Transparent by Design
Evidence, Method & Limits
This experience calculates one defensible astronomical quantity and says clearly what it cannot predict.
Primary Output
Northern summer sunlight
The Lab shows daily-mean incoming solar radiation at 65°N on the northern summer solstice, at the top of the atmosphere. It is not surface sunlight, local temperature, global temperature, or ice-sheet size.
The calculation uses a total solar irradiance of 1361 W/m² and the standard daily insolation geometry associated with Berger's astronomical formulation.
Calculation
From orbit to daily-mean insolation
ρ = (1 − e²) / (1 + e cos(λ − λₚ))δ = asin(sin ε · sin λ)Q = S₀ / (πρ²) · [H₀ sin φ sin δ + cos φ cos δ sin H₀]Here, φ is latitude, ε is obliquity, λ is solar longitude, ρ is Earth–Sun distance in astronomical units, and H₀ handles day length including polar day and night.
Validated Presets
Exact La2004 nodes
Epochs are relative to J2000.
| Preset | Time | Eccentricity | Obliquity | Perihelion | 65°N Q |
|---|---|---|---|---|---|
| Last Glacial Maximum | -21 kyr | 0.018835429 | 22.964135° | 115.234327° | 469.58 W/m² |
| Mid-Holocene | -6 kyr | 0.018748384 | 24.102440° | 1.407994° | 504.90 W/m² |
| Present Reference | 0 kyr | 0.016702362 | 23.439291° | 102.917945° | 477.94 W/m² |
| 50,000 Years From Now | +50 kyr | 0.010533999 | 22.522019° | 21.081862° | 474.87 W/m² |
What the Model Does Not Do
Orbital tendency is not climate destiny
The ±5 W/m² wording in the Lab is a display deadband, not a physical tipping point. It only summarizes whether orbital summer-melt pressure is lower, similar, or higher than the present reference.
Existing ice, snowfall, oceans, greenhouse gases, vegetation, dust, geography, and long response times determine the actual climate response. The +50 kyr preset is orbital geometry—not a climate forecast.
Primary References
Read the source material
Ready to test the geometry?
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