The development of climate warming since the Industrial Revolution provides critical context for future climate change and the processes that control regional warming over land and in the oceans. Instrumental records of climate are rare prior to the 20th Century, and natural archives such as coral, ice cores and tree rings provide a way to reconstruct climate changes before this time. In this talk I will use networks of palaeoclimate records from the last 500 years, assembled by the PAGES2k Consortium, to show that sustained industrial-era warming of the tropical oceans first developed during the mid-19th Century, and was near-synchronous with Northern Hemisphere continental warming. The early onset of sustained, significant warming in palaeoclimate records and model simulations suggests greenhouse forcing of industrial-era warming commenced as early as the mid-19th Century, and included an enhanced equatorial ocean response mechanism. The development of Southern Hemisphere warming was delayed, developing around the end of the 19th Century over mid-latitude continents and not yet evident at the continent scale over Antarctica. This delay is not reproduced in climate simulations, but further regional analysis of an expanded array of Antarctic palaeoclimate records supports the delayed development of warming here, which may be related to Southern Ocean circulation processes. The findings imply that instrumental records are too short to comprehensively assess anthropogenic climate change, and in some regions ~180 years of industrial-era warming has already caused surface temperatures to emerge above pre-industrial variability.
Nerilie Abram is an Associate Professor and Future Fellow at the Research School of Earth Sciences. She is also a Chief Investigator for the new Australian Centre of Excellence for Climate Extremes. Her research focuses on reconstructing climate changes over the last millennium, using a variety of methods including Antarctic ice cores, tropical reef corals and cave deposits.