'If the World Ends in 2100, We’re Probably OK' - by Howard Lee

There’s a myopia in the climate discourse today.

“Everyone is focused on what happens by 2100.  But that’s only 2 generations from today.  It’s like:  If the world ends in 2100 we’re probably OK!” says Professor Richard Zeebe of the University of Hawai’i.  “But It’s very clear that over a longer timescale there will be much bigger changes.”

If the next century seems impossibly far off, bear in mind that if you have a young child now, we’re talking about the world her or his grandchildren will be trying to raise their kids in.

Scientists who take the long view on climate change see parallels between global warming today and mass extinctions in Earth’s past:  “Apart from the stupid space rock hitting the Earth, most mass extinctions were CO2-driven global warming things,” says Professor Andy Ridgwell of Bristol University in the UK.

It has been a consistent pattern throughout geological time:  “If you screw with the climate enough, you have huge extinctions,” says Ridgwell.

So much of what you read and hear about climate change is heavily based on instrument records that only go back 160 years or so.  But Richard Zeebe and Andy Ridgwell are among a few scientists who look millions of years into Earth’s past to learn how the Earth responded to big additions of CO2 into the atmosphere before.  I had the opportunity to chat with each of them about their work during the American Geophysical Union conference in San Francisco at the end of last year.

Beyond the ice ages
... So both Ridgwell and Zeebe have been studying the best equivalent to modern climate change they have found so far, a relatively rapid global warming event that occurred 56 million years ago, called the “Paleocene-Eocene Thermal Maximum,” mercifully shortened to “PETM.”  For Ridgwell, it’s a better analog for the future: 

This is why I like the PETM, at least it’s a warming event.  It had a peak global warming of about 5º or 6ºC, which is a little bit beyond the end-of-the-century worst case scenario.

...
The change already baked in
Ridgwell is skeptical about ambitions to limit warming to 1.5°C: 

We have 1.5°C already programmed in, so even if we bring emissions right, right down, immediately, now, we already have 1.5 degrees!  So how we’re keeping to a 1.5-degree threshold isn’t clear.

So a fun thing we’re doing now with our very fast warming is the ocean surface warms up and the deep ocean is still cold, which is partly why we have this programmed-in warming that we haven’t seen yet.  The deep ocean hasn’t yet noticed that the planet at the surface is rather warmer.  If we just sit here at current CO2 levels and let the system equilibrate, it’s 1.5°C anyway.  Which comes back to COP21 - what is this 1.5°C target?  We’ve emitted the CO2 to reach 1.5°C already, so I don’t know what they’re thinking of!

It seems as if everyone is assuming, without thinking about it, that there is massive carbon geoengineering going on.

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