Prolonged droughts, forest fires and water shortage. Torrential rains that overflow prey and cause catastrophic floods.
Around the world, The increase in temperatures driven by climate change is increasing the probabilities of both severe droughts and more intense rainfall that wreaks havoc in the human population and the environment.
The rains can disappear for years just to return strongly, as happened in California in 2023, with rains and record snowfall. That led to abundant vegetation growth that provided fuel for the devastating January fires in Los Angeles after the drought returned.
1 /18 | The Dana in Spain: the shocking images of the floods in Valencia that have left dozens of dead. A woman is transferred by ambulance after being rescued from floods in Valencia, Spain. – Alberto Saiz
But how can global warming cause both drier and more humid extremes? This is what experts say.
Everything is the water cycle
Water moves constantly between the earth and its atmosphere. But that system, called hydrological cycle, is accelerating as global temperatures are heated, mainly due to burning fossil fuels such as coal and gas.
A hottest atmosphere absorbs more water vapor from bodies of water, vegetation and soil.
On Earth, this atmospheric demand and loss of surface humidity leads to longer and more intense droughts, even causing some arid areas to expand. Although the rain falls less frequently, when it does, it is often in intense and destructive floods.
That is because the atmosphere retains 7% more water vapor for each degree Celsius.
“Basically, global warming is turning the atmosphere into a larger sponge so that it can absorb more moisture … and then, when conditions are suitable for rain, it’s like squeezing that sponge,” said Jonathan Overpeck, a climate scientist at the University of Michigan. “There is more humidity that comes out faster.”
Oceans play a disproportionate role
The oceans absorb most of the extra heat of the planet. That makes the water expand and the ice melt at the poles, raising sea levels. The warmer water also provides fuel for hurricanes and larger cyclones that can download huge amounts of water in a short time.
In 2023, for example, the heavy rains of the Mediterranean storm Daniel caused mass floods in eastern Libya that overflowed two dams, sending a wall of water through the coastal city of Derna that destroyed whole neighborhoods and dragged bridges, cars and people to the sea. Climate scientists say that climate change caused this storm to be much more likely.
The snow layer is decreasing
Climate change is also affecting the snow layer, a critical part of the hydrological cycle.
The thaw of snow helps fill reservoirs and river roads, even for consumption and agriculture. But in general it falls less snow, and what falls is often absorbed by a thirsty ground.
In addition, because winters are becoming warmer in general, the growth season is longer, which means that snow thaw is also lost through evapotranspiration of plants. But, like rain, climate change can also cause more intense snow storms and sometimes harmful.
“All this is related to warming, which we know with perfect confidence that is almost completely due to human activity,” Overpeck said. “The good news is that we know how to stop it if we want.”
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This story was translated from English by an AP editor with the help of a generative artificial intelligence tool.