Global temperatures reached exceptionally high levels in 2023. Copernicus Climate Change Service (C3S) , implemented on behalf of the European Commission by the European Centre for Medium-Range Weather Forecasts with EU funding, monitored several key climate indicators throughout the year, reporting record conditions such as the warmest month on record and daily global temperature averages briefly exceeding pre-industrial levels by more than 2°C. Unprecedented global temperatures since June have led to 2023 becoming the warmest year on record – far surpassing 2016, the previous warmest year. The 2023 Global Climate Highlights report, based mainly on the ERA5 reanalysis dataset, provides a high-level summary of the most important climate extremes in 2023 and the main drivers behind them, such as greenhouse gas concentrations, El Niño and other natural variations.