Global climate history over the last 12,000 years is more complex than previously thought, according to new Modelling
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.
driving climate changes
Lead author Cartapanis said: “The results challenge the paradigm of a Holocene Thermal Maximum occurring at the same time worldwide.”
And, while the warmest temperature was reached between 4,000 and 8,000 years ago in western Europe and northern America, the surface ocean temperature cooled since about 10,000 years ago at mid-high latitudes and remained stable in the tropics.
The regional variability in the timing of maximum temperature suggests that high latitude insolation and ice extent played major roles in driving climate changes throughout the Holocene.
Lukas Jonkers, co-author of the study and researcher at the MARUM – Center for Marine Environmental Sciences in Bremen, Germany, added: “Because ecosystems and people do not experience the mean temperature of the Earth, but are affected by regional and local changes in climate, models need to get the spatial and temporal patterns of climate change right in order to guide policymakers.”
Thus, the new work by Cartapanis and colleagues presents a clear target for climate models as the ability of climate models to reproduce Holocene climate variations in space and time, will increase confidence in their regional projections of future global warming.
Image: The new study highlights the importance of including regional climate variability in climate models. For example, in the high latitudes, solar radiation and ice extent played an important role in climate changes during the Holocene. A scientist stands in front of the Greenland ice sheet (Jakobshavn Isbræ glacier).
Credit: Vincent Jomelli.