Tropical sea surface temperatures and the Earth's orbital eccentricity cycles

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Abstract
The tropical oceanic warm pools are climatologically important regions because their sea surface temperatures (SSTs) are positively related to atmospheric greenhouse effect and the cumulonimbus‐cirrus cloud anvil. Such a warm pool is also present in the central tropical Indian Ocean. Paleo‐SSTs estimated by the radiolarian transfer functions for the last ∼200–1400 kiloyears (ka) in a deep‐sea sediment core from this warm pool fluctuated within 2.75°C (26.14–28.89°C) around the threshold temperature (27 °C) for the super greenhouse effect. It is possible that this SST variation might have led to the corresponding fluctuation in the greenhouse effect and the cirrus cloud anvil in the geological past. These paleo‐SSTs also exhibited cyclicities at ∼100‐ and ∼400‐ka corresponding to the Earth's orbital eccentricity cycles. Results, therefore imply that the tropical Indian Ocean warm pool persisted during the Quaternary and the paleo‐SSTs fluctuating at the orbital eccentricity frequencies might have modulated the intensity of greenhouse effect.