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Comment by bilsbie

3 hours ago

My main skepticism (Shark lover here btw!)

Is that sharks are an ancient species and they’ve survived way warmer oceans even relatively recently.

For example the Medieval Warm Period Sargasso Sea surface temperatures were 1°C warmer than 400 years ago, and Pacific Ocean water temperatures were 0.65°C warmer than the decades before.

14 comments

bilsbie

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mapt  3 hours ago

Sharks are an ancient division of life, roughly 440 million years old, which has survived far warmer oceans.

There are ~500 living species of shark and likely tens of thousands extinct in their lineage.

We are perpetrating a mass extinction event that incorporates not just temperatures, but ocean acidification and trophic cascade for fisheries. In mass extinctions, enough things about the ecosystem change that specialists often go extinct. Great White Sharks are a specialist species in their extreme size; Most size specialists are in a precarious local maxima that disappears too quickly to adapt if conditions change drastically.

ericmcer  2 hours ago

The warmer ocean thing seems to be blanketing over the real issue: we are overfishing.

Which is really heartening to me, because decreasing the temperature of the ocean seems daunting, but not dragging giant nets through the ocean nonstop seems pretty straightforward.

acuozzo  3 hours ago

Were there any periods in which the rate of change in warming was the same or greater?

  • simonsarris  2 hours ago

    Younger Dryas, definitely. It very likely abruptly stopped progress in human agriculture, before allowing it to abruptly restart again. Makes the Medieval warm period and little ice age look like a joke. Two massive shifts that punctuate the timeline of early human prehistory.

    > The Younger Dryas (YD, Greenland Stadial GS-1) was a period in Earth's geologic history that occurred circa 12,900 to 11,700 years Before Present (BP). It is primarily known for the sudden or "abrupt" cooling in the Northern Hemisphere, when the North Atlantic Ocean cooled and annual air temperatures decreased by ~3 °C (5 °F) over North America, 2–6 °C (4–11 °F) in Europe and up to 10 °C (18 °F) in Greenland, in a few decades

    https://en.wikipedia.org/wiki/Younger_Dryas

  • bilsbie  3 hours ago

    I think there’s debate on the current numbers but I’ve heard sea surface temperatures are currently about 0.5°C above the 1981-2010 average.

  • ijustlovemath  2 hours ago

    During the Paleocene-Eocene Thermal Maximum, the rate of change of CO2 concentration was 1/4 what we're at today

ghurtado  2 hours ago

> Is that sharks are an ancient species

For a shark lover, you should know that shark is not a species, but a taxonomy group.

From there, everything else you assume is incorrect (ie: some species of sharks have definitely gone extinct)

moffkalast  3 hours ago

I presume it was due to the temperature gradient being extremely low, so they could gradually adapt to the change over hundreds of years. We're pulling the handbrake in geological terms.

https://xkcd.com/1732

(that chart was made in 2016, given that we were at +1.5C last year we're outdone even the most pessimistic scenario presented on that graph by quite a bit, the line is now almost horizontal)