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The deep ocean, a vast thermal reservoir, absorbs excess heat under greenhouse warming, which ultimately regulates the Earth's surface climate. Even if CO2 emissions are successfully reduced, the stored heat will gradually be released, resulting in a particular pattern of ocean warming. Here, we show that deep ocean warming will lead to El Niño-like ocean warming and resultant increased precipitation in the tropical eastern Pacific with southward shift of the intertropical convergence zone. Consequently, the El Niño-Southern Oscillation shifts eastward, intensifying Eastern Pacific El Niño events. In particular, the deep ocean warming could increase convective extreme El Niño events by 40 to 80% relative to the current climate. Our findings suggest that anthropogenic greenhouse warming will have a prolonged impact on El Niño variability through delayed deep ocean warming, even if CO2 stabilization is achieved. This paper shows that anthropogenic greenhouse warming will have a prolonged impact on El Niño variability through delayed deep ocean warming, even if CO2 stabilization is achieved. [ABSTRACT FROM AUTHOR]

Climate change mitigation through negative CO2 emissions has been recognized as a crucial strategy to combat global warming. However, its potential effects on terrestrial productivity and agricultural activities remain uncertain. In this study, we utilized large ensemble simulations with an Earth system model of full complexity to investigate the response of Gross Primary Production (GPP) to CO2 forcings. Our findings reveal a significant asymmetry in the GPP response to CO2 ramp-up and symmetric ramp-down model experiments, especially in Europe, suggesting that GPP declines rapidly as CO2 levels decrease. Remarkably, during the CO2 removal period, the North Atlantic Sea surface temperature experienced cooling due to a delayed recovery of the Atlantic Meridional Overturning Circulation (AMOC). This cooling led to precipitation and soil moisture deficits, resulting in a rapid reduction in GPP. This asymmetry in GPP response holds consistent across multi-model simulations. These results underscore the potential implications of delayed recovery in ocean circulation, which could unexpectedly accelerate terrestrial GPP reduction. These insights are crucial for policymakers, aiding them in projecting agricultural activity and formulating targeted GPP control policies specific to the European region. [ABSTRACT FROM AUTHOR]

Atmospheric blocking has been identified as one of the key elements of the extratropical atmospheric variabilities, controlling extreme weather events in mid-latitudes. Future projections indicate that Northern Hemisphere winter blocking frequency may decrease as CO2 concentrations increase. Here, we show that such changes may not be reversed when CO2 concentrations return to the current levels. Blocking frequency instead exhibits basin-dependent changes in response to CO2 removal. While the North Atlantic blocking frequency recovers gradually from the CO2-induced eastward shift, the North Pacific blocking frequency under the CO2 removal remains lower than its initial state. These basin-dependent blocking frequency changes result from background flow changes and their interactions with high-frequency eddies. Both high-frequency eddy and background flow changes determine North Atlantic blocking changes, whereas high-frequency eddy changes dominate the slow recovery of North Pacific blocking. Our results indicate that blocking-related extreme events in the Northern Hemisphere winter may not monotonically respond to CO2 removal. [ABSTRACT FROM AUTHOR]