Which of the following gas has highest contribution in global warming?

Question

UnlockIAS · Accepted Answer

Correct — A, carbon dioxide (CO2). Although CO2 traps less heat per molecule than the other gases listed, it is released in vastly larger amounts (fossil-fuel burning, deforestation) and lingers in the atmosphere for a long time. As a result it accounts for roughly three-quarters of anthropogenic greenhouse-gas emissions and is the single largest contributor to global warming.

Why the other options are wrong — (b) CFCs have a very high warming potential per molecule and also destroy ozone, but they are present in tiny quantities and are being phased out under the Montreal Protocol, so their overall contribution is small.  (c) N2O is a potent greenhouse gas per unit mass (mainly from fertilizers), but emitted in far smaller amounts than CO2, so its total share is only a few percent.  (d) Methane is the second-largest contributor and traps more heat per molecule than CO2, but its total emissions and atmospheric amount are much lower, so CO2 still dominates.

Concept: A gas's effect on warming depends on two things: how strongly each molecule traps heat (global-warming potential, GWP) AND how much of it is emitted. CO2 has a low GWP but enormous emission volume and a long lifetime, so it dominates total forcing. CH4, N2O and CFCs have high GWP but small quantities.

State PCS 2019 Q83 — Environment & Ecology PYQ with Answer

State PCS 2019 Q83 — Environment & Ecology PYQ with Answer