The increase in global mean surface temperature is the parameter generally used by the media and policy-makers to convey the magnitude of the changes occurring across the climate system. On its own, however, this single parameter is insufficient to provide a detailed picture of the overall state of the Earth’s climate and any changes that may have occurred. In 2018, the World Meteorological Organization (WMO) therefore identified seven key indicators which it has used since then to describe the global changes in the climate system to the general public and decision-makers. These indicators are:

1. global mean surface temperature,
2. ocean heat content,
3. global mean sea-level change,
4. Arctic and Antarctic sea-ice extent,
5. changes in the mass balance of the Greenland and Antarctic Ice Sheets,
6. global mean ocean pH (ocean acidification) and
7. mean atmospheric carbon dioxide concentrations.

Each of these indicators is scientifically assessed at least once a year, with monitoring data collected using a standardized global methodology. Together, they capture changes in the Earth’s atmosphere and energy balance and provide an initial insight into the current state of the global climate. All seven indicators can be described in simple numerical terms. The latest figures for the seven indicators are published by the WMO in its State of the Climate report, which is produced annually. In 2021/2022, four of the seven indicators set new records. This means that in 2021 and 2022, atmospheric carbon dioxide concentrations, sea-level rise, ocean acidification and ocean heat content were higher than at any time since weather and climate records began.