If your 10-year-old nephew or your colleague Brigitte asked you: ” But what exactly is the greenhouse effect?“, Would you be able to meet the challenge in a few words? We hear about it every day, we all have a vague idea of what it is, but not sure that everyone has understood that this natural phenomenon is essential to our survival… We will fix that.
Yes, the greenhouse effect is good for the planet.
Yes, the greenhouse effect is essential for life on earth.
Yes, the greenhouse effect is of interest and not just for tomato plants.
So what is the greenhouse effect ?
We often do a amalgam between greenhouse effect and global warming, but that’s not quite right.
It is important to fully understand the definition of the greenhouse effect in order to fully understand the climate issues. My goal today is therefore to give you one simple definition.
When solar radiation reaches the Earth’s atmosphere, a part (about 30%) is directly reflected, that is to say returned to space (by the atmosphere and clouds).
The rays that have not been reflected back to space are absorbed by the atmosphere for 20% of them while 50% finally reach the earth’s surface.
Among the latter, a part is still reflected by the earth depending on the nature of the ground surface (for example, ice reflects the sun’s rays better than the earth).
Without the greenhouse effect, we would all be frozen!
The rays that are not reflected are absorbed by soil and oceans, thus causing them to heat up.
Then, part of this heat is released into the air in the form of infrared. These infrared rays remain partially trapped in the atmosphere and heat it up. It is this heating because of the infrared rays which is called the greenhouse effect.
It’s exactly like in a greenhouse which allows the sun’s rays to pass through, but traps the infrared rays which heat up the interior of the greenhouse.
It is thanks to the greenhouse effect that we have an average temperature of 15 ° C on earth.
Without the greenhouse effect, the average temperature would be around -18 ° C.
You noticed that I just explained the greenhouse effect and I didn’t talk about global warming. The greenhouse effect is indeed a physical phenomenon which explains why we are all here today and what we need to survive.
If you are asked: “What is the greenhouse effect?” »: I am sure you will be able to explain it in your own words. But if you want to understand the phenomenon in video, the one I put above explains the phenomenon very well.
Why are we beating our ears with this?
It is true that, if it is natural phenomenon, why do they come to reshuffle our ears with this subject?
The amount of heat retained in the atmosphere by the greenhouse effect depends on the concentration of some gases which are contained in the atmosphere. These gases (called greenhouse gas) capture infrared radiation and increase the amount of radiation that remains in the atmosphere instead of returning beyond.
This therefore increases the temperature of the atmosphere. The higher the concentration of greenhouse gases, the higher the average temperature of the atmosphere.
Ultimately, it is not the greenhouse effect that causes the global warming. It is the increase in the concentration of greenhouse gases which, increasing the natural greenhouse effect, causes global warming.
In conclusion, the greenhouse effect is a physical phenomenon, the greenhouse effect has always existed, the greenhouse effect has created conditions conducive to life.
What needs to be understood now is what greenhouse gases are and how human action changes their concentration.
We will see that in a future article.
