Bad news for climate deniers: an important climate change mystery solved
Data on Holocene temperatures confirm the role played by greenhouse gases over the past millennia.
The “Seasonal origin of the thermal maxima at the Holocene and the last interglacial” study, published in Nature by a team of researchers from Rutgers University, National Taiwan University, Ohio State University, and Nanjing Normal University, has solved an important mystery about climate change, showing that today’s annual global temperature is the hottest in the last 10,000 years, contrary to what recent research cited, often artfully, by climate deniers to show that what is taking place is only a “cyclical” natural warming.
This is the so-called “Holocene temperature puzzle” that has allowed some deniers and skeptics to argue that climate models to predict future warming are wrong.
The international team of scientists is convinced that their findings will challenge longstanding views on the history of temperature in the Holocene era, which began some 12,000 years ago.
The lead author of the study, Samantha Bova, of the Department of marine and coastal sciences at Rutgers –
State University of New Jersey, points out that “Contrary to previous reconstructions of global temperatures, our reconstruction shows that the first half of the Holocene was colder than in the industrial era due to the cooling effects of the residual ice caps of the previous glacial period. The warming of the late Holocene was, in fact, caused by the increase in greenhouse gases, as predicted by climate models, and this eliminates any doubt about the key role of carbon dioxide in global warming.
To reconstruct the histories of temperature change between the two most recent warm intervals on Earth – the last interglacial period from 128,000 to 115,000 years ago and the Holocene – the team of scientists used calcareous marine fossils (containing calcium carbonate) of foraminifera, organisms unicellular living on the surface of the ocean.
To find the fossils, the researchers, during the Expedition 363 of the International Ocean Discovery Program led by Rutgers, extracted a sediment core on the seabed off the Sepik River in northern Papua New Guinea, and explain that “The core has rapidly accumulating sediments that allowed scientists to recreate the history of the western Pacific warm pool., which closely follows changes in global temperatures”.
Rutgers reminds us that “How temperature evolved during the last interglacial and Holocene epoch is controversial.
Some data suggest that the annual average global temperature during modern times does not exceed the early Holocene hot period’s heat, called the “Holocene thermal maximum,” followed by global cooling.
Climate change models have strongly suggested that global temperatures have risen over the past 10,000 years. ‘
Another study author, Yair Rosenthal of the Department of Earth and Planetary Sciences at Rutgers University-New Brunswick, concludes: ‘The apparent discrepancy between climate models and data has raised doubt among skeptics the role of greenhouse gases in climate change in the future, we have found that post-industrial warming has actually accelerated the long and steady warming trend over the past 10,000 years.
Our study also highlights the importance of seasonal changes, particularly Northern Hemisphere summers, drive in various climates.
Our methods will, for the first time, use seasonal temperatures to obtain annual averages.