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Greenhouse gases trap heat by absorbing visible light radiation emitted by the Earth's surface.
Answer: False
Explanation: The fundamental mechanism by which greenhouse gases exert their warming influence involves the absorption and re-emission of infrared radiation, not visible light. While the Earth's surface absorbs visible light from the sun and re-emits energy as infrared radiation, it is this infrared radiation that greenhouse gases interact with.
The 'enhanced greenhouse effect' refers to the natural process that keeps Earth habitable.
Answer: False
Explanation: The 'enhanced greenhouse effect' specifically refers to the *additional* warming caused by increased concentrations of greenhouse gases resulting from human activities, superimposed upon the natural greenhouse effect which is essential for maintaining Earth's habitability.
The natural greenhouse effect is entirely caused by human industrial activities.
Answer: False
Explanation: The natural greenhouse effect is a fundamental planetary process involving naturally occurring atmospheric gases that maintains Earth's temperature at a habitable level. Human industrial activities contribute to the *enhanced* greenhouse effect, not the natural one.
The term 'greenhouse' was first applied to atmospheric heat trapping in the early 20th century.
Answer: True
Explanation: The analogy of a 'greenhouse' to describe the atmospheric heat-trapping phenomenon was first introduced by Nils Gustaf Ekholm in 1901.
Early 19th-century experiments showed that nitrogen and oxygen absorb infrared radiation effectively.
Answer: False
Explanation: Early scientific experiments, particularly in the late 19th century, demonstrated that nitrogen and oxygen molecules, due to their symmetrical structure, do not effectively absorb infrared radiation. This contrasts with molecules like water vapor and carbon dioxide.
What is the primary mechanism by which greenhouse gases affect a planet's temperature?
Answer: They absorb and re-emit infrared radiation, trapping heat.
Explanation: Greenhouse gases possess molecular structures that allow them to absorb and subsequently re-emit infrared radiation. This process is crucial because the Earth's surface, after absorbing solar radiation, emits energy primarily in the infrared spectrum. By trapping and re-emitting this outgoing infrared radiation, greenhouse gases effectively retain thermal energy within the atmosphere, leading to a warming of the planet's surface.
How does the absorption spectrum of carbon dioxide relate to its role in the greenhouse effect?
Answer: CO2 absorbs infrared radiation at wavelengths where Earth emits heat, trapping it effectively.
Explanation: Carbon dioxide absorbs infrared radiation strongly in specific wavelength bands that overlap with the peak emission wavelengths of Earth's thermal radiation. This absorption and subsequent re-emission of infrared energy is the primary mechanism by which CO2 contributes to the greenhouse effect.
What characteristic allows molecules like carbon dioxide to interact with infrared radiation?
Answer: Their asymmetry in electrical charge distribution, enabling interaction with radiation.
Explanation: Molecules composed of different elements, such as carbon dioxide (CO2), possess an asymmetry in their electrical charge distribution. This asymmetry allows their molecular vibrations to absorb and emit infrared radiation, making them 'infrared active' and thus capable of contributing to the greenhouse effect.
What is the primary role of greenhouse gases in maintaining a planet's temperature?
Answer: Absorbing and emitting infrared radiation to trap heat.
Explanation: Greenhouse gases play a critical role in regulating planetary temperature by absorbing and re-emitting infrared radiation. This process traps thermal energy within the atmosphere, preventing it from escaping rapidly into space and thus maintaining a habitable surface temperature.
What does the term 'infrared active' mean for a greenhouse gas molecule?
Answer: Its molecular vibrations allow it to absorb and emit infrared radiation.
Explanation: A molecule is considered 'infrared active' if its vibrational modes cause fluctuations in its dipole moment, enabling it to absorb and emit infrared radiation. This property is fundamental to the greenhouse effect, as it allows gases like CO2 and H2O to trap thermal energy.
Water vapor is the most abundant greenhouse gas in Earth's atmosphere based on average mole fraction.
Answer: True
Explanation: Water vapor is indeed the most abundant greenhouse gas in Earth's atmosphere when considering its average mole fraction. Its significant contribution to the natural greenhouse effect is well-established.
Methane has a longer atmospheric lifetime than carbon dioxide.
