In March 2025, the global CO2 concentration at Mauna Loa, Hawaii averaged 428.15 parts per million (ppm). The highest daily reading that month was 430.60 ppm on March 7th, the highest CO2 concentration for the past 3 million years.

Impacts:

• NOAA have reported on the global temperature figures for March 2025.

• Average global surface temperatures were 14.06°C. That is 1.31°C above the 20th-century average of 12.7°C and 1.60°C above pre-industrial average, making it the the second warmest March globally.

• It was the second warmest March for global sea surface temperatures.

• March 2025 was the 20th month in the last 21 months for which the global-average surface air temperature was more than 1.5°C above the pre-industrial level.

Fig. 1. Surface Temperature Departure from the 1991–2020 Average for March 2025 (°C). Red indicates warmer than average and blue indicates colder than average.

Fig. 2. Monthly global surface air temperature anomalies (°C) relative to 1850–1900 from January 1940 to March 2025, plotted as time series for each year. 2025 is shown with a dark red line, 2024 with a dark orange line, 2023 with a yellow line, and 2016 with a light orange line. All other years are shown with thin grey lines. Data source: ERA5. Credit: Copernicus Climate Change Service /ECMWF.

• Arctic sea ice extent was below average (by 340,000 square miles), ranking lowest on record and Antarctic extent was below average (by 440,000 square miles), ranking fourth lowest on record.

Daily Arctic sea ice extent from October 1978 to 1 April 2025. The year 2025 is shown with a dark blue line, 2024 with a teal line, and 2012 (year of the lowest daily sea ice extent) with a salmon line. Data source: EUMETSAT OSI SAF Sea Ice Index v2.2. Credit: C3S/ECMWF/EUMETSAT.

• "March 2025 was the warmest March ever for Europe highlighting once again how temperatures are continuing to break records. It was also a month with contrasting rainfall extremes across Europe with many areas experiencing their driest March on record and others their wettest March on record for at least the past 47 years.”

  According to Samantha Burgess, Strategic Lead for Climate at ECMWF