What Happened
- The World Meteorological Organization (WMO) released its State of the Global Climate 2025 report confirming that 2015-2025 are the eleven hottest years in the 176-year observational record.
- 2025 was the second or third warmest year on record, with global mean temperatures approximately 1.43°C above the 1850-1900 pre-industrial average.
- 2024 holds the record as the single hottest year, with temperatures reaching 1.55°C above pre-industrial levels — the first year to breach the Paris Agreement's 1.5°C threshold (though a single year above the threshold does not constitute a breach of the Agreement's long-term goal).
- Ocean heat content and greenhouse gas concentrations both set new records in 2024 and continued rising in 2025.
- WMO Secretary-General Celeste Saulo stated it is "virtually impossible" to limit global warming to 1.5°C in the next few years without temporarily overshooting — but that returning below 1.5°C by the end of the century remains achievable.
Static Topic Bridges
World Meteorological Organization (WMO) — Mandate and Climate Reports
The World Meteorological Organization (WMO) is a specialised agency of the United Nations established in 1950, succeeding the International Meteorological Organization (IMO, founded 1873). It coordinates global meteorological, climatological, hydrological, and geophysical observations and services through a network of 193 member states. The WMO's annual State of the Global Climate report (released each year ahead of World Meteorological Day on March 23) consolidates data from leading climate agencies including the Copernicus Climate Change Service (EU), NASA GISS, NOAA, the UK Met Office Hadley Centre, and Japan Meteorological Agency.
- WMO established: 1950; HQ Geneva, Switzerland
- 193 member states and territories
- Annual report: "State of the Global Climate" — tracks key indicators: temperature, ocean heat, sea-ice, glacier retreat, greenhouse gas concentrations, sea level rise, and extreme weather
- Temperature datasets used: ERA5 (Copernicus/ECMWF), NASA GISS Surface Temperature Analysis (GISTEMP), NOAA Global Surface Temperature, HadCRUT (UK Met Office + CRU)
- World Meteorological Day: March 23 annually
- WMO's IPCC relationship: WMO and UNEP jointly established the Intergovernmental Panel on Climate Change (IPCC) in 1988
Connection to this news: The WMO report is the authoritative benchmark for tracking global warming progress (or regression) against Paris Agreement targets — making it the primary data source for UNFCCC negotiations, NDC reviews, and climate litigation worldwide.
Paris Agreement and the 1.5°C Target — Architecture and Status
The Paris Agreement, adopted at COP21 in December 2015, entered into force November 4, 2016. It establishes the long-term global temperature goal of holding warming to "well below 2°C above pre-industrial levels" and pursuing efforts to limit warming to 1.5°C. The Agreement operates through Nationally Determined Contributions (NDCs) — voluntary national emissions reduction pledges — reviewed every 5 years (Global Stocktake, first in 2023 at COP28).
- Paris Agreement: COP21, Paris, December 12, 2015; entered into force November 4, 2016
- Signatories: 196 parties (195 countries + EU)
- Pre-industrial baseline: 1850-1900 average (as used by IPCC and WMO)
- 1.5°C interpretation: Long-term multi-decade average — not a single calendar year; crossing 1.5°C in one year does not formally breach the target
- 70% probability that the 5-year mean 2025-2029 will exceed 1.5°C: WMO projection
- India's updated NDC (August 2022): 45% emissions intensity reduction by 2030 (from 2005 levels); 50% cumulative electric power installed capacity from non-fossil sources by 2030
- Global Stocktake (COP28, Dubai 2023): First formal review; found collective NDCs insufficient to meet 1.5°C — "transitioning away from fossil fuels" language adopted
- COP30: Scheduled for Belém, Brazil, November 2025; NDC updates due before COP30
Connection to this news: The WMO's confirmation that 2024 breached 1.5°C for the first time and that the past decade has been the hottest ever provides the scientific backdrop for escalating pressure on countries at COP30 to submit more ambitious NDCs and accelerate the fossil fuel phase-out.
Key Climate Indicators — Ocean Heat, Sea Ice, and Greenhouse Gas Concentrations
Beyond surface temperature, climate science tracks several "essential climate variables" (ECVs) that together paint a comprehensive picture of planetary heat accumulation. Ocean heat content (OHC) is considered the most robust indicator of global warming because oceans absorb approximately 90% of the excess heat trapped by greenhouse gases. Sea ice extent (Arctic and Antarctic) is a sensitive indicator of polar amplification — the Arctic is warming approximately 4 times faster than the global average. Atmospheric GHG concentrations drive the greenhouse effect.
- Ocean heat content: Oceans absorb equivalent of ~18 times annual human energy use each year (WMO 2025 data); upper 2000 m OHC at record levels in 2024 and 2025
- Arctic sea ice: Near-record low extent in 2024; Arctic warming ~4x global average ("polar amplification" — albedo feedback loop)
- Antarctic sea ice: Third lowest on record in 2025
- CO2 concentration (2024): ~422 ppm — highest in 800,000 years (ice core evidence)
- Pre-industrial CO2 (1850-1900): ~280 ppm; current level = ~51% above pre-industrial
- Sea level rise: Global mean sea level rising ~3.7 mm/year (2006-2018 average); accelerating
- Glacier mass loss: Continued in 2025 — all major global glacier regions (Alps, Himalayas, Andes, Greenland, Arctic) showing net negative mass balance
- Himalayan glaciers: ~50% of world's freshwater dependent on Himalayan-Hindu Kush-Karakoram glaciers (water tower of Asia); critical for India's river systems (Ganga, Brahmaputra, Indus)
Connection to this news: The WMO's tracking of multiple compounding climate indicators (temperature, OHC, sea ice, GHG) reinforces that warming is systemic and accelerating — the "hottest decade" finding is not an isolated data point but reflects a coherent trajectory across all planetary systems.
Key Facts & Data
- Hottest decade on record: 2015-2025 (eleven consecutive warmest years in 176-year record)
- 2025 temperature anomaly: ~1.43°C above 1850-1900 average (second or third warmest year)
- 2024 temperature anomaly: ~1.55°C above pre-industrial (hottest single year on record)
- WMO established: 1950; HQ Geneva; 193 member states
- Paris Agreement: COP21, December 2015; entered force November 2016
- India's NDC target (2022 update): 45% emissions intensity reduction and 50% non-fossil capacity by 2030
- CO2 concentration (2024): ~422 ppm — highest in 800,000 years
- Pre-industrial CO2: ~280 ppm
- Ocean heat content: Absorbs ~18x annual human energy use/year
- Probability 5-year mean 2025-2029 exceeds 1.5°C: 70% (WMO)
- COP30 location: Belém, Brazil, November 2025