Answer: False
Explanation: Methane possesses a considerably shorter atmospheric lifetime, averaging approximately 12 years, compared to carbon dioxide, which can persist in the atmosphere for thousands of years due to its complex removal mechanisms.
Carbon dioxide emissions are the primary driver of global warming, accounting for approximately 75% of the warming effect.
Answer: True
Explanation: Carbon dioxide is identified as the principal contributor to global warming, responsible for approximately three-quarters of the overall warming effect. Methane accounts for most of the remaining warming.
Nitrogen (N2) and oxygen (O2) are considered major greenhouse gases because their molecules are infrared active.
Answer: False
Explanation: Nitrogen (N2) and oxygen (O2) are not considered significant greenhouse gases because their symmetrical diatomic molecular structure renders them largely inactive with respect to infrared radiation. Infrared activity is characteristic of molecules with asymmetrical charge distributions, such as CO2 and H2O.
Water vapor is estimated to be responsible for approximately 18-26% of the total greenhouse effect.
Answer: False
Explanation: The range of 18-26% is typically attributed to carbon dioxide's contribution to the greenhouse effect. Water vapor is responsible for a much larger portion, estimated to be between 41% and 67% of the natural greenhouse effect.
Rice paddies are a negligible source of agricultural greenhouse gas emissions globally.
Answer: False
Explanation: Rice paddies are a significant source of agricultural greenhouse gas emissions, particularly methane, and also contribute to nitrous oxide emissions globally.
Which of the following is listed as the most abundant greenhouse gas in Earth's atmosphere by average mole fraction?
Answer: Water Vapor
Explanation: Water vapor is identified as the most abundant greenhouse gas in Earth's atmosphere based on its average mole fraction. It plays a significant role in the natural greenhouse effect.
What is the approximate contribution of water vapor to the natural greenhouse effect?
Answer: Approximately half (around 50%)
Explanation: Water vapor is estimated to be responsible for a substantial portion of the natural greenhouse effect, contributing approximately 41-67%, often simplified to around half. The range of 18-26% is typically associated with carbon dioxide's contribution.
Which greenhouse gas is identified as the primary cause of global warming, responsible for about three-quarters of the effect?
Answer: Carbon Dioxide
Explanation: Carbon dioxide emissions are recognized as the primary driver of global warming, accounting for approximately 75% of the total warming effect. Methane contributes most of the remainder.
Why are diatomic molecules like nitrogen (N2) and oxygen (O2) not considered significant greenhouse gases?
Answer: Their molecular structure lacks the asymmetry needed to interact with infrared radiation.
Explanation: Nitrogen (N2) and oxygen (O2) molecules are symmetrical, meaning they lack the asymmetric charge distribution necessary for efficient interaction with infrared radiation. This characteristic prevents them from significantly contributing to the greenhouse effect, unlike polyatomic molecules such as CO2 and H2O.
Which of the following gases is identified as a concern, although not among the five most abundant?
Answer: Hydrofluorocarbons (HFCs)
Explanation: Hydrofluorocarbons (HFCs) are identified as greenhouse gases of concern due to their high global warming potential, even though they are not among the five most abundant atmospheric greenhouse gases.
Which of the following is an example of a greenhouse gas with a very long atmospheric lifetime?
Answer: Sulfur Hexafluoride (SF6)
Explanation: Sulfur hexafluoride (SF6) is a potent greenhouse gas with an exceptionally long atmospheric lifetime, estimated to be over 3,200 years. This persistence means its warming effect endures for millennia.
Which of the following is NOT listed as one of the five most abundant greenhouse gases in Earth's atmosphere?
Answer: Sulfur Hexafluoride (SF6)
Explanation: While Methane, Ozone, and Nitrous Oxide are among the major greenhouse gases, Sulfur Hexafluoride (SF6) is not listed among the five most abundant. SF6 is notable for its extremely high global warming potential and long atmospheric lifetime, despite its low concentration.
Radiative forcing measures the impact of external factors on Earth's energy balance, with positive forcing leading to cooling.
Answer: False
Explanation: Radiative forcing quantifies the change in Earth's energy balance. A *positive* radiative forcing indicates that more energy is entering the Earth system than leaving, thus leading to warming. Conversely, negative radiative forcing leads to cooling.
Global Warming Potential (GWP) compares the heat-trapping ability of a greenhouse gas relative to methane over a specific time period.
