Prolonged droughts, raging wildfires, and critical water shortages are becoming more frequent as extreme weather events sweep the globe. Simultaneously, torrential rainstorms bring intense flooding, overwhelming infrastructure and wreaking havoc. The rise in temperatures due to climate change is significantly increasing the likelihood of both extended droughts and heavy precipitation, drastically impacting ecosystems and communities.
In California, 2023 saw an alarming pattern where years of minimal rainfall were suddenly eclipsed by record-breaking downpours and snowfall. This period of heavy rain spurred vigorous vegetation growth, which later served as fuel for devastating wildfires in Los Angeles during January when drought conditions returned. This raises a puzzling question: how can global warming cause such extremes of both drought and rainfall? Experts point to one critical element: the water cycle.
The water cycle, or hydrological cycle, describes the continuous movement of water between Earth’s surface and the atmosphere. This natural cycle is accelerating as global temperatures climb, predominantly driven by the burning of fossil fuels like coal and fossil gas. As the atmosphere heats up, it can hold more water vapor, drawing moisture from land, vegetation, and bodies of water. Over terrestrial regions, this increased evaporation results in prolonged and more intense droughts, while shrinking arid zones further expand. Although rain becomes less frequent, when it does occur, it is often intense and sometimes catastrophic, since for every degree Celsius rise in temperature, the atmosphere’s capacity to hold water vapor increases by 7%.
Jonathan Overpeck, a climate scientist at the University of Michigan, explains that global warming transforms the atmosphere into a massive sponge, absorbing more moisture. When rainfall finally happens, it’s as though the sponge is squeezed, resulting in more intense and swift precipitation. Additionally, oceans, which absorb much of the planet’s excess heat, play a crucial role in these dynamics. The absorption leads to water expansion and the melting of polar ice, contributing to sea-level rise. Warmer ocean waters also intensify hurricanes and cyclones, leading to substantial rainfall over short periods.
For instance, in 2023, Mediterranean storm Daniel led to severe flooding in eastern Libya. The storm overwhelmed two dams, causing devastating floods in the coastal city of Derna, obliterating neighborhoods and sweeping bridges and vehicles out to sea. Scientists agree that such storm events have become more frequent and severe owing to climate change.
Another significant impact of climate change is on snowpack, an essential component of the hydrological cycle. Snowmelt contributes to water supplies critical for drinking and agriculture. However, overall snowfall is decreasing, and more of it is absorbed by dry soils. Warmer winters are extending the growing season, causing increased evaporation through plant transpiration. Yet, similar to rain, climate change can also cause more significant and sometimes damaging snowstorms.
Jonathan Overpeck highlights that these interconnected issues are direct results of global warming, largely driven by human activity. However, he is hopeful, noting that solutions exist to mitigate these changes if there is a collective will to address the root causes of climate change.
