Not enough time for recovery: Coral bleaching occurs when stressful conditions result in the expulsion of the algal partner from the coral. Before anthropogenic climate warming, such events were relatively rare, allowing for recovery of the reef between events. Hughes et al. looked at 100 reefs globally and found that the average interval between bleaching events is now less than half what it was before. Such narrow recovery windows do not allow for full recovery. Furthermore, warming events such as El Niño are warmer than previously, as are general ocean conditions. Such changes are likely to make it more and more difficult for reefs to recover between stressful events. Science , this issue p. 80

A number of novel technologies are emerging in the field of carbon dioxide removal that use electrochemical or photochemical techniques to either alter the alkalinity of seawater before returning it to the ocean (eOAE) or to remove carbon dioxide from seawater before returning it to the ocean (eDOR). These technologies are gaining attention as potential approaches to climate change mitigation, and as such they also require rigorous scrutiny, particularly in terms of their plausibility and potential ecological harms, if deployed at scale. Here, I present a multifaceted review of these technologies that will consider their impact through climatological, environmental, technical, and economic perspectives. While the drawdown potential of some techniques may warrant further consideration, I argue that their broader appeal is limited by the risk of harmful ocean ecosystem impacts and prohibitive resource demands—including infrastructure, energy, and seawater—which challenge their scalability and desirability.