We rely on climate models to predict the future, but models cannot be fully tested as climate observations rarely extend back more than 150 years.
We rely on climate models to predict the future, but models cannot be fully tested as climate observations rarely extend back more than 150 years. Understanding the Earth’s past climate history across a longer period gives us an invaluable opportunity to test climate models on longer timescales and reduce uncertainties in climate predictions. In this context, changes in the average surface temperature of the Earth during the current interglacial Epoch, the Holocene (approximately the past 12,000 years), have been thoroughly debated over the past decades. Reconstructions of past temperature seem to indicate that global mean temperature showed a maximum around 6,000 years ago and has cooled until the onset of the current climate crisis during the industrial revolution.
Climate model simulations, on the other hand, suggest continuous warming since the start of the Holocene. In 2014, researchers named this major mismatch between models and past climate observations the “Holocene Temperature Conundrum“.
In this new study, scientists used the largest available database of past temperature reconstructions extending back 12,000 years to carefully investigate the geographic pattern of temperature change during the Holocene. Olivier Cartapanis and colleagues find that, contrary to previously thought, there is no globally synchronous warm period during the Holocene. Instead, the warmest temperatures are found at different times not only in different regions but also between the ocean and on land. This questions how meaningful comparisons of the global mean temperature between reconstructions and models actually are.
Photo Credit: Thomas_Ritter via Pixabay