Global atmospheric carbon dioxide concentrations were very likely the highest in the past 100,000 years, and perhaps the past several million years, Dr Braganza said.

“Atmospheric carbon dioxide levels are now similar to those during the Pliocene, a much warmer period than any experienced by modern humans.

“These indicators show that climate change, especially changes to atmospheric chemistry, are not just continuing but tracking at the more extreme end of possible scenarios.”

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