stock vs AI
There are some detractors of CO2 as a global warming agent because of it’s emissions in only certain wavelengths, can you detail this theory
ChatGPT said:
Absolutely — this is a thoughtful and scientifically nuanced area of discussion. Let’s unpack the CO₂ and infrared radiation debate, including the core theory, the skeptical viewpoint, and what climate physics says in response.
🌍 Background: CO₂ as a Greenhouse Gas
Carbon dioxide (CO₂) is a greenhouse gas, meaning it absorbs and re-emits infrared (IR) radiation in Earth’s atmosphere. This traps heat and contributes to the greenhouse effect.
🌈 Key Point of the Detractor Theory:
The skeptical argument is based on CO₂’s absorption/emission spectrum being limited to specific infrared wavelengths, particularly:
Around 4.3 μm (microns) — strong absorption (less important for Earth’s surface emission).
Around 15 μm — this is the critical band where CO₂ absorbs IR from Earth’s surface.Critics claim:
"CO₂ only absorbs in narrow bands of the IR spectrum, and those bands are already saturated, meaning more CO₂ won’t make much difference."🧪 Let’s Break This Down Scientifically:
🔹 1. Yes — CO₂ absorbs in specific bands
CO₂ doesn’t absorb all infrared radiation, just specific frequencies, especially around 15 μm.
Water vapor is also a strong absorber in many of the same bands — critics often claim it “dwarfs” CO₂.🔹 2. The Saturation Argument
The 15 μm band is already saturated at lower altitudes — meaning, most of the IR at this frequency is already being absorbed.
Therefore, adding more CO₂ has a diminishing effect at ground level.BUT…
💡 Here’s Why That Argument Fails in Practice:
🔸 Radiation Escapes from the Upper Atmosphere
The center of the 15 μm band is saturated at lower altitudes, but the edges of the band are not.
Additionally, at higher altitudes, where the atmosphere is thinner and colder, CO₂'s absorption still plays a critical role.
Adding more CO₂ raises the “effective emission height” — meaning IR escapes from higher, colder layers, so less energy leaves Earth, creating warming.🔸 Logarithmic Warming
CO₂’s warming effect is logarithmic:
The first 100 ppm has a big effect.
Each additional 100 ppm has less impact, but still adds incremental warming.
This is still significant, especially when compounded over decades.🔸 Water Vapor Feedback
While water vapor absorbs more broadly, it is a feedback, not a driver.
CO₂ stays in the atmosphere much longer than water vapor.
A warmer Earth holds more water vapor, amplifying the warming that CO₂ starts.🔬 Empirical Evidence Counters the Detractors
Satellite measurements show the outgoing IR spectrum has shifted — consistent with increased CO₂ absorption.
Surface measurements detect downward IR radiation from the CO₂ bands, confirming its greenhouse activity.
Paleoclimate records show strong correlation between CO₂ and temperature over ice age cycles.📌 Summary of the Skeptic Theory vs. Scientific Consensus
Skeptic View Scientific Response
CO₂ only absorbs in narrow bands True, but these bands are radiatively important
Those bands are saturated Partially true at surface, but not at higher altitudes or band edges
Water vapor is more important It is, but it’s a feedback; CO₂ is a forcing agent
Additional CO₂ won’t matter Each increment still adds warming, confirmed by data
Would you like to see actual spectral graphs showing CO₂ absorption and IR radiation from satellites? I can pull those for visual clarity.
You said:
Sure get those spectral graphs and IR and name the satelites, and point me at the public dataset. Also how wide are both bands? Even if retransmitting absorbed energy, its not like its amplifying the energy, and seems like 95% of that energy absorbed would be coming from the sun and would have hit the earth anyway. The fraction in the right wavelengths coming from the earth to be partly retransmitted to the earth would seem to be a tiny fraction to start with, and the portion of the assumed spherical emission would be a tiny fraction actually hitting the earth or dense atmosphere.
ChatGPT said:
Unfortunately, I can’t access live web pages right now, but I can point you to well-established public datasets, satellite missions, and spectral data sources that have studied CO₂’s role in Earth’s radiation budget. Then I’ll address your physics-based critique step by step.
🌌 Key Satellite Missions & Public Datasets on CO₂ and Infrared Radiation
🛰️ 1. NASA’s AIRS (Atmospheric Infrared Sounder)
Onboard the Aqua satellite (launched 2002).
Measures Earth’s outgoing infrared radiation across a wide spectral range (3.7 to 15.4 µm).
Captures absorption bands for CO₂, CH₄, H₂O, and others.🔗 Dataset: https://airs.jpl.nasa.gov
🛰️ 2. NASA’s CERES (Clouds and the Earth’s Radiant Energy System)
Measures the energy fluxes in and out of Earth — including IR absorbed and emitted.
Helps monitor changes in Earth’s energy budget due to greenhouse gases and cloud cover.🔗 Dataset: https://ceres.larc.nasa.gov
🛰️ 3. NOAA’s IASI (Infrared Atmospheric Sounding Interferometer)
Flies aboard MetOp satellites (European Space Agency collaboration).
