Response of ocean acidification to atmospheric carbon dioxide removal

Artificial CO_(2)removal from the atmosphere(also referred to as negative CO_(2)emissions)has been proposed as a potential means to counteract anthropogenic climate change.Here we use an Earth system model to examine the response of ocean acidification to idealized atmospheric CO_(2)removal scenarios.In our simulations,atmospheric CO_(2)is assumed to increase at a rate of 1%per year to four times its pre-industrial value and then decreases to the pre-industrial level at a rate of 0.5%,1%,2%per year,respectively.Our results show that the annual mean state of surface ocean carbonate chemistry fields including hydrogen ion concentration([H^(+)]),pH and aragonite saturation state respond quickly to removal of atmospheric CO_(2).However,the change of seasonal cycle in carbonate chemistry lags behind the decline in atmospheric CO_(2).When CO_(2)returns to the pre-industrial level,over some parts of the ocean,relative to the pre-industrial state,the seasonal amplitude of carbonate chemistry fields is substantially larger.Simulation results also show that changes in deep ocean carbonate chemistry substantially lag behind atmospheric CO_(2)change.When CO_(2)returns to its pre-industrial value,the whole-ocean acidity measured by[H^(+)]is 15%-18%larger than the pre-industrial level,depending on the rate of CO_(2)decrease.Our study demonstrates that even if atmospheric CO_(2)can be lowered in the future as a result of net negative CO_(2)emissions,the recovery of some aspects of ocean acidification would take decades to centuries,which would have important implications for the resilience of marine ecosystems.

Simulated carbon cycle and Earth system response to atmospheric CO_(2)removal

To project possible future climate change,it is important to understand Earth system response to CO_(2)removal,a potential key method to limit global warming.Previous studies examined some aspects of Earth system response to different scenarios of CO_(2)removal,but lacked a systematic analysis of the carbon cycle and climate system response in a consistent modeling framework.We expanded previous studies by using an Earth system model to examine the response of land and ocean carbon cycle,as well as a set of climate variables to idealized scenarios of atmospheric CO_(2)removal with different removal rates.In the scenarios considered,atmospheric CO_(2)increases at a rate of 1%per year to four times of its preindustrial level,and then decreases at a rate of 0.5%,1%,and 2%per year to the preindustrial level.Simulation results show that a reduction of atmospheric CO_(2)induces CO_(2)release from both the ocean and terrestrial biosphere,and to keep atmospheric CO_(2)at a lower level requires the removal of anthropogenic CO_(2)not only from the atmosphere,but from the ocean and land carbon reservoirs as well.The response of many variables of the Earth system,including temperature,ocean heat content,sea level,deep ocean acidity,and permafrost area and carbon,lags the decrease in atmospheric CO_(2)ranging from a few years to many centuries.A few centuries after atmospheric CO_(2)returns to the preindustrial level,sea level is still substantially higher than the preindustrial level,and permafrost continues losing CO_(2)to the atmosphere.Our study demonstrates that to offset previous positive CO_(2)emissions by atmospheric CO_(2)removal does not mean to offset climate consequence of positive CO_(2)emissions.Rapid and deep reduction in CO_(2)emissions is key to prevent and limit increasing risks from further warming.Our study provides new insights into the carbon cycle and climate system response to CO_(2)removal,which would help to assess future climate change and the associated impacts.

Simulated effect of sunshade solar geoengineering on the global carbon cycle

Solar geoengineering has been proposed as a potential mechanism to counteract global wanning. Here we use the University of Victoria Earth System Model （UVic） to simulate the effect of idealized sunshade geoengineering on the global carbon cycle. We conduct two simulations. The first is the A2 simulation, where the model is driven by prescribed emission scenario based on the SRES A2 COz emission pathway. The second is the solar geoengineering simulation in which the model is driven by the A2 CO2 emission scenario combined with sunshade solar geoengineering. In the model, solar geoengineering is represented by a spatially uniform reduction in solar insolation that is implemented at year 2020 to offset CO2-induced global mean surface temperature change. Our results show that solar geoengineering increases global carbon uptake relative to A2, in particular CO2 uptake by the terrestrial biosphere. The increase in land carbon uptake is mainly associated with increased net primary production （NPP） in the tropics in the geoengineering simulation, which prevents excess warming in tropics. By year 2100, solar geoengineering decreases A2-simulated atmospheric CO2 by 110 ppm （12%） and causes a 60% （251 Pg C） increase in land carbon accumulation compared to A2. Solar geoengineering also prevents the reduction in ocean oxygen concentration caused by increased ocean temperatures and decreased ocean ventilation, but reduces global ocean NPE Our results suggest that to fully access the climate effect of solar geoengineering, the response of the global carbon cycle should be taken into account.

Neonatal vaccination against respiratory syncytial virus infection

Respiratory syncytial virus （RSV） is the leading cause of pneumonia and bronchiolitis in infants and is the most frequent cause of lower respiratory tract infections in children. Efficacious vaccination has been a longstanding goal in neonates. Due to immaturity of the neonatal immune system, vaccination has shown limited success in stimulating the neonatal endogenous immune system. Advances in the understanding of neonatal immunology have resulted in renewed development of neonatal vaccination. In this article, we review recent advances in neonatal anti- RSV vaccination strategies, including active and passive vaccination approaches, with emphasis on the effect of maternal neutralizing antibody and the role of maternal antibody in neonatal immune modulations. Recent reports in a variety of antiviral vaccine animal models have shown that maternal antibody, different from conventional vaccination, plays an immune modulatory role in the newborn immune system. Active immunization of the pregnant mother and the offspring can effectively stimulate and maintain potent neonatal immune responses, including an endogenous cytotoxic response and neutralizing antibody generation. The induced newborn endogenous antiviral immunity can last up to 6 months, and effectively blunt viral replication. Immune complexes, formed from the integral binding of the maternal neutralizing antibody and viral vaccine antigen, may play an important role in the maternal antibody-mediated neonatal immune response. The underlying mechanisms and future perspectives are discussed.