The Global Warming Potential (GWP) of a substance depends on

A. the spectral band of its absorbing wavelengths

B. its residence time in atmosphere

C. its number of carbon molecules

D. concentration of the substance

Choose the correct answer:

Correct option is D

Introduction
· Global Warming Potential (GWP) is a relative measure of how much heat a greenhouse gas (GHG) traps in the atmosphere compared to the same mass of Carbon Dioxide ($CO_2$).
· It is a key metric used in climate policy (like the Kyoto Protocol) to compare the climate impacts of different gases.
· The calculation of GWP is standardized by the Intergovernmental Panel on Climate Change (IPCC) and is usually calculated over a specific time horizon, commonly 100 years.

Information Booster

Global Warming Potential is determined by three primary factors: the spectral band of its absorbing wavelengths, which dictates how effectively the gas intercepts infrared radiation; its residence time in the atmosphere, which determines how long the gas remains active before being removed by sinks; and the concentration of the substance (D) or the radiative forcing per unit mass. The number of carbon molecules is not a direct determining factor, as many potent greenhouse gases like SF_6 (Sulfur hexafluoride) contain no carbon at all.

· Atmospheric Lifetime (Residence time) is crucial because a gas that stays in the atmosphere for centuries (like $CF_4$) will have a much higher long-term GWP than one that lasts only days.
· CO_2 is assigned a GWP value of 1, serving as the baseline for all other comparisons.
· Methane (CH_4) has a high radiative efficiency but a short lifetime, resulting in a GWP of approx. 28-36 over 100 years.
· Compounds like CFCs and HCFCs have high GWPs because they absorb radiation very strongly and persist in the atmosphere for decades.

Additional Information
· Spectral band: This refers to the specific parts of the electromagnetic spectrum the gas absorbs; if these overlap with other gases, the additional warming effect is diminished.
· Number of carbon molecules : This is an incorrect statement because chemical structure alone (specifically the count of Carbon) does not dictate warming; for instance, CH_4 (1 carbon) is more potent than CO_2 (1 carbon), and non-carbon gases like N_2O are even more powerful.
· Concentration: The current background concentration of a gas affects its marginal impact; adding a gas that is already abundant (like CO_2) has a different per-unit impact than adding a rare gas (like $SF_6$).