The numbers were not surprising to climate scientists, but they were alarming nonetheless. According to data published in January 2026 by the World Meteorological Organisation, the European Union’s Copernicus Climate Change Service, and NASA, 2025 was the hottest year in the 175-year record of global surface temperature observations — the first calendar year to exceed 1.5 degrees Celsius of warming above the pre-industrial baseline across all 12 months.
The 1.5-degree threshold matters because it is the more ambitious target set by the Paris Agreement, adopted in 2015. Crossing it for a single year does not mean the target is permanently lost — climate scientists are careful to define the threshold in terms of long-term averages, not individual years. But it is a milestone, and a sobering one.
“We’ve been warning about this for thirty years,” said Dr. Friederike Otto of Imperial College London, who pioneered the field of climate attribution science. “The question is not whether the climate is changing. It’s whether we can change fast enough.”
The consequences were not abstract. In 2025, heat-related deaths in Europe exceeded 60,000 for the second consecutive year. Wildfire smoke from Canada blanketed the eastern United States for three weeks in July. Bangladesh experienced its worst flooding in recorded history. The economic cost of climate-related disasters globally exceeded $400 billion for the first time.
Early data for 2026 suggests another record year is possible. The La Niña weather pattern that typically moderates global temperatures has been weaker than expected. Atmospheric CO2 concentrations continue to rise. The window for meaningful action, scientists say, is narrowing — not closed, but narrowing.
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