If greenhouse gas emissions continue on their current trajectory, the consequences will compound across every system that sustains human life: food production, coastlines, economies, water supplies, and public health. These aren’t distant hypotheticals. Some tipping points may already be within reach at today’s warming of roughly 1.1°C above pre-industrial levels, and the projected impacts at 2 to 3°C of warming, which current policies are tracking toward, are severe.
Tipping Points That Lock In Permanent Change
Climate tipping points are thresholds beyond which changes become self-reinforcing and essentially irreversible on human timescales. A 2022 analysis published in Science found that five tipping point uncertainty ranges already overlap with today’s 1.1°C of warming. Between 1.5 and 2°C, six tipping points become likely, including the collapse of the Greenland and West Antarctic ice sheets, the die-off of tropical coral reefs, and widespread rapid permafrost thaw. At the roughly 2.6°C of warming expected under current policies, additional tipping points become likely or possible.
What makes these thresholds so dangerous is their cascade potential. Melting permafrost releases stored carbon, which drives further warming, which melts more permafrost. Ice sheet collapse raises sea levels for centuries regardless of what emissions policies change afterward. Once crossed, these thresholds can’t be uncrossed by turning down the thermostat.
Rising Seas and Disappearing Coastlines
Sea levels are already rising, but the range of outcomes by 2100 depends heavily on how fast polar ice sheets destabilize. Under a high-emissions pathway that triggers rapid ice sheet collapse, global sea levels could rise by 2 meters (about 6.6 feet) by 2100 compared to the year 2000. For the contiguous United States specifically, that figure could reach 2.2 meters (7.2 feet) by 2100 and 3.9 meters (nearly 13 feet) by 2150.
To put that in practical terms, a 2-meter rise would submerge large portions of Miami, Shanghai, Mumbai, and dozens of other major coastal cities. Hundreds of millions of people live in areas that would be permanently or regularly flooded. Saltwater intrusion would contaminate freshwater aquifers that coastal communities rely on for drinking water, compounding the crisis well beyond the flood zone itself.
Food Production Under Stress
Staple crop yields decline measurably with each degree of warming, and the losses accelerate past certain temperature thresholds. Wheat loses about 6% of its yield per degree Celsius of warming, but once temperatures exceed roughly 2.4°C above pre-industrial levels, that loss jumps to 8.2% per degree. Rice follows a similar pattern: losses climb from about 1% per degree to over 7% per degree once warming passes 3.1°C. Maize yields drop by about 4% per degree of warming with no threshold effect, meaning the losses are steady and cumulative.
A separate analysis using machine learning across thousands of crop simulations found even steeper losses: a 1°C increase in global mean temperature reduced maize yields by 10%, wheat by 6.5%, soybeans by 5.4%, and rice by 2.8%. These are global averages. Regional impacts vary enormously. Tropical and subtropical farming regions, where billions of people depend on local agriculture, face the sharpest declines. At 3°C of warming, the math becomes grim: staple crops losing 15 to 30% of their yield in regions that already struggle with food security.
Heat, Health, and Rising Death Tolls
Heat is already the deadliest weather-related hazard in many countries, and projections show it getting dramatically worse. Studies across multiple cities and regions consistently find that heat-related deaths will double by the 2050s compared to current levels. In large U.S. cities, increases of 70% to over 100% are projected by 2050, even accounting for some degree of human acclimatization. By the end of the century under high emissions, heat-related mortality could increase by 100% to 1,000% depending on the country.
The exposure to dangerously high heat levels tells a similar story. Even if warming is held to 2°C, exposure to dangerous heat increases by 50 to 100% across the tropics and by 3 to 10 times in many midlatitude regions. At higher warming levels, outdoor labor in tropical countries becomes physically dangerous for much of the year. Agricultural workers, construction crews, and anyone without reliable air conditioning face the highest risks. Heat stress doesn’t just kill directly; it worsens heart disease, kidney disease, and respiratory conditions, and it increases preterm births.
Mass Displacement
The World Bank projects that climate change could force 216 million people to migrate within their own countries by 2050. Sub-Saharan Africa faces the largest burden, with up to 86 million internal climate migrants. East Asia and the Pacific could see 49 million, South Asia 40 million, North Africa 19 million, Latin America 17 million, and Eastern Europe and Central Asia 5 million.
These projections cover only internal migration, not cross-border movement. The drivers include sea level rise, declining crop productivity, and water scarcity. Migration hotspots tend to emerge in areas where agricultural livelihoods collapse or where low-lying coastlines become uninhabitable. The displacement is not one dramatic event but a grinding process: families leaving farms that no longer produce enough food, communities abandoning neighborhoods that flood repeatedly, cities losing their freshwater supply.
Economic Damage at a Global Scale
The economic costs of unchecked climate change are staggering. A report from the Institute and Faculty of Actuaries found that the global economy could lose 50% of its GDP between 2070 and 2090 under a plausible worst-case scenario without urgent decarbonization. That is not a typo. A 50% hit to global GDP would dwarf any economic crisis in recorded history, including the Great Depression, which saw roughly a 15% contraction in the United States.
These losses come from overlapping sources: destroyed infrastructure, reduced agricultural output, healthcare costs, lost labor productivity from heat, supply chain disruptions, and the enormous expense of managing displacement and rebuilding after extreme weather events. The costs are also deeply unequal. Countries in the tropics and the Global South, which have contributed the least to cumulative emissions, face the steepest economic losses relative to their GDP.
Water Scarcity and Freshwater Loss
Climate change reshapes rainfall patterns, shrinks glaciers that feed major river systems, and intensifies droughts. Projections suggest that changing water availability due to climate alone could push an additional 52 million urban residents into water scarcity, on top of the much larger increases driven by population growth and urbanization. That 52 million figure accounts for roughly 4.6% of the total increase in water-stressed populations, but it interacts with every other driver. A city that could have managed its growing population with existing water infrastructure may find itself in crisis when rainfall patterns shift or snowpack disappears.
Regions that depend on glacier-fed rivers, including parts of South Asia, Central Asia, and western South America, face a particularly acute threat. Glaciers act as natural reservoirs, storing water as ice in winter and releasing it as meltwater in summer. As glaciers shrink, the initial years bring increased flow, creating a false sense of abundance. Eventually, the glaciers become too small to sustain summer flows, and rivers that support hundreds of millions of people begin to run low during the seasons when water is needed most.
What “Not Stopping” Actually Means
The question of what happens if we don’t stop climate change isn’t really about a binary outcome. Every fraction of a degree matters. The difference between 2°C and 3°C of warming is enormous in terms of human suffering, species loss, and economic damage. At current policy trajectories, the world is heading toward roughly 2.6°C of warming, which crosses several critical tipping points and locks in centuries of sea level rise, large-scale crop failures in vulnerable regions, and heat exposure that reshapes where and how billions of people can live.
The damage is not evenly distributed, and it is not all in the future. Communities in low-lying island nations, drought-prone regions of East Africa, and flood-vulnerable parts of South Asia are already experiencing the early stages of what projections describe. The longer emissions continue at high levels, the more of these projected outcomes shift from “possible” to “likely” to “unavoidable,” and the narrower the window becomes for limiting the worst of it.