Global warming is probably one of the most extreme challenges that humanity will face in the coming years. Even now, we can already feel its effects, as global mean temperatures have already risen by 1°C from pre-industrial times. It may seem like a negligible difference; however, it can easily disrupt the different natural cycles and systems that occur on Earth. 


One of the major implications of global warming is its effect on water security. Of all the water resources on Earth, only 2 percent is available as fresh water. Of this, 70 percent is in the form of snow and ice. Water is essential for all life, and global warming can change the availability of clean water, potentially putting millions at risk. 


Understanding The Hydrological Cycle 

Water takes on many forms as it spreads and flows through the environment. Ultimately, though, it recirculates through alternating cycles of evaporation and precipitation. Water is dumped on the ground either as rain or snow and flows into streams, rivers, and, finally, larger bodies of water such as lakes or seas.  


Plants and animals take up some of the water and eventually excrete it through the lungs or the kidneys. Evaporation constantly transports water back into the atmosphere to complete the cycle. 


Heavier Rains And Worse Droughts 

The amount of water is practically constant on Earth, but increased temperatures hasten the evaporation process, ultimately increasing the rate at which water passes through the different stages of the hydrological cycle. It would invariably lead to greater overall precipitation, and current climate models suggest that this will come in the form of stronger, not more frequent, rains and storms. 

It would seem that greater rainfall will be beneficial in providing more water for agriculture and human consumption. However, the distribution of the increased precipitation will not be even. Hence, some areas such as Africa will experience more droughts, while other areas will have more catastrophic storms. 


Smaller Supplies Of Clean Water 

The increased rains can cause more extensive flooding, which in turn can overwhelm sewage and wastewater systems. Floods can also contaminate groundwater and other reservoirs of otherwise clean. Trash and other loose garbage can be swept away by floods and block rivers, further disrupting the flow of clean water. Through these methods, global warming can reduce the amount of water that can be used by people. 


Global warming can also accelerate the rate of glacier melting. Temporarily, the runoff from all the melting will increase the flow rate of many river systems. Once the glaciers recede due to excessive melting, eventually the amount of clean water that can be accessed by people downstream will decrease. 


Positive Feedback Loops 

The ability of air to carry water vapor increases with temperature. Coupled with the faster hydrological cycle, this will cause the concentration of water vapor in the atmosphere to rise. Water vapor also constitutes greenhouse gases, and clouds can keep thermal radiation from escaping the planet, further worsening global warming. Global warming encourages further escalation in temperature, forming positive feedback loops. 


Saltwater Intrusion 

Finally, as glaciers and other land-based ice masses melt, the runoff will eventually flow into seas and oceans, causing global sea levels to rise. Saltwater will be able to reach farther inland and seep further into the ground, potentially contaminating freshwater aquifers. Desalination of saltwater is an energy-extensive process, eventually leading to worse water scarcity and higher water prices. 


Access to clean water is both a human right and a part of the Sustainable Development Goals, underscoring its essential role in sustaining life. Global warming threatens to disrupt our access to this critical resource, and millions will suffer unless we take action to address climate change.