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Dirk Dunning's avatar

Actually, we do have a really good idea about what will happen.

The only real question is whether the total heat input we have already made or committed is sufficient to completely melt Greenland, or to break the oceanic clathrates. We can already see the Tundra destabilizing. If we are unable to stop that, well - game over. That's 1,500 gigatons of carbon into the atmosphere. And then there is no possibility that we keep Greenland from melting. The question then is HOW FAST. What appeared to be 300-500 years, now looks like 50-150.

So how do we know where we are?

Easy. Plot the CO2 equivalent over time. Hell, just take the current condition. Since the rest of the line is essentially a vertical line from the baseline.

Today we are about 550-560 ppm CO2(e). Methane is the major and dominant second source. Then add the rest of the warming gases.

Why? Because ALL of the warming gases count towards warming, not just CO2. CO2 vastly understates the hazard and lies about where we are - bad as it suggests.

At 550-560 ppm CO2(e) we are at twice baseline of 278 ppm CO2(e).

We debate about the "short" and "long" term climate sensitivity, And we continually underestimate those as Hanson and others have pointed out. And as the scientists at the COP are finally saying aloud - 30-40 years too late. That is 0.75 C per Watt/m^2.

But we never talk about the equilibrium climate sensitivity. And that is the most important. We know from the paleo climate record that the 105 k year ice age cycles take us from about 215 ppm CO2(e) at a low to about 280 ppm CO2(e) at the high. That then takes us from an arctic temperature of -8 C to + 6 C, so 14 C variation.

The implications are obvious.

But we can then also look back at the paleo climate to the last time we saw an atmospheric CO2(e) of 550-560. That takes us back to about 33 million years ago - long long long before man existed.

And that is about the time that antarctic glaciation was complete. By the time we reach 750 ppm CO2(e), we push that further back to 38 million years ago in the Eocene when the world had an "equable" climate.

No one understood how that could work. The ultra warm arctic breaks all of the models. Well - it does until you realize that it implies a different atmospheric structure that lacks Ferrell and Polar cells and has a single equator to pole Hadley cell, with giant cyclones running far north in a deeper atmosphere where Coriolis forces play a smaller role. I challenged the climate scientists about that in the 1990s, asking where we were thermodynamically. They went away and thought about it. They came back to say "we are close - very close".

Since then we have seen deepening of the Rossby waves and a slowing and destabilization of the polar jet. The huge heat intrusions to the north and cold to the south are artifacts of that destabilizing system and the breakdown of the main jet along with it.

Another climate scientist back in the 1950s modeled this. He and his grad students work stands alone. One of the things he predicted was third order effects causing what look like walls in the atmosphere. We saw the first of those with the Ridiculously Resilient Ridge. They are becoming common.

Where we are headed is to a rapid death of the oceans, and them going anoxic in large areas and vortexes - killing most life in the ocean, combined with the collapse of the tundra, and the breaking of the oceanic clathrates. Also the temporary shutdown of the AMOC and the Pacific circulation and with those the death temporarily of the great oceanic circulation.

In the immediate future, Europe north of Spain goes cold even as the Arctic heats. The oceans get unbelievably warm resulting in more massive storms. Cat 6 hurricanes become common with sustained winds of 185-218 (based on extension of the original scale).

The shift will be rapid, then sudden. And when it does we get perhaps a century to act as the Antarctic and Greenland provide a buffer. But most likely they are insufficient. We go to +11 C and an equable climate.

The transition happens so rapidly that 80+% of all species go extinct. Humans may be among those. Only some of our rare adaptations (like the high altitude genes) might spare a few.

That is where we are headed.

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J. Siegel's avatar

Thank you for this essay. I always appreciate you when you write.

And as one person to another who struggles with the same monster-I understand completely.

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