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AMOC collapse adds only a few ppm of CO2

Forcing CESM2’s AMOC off with North Atlantic freshwater raises 2100 atmospheric CO2 by only 2.6–4.2 ppm under low and high emissions.

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How much extra CO2 does AMOC hosing add by 2100?

2.6 ppm under SSP1-2.6 and 4.2 ppm under SSP5-8.5 versus controls.

How fast does hosing collapse the AMOC?

From 17 Sv in 2015 to 6 Sv in 2045, then below 4 Sv by 2100.

What freshwater forcing was applied?

0.5 Sv uniformly in the North Atlantic at 50–70°N.

Which carbon reservoirs drive the two scenarios?

Both land and ocean in SSP1-2.6; ocean only in SSP5-8.5.

What feedback strengths were reported?

0.44 and 1.3 ppm Sv−1 for SSP1-2.6 and SSP5-8.5.

What climate fingerprints accompany AMOC weakening?

Southward ITCZ shift and the bipolar seesaw.

How much does unhosed SSP5-8.5 raise CO2 by 2100?

From 400 to 1094 ppm.

Does CESM2 include dynamic vegetation?

No; the default CESM2 version has no dynamic vegetation.

Over what years were the runs performed?

2015 to 2100, initialized from NCAR’s emission-driven historical CESM2.

In the control low-emission run, where does the AMOC go?

From 17 Sv in 2015 to 9 Sv in 2100.

Why is the global CO2 response small?

Many compensating land and ocean regional effects.