Answer: False
Explanation: Global Warming Potential (GWP) is defined as a measure comparing the heat-trapping ability of a greenhouse gas to that of *carbon dioxide* (CO2), which serves as the reference gas with a GWP of 1. This comparison is made over specific time horizons, typically 20, 100, or 500 years.
Methane has a higher warming impact per unit mass than carbon dioxide over a 20-year period.
Answer: True
Explanation: Methane exhibits a significantly higher warming impact per unit mass than carbon dioxide over shorter time scales. For instance, over a 20-year period, methane's GWP is substantially greater than that of CO2, reflecting its potent but shorter-lived warming effect.
A carbon dioxide equivalent (CO2e) is used to measure the mass of a specific greenhouse gas.
Answer: False
Explanation: A carbon dioxide equivalent (CO2e) is not a measure of mass for a specific gas, but rather a standardized unit representing the warming impact of different greenhouse gases relative to carbon dioxide. It is calculated by multiplying the mass of a gas by its Global Warming Potential (GWP).
The concentration of a greenhouse gas is determined by the balance between its sources and its sinks.
Answer: True
Explanation: The atmospheric concentration of any greenhouse gas is fundamentally determined by the equilibrium between its emission rates (sources) and its removal rates (sinks) from the atmosphere.
The 'airborne fraction' refers to the proportion of a greenhouse gas emission that is removed from the atmosphere by natural sinks.
Answer: False
Explanation: The 'airborne fraction' (AF) of a greenhouse gas emission represents the proportion of the emission that *remains* in the atmosphere after a specified period, rather than the proportion removed by sinks. It is a key indicator of how effectively natural sinks are absorbing anthropogenic emissions.
Carbon dioxide has a fixed and easily specified atmospheric lifetime due to its rapid absorption.
Answer: False
Explanation: Carbon dioxide does not have a fixed or easily specified atmospheric lifetime because it is not destroyed over time but rather cycles between the atmosphere, oceans, and land biosphere. While some absorption is rapid, a significant portion persists for centuries to millennia, making its effective lifetime highly variable and complex to define with a single number.
Compared to carbon dioxide, what is the atmospheric lifetime of methane?
Answer: Approximately 12 years
Explanation: Methane possesses a significantly shorter atmospheric lifetime, averaging approximately 12 years, compared to carbon dioxide, which can persist in the atmosphere for thousands of years due to its complex removal mechanisms.
What does a positive radiative forcing indicate?
Answer: More energy entering the Earth system than leaving, leading to warming.
Explanation: A positive radiative forcing signifies an imbalance in Earth's energy budget, where incoming energy exceeds outgoing energy. This net energy gain results in a warming trend for the planet's climate system.
What does Global Warming Potential (GWP) measure?
Answer: The heat-trapping ability of a greenhouse gas relative to CO2 over a specific time.
Explanation: Global Warming Potential (GWP) quantifies the heat-trapping ability of a greenhouse gas relative to carbon dioxide (CO2) over a specified time horizon, typically 100 years. It allows for the comparison of the climate impact of different gases.
What is the primary natural sink for atmospheric carbon dioxide?
Answer: Photosynthesis by plants and absorption by the oceans
Explanation: The primary natural sinks that remove carbon dioxide from the atmosphere are the biological processes of photosynthesis carried out by terrestrial plants and phytoplankton, and the physical absorption of CO2 by the world's oceans.
What is the 'airborne fraction' (AF) of a greenhouse gas emission?
Answer: The proportion of emissions that remains in the atmosphere after a specified period.
Explanation: The airborne fraction (AF) quantifies the portion of a greenhouse gas emission that persists in the atmosphere after a given time interval. It is calculated as the ratio of the increase in atmospheric concentration to the cumulative emissions over that period.
How is the warming impact of a greenhouse gas typically measured relative to carbon dioxide?
Answer: Using its Global Warming Potential (GWP).
Explanation: The Global Warming Potential (GWP) is the standard metric used to compare the warming impact of different greenhouse gases relative to carbon dioxide over specific time horizons. It allows for the aggregation of diverse emissions into a common unit (CO2e).
Human activities since the Industrial Revolution have led to a decrease in atmospheric concentrations of carbon dioxide and methane.
