The concurrence of cooling events on both land and sea suggests that a global cooling phenomenon was erased by subsequent global warming.

Lead author Helen McGregor from University of Wollongong in New South Wales, Australia, said, "With this research, we now have new insight into the century-scale global sea-surface temperature variations that came before man-made greenhouse gas forcing."
The researchers combined 57 previously published marine surface temperature reconstructions that cover all of the world's oceans, from near-polar to tropical regions. They compiled the data within 200-year brackets to observe long-term trends, and then compared the findings to land-based reconstructions, which revealed similar cooling trends. To investigate the cause of the cooling trend, the research team turned to climate models. They examined how sea-surface temperatures reacted to various 'forcing' factors, such as changes in solar output, Earth's orbit, land use, volcanic activity and greenhouse gases.
The study was published in Nature Geoscience.
Source-IANS