Abstract

Anthropogenic emissions drive global-scale warming yet the temperature increase relative to pre-industrial levels is uncertain. Using 300 years of ocean mixed-layer temperature records preserved in sclerosponge carbonate skeletons, we demonstrate that industrial-era warming began in the mid-1860s, more than 80 years earlier than instrumental sea surface temperature records. The Sr/Ca palaeothermometer was calibrated against ‘modern’ (post-1963) highly correlated (R2 = 0.91) instrumental records of global sea surface temperatures, with the pre-industrial defined by nearly constant (<±0.1 °C) temperatures from 1700 to the early 1860s. Increasing ocean and land-air temperatures overlap until the late twentieth century, when the land began warming at nearly twice the rate of the surface oceans. Hotter land temperatures, together with the earlier onset of industrial-era warming, indicate that global warming was already 1.7 ± 0.1 °C above pre-industrial levels by 2020. Our result is 0.5 °C higher than IPCC estimates, with 2 °C global warming projected by the late 2020s, nearly two decades earlier than expected.

This is a BFD! 2c by late 2020s. And it's a Nature article. Good bye food security and hello mass deaths.

A fantastic paper. Is there a biologist here that can explain why Sr/Ca uptake is impacted by temperature? Given that ocean pH has been decreasing, what impact might that have on the calibration that was done?

This is such a contentious paper, academics fighting over whether that's the accurate way to record or measure changes in temperature as we were in a particularly cold period and we shouldn't be counting before we were dumping more CO2 into the environment and yet, any data is good data and should give us a more complete look at our scenario.

That being said I get why people would want to argue that we aren't past 2° or are past 2° for personal belief reasons and that adds a personal spin to this paper for those reading it. I think the line doesn't really matter as much as the response and the current situation.

The response has been fighting and no action and the current situation is if you are rich you can ignore it. So that's not great.