New Study: Sea Levels 3-4 Meters Higher Than Today When CO2 Was At ‘Safe’ Levels

Both the history of the Holocene as well as trends from recent decades continue to undermine claims of unprecedented sea level or coastal changes operating in tandem with rising CO2 concentrations.

Per a new published study (Martins et al., 2023), during the Mid-Holocene (~7000 to ~4000 years ago), when CO2 was a “safe” ~265 ppm, the sea levels on the coasts of Brazil were 3 to 4 meters higher than they are now. Sea levels have been falling to the present levels for millennia.

From 1993-2015 the sea levels around South America sea have risen (shown in red in the figure) overall by about 1-2 mm/yr, but there are large regions where sea levels have fallen (blue, shown especially in the southeast, west) by -1-2 mm/yr too.

The Brazilian mangrove forest area has increased from 9,564 km² in 1985 to 9,800 km² in 2020, In other words, coastal mangrove forests grew seaward (rather than shrinking inland due to sea level rise) by 2.5%.

Image Source Martins et al., 2023

2 responses to “New Study: Sea Levels 3-4 Meters Higher Than Today When CO2 Was At ‘Safe’ Levels”

  1. Andy

    Hello Kenneth, thank you again for your research and your invaluable work.

    I think you should be much more active on Twitter to counter the alarmists, I regularly watch your responses to alarmist arguments in the rare thread you’re in, and you’re consistently unstoppable.

    You should do the same on some of the big alarmist Twitter accounts, I’m sure you’d gain in visibility, followers etc. Your research is of public use in these dark times.

    Here’s an example of a tweet ( to which it would be good to see you respond, or make a thread to debunk, even though I know that’s not your usual approach, we need you, and I know you’re one of the best climate realists I’ve seen.


  2. Laura Ingraham: AOC uses wildfire smoke to push green agenda – Newsfeed Hasslefree Allsort

    […] New Study: Sea Levels 3-4 Meters Higher Than Today When CO2 Was At ‘Safe’ Levels […]

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