Week 5 Flashcards
(19 cards)
What is radiative forcing? Include calculations
-defined as the change in the radiation balance at the tropopause between the incoming solar radiation and the outgoing Earth’s radiation
-also referred to as net irradiance
-A positive forcing warms the climate system, while a negative forcing cools it
A simple formula for calculating radiative forcing (ΔF) due to changes in greenhouse gases, as suggested in the IPCC AR4, is: ΔF = α * ln (C(t) / C0) where:
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ΔF is the radiative forcing in W/m².
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α is a constant that differs for each greenhouse gas.
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C0 is the concentration at the start time.
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C(t) is the concentration at a later time. For CO2, α is equal to 5.35. For CH4, α is about 0.525, and for N2O, it is about 0.590. These are approximations, plus or minus 10 percent.
What is Effective Radiative Forcing?
defined as the net downward radiative flux at the top of the atmosphere after allowing for atmospheric temperature, water vapour, and clouds to adjust, but with the surface temperature or a portion of surface conditions unchanged
-considered a more accurate predictor of the temperature response
Briefly discuss contributions to future warming
Future warming would be relatively straightforward to calculate if only the radiative impacts of greenhouse gases contributed. However, the climate system is much more complex due to numerous feedbacks and interactions
What are feedback mechanisms? Distinguish between positive and negative feedback with examples
Feedback mechanisms are processes within the climate system that respond to an initial climate change and then either amplify or dampen that change
Positive:
-where an initial change in the system results in further changes that amplify and reinforce the initial change
-example: ice-albedo effect, water vapour feedback, ocean CO2 solubility
Negative:
where an initial change in the system is counteracted by another process, diminishing the initial change
-examples: increased plant growth, cloud feedback
What is the role of the cloud in warming or cooling of the atmosphere?
ll clouds scatter incoming shortwave solar radiation, which has a cooling effect (increasing albedo).
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All clouds emit longwave radiation at their cloud top temperature.
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Clouds also intercept and absorb longwave radiation from below.
The net effect depends on the cloud’s altitude and properties
low clouds= cooling because warm tops and high albedo reflecting more incoming shortwave radiation back to space than the outgoing longwave radiation they trap
high clouds= warming because they have cold tops and are better at absorbing outgoing longwave radiation from below (greenhouse effect) than they are at reflecting incoming solar radiation
other factors include:
-loud optical thickness: In a warmer world, clouds can become optically thinner (allowing more radiation through) or thicker (blocking more sunlight)
-Cloud lifetime and precipitation: A warmer atmosphere potentially increases cloud lifetimes and alters precipitation
cent models suggest that, on average, cloud feedbacks are likely to be positive-uncertainty remains high
How do modern climate models operate?
-simulate and predict climate change
-concept of radiative forcing is central to these models
-These models incorporate various factors, including anthropogenic (man-made) emissions and natural emissions and responses, trying to take into account as many positive and negative effects as possible
State what the geoengineering techniques are
Geoengineering refers to large-scale interventions in the Earth’s climate system to counteract climate change
2 general approaches:
1.Carbon capture from the atmosphere
2.Solar management techniques
How does geoengineering by clouds work?
-cloud seeding, is a solar management technique aimed at increasing the cloud’s albedo to reflect more shortwave incoming sunlight back to space, thereby causing cooling
by seeding clouds with lots of Cloud Condensation Nuclei (CCN), you increase the number of droplets in the cloud. If the amount of water vapour remains the same, this means the droplets will be much smaller on average, but their total surface area is larger compared to fewer, larger droplets formed naturally. More numerous, smaller droplets make the cloud more reflective, increasing its albedo
study by Slingo in the late 1990s suggested that to compensate for the radiative forcing of CO2 doubling, the number of droplets in ocean clouds would need to increase by at least 120%
What is the historical perspective on clouds?
Humans have already been affecting clouds indirectly for many decades. For example, ship tracks seen in satellite photographs are evidence of this
How does variation in solar constant affect our climate?
Changes in the Earth’s orbit around the Sun, known as Milankovitch cycles, are responsible for altering the total and seasonal solar radiation received by the Earth and are linked to the comings and goings of ice ages
However, the warming seen in recent decades is far too rapid to be linked to changes in the Earth’s orbit and much too large to be caused by solar activity changes alone
How does geoengineering by seeding boundary layer cloud work?
