Earth and space science summary

Astronomy: Hertzsprung-Russell Diagram and Magnitude

• H-R Diagram: relates a star's temperature, color, and absolute magnitude.
• Temperature/color: hotter stars are blue/white; cooler stars are yellow/orange/red.
• Spectral classes: B, A, F, K, M, spanning roughly a few thousand to $~30,000\text{ K}$. Blue → White → Yellow → Orange → Red.

Climate Change and Carbon Cycle

• CO2e projections for 2100: $795 \text{ to } 805\ \text{tCO}_2\text{e}$.
• Projected global surface temperature change: $2.4^\circ\text{C}$.
• Trees absorb CO2 via photosynthesis; reforestation reduces atmospheric CO2.

Solar Activity and Orbital Mechanics (conceptual notes)

• Sunspot counts vary in $~11$-year cycles.
• Solar output fluctuations can influence climate.

Geography, Hydrology, and Water Resources

• Freshwater input affects salinity in river estuaries (saltfront may move closer to the Atlantic).
• Saltwater intrusion can compromise drinking water quality.

Pollution and Environmental Monitoring

• PCBs in fish: levels may remain above EPA targets (e.g., $0.7\ \text{mg/kg}$).

Geology, Radiometric Dating, and Earth's Age

• Age of Earth: about $4.5\text{ billion years}$, supported by meteorite dating.
• Uranium-238 dating: ~50% remaining indicates an age of roughly $4.5\ \text{Ga}$ for samples aligning with Earth’s age.

Oceanography and Atmospheric Evolution

• Ocean photosynthetic life released oxygen, contributing to higher atmospheric oxygen levels and enabling animal evolution.

Transportation, Emissions, and Energy Choices

• BEV CO2e: $41\ \text{tCO}<em>2\text{e}$; Hybrid: $48\ \text{tCO}</em>2\text{e}$; ICE: $57\ \text{tCO}_2\text{e}$.
• BEVs generally have lower total emissions over their lifetime than ICE vehicles.

Economics, Policy, and Society

• Off-peak driving incentives (e.g., Green Pass) offer economic benefits and societal improvements (e.g., toll savings, emissions reductions).

Natural Resources and Environmental Impacts

• Freshwater: saltwater intrusion degrades drinking water quality; requires filtration or alternative sources.
• Wood/timber: saltwater intrusion can kill trees in freshwater wetlands, reducing lumber supply.

Temporal Scales: Land Subsidence and Ghost Forests

• Earthquakes: land subsidence occurs over seconds to hours.
• Ghost forests (subsidence-related): develop over years to centuries, much longer than earthquakes.

Habitat, Ecology, and Wildlife Management

• Thornbush proliferation limits predator hunting (e.g., cheetahs).
• Removing thornbush (e.g., via bushblok) improves hunting habitat for cheetahs.

Additional Notes on Climate and Ecosystem Interactions

• Photosynthesis in oceanic microorganisms oxygenated the atmosphere, facilitating diverse life and supporting the evolution of complex ecosystems.