State of the climate [Chapter 2]

•The global climate is rapidly changing. Human activities have increased the concentrations of greenhouse gases in the atmosphere to levels not experienced for over a million years, trapping more heat within the atmosphere and oceans. Globally, temperatures, precipitation and extreme weather phenomena such as heatwaves and downpours are rising and breaking historic records by bigger margins. The rate of global sea-level rise has increased, with significant contributions from melting glaciers and ice sheets, as well as from the thermal expansion of warmer sea water. In the 2024 calendar year, global mean surface temperature (GMST) exceeded 1.5 °C above pre-industrial temperatures for the first time since observational records have existed.

•National temperature records around the world are now frequently broken, in some cases by several degrees Celsius. The heatwave in July 2022 broke the UK temperature record, set only in 2019, by 1.6 °C; the heat exceeded 40 °C and contributed to approximately 2,200 excess deaths from 10 to 25 July. A warmer atmosphere can also hold more moisture, enabling larger precipitation and hydrological extremes. In 2015, Storm Desmond broke 48hr UK rainfall records and caused record breaking floods over a broad swathe of Northern England. The Environment Agency estimates the winter floods in 2015 caused £1.7-2.5 billion in economic damages (Flood and Coastal Erosion Risk Management Research and Development Programme, 2021). In 2023, the storm series Babet, Ciarán, and Debi caused insured losses of about £570 million in the UK (Association of British Insurers, 2025). In 2023 the sea level was the highest on record at the Newlyn tide gauge, one of the longest available sea level records in the UK, recording data since 1915. This continues the long-term increase in sea level around the coast of the UK. Further increases in temperature, changes in rainfall and increases in sea level are projected to occur over the coming decades. Some future changes are already locked-in, and the magnitude of these changes is dependent on greenhouse gas emissions.