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Carbon dioxide removal (CDR) from the atmosphere has been proposed as a measure for mitigating global warming and ocean acidification. To assess the extent to which CDR might eliminate the long-term consequences of anthropogenic CO2emissions in the marine environment, we simulate the effect of two massive CDR interventions with CO2extraction rates of 5 GtC yr−1and 25 GtC yr−1, respectively, while CO2emissions follow the extended RCP8.5 pathway. We falsify two hypotheses: the first being that CDR can restore pre-industrial conditions in the ocean by reducing the atmospheric CO2concentration back to its pre-industrial level, and the second being that high CO2emissions rates (RCP8.5) followed by CDR have long-term oceanic consequences that are similar to those of low emissions rates (RCP2.6). Focusing on pH, temperature and dissolved oxygen, we find that even after several centuries of CDR deployment, past CO2emissions would leave a substantial legacy in the marine environment.

There is enough power in Earth’s winds to be a primary source of near-zero-emission electric power as the global economy continues to grow through the twenty-first century. Historically, wind turbines are placed on Earth’s surface, but high-altitude winds are usually steadier and faster than near-surface winds, resulting in higher average power densities. Here, we use a climate model to estimate the amount of power that can be extracted from both surface and high-altitude winds, considering only geophysical limits. We find wind turbines placed on Earth’s surface could extract kinetic energy at a rate of at least 400 TW, whereas high-altitude wind power could extract more than 1,800 TW. At these high rates of extraction, there are pronounced climatic consequences. However, we find that at the level of present global primary power demand (∼ 18 TW; ref. ), uniformly distributed wind turbines are unlikely to substantially affect the Earth’s climate. It is likely that wind power growth will be limited by economic or environmental factors, not global geophysical limits.