When most people hear the term Climate Change, they think of Global Warming, deforestation and greenhouse gasses like carbon dioxide and methane. However, many people don’t know that Climate Change is also responsible for the increase in deadly storms over the past decades. 

Large storms like tornadoes and hurricanes start from mere thunderstorms. In simple terms, thunderstorms require moisture and unstable air. Both of these can be found over the ocean, where the water at the ocean’s surface evaporates and rises. This warm, moist air is much less dense than the cool dry air surrounding it, so it rises to form tall cumulonimbus clouds. While these clouds are still over the ocean, the storms can continue to be fueled by the updrafts of warm air. Once the storm reaches land, warm updrafts are no longer available, causing the storm to weaken and eventually end. Updrafts of warm, moist air and downdrafts of cool dry air exist in the same cloud, which is a crucial ingredient for the formation of larger, more destructive storms. 

Photo: NOAA Caption: A hurricane is pictured approaching the east coast.

Tornadoes form under very specific conditions, but start within huge thunderstorms called supercells. First, the condensation put out by clouds releases heat, which becomes the energy that supports the rising air. As the amount of condensation increases, the clouds sink farther down, causing the drafts of rising air to become stronger. This rising air can change directions rapidly, and begins to move quickly. If all conditions are present, a vortex enclosed by the storm can form, followed by a wide and tall spinning tube of air. When this tube is pulled upwards, a mesocyclone forms. A mesocyclone is the region of rotation found around the right rear flank of the supercell, and is often around 2-6 miles in diameter. The cool, dry air still present from the storm’s formation begins to wrap around the mesocyclone, forming the rear flank downdraft and creating an extreme temperature difference between the air outside and inside of the storm. Eventually, the wind at the bottom of the mesocyclone will spin faster, and the storm will become tighter at its vertex. Once this storm touches the ground, it is officially considered a tornado. A tornado grows weaker and eventually comes to a stop when either the temperature difference between the outside and inside of the storm disappears or the updrafts of moisture feeding the storm dry out, causing the supercell to lose momentum and draw the tornado back inside itself. 

Hurricanes typically form near the equator, where the ocean’s surface temperature is at least 80° F. The ocean water evaporates and creates warm, moist air that acts as fuel for the hurricane. This air cools and rises back into the atmosphere, where it condenses and forms cumulonimbus clouds. While the warm air continues to rise, wind begins to move around the center (the ‘eye’ of a hurricane) in a circular motion. Most American hurricanes are caused by winds from the Atlantic coast of Africa. These winds gather a cluster of storm clouds, and once they reach 74 miles per hour (mph), the storm is officially categorized as a hurricane. When the hurricane hits land, it runs out of warm, moist ocean air and begins to weaken, causing the wind speeds to drop. However, even in this state, the storms can be detrimental to coastal communities. 

In all of these cases, warm air is one of the driving forces that leads to the formation of incredibly destructive storms. With Climate Change and Global warming, sea levels have risen significantly over the past 20 years, and models predict that by the end of this century, ocean surface temperatures will have risen by 5° F. While this may not seem like much, it means that the ocean will reach the ideal temperature for hurricanes and other storms to start (80° F) much quicker in the calendar year, resulting in a longer and more intense hurricane season. This will allow for an increase in incredibly destructive hurricanes like Katrina, which the National Oceanic and Atmospheric Administration (NOAA) reports to have caused 1,200 deaths and $75 billion in damages. Hurricanes, tornadoes and thunderstorms would obviously still occur without Global Warming and Climate Change, but the seasons for those storms would be a lot shorter, and the storms themselves would be less powerful and less likely to reach land. 

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