Climate mitigation strategies banking on forests to absorb increasing atmospheric CO2 may need recalibration. The assumption that phosphorus-starved forests could dramatically increase carbon storage with nutrient supplementation appears flawed based on new modeling data. Forest ecosystems have long been considered critical carbon sinks, with theories suggesting that phosphorus-limited soils constrain their CO2 absorption potential. The prevailing hypothesis held that enriching these nutrient-poor environments would unlock substantially greater carbon sequestration capacity as atmospheric CO2 levels rise. However, comprehensive modeling published in PNAS challenges this fundamental assumption. The research demonstrates that phosphorus supplementation does not amplify the CO2 fertilization effect in forest systems as previously predicted. Even when phosphorus availability increases, forests do not exhibit the enhanced carbon uptake rates that climate models have incorporated into their projections. This finding carries profound implications for global climate policy and forest management strategies. Many carbon offset programs and national climate commitments rely on projections of enhanced forest carbon sequestration under rising CO2 conditions. The research suggests these estimates may be overly optimistic, particularly for phosphorus-limited ecosystems that comprise significant portions of global forestlands. The disconnect between theoretical nutrient limitation and actual carbon sequestration responses indicates that forest carbon dynamics operate through more complex mechanisms than simple nutrient-CO2 interactions. This complexity challenges the reliability of current Earth system models used for climate projections. The findings underscore the need for more conservative estimates in climate mitigation planning and highlight the importance of protecting existing forest carbon stocks rather than relying solely on enhanced sequestration potential.