ASUx31s Climate Change, Energy and Water Issues Fall 2024 PDF

ASUx31s Climate Change, Energy and Water Issues Fall 2024 Presented by Assistant Prof. Ahmed M. Abdulmohsen Lecture 1: Introduction to Global Climate and the Greenhouse Effect A deep dive into Earth's natural and enhanced warm...

ASUx31s Climate Change, Energy and Water Issues Fall 2024 Presented by Assistant Prof. Ahmed M. Abdulmohsen Lecture 1: Introduction to Global Climate and the Greenhouse Effect A deep dive into Earth's natural and enhanced warming 2 Outlines: Introduction to the Global Climate System Composition of the Atmosphere The Greenhouse Effect Energy Balance and Earth's Climate Mathematical Representation of the Greenhouse Effect Examples 3  Introduction to the Global Climate System Climate refers to the long-term patterns of temperature, humidity, wind, etc., in a region, while weather refers to short-term variations. Earth’s climate is influenced by both external forces (e.g., solar radiation) and internal interactions (e.g., oceans, atmosphere, land). The Earth-atmosphere system regulates the balance between incoming energy from the Sun and outgoing energy back to space. 4  Introduction to the Global Climate System Key Concepts: The Earth’s climate system is powered by energy from the Sun, and this energy is distributed around the planet, creating different climate zones (tropical, temperate, polar). Solar radiation is absorbed by Earth’s surface, and some of this energy is re-radiated as infrared radiation (heat), which is partially trapped by greenhouse gases. 5  Composition of Atmosphere The atmosphere consists of: Nitrogen (N₂): ~78% Oxygen (O₂): ~21% Argon (Ar): ~0.93% Carbon Dioxide (CO₂): ~0.04% (but a key contributor to the greenhouse effect) Trace gases: Methane (CH₄), Nitrous oxide (N₂O), Ozone (O₃), and Water vapor (H₂O). These gases play a crucial role in maintaining Earth’s temperature by trapping some of the outgoing infrared radiation. 6  The Greenhouse effect “The greenhouse effect is the process by which certain gases (known as greenhouse gases) in Earth's atmosphere trap heat, preventing it from escaping into space and keeping the planet warm” Steps of the Greenhouse Effect: 1. Solar radiation passes through the atmosphere and reaches the Earth's surface. 2. The Earth's surface absorbs this solar energy and re-radiates it as infrared radiation (heat). 3. Greenhouse gases (CO₂, CH₄, N₂O, H₂O vapor) absorb some of the infrared radiation, warming the atmosphere. 4. The atmosphere re-radiates the heat back toward the Earth's surface, maintaining a temperature that supports life. 7  The Greenhouse effect “The greenhouse effect is the process by which certain gases (known as greenhouse gases) in Earth's atmosphere trap heat, preventing it from escaping into space and keeping the planet warm” 8  The Greenhouse effect Natural vs. Enhanced Greenhouse Enhanced greenhouse Natural greenhouse effect effect Human activities, such as Without greenhouse burning fossil fuels, gases, the Earth would be increase the concentration approximately 33°C of greenhouse gases, colder. enhancing the greenhouse effect and causing global warming. 