Answer: False
Explanation: Contrary to this statement, human activities since the Industrial Revolution have led to a significant *increase* in atmospheric concentrations of carbon dioxide and methane, driving global warming.
The rate of increase in atmospheric CO2 concentrations has slowed down since the Industrial Revolution.
Answer: False
Explanation: The rate of increase in atmospheric CO2 concentrations has *accelerated* significantly since the Industrial Revolution. The time required for a given increase in parts per million (ppm) has progressively shortened, indicating an accelerating trend.
Current carbon dioxide levels are lower than they have been in the last million years.
Answer: False
Explanation: Current atmospheric carbon dioxide levels are significantly higher than they have been for at least the last million years, and potentially the last 14 million years, indicating a profound departure from pre-industrial conditions.
The 'faint young sun paradox' suggests that early Earth was warmer than expected due to a dimmer sun, requiring a stronger greenhouse effect.
Answer: True
Explanation: The 'faint young sun paradox' posits that early Earth should have been frozen given the Sun's lower luminosity. The resolution typically involves higher concentrations of greenhouse gases in the early atmosphere, which would have provided the necessary warming to maintain liquid water.
How have human activities impacted methane concentrations since the Industrial Revolution?
Answer: Methane concentrations have increased by approximately 150%.
Explanation: Since the onset of the Industrial Revolution, human activities have led to a significant increase in atmospheric methane concentrations, estimated to be around 150%.
What are the main human activities contributing to methane emissions?
Answer: Agriculture, fossil fuel production, and waste management.
Explanation: The primary anthropogenic sources of methane emissions include agricultural practices (such as livestock digestion and rice cultivation), the production and transport of fossil fuels, and the decomposition of organic waste in landfills.
What is the significance of the year 1750 mentioned in the context of greenhouse gas concentrations?
Answer: It is used as a baseline for pre-industrial greenhouse gas concentrations.
Explanation: The year 1750 is conventionally adopted as a reference point representing pre-industrial atmospheric concentrations of greenhouse gases. This baseline is crucial for quantifying the extent of anthropogenic influence on the climate system by measuring the increase in these gases since that period.
How do current carbon dioxide levels compare to those from millions of years ago?
Answer: Current levels may be the highest seen in the last 14 million years.
Explanation: Paleoclimatic reconstructions suggest that current atmospheric carbon dioxide concentrations may be the highest observed in approximately 14 million years, indicating a significant deviation from long-term geological norms.
What is the significance of the 'faint young sun paradox' in relation to early Earth's atmosphere?
Answer: It highlights the need for higher greenhouse gas concentrations to explain early liquid water.
Explanation: The 'faint young sun paradox' implies that early Earth's atmosphere must have contained higher concentrations of greenhouse gases to maintain surface temperatures warm enough for liquid water, despite the Sun's lower luminosity during that period.
What is the approximate increase in carbon dioxide levels since the Industrial Revolution?
Answer: Approximately 50%
Explanation: Since the beginning of the Industrial Revolution (circa 1750), atmospheric carbon dioxide concentrations have increased by over 50%, a significant rise attributed to anthropogenic activities.
What is the primary human activity responsible for the vast majority of carbon dioxide emissions?
Answer: Burning of fossil fuels
Explanation: The combustion of fossil fuels (coal, oil, and natural gas) for energy production constitutes the largest source of anthropogenic carbon dioxide emissions globally.
What is the role of natural carbon flows mentioned in the source?
Answer: They historically maintained balance, keeping greenhouse gas levels stable before human disruption.
Explanation: Natural carbon flows between Earth's systems historically maintained a state of balance over long periods, which helped to stabilize atmospheric greenhouse gas concentrations. Human activities have significantly disrupted this equilibrium.
Increasing concentrations of greenhouse gases in the lower atmosphere cause the upper atmosphere to warm and expand.
Answer: False
Explanation: An increase in greenhouse gases in the lower atmosphere leads to a trapping of heat, which in turn causes the lower atmosphere to warm. This effect results in the upper atmosphere becoming cooler and contracting, as heat is less efficiently retained at higher altitudes.
The Montreal Protocol was primarily designed to regulate greenhouse gas emissions to combat global warming.
Answer: False
Explanation: The Montreal Protocol's primary objective was the protection of the ozone layer by phasing out ozone-depleting substances. While many of these substances are also potent greenhouse gases, the protocol's direct aim was not climate change mitigation.
