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Difficulty: Very hardClimate Change, Global Warming and Ozone Layer Depletion

In climate science and global environmental policy under the Intergovernmental Panel on Climate Change (IPCC) frameworks, metrics such as Global Warming Potential (GWP) and Global Temperature Change Potential (GTP) are used to compare the climate impacts of non-CO2CO_2 greenhouse gases. Which of the following statements accurately distinguishes Global Warming Potential (GWP) from Global Temperature Change Potential (GTP)?

  1. A
    GWP measures instantaneous radiative forcing per unit mass at a specific future date, whereas GTP calculates the cumulative thermal energy trapped over an entire time horizon.
  2. GWP measures the integrated radiative forcing of a pulse emission over a chosen time horizon relative to CO2CO_2, whereas GTP measures the change in global mean surface temperature at a chosen point in time relative to CO2CO_2.Answer
  3. C
    For short-lived climate pollutants such as methane (CH4CH_4), the 100-year GTP value is consistently higher than its 100-year GWP value.
  4. D
    Both GWP and GTP assume an infinite atmospheric residence time for carbon dioxide (CO2CO_2) without incorporating carbon cycle decay models.

Answer

Global Warming Potential (GWP) integrates radiative forcing over a designated time horizon relative to carbon dioxide, whereas Global Temperature Change Potential (GTP) calculates the relative change in global mean surface temperature at a specific future point in time.
The correct answer accurately states the physical basis of both IPCC climate metrics: Global Warming Potential (GWP) integrates total radiative forcing (energy absorbed) over a time window, whereas Global Temperature Change Potential (GTP) evaluates the resulting global surface temperature change at a specific point in time relative to reference carbon dioxide emissions.

Step-by-Step Solution

1
Analyze the definition of Global Warming Potential (GWP)
GWP is defined as the time-integrated radiative forcing caused by a pulse emission of 1 kg of a trace gas relative to 1 kg of reference gas carbon dioxide (CO2CO_2) over a specified time horizon THTH (e.g., GWP100=∫0THRFi(t)dt∫0THRFCO2(t)dtGWP_{100} = \frac{\int_{0}^{TH} RF_i(t) dt}{\int_{0}^{TH} RF_{CO_2}(t) dt}).
Understanding GWP as a cumulative energy metric is essential for differentiating it from temperature-endpoint metrics.
2
Analyze the definition of Global Temperature Change Potential (GTP)
GTP is defined as the change in global mean surface temperature at a chosen point in time tt relative to the temperature change caused by CO2CO_2 (GTP(t)=ΔTi(t)ΔTCO2(t)GTP(t) = \frac{\Delta T_i(t)}{\Delta T_{CO_2}(t)}).
GTP measures an endpoint climate outcome (surface warming) rather than cumulative energy input.
3
Compare GWP and GTP behavior for short-lived climate pollutants (SLCPs) like methane (CH4CH_4)
Because CH4CH_4 has a relatively short atmospheric lifetime (~11.8 years), its instantaneous radiative forcing rapidly diminishes after pulse emission. Thus, cumulative integrated forcing over 100 years (GWP100≈28GWP_{100} \approx 28) yields a higher numerical value than its point-in-time surface temperature impact at year 100 (GTP100≈4GTP_{100} \approx 4).
This physical behavior confirms that statement claiming higher GTP values for short-lived pollutants is erroneous.

Key Concept

Atmospheric Climate Metrics: Radiative Forcing (GWP) vs Surface Temperature Response (GTP)
Estimated Time:3m 0s
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Topics

Climate Change, Global Warming and Ozone Layer Depletion