As they approached the publication of their findings, the researchers were troubled by something. Their study showed that the future of ocean life could go in very different directions depending on how greenhouse gas emissions were managed. The original title of their study seemed to only focus on the negative outcomes, so the researchers decided to add a word to emphasize that there was still a way to prevent the grim scenario outlined in their results. On Thursday, an article titled "Avoiding Ocean Mass Extinction From Climate Warming" was published in Science. This research highlights the critical point at which humanity currently stands, with decisions made today about greenhouse gas emissions having a significant impact on the future of life on Earth. The scientists' high emissions scenario predicts that if pollution from fossil fuels continues to rise, ocean species loss by 2300 could rival the five mass extinctions in Earth's history, including the event that led to 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 rather than a sudden realization. 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 only about 4% of species being lost by the end of the century if warming were to stop at that point. Deutsch emphasized that our choices have significant impacts on the environment. While there is agreement that moving away from coal and towards renewable energy sources would make the worst-case scenario less likely, the continued use of oil and gas is on the rise, and the world is not currently on track to achieve the lower-emissions scenario outlined by the scientists. The latest research expands upon the previous work of Deutsch and Penn, who developed a computer simulation that examined the most severe extinction event on Earth around 252 million years ago. Referred to as "the Great Dying," this event led to the extinction of over 90% of ocean species. The primary cause was global warming, which was initiated by volcanic eruptions. As a result, the oceans experienced a decrease in oxygen levels, causing fish to perish from heat stress, lack of oxygen, or a combination of both factors. The computer model revealed a higher rate of extinctions at the poles compared to the tropics, a finding that was supported by the fossil record. The scientists used a complex model to predict the impact of global warming caused by human activity. This model considered various factors such as sunlight, clouds, ocean and air currents, and chemical interactions among heat, oxygen, water, and air. They also assessed potential shifts in fish habitats and estimated survivability thresholds. The study focused on the effects of warming and oxygen loss, but warned that ocean acidification and other consequences could exacerbate species loss. The ocean has historically played a crucial role in mitigating climate change by absorbing carbon dioxide and trapped heat from human activities like burning fossil fuels and deforestation. However, providing that service has had consequences. The ocean experienced its highest temperature and lowest oxygen levels last year since humans began recording data. Alterations in the ocean's chemistry are currently endangering fish populations, and coral reefs are rapidly deteriorating. Deutsch noted that he frequently hears the question, "How much trouble are we in?" “If we fail to take action, we are in trouble.” Countries have not yet taken the necessary steps to prevent catastrophic climate change. UN Secretary-General António Guterres recently warned that the critical goal of limiting global warming to 1.5 degrees Celsius above preindustrial levels is in jeopardy. The International Energy Agency has urged countries to halt new fossil fuel projects, but this has not been done, with some countries even pushing for more drilling in the name of energy security, exacerbated by Russia’s invasion of Ukraine. Scientists Deutsch and Penn feel like the overlooked experts in the movie "Don't Look Up," where a comet symbolizes climate change. Just like in the film, the planet is at a crucial point, with the decisions made by current generations having a significant impact on the future. Deutsch emphasized the importance of recognizing the responsibility that comes with great power, particularly in relation to future generations and the diverse life forms with whom we share the planet. Pippa Moore, a marine science professor at Newcastle University, praised the study for its thoroughness and warned of the severe consequences of failing to reduce greenhouse gas emissions on marine ecosystems. The article also credits Brad Plumer for his reporting.