Scientists have found links between a warming planet and hurricanes, heat waves, and droughts, suggesting that climate change may have influenced these events. However, the connection between tornadoes and climate change remains uncertain. Despite ongoing research on tornado trends and behavior, the role of climate change in tornadoes is still not fully understood. Researchers continue to have unanswered questions about the relationship between climate change and tornadoes. Tornadoes are created within large rotating thunderstorms when there is a combination of specific temperature, moisture, and wind conditions. The instability of the air causes cold air to move over warmer humid air, creating an updraft as the warm air rises. Changes in wind speed or direction within the clouds can cause the air to start spinning. Tornadoes, like hurricanes and earthquakes, are evaluated using the Enhanced Fujita (EF) scale, which ranges from 0 to 5. The tornado that swept through northeast Arkansas, Tennessee, and western Kentucky recently was approximately three-quarters of a mile wide, with wind speeds reaching 158 to 206 mph, classifying it as at least an EF3 tornado. Surveyors typically assess tornadoes based on the extent of damage to various structures since directly measuring the winds in a tornado is difficult. By examining if the damage is limited to missing roof shingles or involves entire sections of roofs or walls, scientists can determine the wind speeds and assign a rating to the tornado. Researchers have observed a trend of tornadoes occurring in more frequent clusters in recent years, and there appears to be a shift eastward in the region known as tornado alley in the Great Plains where most tornadoes typically occur. The total amount of tornadoes each year remains constant at approximately 1,200. Tornadoes in December are rare in the United States, as they usually occur in the spring. The tornadoes on Friday could have been caused by high wind shear, which typically peaks in the winter, and warmer than usual weather. The question of whether climate change is the cause is raised. The ingredients necessary for tornado formation include warm, moist air near the ground, cool dry air higher up, and wind shear, which refers to changes in wind speed or direction. Climate change may affect these factors differently, with some potentially increasing while others do not. According to Brooks from NOAA, as the planet warms and the climate shifts, these factors may not all change in the same way. For example, while overall temperature and humidity may rise, wind shear may not increase. Brooks emphasized that without sufficient wind shear to create rotation, the strength of the energy in the air becomes irrelevant. The small size of tornadoes makes it difficult to model them accurately, hindering scientists' ability to attribute extreme weather events to climate change. Tornado records are limited compared to other types of events, possibly due to their localized nature and reliance on eyewitness reports to the National Weather Service. This indicates that smaller or unobserved tornadoes might go unreported. ©2021 The New York Times Company.