week 1 Flashcards
(16 cards)
- Define greenhouse gases
-GHGs = key compounds and molecules that drive the climate change we are seeing today
-trace gases including GHGs make up less than 0.1% of atmosphere
-include CO2 (most significant due to human activities), CH4 (methane), N2O (nitrous oxide), ozone (also important) and halogenated species
1b. Explain GHGs role in global warming
-primarily because of their contribution to radiative forcing
-have the largest warming impact on the Earth (largest positive radiative forcing- CO2 being the largest out of them)
-downwelling radiation from the absorption by greenhouse gases is largely what is driving the net absorption of energy in the atmosphere= hence warming
-increasing emission of the GHGs shows strong positive correlations with temperature seen at the surface of Earth
-anthropogenic activities are leading to increased concentrations that are now the highest in millions of years (CO2)
- What are aerosols? How do they influence Earth’s climate?
-aerosols= particles in the atmosphere such as those released from volcanoes, also key components of particulate matter like organic carbon, nitrate and sulfate.
-usually have a cooling effect on the atmosphere
-contribute a negative radiative forcing
-level of scientific understanding for aerosols has large uncertainties (compared to GHGs, ozone etc)
-lifetime of aerosols is much lower than GHGs so impact is more continental
-bad for our health
-reducing the components of particulate matter (aerosols) has major health benefits, but it results in a “climate penalty” as we lose some of these previous offsets to warming
- How does air pollution exacerbate the effects of climate change?
-air pollution and climate change are closely linked and their effects can exacerbate each other
-extreme heat increases number of wildfires=release large amounts of pollutant gases and aerosols in the atmosphere (such as black carbon, NOx and hydrogen cyanide)= detrimental effects on air quality and health
-extreme heat=increase pollution levels directly=exacerbates health effects of breathing pollutant air
-anthropogenic activities (burning fossil fuels for cars, electricity or industry)= produce air pollutants like CO2 and methane.
- Explain the term “radiative forcing” and its relevance to climate science.
-radiative forcing (term set by IPCC)= defines what processes and what compounds are warming the atmosphere and what are cooling it
-i.e represents the change in balance between incoming solar radiation and outgoing infrared radiation from Earth’s atmosphere
-positive radiative forcing= warming (GHGs)
-negative forcing= cooling (aerosols)
- Describe how heatwaves influence the severity of air pollution.
-Warmer air can hold more water, leading to a more intense hydrological cycle, which can result in more evaporation and droughts, further contributing to conditions that can lead to wildfires.
-wildfires release significant amounts of polluting gases and particulate natter in the atmosphere
- Using examples, explain the difference between short-lived and long-lived climate forcers.
-Atmospheric compounds have different lifetimes depending on the type of molecule
-determines how well-mixed they are across Earth
Short lived:
-very short lifetimes
-e.g OH radical- drives oxidation and reacts with almost anything- lasts only on the order of a couple of seconds after its produced
-spatial scale is more continental
-e.g aerosols- much lower lifetime than GHGs
Long lived:
-lasts much longer in the atmosphere
-e.g CFCs, N2O, methane…
-these gases can last up to 100 years in the atmosphere
-have lasting effects on climate
-much more homogenous across the surface of the Earth
- Analyse the role of anthropogenic activities in increasing the frequency of extreme weather events.
Observational evidence shows that climate change has led to:
-longer wildfire seasons, increased frequency, and larger burned areas
-linked to warmer springs
-longer summer dry seasons
-drier soils
-reduced snowpack
-earlier spring melting
-number of reported weather-related disasters, such as droughts, extreme temperatures, flooding, landslides, storms, and wildfires, has increased significantly, by about a factor of five, from the period 1970-1980 up to the present day
-observed rate of change in temperature is unprecedented over the last thousand years- driven by the huge increases in CO₂ concentrations since the 1950s
- Interpret a graph showing CO₂ concentrations over the past century and discuss its implications.
