Understanding the Intensity of the Recent Heatwave in the West as It Comes to an End

The intense spring heat dome that has gripped the West for over a week is finally starting to shift. This extreme weather event has set over 1,500 temperature records across 11 states, according to Climate Central, a leading research organization in climate analysis.

The ongoing heatwave is causing climate scientists, irrigation managers, and local authorities to weigh the potential for a significant water crisis and to assess the unprecedented nature of this weather phenomenon. Even before the surge in temperatures, Western states were noting record low snowfall—a situation that has persisted, leaving many areas nearly devoid of snow.

Researchers have long established that climate change is likely to exacerbate heat waves. However, some scientists are exploring whether lesser-known climate factors could account for the exceptional longevity, intensity, and scope of this month’s heat events.

Jennifer Brady, a senior data analyst at Climate Central, noted that the heatwave’s extensive effects and duration qualify as an anomaly, “even given the climate change we’re currently experiencing, which many refer to as the new normal.”

Climate Central has developed a climate change index that assesses the influence of climate change on daily temperature averages, rating them from 1 to 5.

Around 29% of the country recorded maximum temperatures classified as a “5” by Climate Central—indicating that these temperatures are at least five times more likely to occur due to climate change. Historical data since 1970 shows that the region is experiencing unprecedented temperature anomalies.

“This is unprecedented and potentially very dangerous,” Brady stated.

The World Weather Attribution Group, comprising scientists who publish statistical analyses of climate impacts, confirmed that climate change played a significant role in the early March heatwave. They stated that these temperatures were statistically practically impossible without climate change, with measurements showing some areas experienced temperatures 20 to 30 degrees Fahrenheit above the average.

In a report released on March 20, the group asserted that climate change is raising the intensity of heatwaves in the West by more than 7 degrees Fahrenheit, making them 800 times more likely to happen compared to a world without global warming.

Climate change is shifting temperature distributions globally. According to Karen McKinnon, an associate professor at UCLA’s Department of Atmospheric and Oceanic Sciences, land is heating up more rapidly than oceans, with the western U.S. warming faster than other regions.

While the global average temperature last year exceeded pre-industrial levels by 1.47 degrees Celsius (2.65 degrees Fahrenheit), McKinnon noted that “depending on your location, we may have already encountered warming of 4 to 5 degrees Fahrenheit.”

Researchers are increasingly curious if factors beyond base-level warming are enhancing the severity of heatwaves like this one. Some are investigating whether climate changes are affecting atmospheric dynamics.

This month’s heatwave resulted from a phenomenon known as a heat dome, which occurs when high pressure and clear skies stagnate over a region, trapping heat like a lid on a stovetop and intensifying global warming.

Scientists propose that climate change is shifting large-scale atmospheric circulation patterns, contributing to the prevalence of heat domes and influencing the jet stream’s behavior. The polar jet stream generally separates cold Arctic air from warmer southern air, and changes in its pattern may lead to extreme weather events.

Researchers speculate that climate change has enlarged jet stream waves, leading to more significant shifts in temperature across the continental U.S.

McKinnon stated that while scientists are probing these trends, conclusive answers remain elusive. Competing theories are surfacing, and it may take years to establish a consensus on these critical climate questions.

“This poses a million-dollar question,” McKinnon said. “Are these atmospheric changes primarily driven by climate change?”