Greenhouse Effect – is it good or bad?

Contrary to most people belief, greenhouse effect is a natural and healthy phenomenon, which allows life on Earth.

To understand it, we have to look at the Earth's energy balance.

Almost all the energy on the Earth comes from solar radiation. However, our planet doesn’t absorb all off this energy, otherwise it will explode. 30% of solar radiation is reflected by the Earth and its atmosphere, going back to Space, and the other 70% is absorbed and reemitted.
Hence, there is a balance between incoming sunlight radiation and outgoing heat radiation, which has been allowing a constant temperature on Earth for millions of years.

According to scientists’ calculations that temperature would be 18 degrees Celsius below zero which wouldn’t allow liquid water or life.

But we know that the average temperature of the Earth’s surface is about 15 degrees. Greenhouse effect is the responsible for that.

From the 70% of absorbed solar radiation, 44% are absorbed by the Earth’s surface. Than, that energy is reemitted as infrared radiation. Some of that passes through the atmosphere, but most is absorbed by greenhouse gases and reemitted in all directions. This process creates a cycle of radiation that warms the Earth’s surface and the lower atmosphere.

If greenhouse effect is natural, what’s the problem?

We are! The problem is the increasing of the greenhouse effect by human action.

Although most of the greenhouse gases are natural and essential to life, they have anthropogenic sources too, which contribute to the increasing of theirs concentrations on the atmosphere. Carbon dioxide, methane, nitrogen oxide, fluorocarbons and water vapor are the most important greenhouse gases.

As we will see further on this blog, fossil fuels burn and deforestation are the main causes of the increasing of the greenhouse effect, which leads to global warming and its serious consequences.

Sources:
RODRIGUES, M. Margarida R. D. e DIAS, Fernão Morão Lopes, Física e Química A – Física – 10º ou 11º (ano 1), Porto Editora, 2007.
http://www.umich.edu/~gs265/society/greenhouse.htm