfall in the eastern Australia Drought conditions, in South America Strong upwelling over the west coast of South America.
Impact on Indian Monsoon	The winds don’t carry the moisture towards Indian landmass during El Niño, causing deficiency in rainfall.	High temperatures over the Indian Ocean, off the Somalian coast, and a comparatively better monsoon rains in India.