Climate extremes dominate headlines around the world as the IPCC releases its physical climate assessment report.
July 2021 was the hottest month ever recorded (according to the US National Oceanic and Atmospheric Administration monthly global report1), with the global average surface temperature 0.93 °C above the twentieth century average. This puts 2021 on track to be one of the seven warmest years on record, pushing the planet ever close to exceeding the aspirational Paris Agreement 1.5 °C warming limit. The recent IPCC Working Group 1 report2 outlines how close we are to exceeding that limit — with the best estimate for human-caused warming approximately 1.1 °C for 2010–2019, relative to the 1850–1900 average. The report, and its headline statements, is a sombre read, but is ultimately unsurprising. There is now greater confidence — unequivocal on the global scale — in the effect of anthropogenic emissions on warming the planet and causing extreme events. And those events are occurring on a regular basis.
The droughts seen across the globe in the first half of the year3, and record heat, provided dry conditions for fires to take hold in July — areas around the Mediterranean burnt furiously, and the USA west coast again experienced some of their largest fires. Yet as fires rage, other regions, sometimes neighbouring countries, experience extreme rainfall and devastating floods. Images of roads turned into rivers and buildings being washed away alongside and yet contrasting with those of blackened skies and uncontrolled flames make all too clear our vulnerability to extreme climate events.
These images of infernos and floods are visually shocking, but the effects of climate change are everywhere, and not everything can be captured in this way. The recent report captures the extremes and their increase but also the unseen effects of climate change — improved estimates of climate sensitivity and changes in radiative forcing, as well as changes in atmospheric and ocean circulation, with implications for the hydrological cycle. This physical science report and the three Special reports released in this assessment cycle make it clear that aggressive action needs to start now to avoid the worst predicted effects. We hope that national and corporate leaders will respond now, before the next two sections Impacts, Adaptation and Vulnerability and Mitigation of Climate Change, due in early 2022, remind us that further time has slipped away.
Assessing the Global Climate in July 2021 (National Centers for Environmental Information, NOAA, 13 August 2021); https://go.nature.com/2WrF3VO
IPCC Climate Change 2021: The Physical Science Basis (eds Masson-Delmotte, V. et al) (Cambridge Univ. Press, in the press).
Langenbrunner, B. Nat. Clim. Change 11, 650 (2021).