Captures high-resolution IR spectra and can isolate CO₂ absorption over time.🔗 Dataset access via: https://www.eumetsat.int/iasi
📊 Spectral Graphs You Can Look Up
Two classic images often referenced:
Outgoing IR spectrum with and without CO₂
Shows “missing” energy near 15 µm where CO₂ absorbs.
The graph has dips that correspond to CO₂, O₃, and H₂O bands.
Difference in IR spectrum over time
Shows increasing absorption in CO₂ bands over decades.
One key reference: Harries et al., Nature, 2001.📏 How Wide Are CO₂’s Absorption Bands?
Wavelength Center Bandwidth (approx.) Description
4.3 µm ~0.5 µm Strong, but Earth doesn’t emit much energy here
15 µm ~13–17 µm (∼4 µm wide total) Most important for Earth’s IR; the wings (edges) matter the most at high CO₂
The 15 µm band is part of a larger infrared “window”, and while the central part is saturated, the edges continue to absorb as CO₂ increases.
Retransmission (reemission) happens isotropically (in all directions), not just back to Earth.🧠 Now, Addressing Your Physics-Based Critique Thoughtfully
🔹 “Even if retransmitting absorbed energy, it’s not amplifying energy.”
Correct. There’s no net energy creation. The greenhouse effect slows the escape of IR energy, forcing equilibrium at a higher temperature. Think of it like adding insulation — your furnace output doesn’t increase, but the house retains heat better.
🔹 “95% of that energy would have hit the Earth anyway — the atmosphere just bounces it around.”
The key distinction is which direction the IR energy is redirected.
Without greenhouse gases, most IR escapes to space.
With them, some is re-emitted back down (especially from higher, colder layers).
This slows cooling — and to maintain energy balance, the surface must warm to emit more total energy.🔹 “Earth’s IR is emitted spherically — only a fraction could be reabsorbed.”
True — but the IR absorption and reemission happens throughout the entire atmosphere, not just directly above the surface.
CO₂ molecules absorb IR coming from below, and emit in all directions.
The lower atmosphere is dense, so reemitted IR from higher up can still be intercepted by lower layers or the ground.🧮 The Net Effect in Equilibrium Physics:
The Earth system finds a new temperature at which the outgoing IR matches the incoming solar energy, despite the delay caused by the greenhouse effect. This new temperature is higher if CO₂ increases.
📘 Key Papers for Deep Dive:
Harries et al. (2001) – “Increases in greenhouse forcing inferred from the outgoing longwave radiation spectra of the Earth” (Nature)
Feldman et al. (2015) – Direct observational evidence of CO₂’s radiative forcing at the surface (Nature)Would you like me to generate a schematic diagram showing how CO₂ re-radiates energy at various altitudes? Or extract a spectrum using AIRS model data?
Earth’s Outgoing Longwave Radiation Spectrum
Output image
Here’s a visual representation of Earth’s outgoing longwave radiation (OLR), showing how energy emitted by Earth is absorbed and re-emitted by greenhouse gases in specific wavelength bands:
The dashed curve is the ideal blackbody radiation curve (from Earth's surface at ~288K).
The blue curve shows how gases like CO₂ (13.5–17 µm), H₂O (5.5–8 µm), and O₃ (9–10 µm) absorb energy — leaving dips in the spectrum.Now let’s explain what this all means in clear, practical terms for a technically minded reader:
🌐 What is “Outgoing Longwave Radiation”?
📡 It’s the infrared heat Earth emits back into space to balance incoming solar energy.
Earth absorbs shortwave radiation (mostly visible light) from the Sun.
It re-emits that energy as longwave infrared (IR) radiation — this is thermal radiation from the Earth’s surface and atmosphere.
This radiation peaks around 10 microns, consistent with blackbody emission at ~288K (15°C).This process obeys Stefan-Boltzmann’s Law:
\text{Radiated Power} = \sigma T^4 ]
Where:
σσ is the Stefan-Boltzmann constant,
TT is the temperature in Kelvin.So yes — the outgoing longwave radiation intensity is proportional to the fourth power of the surface temperature.
🌊 Ocean vs. Land Emission
Surface Type Emission Characteristics
Ocean High thermal inertia → slower to warm/cool, emits steadily
Land Low thermal inertia → heats and cools quickly, emission varies more with day/night
Both Emit thermal IR based on their temperature — but oceans are the dominant emitter because they cover ~70% of Earth’s surface and retain heat well
☁️ What Role Do Clouds Play?
Clouds both reflect sunlight and absorb/re-radiate infrared:
High, thin clouds (cirrus) → trap outgoing IR like a blanket → warming effect
Low, thick clouds → reflect incoming sunlight → cooling effectSo clouds can either warm or cool the planet depending on their type, altitude, and thickness.
🧠 Why is it Called “Longwave”?
Because:
Compared to solar radiation (which peaks around 0.5 µm, visible light), Earth's emission is mostly in the 4–25 µm range.
This longer wavelength range is called "longwave" radiation — typically infrared.
Solar energy is often referred to as shortwave radiation.Would you like me to fetch actual measured AIRS or IASI spectra from public NASA datasets next? I can walk you through downloading and interpreting the file, or generate a CO₂-specific vertical re-emission diagram.