The article discusses the impacts of climate change and ocean acidification on coral reefs. Atmospheric carbon dioxide levels are expected to rise to over 500 parts per million by 2100, significantly higher than in the past 420,000 years. This increase will lead to global warming and ocean acidification, which will compromise carbonate accretion in corals, making them increasingly rare on reef systems. The result will be less diverse reef communities and carbonate reef structures that fail to be maintained. Climate change also exacerbates local stresses from declining water quality and overexploitation of key species, driving reefs toward the tipping point for functional collapse. Coral reefs are among the most biologically diverse and economically important ecosystems on Earth, providing vital services such as fisheries, coastal protection, building materials, new biochemical compounds, and tourism. However, coral reefs have continued to deteriorate due to human influences since the International Year of the Reef in 1997. Rapid increases in atmospheric carbon dioxide concentration are driving global warming and ocean acidification, which may be the final insult to these ecosystems. The article reviews the current understanding of how anthropogenic climate change and increasing ocean acidity are affecting coral reefs and offers scenarios for how coral reefs will change over this century. The scenarios are intended to provide a framework for proactive responses to the changes that have begun in coral reef ecosystems and to provoke thinking about future management and policy challenges for coral reef protection. The article highlights the effects of warming and acidifying seas on coral reefs. The concentration of carbon dioxide in Earth's atmosphere now exceeds 380 ppm, which is more than 80 ppm above the maximum values of the past 740,000 years. During the 20th century, increasing atmospheric carbon dioxide has driven an increase in the global oceans' average temperature by 0.74°C and sea level by 17 cm, and has depleted seawater carbonate concentrations by approximately 30 μmol kg⁻¹ and acidity by 0.1 pH unit. These changes are expected to have significant impacts on coral reefs, including reduced calcification and growth, and the potential for reef erosion. The article also discusses the resilience and tipping points of coral reefs. Maintaining ecological resilience is crucial for preserving coral reef ecosystems. However, recent changes to the frequency and scale of disturbances such as mass coral bleaching, disease outbreaks, and destructive fishing are pushing reef ecosystems from coral- to algal-dominated states. If pushed far enough, the ecosystem may exceed a "tipping point" and change rapidly into an alternative state with its own inherent resilience and stability, often making the possibility of returning to a coral-dominated state difficult. The article outlines the socioeconomic impacts of coral reef decline, including serious consequences for subsistence-dependent societies and wider regional economies through their impact on coastal protection, fisheries, and tourism. These consequences become increasingly severe as atmospheric carbon dioxide levels increase, and unThe article discusses the impacts of climate change and ocean acidification on coral reefs. Atmospheric carbon dioxide levels are expected to rise to over 500 parts per million by 2100, significantly higher than in the past 420,000 years. This increase will lead to global warming and ocean acidification, which will compromise carbonate accretion in corals, making them increasingly rare on reef systems. The result will be less diverse reef communities and carbonate reef structures that fail to be maintained. Climate change also exacerbates local stresses from declining water quality and overexploitation of key species, driving reefs toward the tipping point for functional collapse. Coral reefs are among the most biologically diverse and economically important ecosystems on Earth, providing vital services such as fisheries, coastal protection, building materials, new biochemical compounds, and tourism. However, coral reefs have continued to deteriorate due to human influences since the International Year of the Reef in 1997. Rapid increases in atmospheric carbon dioxide concentration are driving global warming and ocean acidification, which may be the final insult to these ecosystems. The article reviews the current understanding of how anthropogenic climate change and increasing ocean acidity are affecting coral reefs and offers scenarios for how coral reefs will change over this century. The scenarios are intended to provide a framework for proactive responses to the changes that have begun in coral reef ecosystems and to provoke thinking about future management and policy challenges for coral reef protection. The article highlights the effects of warming and acidifying seas on coral reefs. The concentration of carbon dioxide in Earth's atmosphere now exceeds 380 ppm, which is more than 80 ppm above the maximum values of the past 740,000 years. During the 20th century, increasing atmospheric carbon dioxide has driven an increase in the global oceans' average temperature by 0.74°C and sea level by 17 cm, and has depleted seawater carbonate concentrations by approximately 30 μmol kg⁻¹ and acidity by 0.1 pH unit. These changes are expected to have significant impacts on coral reefs, including reduced calcification and growth, and the potential for reef erosion. The article also discusses the resilience and tipping points of coral reefs. Maintaining ecological resilience is crucial for preserving coral reef ecosystems. However, recent changes to the frequency and scale of disturbances such as mass coral bleaching, disease outbreaks, and destructive fishing are pushing reef ecosystems from coral- to algal-dominated states. If pushed far enough, the ecosystem may exceed a "tipping point" and change rapidly into an alternative state with its own inherent resilience and stability, often making the possibility of returning to a coral-dominated state difficult. The article outlines the socioeconomic impacts of coral reef decline, including serious consequences for subsistence-dependent societies and wider regional economies through their impact on coastal protection, fisheries, and tourism. These consequences become increasingly severe as atmospheric carbon dioxide levels increase, and un