The Early Cretaceous Epoch, about 145–100 million years ago, is generally thought of as a greenhouse period, with high atmospheric CO2 concentrations1 and high global mean temperatures2. But evidence for episodes of cooler conditions, and even transient glaciations, has been proposed3, 4, 5, 6, 7, 8, 9. Here we present sea-surface temperature records spanning the period from 142 to 128 million years ago (Berriasian–Barremian ages) from low and mid latitudes, reconstructed using the TEX86 palaeotemperature proxy. During this period, we find sea-surface temperatures exceeding 32 °C at 15°–20° N and averaging 26 °C at ~53° S. These temperatures substantially exceed modern temperatures at equivalent latitudes, and are incompatible with the notion of consistently cooler conditions in the earliest Cretaceous. Moreover, we find little variability in the sea-surface temperature records, even during the Valanginian carbon-isotope excursion ~138–135 million years ago, which was thought to be associated with marked temperature fluctuations5. We conclude that the earliest Cretaceous was characterized by a warm, stable climate, with a lower meridional temperature gradient than today.
At a glance
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