The Kigali Amendment aims to phase out the production and use of hydrofluorocarbons (HFCs).
Answer: True
Explanation: The Kigali Amendment, an international agreement, specifically targets the phasedown of production and consumption of hydrofluorocarbons (HFCs), which are potent greenhouse gases used in refrigeration and air conditioning.
To limit global warming to 1.5°C, global annual greenhouse gas emissions need to be cut by approximately 45% by 2030.
Answer: True
Explanation: Scientific consensus, as reported by bodies like the IPCC and UNEP, indicates that achieving the 1.5°C warming limit necessitates substantial and immediate reductions in global greenhouse gas emissions, with estimates suggesting a cut of around 45% by 2030.
Negative emissions technologies aim to increase greenhouse gas concentrations in the atmosphere.
Answer: False
Explanation: Negative emissions technologies are designed for the opposite purpose: to actively remove greenhouse gases, particularly carbon dioxide, from the atmosphere, thereby reducing their concentration and mitigating climate change.
The NOAA Annual Greenhouse Gas Index (AGGI) measures the ratio of radiative forcing from long-lived GHGs compared to the forcing in 1990.
Answer: True
Explanation: The NOAA Annual Greenhouse Gas Index (AGGI) quantifies the cumulative change in the total direct radiative forcing from long-lived, well-mixed greenhouse gases, using 1990 as the baseline year.
What is the projected consequence if current greenhouse gas emission rates continue, according to the IPCC?
Answer: Global warming will surpass 2.0°C between 2040 and 2070.
Explanation: The IPCC's projections indicate that if current greenhouse gas emission rates persist, global warming is likely to exceed 2.0°C (3.6°F) within the period of 2040 to 2070, a threshold considered indicative of 'dangerous' climate change.
What is the purpose of 'negative emissions' in climate change mitigation?
Answer: To remove greenhouse gases, particularly CO2, directly from the atmosphere.
Explanation: Negative emissions refer to deliberate interventions aimed at removing greenhouse gases, predominantly carbon dioxide, from the atmosphere. These technologies and practices are considered essential in many climate mitigation scenarios to counteract residual emissions and potentially reduce atmospheric concentrations.
Which international agreement aims to phase out the production and use of hydrofluorocarbons (HFCs)?
Answer: The Kigali Amendment
Explanation: The Kigali Amendment, adopted in 2016, is an international agreement specifically designed to phase down the production and consumption of hydrofluorocarbons (HFCs), which are potent greenhouse gases.
What is the NOAA Annual Greenhouse Gas Index (AGGI) a ratio of?
Answer: The total radiative forcing from long-lived GHGs in a given year compared to 1990.
Explanation: The NOAA Annual Greenhouse Gas Index (AGGI) represents the ratio of the total direct radiative forcing from long-lived, well-mixed greenhouse gases in a specific year relative to the forcing recorded in 1990.
What is the primary motivation behind the Montreal Protocol?
Answer: Protecting the ozone layer by phasing out ozone-depleting substances.
Explanation: The primary objective of the Montreal Protocol is the protection of the stratospheric ozone layer through the global phase-out of substances that deplete it, such as chlorofluorocarbons (CFCs). While these substances are also greenhouse gases, the protocol's focus was ozone depletion.
What does the Intergovernmental Panel on Climate Change (IPCC) do?
Answer: Assesses scientific, technical, and socio-economic information relevant to climate change.
Explanation: The Intergovernmental Panel on Climate Change (IPCC) is a United Nations body that assesses the scientific, technical, and socio-economic information pertinent to understanding climate change, its impacts, and potential adaptation and mitigation strategies.
What is the main consequence of the 'enhanced greenhouse effect'?
Answer: Additional warming of the planet's surface.
Explanation: The enhanced greenhouse effect, driven by increased concentrations of anthropogenic greenhouse gases, leads to an intensification of the natural greenhouse effect, resulting in additional warming of the Earth's surface and lower atmosphere.
According to the source, what is the projected timeframe for global warming to surpass 2.0°C if current emission rates continue?
Answer: Between 2040 and 2070
Explanation: The IPCC's projections indicate that if current greenhouse gas emission rates persist, global warming is likely to exceed 2.0°C (3.6°F) within the period of 2040 to 2070.