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It's Not the Heat: It's the Humidity

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While I was baking in the 110-degree heat in the Arizona desert a few weeks ago, I didn't believe that I could ever feel any hotter than I did then. After two broiling weeks, I left the sauna of the Southwest with much relief and returned home, only to find myself immersed in the steam bath of the Northeast.

Or maybe I should say, "submerged." I stepped off of the plane and into a pot of boiling soup. The air was hot, but worse, it was swampy. The second that I stepped out of the terminal, I began to perspire. The sweat started at my hairline and dripped down my face and neck. It poured through my pores and drenched my clothes. And I have been soaking wet ever since. Not a particularly pleasant feeling.

When I complained about the oppressive heat in the west, folks kept telling me that at least it was dry heat. I was not consoled. I was miserable. But even though I felt completely overwhelmed and debilitated by the desert heat, I hadn't really broken a sweat.

"It's not the heat, it's the humidity," they would say. And you know, I didn't believe them at the time, but they turned out to be right. It is most definitely the humidity.

"Why is that?" I wondered. So I set about to find out.

Humidity is the amount of water vapor in the air. Humans and animals are very sensitive to humidity, as we rely on the air to get rid of the moisture that has accumulated on our skin as perspiration. This cools us and keeps our body temperature at an acceptable level. When the humidity is high, the cooling evaporation of sweat from the skin is decreased.

As a result, we feel much hotter than the actual temperature when the humidity is high. If the humidity is low, we can feel much cooler than the actual temperature because our sweat evaporates easily, cooling us off.

Humidity combined with hot temperatures makes the heat more dangerous. If the atmosphere is as warm or warmer than the skin during times of high humidity, the blood is brought to the surface of our body and it cannot lose its heat, resulting in a condition called hyperpyrexia.

With so much blood going to the external surface of our body, relatively less goes to our muscles, brain and internal organs. So we feel weak and tired, physically and mentally, both. If there is no relief, this can result in hyperthermia or heat stroke.

The U.S. Geological Survey estimates that at any one time the earth has about 3,100 cubic miles of water in the air mostly in the form of vapor, but also as clouds and precipitation. There are 326 million cubic miles of water on our planet -- flowing and frozen -- including all of the water in the oceans, lakes, rivers and streams, the deposits underground and the water locked in ice.

Though the water vapor in the air represents such a small percentage of Earth's water, it would be a very different planet without it. If the air on Earth didn't contain humidity, our weather would be unrecognizable. Mars-like. There would be no clouds (except dust), no rain, sleet or snow. No thunder. No lighting. No fog.

We have, certainly here in the east, had our share of clouds, rain, lightning and thunder. This spring we had months of unrelenting rain. There was so much precipitation that mushrooms sprouted in the cracks of the sidewalks and moss grew on the Astroturf floor of my terrace.

I guess the ground can absorb but so much moisture. All the rest of it apparently goes right back into the air. Even places that once had a dry atmosphere, like Phoenix, for example, have now become humid due to the preponderance of swimming pools, well-groomed golf courses with sprinkler systems and fancy malls with spouting fountains.

Humidity plays an important part in global climate. Water vapor, like carbon dioxide, is a greenhouse gas. Greenhouse gases are responsible for depleting the ozone layer and heating the planet. Which causes us to use more air conditioning. Which releases Freon and other hydrocarbons, also greenhouse gases, which warm the air some more. And warm air, it would seem, can hold more water than cold air. This is a most vicious circle.

This was the hottest spring on record and so far the summer has followed suit. I shudder to think what it will be like in the future.

Unless. Unless we realize that we have brought this swamp upon ourselves. Unless we take climate change more seriously. Unless we change our wanton ways.

Around the Web

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