Global lake phytoplankton proliferation intensifies climate warming

In lakes, phytoplankton sequester atmospheric carbon dioxide (CO2) and store it in the form of biomass organic carbon (OC); however, only a small fraction of the OC remains buried, while the remaining part is recycled to the atmosphere as CO2 and methane (CH4). This has the potential effect of adding CO2-equivalents (CO2-eq) to the atmosphere and producing a warming effect due to the higher radiative forcing of CH4 relative to CO2. Here we show a 3.1-fold increase in CO2-eq emissions over a 100-year horizon, with the effect increasing with global warming intensity. Climate warming has stimulated phytoplankton growth in many lakes worldwide, which, in turn, can feed back CO2-eq and create a positive feedback loop between them. In lakes where phytoplankton is negatively impacted by climate warming, the CO2-eq feedback capacity may diminish gradually with the ongoing climate warming. In lakes, phytoplankton sequester atmospheric carbon dioxide as organic carbon, but most of this organic carbon is recycled back to the atmosphere as carbon dioxide and methane, contributing to warming due to the higher radiative forcing of methane.