Examkin

Soru

Zorluk: ZorClimate Change, Global Warming and Ozone Layer Depletion

Regarding the atmospheric behavior of halogenated greenhouse gases and ozone-depleting substances, which of the following statements accurately explains why Hydrofluorocarbons (HFCs) are targeted for global phase-down under the Kigali Amendment to the Montreal Protocol despite possessing an Ozone Depletion Potential (ODP) of zero?

  1. HFCs absorb outgoing longwave infrared radiation within the atmospheric thermal window with high efficiency, giving them high Global Warming Potentials (GWPs) that accelerate global climate change.Cevap
  2. B
    HFCs photolyze under stratospheric ultraviolet radiation to yield reactive fluorine radicals that catalytically destroy stratospheric ozone at rates comparable to chlorine radicals.
  3. C
    HFCs undergo heterogeneous reactions on polar stratospheric clouds (PSCs) to release chlorine monoxide dimers, which directly drive seasonal ozone depletion over Antarctica.
  4. D
    HFCs react with tropospheric hydroxyl (OHOH) radicals to generate ground-level tropospheric ozone, which acts as the primary ODP-contributing mechanism.

Cevap

Hydrofluorocarbons (HFCs) are regulated under the Kigali Amendment because they absorb outgoing longwave infrared radiation within the atmospheric thermal window with high efficiency, giving them high Global Warming Potentials (GWPs) despite having an Ozone Depletion Potential (ODP) of zero.
The correct answer explains that HFCs have an Ozone Depletion Potential of zero because they lack chlorine and bromine. However, they act as potent greenhouse gases because their molecular structure allows strong absorption of outgoing terrestrial longwave infrared radiation in the atmospheric window, resulting in Global Warming Potentials thousands of times greater than carbon dioxide (CO2CO_2). This climate impact led to their phase-down under the 2016 Kigali Amendment to the Montreal Protocol.

Adım Adım Çözüm

1
Analyze the chemical composition and Ozone Depletion Potential (ODP) of Hydrofluorocarbons (HFCs).
HFCs contain carbon, hydrogen, and fluorine, but no chlorine or bromine atoms.
Without chlorine or bromine, HFCs cannot participate in catalytic ozone breakdown cycles in the stratosphere, resulting in ODP = 0.
2
Examine the radiative properties and Global Warming Potential (GWP) of HFCs.
HFC molecules efficiently trap thermal radiation escaping from the Earth's surface.
HFCs possess strong vibrational absorption modes in the 8–12 μm\mu m atmospheric infrared window, making their GWP hundreds to thousands of times higher than CO2CO_2.
3
Connect HFC atmospheric impacts to international regulatory frameworks.
The Kigali Amendment (2016) extended the mandate of the Montreal Protocol to phase down HFC consumption and production worldwide.
Phasing down HFCs prevents up to 0.5°C of global temperature rise by the end of the century, aligning climate change mitigation with atmospheric protection.

Anahtar Kavram

Radiative efficiency, Global Warming Potential (GWP), and atmospheric policy under the Kigali Amendment to the Montreal Protocol.
Tahmini Süre:1m 30s
Bu soruyu puanla

Konular

Climate Change, Global Warming and Ozone Layer Depletion