9  The Greenhouse effect Natural vs. Enhanced Greenhouse Natural Enhanced greenhouse greenhouse effect effect 10  Energy balance and the earth’s climate The energy balance on Earth can be expressed as: 𝑰𝒊𝒏 = 𝑰𝒐𝒖𝒕 Where: 𝐼𝑖𝑛 ≡ 𝑡ℎ𝑒 𝑖𝑛𝑐𝑜𝑚𝑖𝑛𝑔 (𝑎𝑏𝑠𝑜𝑟𝑏𝑒𝑑) 𝑠𝑜𝑙𝑎𝑟 𝑟𝑎𝑑𝑖𝑎𝑡𝑖𝑜𝑛𝑠 𝐼𝑜𝑢𝑡 ≡ 𝑡ℎ𝑒 𝑜𝑢𝑡𝑔𝑜𝑖𝑛𝑔 𝑖𝑛𝑓𝑟𝑎𝑟𝑒𝑑 𝑟𝑎𝑑𝑖𝑎𝑡𝑖𝑜𝑛𝑠 Hence, if : 𝑰𝒊𝒏 > 𝑰𝒐𝒖𝒕 −→ 𝒕𝒉𝒆 𝒑𝒍𝒂𝒏𝒆𝒕 𝒘𝒊𝒍𝒍 𝒘𝒂𝒓𝒎 𝒍𝒆𝒂𝒅𝒊𝒏𝒈 𝒕𝒐 𝒈𝒍𝒐𝒃𝒂𝒍 𝒘𝒂𝒓𝒎𝒊𝒏𝒈 𝑰𝒊𝒏 < 𝑰𝒐𝒖𝒕 −→ 𝒕𝒉𝒆 𝒑𝒍𝒂𝒏𝒆𝒕 𝒘𝒊𝒍𝒍 𝑪𝒐𝒐𝒍 11  Mathematical representation of greenhouse effect A simplified model of the Earth's energy balance involves calculating the effective radiating temperature (Tₑ) using Stefan-Boltzmann Law: 𝑰𝒐𝒖𝒕 = 𝝈 𝑻𝟒𝒆 Where: 𝑊𝑎𝑡𝑡 𝐼𝑜𝑢𝑡 ≡ 𝑡ℎ𝑒 𝑜𝑢𝑡𝑔𝑜𝑖𝑛𝑔 𝑖𝑛𝑓𝑟𝑎𝑟𝑒𝑑 𝑟𝑎𝑑𝑖𝑎𝑡𝑖𝑜𝑛𝑠 𝑖𝑛 ( 2 ) 𝑚 𝜎 ≡ 𝑆𝑡𝑒𝑓𝑎𝑛 − 𝐵𝑜𝑙𝑡𝑧𝑚𝑎𝑛𝑛 𝑐𝑜𝑛𝑠𝑡𝑎𝑛𝑡 = 5.67 × 10−8 𝑊/(𝑚2 𝐾 4 ) 𝑇𝑒 ≡ 𝑡ℎ𝑒 𝑡𝑒𝑚𝑝𝑟𝑎𝑡𝑢𝑟𝑒 𝑖𝑛 𝐾𝑒𝑙𝑣𝑖𝑛 𝐾 12  Mathematical representation of greenhouse effect As for the absorbed radiations from the sun we have: The Solar constant S (the average solar energy received per square meter at the top of the atmosphere) 𝟐 𝑺 = 𝟏𝟑𝟔𝟏 𝑾𝒂𝒕𝒕/𝒎 But The planetary albedo α(reflectivity of Earth) is about 0.3. Then the amount of solar energy absorbed by the Earth would be 𝑺(𝟏 − 𝜶) 𝑰𝒊𝒏 = 𝟒 The factor 4 accounts for the distribution of solar energy across the entire surface of a spherical Earth. 13  Mathematical representation of greenhouse effect Finally, to find Earth's equilibrium temperature 𝑰𝒊𝒏 = 𝑰𝒐𝒖𝒕 𝑺(𝟏 − 𝜶) 𝝈 𝑻𝟒𝒆 = 𝟒 𝟒 𝑺(𝟏 − 𝜶) Then 𝑻𝒆 = 𝟒𝝈 14  Example: calculating the earth’s Temperature Calculate the Earth’s average radiating temperature and compare it to the actual temperature of 288 Kelvin 4 𝑆(1 − 𝛼) 4 1361(1 − 0.3) 𝑇𝑒 = = −8 = 255 𝐾𝑒𝑙𝑣𝑖𝑛 4𝜎 4 × 5.67 × 10 Then the Earth’s warming due to greenhouse effect would be ∆𝑇 = 𝑇𝑎𝑐𝑡𝑢𝑎𝑙 − 𝑇𝑒 = 288 − 255 = 33 𝑑𝑒𝑔𝑟𝑒𝑒 15  Impact of Increased Greenhouse gases on Earth's Energy Balance Enhanced Greenhouse Effect: Higher greenhouse gases levels increase the greenhouse effect by trapping more outgoing infrared radiation. Energy Imbalance: The increased absorption of IR radiation leads to​, causing an energy imbalance. 𝑰𝒊𝒏 > 𝑰𝒐𝒖𝒕 Temperature Increase: To restore balance, Earth's surface temperature rises until 𝑰𝒐𝒖𝒕 increases enough (via Stefan-Boltzmann Law) to match 𝑰𝒊𝒏 16  Conclusion To conclude today’s Lecture The natural greenhouse effect is essential for maintaining life- supporting temperatures on Earth. However, human activities have enhanced this effect, leading to global warming. Understanding the energy balance and greenhouse gases' role is key to addressing climate change 17  End of lecture 1 Thanks for your Attention Any Questions Assistant prof. Ahmed M. Abdulmohsen [email protected]