Climate Signal

Physics: ice reflects ~85% of incident sunlight back to space; open ocean absorbs ~94%. Each million km² of ice lost to the historical per-DOY mean absorbs an additional Δα × S_eff watts, where Δα = 0.79 and S_eff is the all-sky daily mean insolation at 75°N (clear-sky astronomical formula × 0.50 Arctic cloud-transmission factor). Value is 0 during polar night — no additional absorption when there is no sun. Conservative: only counts deficits relative to the 1979–2025 per-DOY mean; a day where 2026 extent exceeds the mean is treated as 0. Note: the '2026 Year to Date · Days Below Historical Floor' card uses a stricter reference — the per-DOY historical minimum — so both cards can be nonzero simultaneously (deficit vs mean, but not yet below the all-time floor for that day). Energy impact W/m² derived from TW ÷ Arctic Ocean area (14.056 million km²). CERES measured albedo (stat strip below) is the global mean planetary albedo including tropics, land, and clouds — not directly comparable to the Arctic regional effective albedo derived from sea ice extent above. Both are shown because they tell different parts of the same story: the Arctic is losing its mirror, and Earth’s total reflectivity is declining as a consequence.