- Take some seawater.
- Convert it into very small droplets.
- Introduce these tiny droplets near the ocean surface.
- As the droplets ascend via thermals, they evaporate, leaving behind tiny salt particles (sodium chloride).
- Sodium chloride particles act as very good CCN.
- These particles enter the clouds and increase the number of droplets within the cloud
How is sea ice affected by global warming and geoengineering? State evidence
Climate models projecting a doubling of CO2 show a significant reduction in sea ice fraction, potentially down to a 50% reduction in some places, which could open up ship pathways in the Arctic Ocean
- studies like Rasch et al., 2009, suggests that if clouds were seeded, the ice coverage could return due to the cooling impacts
-but it could be possible to OVERDO it leading to unintended consequences related to cloud lifetime
How has precipitation changed from geoengineering + CO2 doubling? State evidence
Early studies indicated that some regions, particularly South America, South Africa, and India, might suffer significantly from decreased precipitation. Another study by Jones et al. (who worked at the University of Manchester) also showed similar changes, highlighting South America as a region that could be particularly impacted by decreased precipitation
What is Latham’s geoengineering scheme?
John Latham’s geoengineering scheme is the proposal to increase the albedo of marine stratocumulus clouds by introducing natural sea salt particles into the boundary layer over the oceans
-using robot ships to spray seawater droplets upwards, which evaporate and leave behind sodium chloride particles that act as CCN
How can solar management through geoengineering work?
- Aerosol injection into the stratosphere: This technique involves pumping aerosols (like sulphate aerosols) into the stratosphere to simulate the cooling effect of volcanic emissions:
-stay there for a long time due to strong winds and lack of precipitation
-major drawback is that it’s hard to switch off if the effects become detrimental - Mirrors in space: This involves placing satellites with mirrors in space to physically reflect incoming radiation before it reaches the Earth
-reduces incoming solar radiation and causes cooling. However, it is considered very, very expensive and hard to stop
ainting deserts white: This involves increasing the albedo of large areas of deserts, particularly near equatorial regions where most solar radiation comes in
-cheaper than space mirrors or stratospheric aerosols, it is harder to stop than cloud seeding
What is carbon sequestration and how does it work?
Carbon sequestration (CS) refers to techniques that remove carbon (specifically CO2) from the atmosphere.
one form is Direct Air Capture (DAC), where carbon emissions are captured directly from the air then can be:
-Moved directly to permanent underground storage. This process is known as Carbon Capture and Storage (CSS)
OR
-Used in another industrial application prior to storage. This is called Carbon Capture Utilisation and Storage (CCUS)
What are the problems and risks associated with CSS/CCUS?
High cost and energy inefficiency
Potential for leaks from storage sites
Unpredictable geological reactions when injecting CO2 underground
Concerns about safety and monitoring of the storage sites.
Potential for leaks to contaminate groundwater and soil on land.
CO2 injections can potentially cause local earthquakes
Concerns that CCUS might be used to justify continued fossil fuel use,
Has carbon capture been succesful so far?
A detailed analysis in 2022 by the International Energy Economics and Financial Analysis (IEEFA) concluded that, while CCS might play a role in hard-to-abate sectors like cement, fertilisers, and steel, overall results indicate a financial, technical, and emissions-reduction framework that continues to overstate and underperform
However, the technology is expected to improve to address some of these issues
What if we fail to correct anthropogenic climate warming?
This led to O’Neill’s concept of Space Habitats (sometimes called Island 3). He argued that the “space-colonization technique” had enormous power and, if used wisely and soon enough, could help solve “at least five of the most serious problems now facing the world without recourse to repression”. These problems included:
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Raising the global living standard.
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Protecting the biosphere from pollution.
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Finding high-quality living space for a growing population.
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Finding clean, practical energy sources.
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Preventing overload of Earth’s heat balance (i.e., climate change).
The idea involved building massive rotating cylinders in space, placed at gravitational balance points between the Earth and the Moon. These cylinders would generate artificial gravity through rotation, have large windows for sunlight, and be powered by solar panels. While engineers studied the technical feasibility in detail, the main problems were the extremely high cost and finding materials (potentially through mining the moon)
