greenhouse effect

Greenhouse effect: what is it? Definition and role in global warming

Last modified on 21thJanuary 2019

What is the greenhouse effect? Is it something good or bad? How do human activities impact it? Let’s find out.
greenhouse effect

Definition Of The Greenhouse Effect

In terms of climate, the greenhouse effect is a natural phenomenon that contributes to the average temperature level on the surface of a planet with an atmosphere.
On Earth, 30% of solar radiation is directly returned to space because of the repercussion effect. The other 20% is absorbed by the atmosphere and a little more than 50% get absorbed by the planet’s crust and the oceans. The stored heat is then returned to the atmosphere by convection and in the form of infrared radiation.
That’s where the phenomenon comes in: part of this infrared radiation goes back to space, and another part is trapped by the greenhouse gases (GHGs) in the atmosphere and then sent back to the Earth. The surface heats up to a variable level depending on the concentration of GHG.
In the absence of a greenhouse effect, the average temperature (+ 15°C) on the surface of the planet would be much lower:  -18ºC.
The greenhouse gases naturally present in the atmosphere are mainly:

  • Water vapor,
  • Carbon dioxide (CO2),
  • Ozone,
  • Methane,
  • Nitrous oxide.


Influence Of Human Activity In The Greenhouse Effect

Since the beginning of the industrial era, the growing use of fossil fuels (coal, oil, lignite) and natural gas ended in additional GHG emissions which reinforce this effect. Deforestation (because of less CO2) and intensive livestock farming (due to methane emissions) have also contributed to increasing GHG emissions.
The increase in the “classical” GHGs of anthropogenic origin (related to human activity) is not the only cause. The industry sector, in fact, releases into the atmosphere specific greenhouse gases too, such as sulfur hexafluoride.
It is now undeniable that these additional GHG emissions have significantly increased the natural greenhouse effect. Consequently, human activities have been contributing to the ongoing global warming phenomenon.

Greenhouse Effect: The Risk Of Runaway

On what concerns the planet getting warming, it may seem paradoxical to speak of a “snowball effect”. However, the hypothesis of a runaway phenomenon is not excluded.
Indeed, the rise in temperatures already underway can eventually cause an excessive decrease in the reverberation, especially by melting glaciers and ice floes. In addition, the extension of arid climate zones leads to a decrease in plant biomass and thus to a loss of natural storage of carbon. Oceans getting warmer, as well as permafrost thaw can also release large quantities of methane.
In the end, the combination of all these circumstances may accelerate the greenhouse effect until it gets out of control. It is, therefore, extremely important to fight global warming an promote a sustainable development path that’s built upon resilience and renewable energies.

Image credits to greenhouse effect on Shutterstock

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