Biospheric carbon is miniscule compared to atmospheric carbon. Not only that, the biosphere is not a permanent carbon-sink. The extra 30% plant growth in spring

Biospheric carbon is miniscule compared to atmospheric carbon. Not only that, the biosphere is not a permanent carbon-sink. The extra 30% plant growth in spring becomes 30% extra carbon from plant decay in fall. And regardless, any effect that increased plant growth rates provide is already factored into our runaway atmospheric carbon rate.