In the Northern Hemisphere, the more than twofold difference between the atmospheric inversion and remote sensing–derived estimate of the net land carbon sink is an unresolved puzzle that challenges our fundamental understanding of the global carbon cycle. We provide several lines of evidence that much of this discrepancy can be resolved by a weak net land carbon sink that is distributed mainly in the Northern Hemisphere, together with a relatively small reduction in the magnitude of fossil fuel emissions and a small increase in ocean uptake. …A strong land carbon sink, as identified in past research, has often been used to support the potential of nature-based climate solutions in meeting climate stabilization targets. However, if the weak land sink hypothesis is correct, then the role of CO2 fertilization in enhancing forest carbon stocks might be overestimated. At the same time, projections of carbon accumulation in reforestation and afforestation projects may be optimistic too.