Greenhouse effect diagram

What Is Greenhouse Effect And What Causes It

What Is Greenhouse Effect And What Causes It

It is becoming hard not to hear the words “greenhouse gases”, “greenhouse effect” and “global warming” in everyday conversation these days. If you mystified by those, today is your lucky day as we are going to do an in-depth discussion on the greenhouse effect.

What is the greenhouse effect?

Greenhouse effect is the trapping of the sun’s radiant heat in a planet’s lower atmosphere, due to the greater transparency of the atmosphere to incoming infrared radiation from the sun than to infrared radiation emitted from the planet’s surface.

Greenhouse Effect Diagram

How does the greenhouse effect work?

Here is how greenhouse effect occurs. The Sun shines on Earth with light made of electromagnetic radiation of different wavelengths. The different electromagnetic components of sunlight include:

  • ultraviolet, which has the highest frequency and shortest wavelength.
  • visible light which enables us to see.
  • infrared, which has the lowest frequency and longest wavelength. Infrared is also known as radiant heat because is causes a substance that absorbs it to heat up.

All the three components mentioned above constitutes what we know as solar energy. About one-third of the sun’s solar energy that reaches the earth is reflected back to space directly in the top atmosphere. The remaining two-thirds is absorbed by both the earth’s surface and by the atmosphere.

What Is Greenhouse Effect And What Causes It
As shown in this NASA illustration by Robert Simmon, of the 340 watts per square meter of solar energy that falls on the Earth, 29% is reflected back directly into space, 23% is absorbed by the atmosphere and the remaining 48% is absorbed at the surface.

This causes the earth to warm up during the day.

What Is Greenhouse Effect And What Causes It
Image source: NASA illustrations by Robert Simmon.

The Earth must also radiate back to space just about the same amount of thermal energy it absorbs, to remain cool. This happens especially during the night. But because the earth is much cooler than the sun, it radiates back heat that is of a higher wavelength than it receives from the sun.

Image source: NASA illustrations by Robert Simmon.

The atmospheric gases, including the clouds, are “transparent” to infrared radiation of relatively shorter wavelengths emitted by the sun but opaque to infrared of longer wavelengths radiated back by the earth. This means that, while the heat from the sun reaches the earth safely, much of the thermal radiation radiated back by the land and ocean is absorbed by the atmosphere and reradiated back to Earth again. The heat is literally trapped on earth. This effect is known as the greenhouse effect.

Naturally, greenhouse effect is essential to earth’s ability to sustain life. Without the natural greenhouse effect, the average temperature on the Earth’s surface would be below 0 and harsh to life as we know it. So the Earth’s natural greenhouse effect makes life possible.

What Is Greenhouse Effect And What Causes It

However, human activities, such as the burning of fossil fuels and destruction of forests, accelerates the natural greenhouse effect, towards a point where the earth becomes too hot to sustain life. That is now called global warming.

What Is Greenhouse Effect And What Causes It

Greenhouse effect diagram by IPCC

Greenhouse effect diagram

Image courtesy of IPCC

The Intergovernmental Panel on Climate Change (IPCC) is the international body for assessing the science related to climate change.

What causes the greenhouse effect?

Now that we know what greenhouse effect is, let us look at what causes greenhouse effect.

The greenhouse effect is caused by less abundant gases in the atmosphere, such as:

During photosynthesis, green plants absorb carbon dioxide out of the atmosphere and convert it to carbohydrates. Photosynthesis is one of the processes that reduce the amount of carbon dioxide, a greenhouse gas, in the atmosphere. This slows down the acceleration of the greenhouse effect. However, human activities are causing deforestation, reducing the number of trees that scrub the carbon dioxide from the atmosphere.

Air pollution

We are living in the industrial era where large industries are not held responsible for the tons of carbon dioxide they recklessly spew into the atmosphere on daily basis. Industrial activities are adding greenhouse gases into the atmosphere at an alarming rate, primarily through the burning of fossil fuels.

Adding greenhouse gases, such as carbon dioxide, to the atmosphere intensifies the greenhouse effect, accelerating global warming.

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