Giant clam reveals Middle Ages were warmer than today

China's Sea's biggest bivalve proves climate scientists were wrong to abolish the Midieval Warm Period

Two recent papers, one is in Earth-Science Reviews and the other is in Chinese Science Bulletin, have studied key chemical contents in micro-drilled giant clams shells and coral samples to demonstrate that in the South China Sea the warm period of the Middle Ages was warmer than the present.

The scientists examined surveys of the ratio of strontium to calcium content and heavy oxygen isotopes, both are sensitive recorders of sea surface temperatures past and present. The aragonite bicarbonate of the Tridacna gigas clam-shell is so fine-grained that daily growth-lines are exposed by micro-drilling with an exceptionally fine drill-bit, allowing an exceptionally detailed time-series of sea-temperature changes to be compiled – a feat of detection worthy of Sherlock Holmes himself.

By using overlaps between successive generations of giant clams and corals, the three scientists – YAN Hong of the Institute of Earth Environment, Chinese Academy of Sciences, Willie Soon of the Harvard-Smithsonian Center for Astrophysics and WANG Yuhong of Fudan University, Shanghai – reconstructed a record of sea-surface temperature changes going back 2500 years.

The Roman and Mediaeval Warm Periods both showed up prominently in the western Pacific and East Asia. Sea surface temperatures varied considerably over the 2500-year period.

Changing patterns of winter and summer temperature variation were also detected, disproving the notion that until the warming of the 20th century there had been little change in global temperatures for at least 1000 years, and confirming that – at least in the South China Sea – there is nothing exceptional about today’s temperatures.

"This new paper adds further material to the substantial body of real-world proxy evidence establishing that today’s global temperature is within natural ranges of past changes.”  Dr. Soon added: “The UN’s climate panel should never have trusted the claim that the medieval warm period was mainly a European phenomenon. It was clearly warm in South China Sea too,” said Dr. YAN.

Further details from Drs YAN Hong: yanhong@ieecas.cn and Willie soon: wsoon@cfa.havard.edu