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Natural Awakenings National

It’s Not the Heat, It’s the Humidity

Sky with clouds and humidity image

For more than 20 years, a large part of the tropical North Atlantic Ocean has been warmer than usual, causing more moisture to evaporate and fueling strong hurricanes. The amount of vapor in the atmosphere has increased about 4 percent since the 1990s, and a wetter atmosphere provides extra energy and moisture for storms of all kinds. According to data from the Bulletin of the American Meteorological Society, midlatitude storms are feeding on the atmosphere’s extra vapor too, creating more precipitation. Although carbon dioxide is the more recognized problem, water vapor is a more impactful greenhouse gas by far because it absorbs a greater amount of the infrared energy radiated off the planet’s surface than other greenhouse gases, thus trapping more heat.

A doubling of atmospheric carbon dioxide concentrations alone would warm the globe approximately one degree Celsius, but feedback loops make the temperature rise twice as much. Even though disappearing sea ice may be dramatic, the extra vapor causes evaporation, which traps heat and creates even more warming, representing the strongest feedback loop in the climate system. We can reduce the effect indirectly by reducing the warming caused by emissions of carbon dioxide and methane, as well as propagating trees that absorb carbon from the air.

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