Charles Dubouix

Climate change (1/3): The Greenhouse effect The climate is warming, fast

The Greenhouse Effect: A Natural Phenomenon

The greenhouse effect is a natural process that warms up the Earth

Specifically, certain gases in Earth's atmosphere, known as greenhouse gases or GHGs, trap the heat from the Sun.

Despite being viewed as a threat today, the greenhouse effect is one of the characteristics that makes Earth a habitable planet. Without it, the average temperature on Earth would be -18°C instead of +14°C.

Physical explanation

Planet Earth constantly receives energy from the Sun through sunlight. Part of this energy is absorbed by the Earth’s surface, causing it to warm up.

Like any hot body, the Earth dissipates this energy into space using infrared radiation.

However, the greenhouse gases in the atmosphere specifically react with infrared radiation and trap this heat on Earth.

Actually, there are two types of greenhouse effects:

• The natural greenhouse effect, that was just explained.
• The additional (or anthropogenic) greenhouse effect, caused by human activity.

The Additional Greenhouse Effect: 100% Human-Made

🚂 It All Started with Fossil Fuels

Since the 19th century and the industrial revolution, humans have greatly increased the volume of greenhouse gases in the atmosphere by burning fossil fuels that contain a lot of carbon.

The concentration of atmospheric CO2 has increased by 51% relative to pre-industrial levels.

🛁 The Bathtub Metaphor

Imagine that the Earth's atmosphere is a bathtub:

• 🧑‍🌾 Prior to the human industrial revolution, this "bathtub" was already filled to a stabilized level of 2.240 GtCO2 or 280 ppm (parts per million) of CO2, according to CO2-Concentration.
• 🚂 However, since 1850 (industrial revolution), humans have been burning fossil fuels and adding more carbon to the atmosphere.
• 📈 Today, after 170 years, the atmospheric CO2 concentration has reached an unprecedented level of 417 ppm (3.157 GtCO2), the highest it has been in the last three million years! This represents a 40% surge.

Here is the additional greenhouse effect we were looking for

Increased CO2 emissions lead to a higher concentration of GHGs (our bathtub has an invariant size and the drain is far from being large enough.

As a result, the greenhouse effect is getting more intense.

This additional greenhouse effect is heavily disrupting our climate

Without diving into too much detail, we can briefly mention:

• The average temperature has increased by 1.1°C
• Melting ice sheets, glaciers, and sea ice
• Oceans are warming and acidifying