Many people wonder why it’s colder at higher altitudes, even though they are technically closer to the Sun. It might seem logical to think that being closer to the Sun would make it warmer, but that’s not how it works on Earth.
Solar Radiation and Earth’s Atmosphere
The Sun’s energy reaches Earth in the form of solar radiation, which includes visible light and other wavelengths across the electromagnetic spectrum. This energy interacts with particles in Earth’s atmosphere, warming the planet. The key point to understand is that the heat we feel isn’t direct heat from the Sun, but rather the result of solar radiation being absorbed and re-emitted by the Earth’s surface and atmosphere.
Even though the top of Mount Everest is about 8,849 meters (29,032 feet) above sea level, this height is negligible compared to the Sun’s distance from Earth, which is about 151.88 million kilometers (93 million miles). Therefore, being slightly closer to the Sun at higher altitudes doesn’t significantly increase temperature.
The Role of Atmospheric Pressure
The primary reason higher altitudes are colder lies in the thickness of the atmosphere. At sea level, the atmosphere is denser, meaning there are more air molecules to absorb and retain heat. As you ascend, air pressure decreases because there is less weight of the air above pressing down. For example, the air pressure on Everest is roughly one-third of that at sea level, though it varies with the weather.
When air is heated, it expands and becomes less dense. This less dense, warm air rises due to buoyant force. However, as air rises and pressure decreases, it expands further. This expansion causes the air to cool, a process known as adiabatic cooling.
Understanding Adiabatic Cooling
Adiabatic cooling explains why higher elevations are cooler than lower ones. When a parcel of air moves from a low elevation to a high elevation, it expands because of the reduced pressure. As it expands, its temperature drops.
NASA explains this phenomenon: “Higher elevations are cooler than lower elevations because of adiabatic heating. When a parcel of air moves from a low elevation to a high elevation, it expands because it is under less pressure. It has less weight pressing down on it from the air above it. As the air expands, its temperature drops.”
The Impact on Weather and Precipitation
The cooler temperatures at higher altitudes have significant effects on weather patterns. When the air temperature is low enough, precipitation falls as snow rather than rain. This is why mountain tops are often snowy. The cold air not only cools the ground but also helps snow accumulate rather than melt.
In summary, the colder temperatures at higher altitudes are due to the decrease in atmospheric pressure, leading to adiabatic cooling, rather than the proximity to the Sun. Understanding this helps explain why mountain tops remain cold and snowy despite their elevation.
Katy Willis is a writer, master herbalist, master gardener, and certified canine nutritionist who has been writing since 2002. She’s finds joy in learning new and interesting things, and finds history, science, and nature endlessly fascinating.
