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.