Scientists have found connections between a warming planet and hurricanes, heat waves, and droughts, suggesting that climate change may have influenced these events. However, the link between climate change and tornadoes remains uncertain. Despite ongoing research on tornado trends and behavior, the role of climate change in tornado activity is still unclear. According to Michael Tippett, an associate professor at Columbia University, tornadoes are the most challenging weather phenomenon to connect to climate change. Harold Brooks, a senior research scientist at the National Severe Storms Laboratory, also acknowledges that many questions about the relationship between climate change and tornadoes remain unanswered. Tornadoes are created within large rotating thunderstorms due to a combination of temperature, moisture profile, and wind profile. They form when unstable air pushes cold air over warmer humid air, creating an updraft as the warm air rises. If wind speed or direction changes suddenly within the clouds, the air can begin to spin and result in a tornado. Tornadoes can intensify when the air column begins spinning vertically and rotating near the ground, increasing friction on Earth's surface and accelerating the air inward. Similar to hurricanes and earthquakes, tornadoes are measured on the Enhanced Fujita, or EF, scale, which ranges from 0 to 5. The tornado that moved across northeast Arkansas, Tennessee, and western Kentucky recently was approximately three-quarters of a mile wide with wind speeds reaching between 158 and 206 mph, earning it a minimum EF rating of 3. Surveyors assess tornadoes by examining the extent of damage to different structures since it is difficult to measure winds directly. They determine the severity of the tornado by evaluating if the damage is limited to minor roof shingles or if entire sections of roofs and walls are missing. Based on the level of destruction, scientists estimate the wind speeds and assign a rating to the tornado. Researchers have observed a trend in recent years where tornadoes are occurring in clusters and the traditional tornado alley in the Great Plains may be shifting eastward. The total amount of tornadoes each year remains consistent at approximately 1,200. Tornadoes in December are atypical in the United States, as they usually occur in the spring. The tornadoes on Friday may have been caused by high wind shear, which is more common in winter, and warmer than usual weather. The question is raised - could climate change be the reason for this? The ingredients that lead to tornadoes consist of warm, moist air near the surface, cool dry air higher up, and wind shear, which involves changes in wind speed or direction. Climate change can impact each of these factors differently. According to Brooks from NOAA, as the planet warms and the climate shifts, these factors may not all change in the same way. While overall temperature and humidity, which contribute to the energy in the atmosphere, may increase with a warmer climate, wind shear may remain unchanged. If there is not enough wind shear to create rotation, the strength of the energy becomes irrelevant. The small size of tornadoes makes it difficult for scientists to accurately model them, hindering attribution studies to climate change. The tornado record is sparse compared to other events, possibly due to their localized nature and reliance on reports to the National Weather Service. This indicates that smaller or undetected tornadoes might go unreported. ©2021 The New York Times Company.