Yes, climate change influences atmospheric rivers

We are often asking the wrong questions about atmospheric rivers and climate change.

It’s understandable that people in California are preparing for the next system. View pajaro river embankment breach videosI’m wondering what fails next.

Not just Californians. Our atmospheric rivers don’t always stop at the Sierra. They can bring more rain and snow to plow through the rest of the country if the conditions are right, as they did in the Northeast earlier this week.

This year’s storms have looked worse than many remember. The data bears it out. This winter, we set new records for snow cover, rainfall intensity, and snowfall. The weather can be erratic and memory can be distorted, but clearly something is wrong. It is natural to ask, “Is climate change causing this?”

But the right question is, “How is climate change affecting all of this?”

The answer is easier than you might expect, but I’d like to start with some background.

I’m a climatologist from California. Atmospheric rivers are nothing new here. The scientific definition may sound technical, but it’s basically a long, narrow strip of water that flows through the atmosphere and plays an important role in the health of many Western ecosystems. At lower elevations it replenishes depleted soil, at higher elevations it forms snow packs and stores water for delivery in summer and fall. In some years atmospheric rivers account for 30-50% of the total western precipitation.

Atmospheric rivers existed long before the planet warmed by trapping heat from carbon dioxide emissions, but their effects are different today. Simply put, climate change is making rivers worse.

First, climate change has warmed the atmosphere, allowing it to hold and release more water, resulting in more intense precipitation.

For every degree Fahrenheit increase in temperature, the atmosphere can hold about 4% more water. Carbon dioxide emissions have warmed the planet by nearly 2 degrees Fahrenheit, so the atmosphere can store about 7% more water. Statistically, when it rains in a warm world, it rains heavily.

Second, in an increasingly warming world, we have more rain than snow. That’s what we’ve seen recently when warmer storms brought rain, even at higher elevations. Collapsed roofs around Lake Tahoe.)

With winter temperatures trending higher across the country, rain instead of snow is already commonplace. As we crossed the Great Lakes earlier this winter and across New England this week, we can expect a lot of snow when temperatures are cold enough to cause it. , making more water available to increase precipitation. It’s been mostly rain in the East this year, and unlike the West, most cities in the East will see record warmth in 2023 and little snow.

The first major problem from warming western atmospheric river systems is the risk of flooding, with rains directly causing displacement and large losses, with more to come early next week. can occur. That could put more strain on embankments and dams.

Melting snow from storms that bring rain at higher elevations can exacerbate risks and overwhelm flood control structures that weren’t built for so much water. Like infrastructure, urban planning, and building codes, they are designed for cooler climates, with less rainfall and less drastic changes between extremes.

The risk of catastrophic flooding is not limited to a single storm. The final snowpack measurement of the year is usually taken on April 1st. This is because it is close to the annual peak. In many places, this week’s storms may have already begun to thaw, and the shift to warmer, wetter weather means record 2023 snowfall is already at peak depth. It could mean. The transition to spring temperatures, where temperatures tend to rise as the climate warms, will only accelerate the thaw, causing vast amounts of water to descend the hills for weeks.

The effects of climate change will make it more likely that violent shaking will occur again. Rising temperatures are drying up snow cover earlier in the season, reducing water availability for natural systems as well as farms and cities during the dry months. This year’s snowfall does not mean that the trend will be reversed. Instead, after a season of rapid snowmelt and devastating floods, all the water stored in this historic year would be lost in an instant, followed by more drought and possibly even fires. there is.

People logically assume that wet years are less risky for fires, but the opposite can be true when humid conditions encourage spring flowering and then make way for hot, dry summers. There is. New vegetation can turn into abundant fuel for wildfires.

Like rivers in the atmosphere, if anyone asked whether climate change would cause wildfires, they would be missing the point. It makes extreme weather more intense and unstable. It increases the set of risks. more likely to have disastrous consequences.

Questions should be asked when it comes to these events so that we can better understand what we need to prepare for and how to protect ourselves in a changing climate.

Kaitlyn Trudeau is a data analyst for Climate Central’s Climate Matters program. Her research includes an analysis of atmospheric effects on wildfire risk in the West. She holds a BS in Physical Geography from California State University, Sacramento and an MS in Geography from the University of Nevada, Reno, where her research has focused on climate change in the Arctic. increase.