2023 was the hottest year ever recorded, marked by stark temperature increases in polar and cold regions, and more frequent extreme temperatures in tropical and arid regions
Every month between June and December in 2023 – the hottest year every recorded – broke previous records. The global mean temperature in 2023 was just under 1.5 degrees Celsius (°C) above the 1850‑1900 pre-industrial level, which was not expected until 2045 when the Paris Agreement was signed (ECMWF, 2024). In ten OECD countries and three out of ten OECD large regions, 2023 was the hottest year. Moreover, in 30 OECD countries and about 7 of 10 OECD regions, the hottest year occurred in 1 of the last 5 years.
Across large regions of the OECD, air temperatures rose by an average of 1.4°C in 2023 compared to 1981-2010. Temperature increases were even more pronounced in OECD polar and cold regions, covering more than 40% of the total OECD area, where air temperatures rose by close to 2°C in 2023 compared to 1981-2010. This is more than double the increase observed in OECD arid regions (+0.8°C).
Worryingly, this trend is foreseen to continue across all emission scenarios. In polar regions, temperatures are projected to rise by mid-century by 3°C compared to 1981-2010 in a low-emissions scenario and up to 4.3°C in a high-emissions scenario. In arid regions, temperatures are predicted to rise by 1.3°C in a low‑emissions scenario and up to 1.9°C in a high-emissions one (Figure 3.1).
The rapid rise in temperatures in polar and cold regions coincides with a notable drop in icing days. In 2023, OECD polar and cold regions had 17 and 9 fewer icing days respectively compared to 1981-2010 and, for polar regions, these losses are expected to increase to between 20 to 28 days by 2041-60 (Figure 3.2). Higher temperatures will not only impact ice sheets and glaciers, adding to the ongoing rise in sea levels, but they will also impact permafrost areas, leading to large methane and carbon dioxide emissions, triggering negative feedback loops and further accelerating climate change.
Hot days also raise myriad household challenges related to well-being, health systems, the labour market and energy use. While average temperature increases are higher in colder regions, arid and tropical OECD regions remain the regions most exposed to days with extremely high temperatures (hot days). In 2023, people in these regions were exposed to 11 and 8 additional hot days respectively compared to 1981‑2010. By 2041‑60, people in tropical regions are expected to endure 40 to 60 more hot days per year compared to 1981-2010 (Figure 3.3). Those in arid regions will likely experience 20 to 30 more hot days. By 2041‑60, regardless of the emission scenario, these regions are likely to endure 50 extra hot days per year compared to the baseline of 1981-2010 (Figure 3.4 and Figure 3.7). The 20 regions projected to be most affected, hosting more than 29 million people, are all in Australia, Colombia and Mexico.
