1. Nature

   Arctic, September: 33% more ice than in the record-low 2012, 33% less than in 1979

   In September 2025, ice covered 4.75 million km². Whether that is growth or decline depends on the starting year, so the chart shows the whole series.

   Source: NOAA/NSIDC Sea Ice Index v4Open on the chart →

   More

   A rebound from the historical low and a decline relative to the early satellite record can both be true.

   All points represent September. The record low and endpoint appear within the full history.

   • September extent million km²

     7.051 (1979) → 4.747 (2025)

     Sea ice in both hemispheres: area and extent

   • Lowest September mean million km²

     3.566 (2012)

     Sea ice in both hemispheres: area and extent

   Select the lowest September average in 1979–2025 and explicitly label that record selection. The two percentages use 2012 and 1979 as baselines. Neither replaces a trend estimated from all points.

   Fetterer et al. (2025), Sea Ice Index v4, DOI 10.7265/a98x-0f50. Northern/Southern Hemisphere are not countries. Extent counts whole grid cells with ice concentration ≥15%; area weights by concentration. Monthly satellite estimates in million km², not volume or land glaciers. Recent points may be preliminary. The published annual mean is calendar-day weighted and retained only with all 12 months present. Hemispheres are not summed into a universal climate index.

   A question for this picture

   Which measure would change this story?

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