Human-caused Indo-Pacific warm pool expansion

"We've long suspected climate change to be behind the changes [seen in ocean surface temperatures near the equator across Asia], but no one had yet proven it...This has important implications for understanding changes in rainfall patterns for a large, and vulnerable population across Asia."

Evan Weller, lead-author

• States the Indo-Pacific warm pool (IPWP) has warmed and grown substantially during the past century
• Reviews that the IPWP is Earth’s largest region of warm sea surface temperatures (SSTs), has the highest rainfall, and is fundamental to global atmospheric circulation and hydrological cycle
• Reviews that the region has also experienced the world’s highest rates of sea-level rise in recent decades, indicating large increases in ocean heat content and leading to substantial impacts on small island states in the region
• States that previous studies have considered mechanisms for the basin-scale ocean warming, but not the causes of the observed IPWP expansion, where expansion in the Indian Ocean has far exceeded that in the Pacific Ocean
• Identifies human and natural contributions to the observed IPWP changes since the 1950s by comparing observations with climate model simulations using an optimal fingerprinting technique
• Finds greenhouse gas forcing is the dominant cause of the observed increases in IPWP intensity and size, whereas natural fluctuations associated with the Pacific Decadal Oscillation have played a smaller yet significant role
• Shows that the shape and impact of human-induced IPWP growth could be asymmetric between the Indian and Pacific basins, the causes of which remain uncertain
• States that human-induced changes in the IPWP have important implications for understanding and projecting related changes in monsoonal rainfall, and frequency or intensity of tropical storms, which have profound socioeconomic consequences