An international team of scientists tracked temperature trends over the past 12,000 years and found that climate history is more complex than previously thought, reports an electronic publication EurekAlert reported.
Specialists from Germany, Great Britain, Canada, France and Switzerland participated in the study. The researchers used the largest available database of temperature reconstructions, covering 12,000 years, to analyze in detail the geographic pattern of temperature change during the Holocene.
Olivier Kartopanis and his colleagues found that, contrary to previous beliefs, there was no concurrent global warm period in the Holocene. Instead, the highest temperatures were at different times, not only in different regions, but also between ocean and land. That calls into question how meaningful the global average temperature comparisons between reconstructions and models are, experts say.
Lead author Kartopanis believes that “the results challenge the paradigm of a Holocene thermal maximum occurring simultaneously around the world.” And while the highest temperatures were reached between 4000 and 8000 years ago in the West Europe and North America, the ocean surface cooled about 10,000 years ago in the midlatitudes and remained stable in the tropics. Regional variability in the period of maximum temperature suggests that high-latitude insolation and glaciation rates played a major role in Holocene climate change.
“As ecosystems and people … are affected by regional and local climate change, relevant spatial and temporal models are needed … to guide policymakers,” said Lucas Jonkers, co-author of the study and researcher at MARUM – Center for Study on the Marine Environment in Bremen , Germany.