As they neared publication, they felt uneasy about their research findings which showed two very different outcomes for ocean life in the next three centuries depending on actions taken to reduce greenhouse gas emissions. The study's title seemed to only emphasize negative consequences, so the researchers added a word to emphasize that their grim results could still be prevented. The latest research published in Science on Thursday, titled "Avoiding Ocean Mass Extinction From Climate Warming," highlights the critical moment that humanity is currently facing. The decisions made now regarding greenhouse gas emissions will have a significant impact on the future of life on Earth, even though the most severe consequences may seem distant. According to the scientists' high emissions scenario, if pollution from fossil fuel combustion continues to increase, warming could lead to a loss of ocean species by 2300 comparable to the five mass extinctions in Earth's history, one of which resulted in the extinction of the dinosaurs. Penn, a postdoctoral researcher at Princeton, described his reaction to seeing a graph comparing past extinctions with future forecasts as more of an "oh, my God" moment than an "aha" moment. Scientists found that reducing emissions to stay within the upper limit of the Paris climate agreement could decrease ocean extinction risks by over 70%. This would result in about 4% of species being lost by the end of the century, with warming stopping at that point. Deutsch emphasized that our choices have significant impacts. While there is a general agreement that shifting away from coal and towards wind and solar energy could prevent the worst-case scenario, the continued use of oil and gas is on the rise, and the world is not currently on track to meet the lower-emissions scenario proposed by scientists. The recent study expands on Deutsch and Penn's previous research by developing a computer simulation that examines the most devastating extinction event on Earth around 252 million years ago. Known as "the Great Dying," this event led to the extinction of over 90% of ocean species due to global warming caused by volcanic eruptions. The oceans suffered from oxygen depletion, leading to the demise of fish due to heat stress or lack of oxygen. The computer model revealed higher extinction rates at the poles compared to the tropics, a finding that was supported by the fossil record. The scientists utilized a complex model to predict the impacts of human-driven global warming, taking into consideration various factors such as sunlight, clouds, ocean and air currents, and chemical interactions among heat, oxygen, water, and air. The study also considered potential shifts in fish habitats and estimated survivability thresholds. While the focus was on warming and oxygen loss, other effects like ocean acidification could exacerbate the predicted species loss. The ocean has traditionally served as a buffer against climate change by absorbing carbon dioxide and trapped heat from human activities like burning fossil fuels and deforestation. The service provided has resulted in negative consequences. The ocean experienced its highest temperature and lowest oxygen content on record last year. These changes are posing a threat to fish and causing a decline in coral reefs. Many people are asking how much trouble we are in. Nations are failing to take the necessary actions to avoid catastrophic climate change, with the goal of limiting global warming to 1.5 degrees Celsius in jeopardy. The International Energy Agency has called for an immediate halt to new fossil fuel projects, but countries continue to approve them, with calls for more drilling in the name of energy security. Scientists feel like the ignored characters in the movie "Don't Look Up," where a comet represents climate change. The planet is at a crucial moment, with current generations holding significant power in shaping the future. Deutsch stated that with great power comes great responsibility, but society is not fully understanding its responsibility to future generations and the planet's other life forms. Pippa Moore, a marine science professor at Newcastle University, praised the study for its thoroughness and added that it reinforces the need to reduce greenhouse gas emissions to prevent significant changes in marine ecosystems and potential extinction events. Brad Plumer also contributed to the reporting.