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Atm. CO₂ ~428 ppm · Atm. CH₄ ~1,930 ppb · Temp. anomaly +1.44 °C (2025, WMO) · Sea level rise +4.5 mm/yr · Arctic sea ice −13% per decade · Remaining carbon budget ~200 GtCO₂ · Global emissions ~37.4 GtCO₂/yr · Tropical forest loss 6.7 Mha in 2024 · Ocean pH 8.08 (−0.12 since 1850) ·

Climate

Climate 6 Avr 2026 · 2 min read

The Atmosphere

The atmosphere is the gaseous envelope surrounding the Earth. Its composition is generally described in terms of dry air, since water vapor (H₂O), which typically ranges from about 1% to 5% by volume, is highly variable depending on meteorological conditions. Atmospheric concentrations are commonly expressed in ppmv (parts per million by volume), where 1 ppmv […]

Climate 6 Avr 2026 · 3 min read

The Ozone layer

The ozone layer is essential to life on Earth. Although ozone (O₃) is present throughout the atmosphere, it reaches its highest concentrations in the stratosphere. This region is commonly referred to as the “ozone layer” (Figure 1) [1]. Figure 1: Ozone concentration as a function of altitude. The vast majority of ozone molecules are concentrated […]