The “2100 Vision” represents the scientific community’s projection of Earth’s state by the end of the current century. This concept is built upon climate models that simulate the planet’s response to different levels of greenhouse gas emissions. These projections serve as a framework for understanding the future scale of planetary change and underscore the urgency of current policy decisions. The paths chosen today directly determine the severity of environmental shifts that will occur over the next eight decades.
Projected Global Temperature Changes
The extent of global warming by 2100 is highly dependent on the trajectory of human emissions. Under a high-emission pathway, where reliance on fossil fuels continues to grow, models project a substantial increase in global temperature. This scenario could see the planet warm by 4°C (7.2°F) or more above pre-industrial levels by the century’s end. The Intergovernmental Panel on Climate Change (IPCC) uses different pathways to model this range of possible futures.
Conversely, a low-emission pathway involves immediate global action to reduce greenhouse gas output. In this scenario, the temperature rise is projected to be much smaller, potentially around 1.1°C to 1.5°C (2°F to 2.7°F) above present-day levels. If current government policies are followed, the world is on track for an intermediate warming of approximately 2.6°C above pre-industrial levels. This difference represents a vast disparity in resulting environmental impacts.
The range of potential warming by 2100 is estimated to be between 1.1°C and 5.4°C (2°F to 9.7°F), depending on emission choices. Temperature changes are not expected to be uniform; land areas and polar regions are projected to warm more rapidly than the oceans. These varying pathways illustrate that the future climate is not fixed but remains a consequence of collective human action.
The Future of Global Water Systems
Rising global temperatures directly influence the planet’s water systems, primarily through sea level rise and changes in ocean chemistry. Sea levels climb due to two mechanisms: the thermal expansion of seawater as it warms and the addition of water from melting ice sheets and glaciers. Under a scenario with significant emission reductions, global average sea level is expected to rise by at least 0.3 to 0.6 meters (1 to 2 feet) by 2100.
In a high-emission scenario, the rise could be much greater, reaching up to 2 meters (6.6 feet) or more if major ice sheets rapidly collapse. Oceans absorb excess carbon dioxide from the atmosphere, changing their chemical composition. This process, known as ocean acidification, is projected to decrease the surface ocean’s pH by 0.3 to 0.4 units by 2100, representing a substantial increase in acidity.
Warmer waters affect marine life directly, with the upper layer of the ocean projected to warm by 1.2°C to 2.6°C on average. This combination of warming and acidification threatens marine ecosystems, particularly those that rely on calcium carbonate to build shells and skeletons. Models suggest that nearly all existing coral reef habitats may be eliminated by the end of the century.
Consequences for Human Habitability
Changes in temperature and water systems translate into widespread consequences for human societies and the natural world. A warmer planet will increase the frequency and intensity of extreme weather events, including longer heat waves, prolonged droughts, and major storms. The risk of life-threatening heat stress, where the human body can no longer cool itself effectively, could affect between 50 and 75 percent of the global population by 2100.
These climatic shifts will significantly affect global food production and security. Irregular rainfall and prolonged heat can render agricultural lands infertile, contributing to land degradation and reduced crop yields. Ocean warming and acidification diminish the productivity of fisheries, threatening a food source for billions; for instance, sea scallop populations are projected to decline by over 50 percent in some regions under a high-warming pathway.
The combination of extreme events and resource scarcity will act as a threat multiplier, exacerbating existing social and economic vulnerabilities. Sea level rise and coastal flooding are already displacing millions annually, and this trend is expected to increase human displacement and migration. While some populations have resources to move away from high-risk areas, the poorest communities may face involuntary immobility, leaving them exposed to heightened climate risks.