Unusual Weather in an Unusual Time
Two tornadoes touched down in Southern California in late March, devastating a mobile home park and killing five people. The previous month, in February, a layer of snow dusted the Hollywood sign, a sight seldom seen in Los Angeles. And throughout the fall and winter seasons, atmospheric river storms swept through much of the state, battering the area with high winds and unpredictable flooding. This extreme weather demonstrates the links that climate scientists have discovered between changing weather patterns and the warming planet.
Scientists have been warning the public for decades about the effects of climate change and how it will affect weather patterns. Experts have been careful to emphasize that while weather patterns can act unpredictably regardless of the effects of climate change, an important distinction must be made between “weather” and “climate.” According to NASA, weather describes the short-term conditions of the atmosphere, while climate describes the atmosphere over relatively long periods. Actors with political agendas may intentionally confuse the two to sow doubt and misinformation about the reality of climate change, but the distinction is incredibly important.
One of the most significant consequences of climate change is the increased frequency and intensity of abnormal weather patterns, including tornadoes, hurricanes, and periods of extreme heat or cold. The irregular weather events that struck California are highly unusual for the region, and this is a phenomenon being observed globally. These particular events represent a small sample of how climate change is affecting our planet, and the need to adapt to and mitigate these impacts.
According to the National Oceanic and Atmospheric Administration (NOAA), tornado frequency has increased in the United States over the past few decades. In 2020, the United States experienced 1,254 tornadoes, which is above the 30-year average of 1,200 tornadoes per year. This increase in extreme weather activity is consistent with what the scientific community observes with climate change. As air temperatures begin to warm, there is increased instability in the atmosphere.
Tornadoes are generated partially from warmer air rising through storm clouds, which causes the clouds to spin. These so-called “supercell” storms are characterized by updrafts that rotate with particularly great strength due to wind speeds circulating the storm at different elevations. Clouds favorable to tornadoes will form when the air that these rotating drafts draw in is particularly moist, a condition that can be exacerbated by global warming. Not all supercells form tornadoes, because the conditions at the surface need to be just right for the cloud to rotate fast enough and reach the ground. However, the addition of warm air from climate change at both the surface and in the atmosphere can result in more severe and more frequent tornado events.
From an environmental science perspective, the warming of the Arctic may also be leading to more extreme weather. The temperatures at the Earth’s poles control a lot of what happens in each of the hemispheres. Temperature variation in the Arctic causes disturbances in jet streams, which ultimately intensifies the weather patterns we experience at lower latitudes. This is an example of a concept called Arctic Amplification, which explains the larger difference in temperature near the North and South Poles compared to the rest of the world.
The locations of tornado occurrences may also be altered by the changing climate. A 2018 study on the location trends in United States tornado frequency found that since 1979, tornadoes have occurred more and more frequently to the east of the Mississippi River in states like Kentucky and Arkansas, with increased frequency as far southeast as Mississippi and Alabama. This could be due to a variety of natural causes, but given the increase in global temperature at the same time, it is hard to discount the influence of climate change on this unusual weather. Many of these states and communities are less resilient to the impacts of increased tornadoes, as they typically do not occur in these areas.
Tornadoes are just one example of how climate change is affecting weather patterns, and may be a feature of California’s recent overexposure to atmospheric river phenomena. Atmospheric rivers refer to the bands of air that transport water vapor in the atmosphere in amounts that can vary depending on a variety of conditions. Particularly strong atmospheric rivers can contain the equivalent of fifteen times the average flow of water at the mouth of the Mississippi River. These conditions lead to more moisture, which can fuel both tornadoes and storm events that bring about flooding. All of these factors combine to create an unusual pattern of weather in California and the United States as a whole. these factors combine to create an unusual pattern of weather in California and the United States as a whole.
Further areas of interest related to changing weather patterns due to climatic warming include ocean acidification, wildfires, heat waves, droughts, sea level rise, biodiversity loss, and displacement of communities, among countless other impacts.
The takeaway from these abnormal events is twofold. We should recognize the ability of climate change to affect weather patterns in ways that we cannot always predict – we are witnessing this now with certain unprecedented weather events nationally and globally. Secondly, we should be careful not to confuse short term weather events with long-term atmospheric climate conditions, or rely on people who intentionally do so. In 2015, then-Senator of Oklahoma James Inhofe, a vehement climate change denier, displayed a snowball on the Senate floor to prove that the globe is not warming. Those that are serious about science and in a position to effect policy should be able to understand the difference between weather and climate.