-a figure showing that CO₂ concentrations have gone from something like 280 ppm in pre-industrial times all the way up to 400 ppm currently, with a particularly rapid increase over the last 30 to 40 years
-shows CO₂ concentrations over the last 800,000 years, made up of proxy measurements, indicating repeated concentrations around 220 ppm
-since the 1950s, there have been huge increases to around 400 ppm
-implication is that this dramatic increase in CO₂ concentrations, linked to anthropogenic emissions, is what is driving the temperature increase that has been observed
- Identify the main contributors to current warming trends.
-Carbon dioxide (CO₂) has the largest radiative forcing, contributing significantly to warming
-significant long-lived greenhouse gases contributing to warming include methane (CH₄) and nitrous oxide (N₂O), along with other hydrocarbons
-Anthropogenic activities are the primary drivers of greenhouse gas emissions and the primary source of the positive radiative forcing that is driving global warming
- If a country implements policies to reduce methane emissions, what immediate climate benefits might result?
-reducing emissions now would prevent future lasting effects
-methane has a shorter lifetime than CO₂, implying that a reduction in emissions would lead to a concentration decrease and reduced warming impact faster than an equivalent reduction in CO₂ emissions might, though not instantaneously.
- Propose a strategy to simultaneously improve air quality and combat climate change.
-Reducing emissions from sources like cars, power generation, and industry can decrease both greenhouse gases (like CO₂) and air pollutants (like VOCs and NOx)
-Reducing precursors like NOx and VOCs can lead to a concurrent reduction in tropospheric ozone, which is beneficial for climate (as ozone is a greenhouse gas), air quality (as ozone is a respiratory irritant), and crop yields
-complexity: while reducing particulate matter (aerosols) improves health, it also removes a cooling effect that has offset some warming, potentially leading to a “climate penalty”
-a comprehensive strategy would focus on reducing the emissions of substances that are clearly detrimental to both, while carefully considering the full climate implications of reducing aerosols.
- How do deforestation and land-use changes contribute to global climate change?
-one of the primary drivers of greenhouse gas emissions
- Describe the feedback mechanisms in the climate system, such as the ice-albedo effect and the water vapour feedback.
- Discuss the significance of the 1.5°C and 2°C warming thresholds for global climate policy and impacts.
- 1.5°C warming threshold is described as incredibly important and a target set out by the IPCC
-2024 was the first year this limit was exceeded for a full year at an annual average
-even a relatively small increase in temperature, such as the 0.5°C increase over the last 50 years, has been associated with a massive increase in weather-related disasters
-as global warming increases to 1.5°C and 2°C, the level of risk for large scale events, aggregate impacts, and different impacts of global warming increases significantly and quickly
-achieving these targets is projected to require negative greenhouse gas emissions, in addition to massive reductions in current emissions
-current policies in place are not sufficient to meet the target of 1.5°C warming by 2021
- Examine how global climate models (GCMs) are used to project future climate scenarios and their limitations.
-Global climate models (GCMs) are a large part of the work done in atmospheric sciences
-are essentially simple lines of code that build up to a clear picture of what is happening across the Earth
-involves running a GCM for many decades with no external forcing to assess its performance against observations. The model is then re-run with changes in forcing, such as greenhouse radiative forcing. The difference between the two climates provides an estimate of the climate change arising from that forcing factor
-field studies are very often used to validate models
-without significant mitigation, models project 4 to 8 degrees of warming by 2100; with current policies, 2.8 to 3 degrees; and with currently negotiated targets, 2.5 to 2.8 degrees
-level of scientific understanding varies for different climate processes, with uncertainties increasing for things like aerosol effects compared to long-lived greenhouse gases- suggests that accurately modelling processes with lower scientific understanding could be a limitation.
-development of machine learning in models is mentioned as an active area of research, suggesting ongoing efforts to improve modelling capabilities
