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Xha’Ruun

Chapter 29: Climatic History of Théxar

"Ice remembers everything. Each layer — a year, each bubble — a breath of the ancient atmosphere. Reading the ice, we read time." — Glaciologist Ven-Shar, +3 800 E.U.

Eccentricity, axial tilt and precession change irradiation across latitudes and seasons. The climate response also depends on oceans, ice and atmospheric composition.

The edge of the polar ice sheet
The edge of the polar ice sheet

29.1 Paleoclimatic Methods

Method Resolution Depth (cycles back) Reliability
Ice cores (southern sheet) 1 cycle up to 500 thousand High
Tree rings (Mor-Ven) 1 cycle up to 12 thousand Very high
Lake sediments 10–100 cycles up to 50 million Moderate
Isotopes δ¹⁸O, δD 1 000 cycles up to 500 million Moderate
Paleosols 10 000 cycles up to 200 million Low

29.1.1 Ice Cores

Deepest borehole — Ven-Deep (southern sheet, 4 390 sha). Core contains ~500 thousand cycle layers.

Depth (sha) Age (cycles) Information
0–610 0–50 thousand Current interglacial, anthropocene
610–2 200 50 thousand–200 thousand Last glaciation
2 200–3 410 200 thousand–350 thousand Ven-Mor interglacial
3 410–4 390 350 thousand–500 thousand Penultimate glaciation

29.2 Climatic Cycles

29.2.1 Orbital Cycles (Kharak Cycles)

Cycle Cause
Orbital eccentricity Change in orbit shape
Axial tilt Nutation
Precession Equinox drift

Eccentricity, axial tilt and precession change irradiation across latitudes and seasons. The climate response also depends on oceans, ice and atmospheric composition.

29.2.2 Climate Curve (500 thousand cycles)

Climate curve of Théxar

Climate curve of Théxar

AxisScale marks
T anomaly (°X)+1.1; 0; −1.1; −2.2; −3.3
Thousand cycles ago500; 400; 300; 200; 100; present
  • Start of profile

    −3.3 °X

  • Repeated rises

    Upper peaks reach approximately +1.1 °X.

  • Repeated falls

    Lower troughs reach approximately −2.2 °X.

Rises and falls alternate.

Fig. 29.1. Climate curve of Théxar over 500 thousand cycles.

29.2.3 Interglacials

Interglacial T Peak Duration When (c.a.) Feature
Current +51.6°X ~12 thousand cycles 0 — present Xha'Ruun civilization
Ven-Mor +51.3°X 18 thousand cycles 125 thousand High ocean level
Khal-Ven +51.0°X 22 thousand cycles 240 thousand Stable climate
Thal-Mor +51.2°X 16 thousand cycles 350 thousand Rapid warming
Ven-Khal +50.8°X 20 thousand cycles 460 thousand Weak interglacial

29.3 Major Climatic Events

29.3.1 Volcanic Winters

Event Time VEI T Drop Duration
Tor-Ven (supervolcano) ~8 thousand c.a. 7.2 −1.7°X 5 cycles
Raal eruption ~48 thousand c.a. 8.1 −3.2°X 8 cycles
Irkhen Chain +3 890 E.U. 6.8 −0.8°X 2 cycles

29.3.2 Glaciations

Glaciation Time Duration Max. Cover T Drop
First (Great) 3.2–3.0 billion c.a. 200 million cycles 45% −4.4°X
Second (Kharak) 2.1–1.9 billion c.a. 200 million cycles 38% −3.3°X
Third (Rhuval) 0.8–0.6 billion c.a. 200 million cycles 32% −2.7°X
Last (maximum) 32 thousand c.a. — 24% −2.8°X

All three major glaciations are associated with periods of reduced volcanic activity and falling CO₂.

29.4 CO₂ and Temperature

29.4.1 CO₂ — Temperature Relationship

Correlation between CO₂ and T over 500 thousand cycles (from ice cores):

Epoch CO₂ (ppm) T Anomaly CO₂ Source
Interglacial (current) 8 000 +0.0°X Volcanism + biota
Interglacial (Ven-Mor) 7 500 −0.3°X Volcanism
Glacial (max.) 5 200 −2.8°X Minimum volcanism
After Tor-Ven eruption 9 200 +0.7°X Volcanic emission

29.4.2 Equilibrium Greenhouse Effect

At a stellar luminosity of 0.41 L☉ and a distance of 0.63209 AU, the flux at Théxar’s orbit is about 1.026 times Earth’s solar constant. Surface temperature also depends on reflection, atmosphere, clouds and ocean heat transport.

29.5 Modern Changes

Over the last 500 cycles, Théxar's average temperature has risen by +0.2°X.

Period T Anomaly Cause
3 520–3 700 −0.2°X Mini-ice age phase
3 700–3 900 +0.05°X Exit from mini-ice age
3 900–4 028 +0.2°X Natural variation

Observed warming is assessed through several independent records. A small energy-sector share in gross carbon flux does not by itself determine civilisation’s contribution: changes in reservoirs, land use and feedbacks also matter.

Chapter Summary

    Eccentricity, axial tilt and precession change irradiation across latitudes and seasons. The climate response also depends on oceans, ice and atmospheric composition.

  1. The last glaciation reached its maximum 32 thousand cycles ago.

    2. Eccentricity, axial tilt and precession change irradiation across latitudes and seasons. The climate response also depends on oceans, ice and atmospheric composition.

  2. Over the last 500 cycles: warming of +0.2°X (natural).
  3. Equilibrium greenhouse effect maintains CO₂ at 8 000 ppm.
  4. Ice cores: continuous record over 500 thousand cycles.