evidence: On the basis of the sclerosponge OML record, industrial-era warming can be categorized into three broad stages (Fig. 4c). The first is the early industrial period from the mid-1860s to early 1900s, when temperatures increased by 0.3 ± 0.1 °C at an average rate of ∼0.09 ± 0.03 °C decade−1. This was followed by a similar amount of warming (∼0.3 °C) from the early 1900s to the early 1960s (the mid-industrial period) but at nearly half the average rate (0.04 ± 0.02 °C decade−1). Finally, starting from the mid-1960s (the ‘modern’ period) temperatures increased at a much faster rate of 0.15 ± 0.05 °C decade−1 (Fig. 4c) in response to rapidly increasing atmospheric CO2. Since the mid-1980s, the temperature sensitivity to increasing CO2 has halved, from ∼0.17 ± 0.02 °C per 10 ppm CO2 during 1964–1984 to the present-day (1985–2020) 0.08 ± 0.02 °C per 10 ppm CO2 (Figs. 3c and 4c).