Extreme rainfall will wreak havoc on mountain ranges as warming climate turns snow to rain

In an era characterized by rising global temperatures, the world is not only witnessing an increase in extreme rainfall and other weather events, we are also observing a shift in the severity of these storms.

Researchers at the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) have discovered that climate change is transforming snowfall into rainfall on mountains across the Northern Hemisphere.

This shift isn’t a mere scientific curiosity. This new reality comes with a tangible, and sometimes dangerous, set of outcomes. These include floods, landslides, and increased soil erosion, to name a few.

Extreme rainfall on mountain ranges will impact 25% of the world

Scientists cannot overstate the significance of this finding, considering the sheer volume of people this change will directly affect.

“One quarter of the global population lives in or downstream from mountain regions,” remarked Mohammed Ombadi. He is the lead author of the paper that got published in the renowned journal, Nature. “They are going to be directly affected by this risk.”

While experts had anticipated that climate change would result in a surge in the volume of water produced during extreme events, this new study marks the first-time researchers have considered whether that water would manifest as rain or snow.

The researcher team has discovered that snow is giving way to extreme rainfall in mountain ranges. This transition exposes mountain areas to the risks associated with heavy rainfall.

What exactly happens when snow turns into extreme rainfall

Scientists even quantified this phenomenon. For every 1-degree Celsius rise in global temperature, they forecast an average increase of 15% in rain at high elevations.

Ombadi clarified the immediacy of the problem by saying, “This increase in extreme rainfall is not only something that is going to happen from now until the end of the 21st century – we’re already seeing it.”

He further stressed that the rate has been consistent in the data from 1950 to 2019. “Extreme rainfall events in mountain ranges have already been increasing and will continue to change with that 15% rate.”

Among all the mountain ranges in the Northern Hemisphere, those at the greatest risk of extreme rainfall events are the North American Pacific mountain ranges.

These include the Cascades, Sierra Nevada, and coastal ranges from Canada to Southern California. Also at great risk are the Himalayas and high-latitude regions.

Why extreme rainfall won’t impact all mountain ranges

The question as to why these areas are at higher risk compared to other mountain ranges, such as the Rockies or the Alps, remains unanswered.

“We think that North American Pacific mountain ranges are more susceptible to the risk of extreme rainfall than other mountain ranges because a significant portion of snowfall in this region typically occurs at temperatures just below zero degrees Celsius,” Ombadi explained.

“The slightest change in air temperature will shift this snowfall to rainfall. This is unlike other mountain ranges where snowfall may occur at very low temperatures below zero degrees.”

Ombadi’s hope is that his fellow climate scientists will integrate this distinction between snowfall and rainfall into their climate models. He also wants civil engineers and planners to use this data to improve their strategies for handling extreme rainfall events.

“We need to factor these results into how we design and build the infrastructure in these mountainous regions, so that they can withstand the negative consequences of increases in rainfall extremes,” he asserted.

Real numbers will result in real consequences

As nations worldwide continue striving to limit global warming to less than 2 degrees Celsius above pre-industrial levels, as per the Paris Agreement, Ombadi’s research highlights a crucial linear relationship.

Each degree of warming causes a 15% increase in extreme rainfall. This means that a 3-degree rise would lead to a 45% surge in rainfall.

Ombadi concluded, “There are many technologies in progress that could help us reduce greenhouse gas emissions and how much the planet warms. To me, this study shows the need to invest in those clean solutions, and also start preparing for the consequences of warming now.”

This thought-provoking research was generously funded by the DOE Office of Science Biological and Environmental Research program.

More about climate change and extreme weather

Climate change, also referred to as global warming, is a shift in long-term weather patterns around the world. Human activities largely drive climate change, primarily through the emission of greenhouse gases.

The main culprits are carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O). These gases trap heat from the sun in the Earth’s atmosphere, leading to an overall increase in the planet’s temperature.

The global temperature rise, even if it seems slight, can have profound impacts on weather patterns. These changes lead to what is often referred to as ‘extreme weather events.’

Here are some ways that climate change drives these events:

Heatwaves

As average global temperatures rise, heatwaves become more frequent and severe. This is one of the most direct impacts of climate change on weather. Extreme heat can exacerbate drought conditions and increase the risk of wildfires.

Extreme Rainfall and Floods

Warmer air holds more moisture. For each degree rise in temperature, the air’s capacity to hold water vapor increases by about 7%. This can result in extreme rainfall, leading to an increased risk of flooding.

Storms and Hurricanes

As mentioned above, warmer air can hold more moisture, providing more fuel for storms and hurricanes. Additionally, hurricanes draw their energy from warm ocean waters, so as ocean temperatures rise due to climate change, we could see more intense and possibly more frequent hurricanes.

Droughts

Changes in precipitation patterns combined with increased evaporation due to higher temperatures can lead to more frequent and severe droughts in some regions. While some areas may see more rainfall, others may see less, leading to drought conditions.

Snow and Cold Extreme

Warmer temperatures can cause more precipitation to fall as extreme rainfall rather than snow, reducing snowpack. This can impact freshwater resources and winter sports industries.

Additionally, while it might seem counterintuitive, global warming can also cause spikes in very cold weather. Melting Arctic ice can disrupt the polar vortex, causing frigid Arctic air to spill into lower latitudes.

Sea-Level Rise

Global warming causes glaciers and ice sheets to melt, which raises sea levels. Warmer water also expands, which is another factor contributing to sea-level rise. This can lead to more frequent and severe coastal flooding.

Changes in Wind Patterns

Climate change can alter large-scale wind patterns, which can change weather patterns and potentially lead to more extreme events.

Wildfires

Higher temperatures, changes in rainfall patterns, and an increase in lightning events due to climate change can all contribute to an increased frequency and intensity of wildfires.

It’s important to note that individual weather events can’t be directly attributed to climate change. However, scientists can estimate the extent to which climate change has made certain types of extreme weather events more likely or more severe.

Climate change exacerbates the intensity and frequency of some types of extreme weather, leading to greater instability and unpredictability in our climate systems. This is why it is crucial to mitigate the impacts of climate change through both international cooperation and individual action.