Water Vapor & Its impact towards Greenhouse Gasses!

Earth’s temperature depends on the balance between energy entering and leaving the planet. When sunlight reaches the earth’s surface, it can either be reflected back into space or absorbed. Incoming energy that gets absorbed by the Earth warms the planet. Once absorbed, the planet releases some of the energy back into the atmosphere as heat (also called infrared radiation). This solar energy that is reflected back to space does not warm the earth.

However, certain gases in the atmosphere absorb energy, slowing or preventing the loss of heat to space. Those gases are known as “greenhouse gases.” They act like a blanket, making Earth warmer than it would otherwise be. This process, commonly known as the “greenhouse effect” is natural and necessary to support life. However, the recent buildup of greenhouse gases in the atmosphere due to human activities has impacted the Earth’s climate patterns, posting serious threats to the planet’s ecosystems. .

Greenhouse-effect occurs naturally on Earth due to trace amounts of water vapour (H2O), carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) in the atmosphere. These gases re-emit the heat that’s absorbed in the Earth’s atmosphere, and emit as radiation in all directions with the help of gas molecules to keep our planet warm and habitable.  

However, one needs to distinguish between the natural greenhouse effect and the enhanced greenhouse effect. The natural greenhouse effect is caused by the natural amounts of greenhouse gases, and is vital for life. In the absence of the natural greenhouse effect the surface of Earth would be approximately 33 °C cooler. The enhanced greenhouse effect refers to additional radiative force resulting from increased concentrations of greenhouse gases induced by human activities. The main greenhouse gases which have risen in concentration are carbon dioxide, methane, nitrous oxide, hydrochlorofluorocarbons (HCFCs), hydrofluorocarbons (HFCs) and ozone in the lower atmosphere. More can be read from here  Archived. 

This table shows 100-year global warming potential, which describes effects that occur over a period of 100 years after a particular mass of gas is emitted. More details can be gathered from here |  Archived.

When compared to other greenhouse gases, water vapor stays in the atmosphere for a much shorter period of time. Water vapor will generally stay in the atmosphere for days (before precipitation) while other greenhouse gases, such as carbon dioxide or methane, will stay in the atmosphere for a much longer period of time (ranging from years to centuries) showing  a bigger contribution towards global warming. More can be read from here   Archived. 

Further details on other greenhouse gases can be reached here  Archived.

Despite the fact water vapor accounts for about 60% of Earth’s greenhouse warming effect, water vapor does not control the Earth’s temperature. Instead, the amount of water vapor is controlled by the temperature. This is because the temperature of the surrounding atmosphere limits the maximum amount of water vapor the atmosphere can contain. Although Water vapor is the most abundant greenhouse gas in the atmosphere. Human activities have only a small direct influence on atmospheric concentrations of water vapor, primarily through irrigation and deforestation. The surface warming caused by human production of other greenhouse gases, however, leads to an increase in atmospheric water vapor because warmer temperatures make it easier for water to evaporate and stay in the air in vapor form. This creates a positive “feedback loop” in which warming leads to more warming. More can be read here   Archived.

Greenhouse gases keep our planet livable. Without them, Earth’s surface temperature would be about 59 degrees Fahrenheit (33 degrees Celsius) colder. Some people mistakenly believe water vapor is the main driver of Earth’s current warming. However, water vapor is a key part of Earth’s water cycle: the path that all water follows as it moves around Earth’s atmosphere, land, and ocean as liquid water, solid ice, and gaseous water vapor and is also essential for life. More can be read here   Archived.