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Focus Topic 1
Past and Future Climate Cycles
| Question | Answer |
|---|---|
| Absorption | Earth absorbs 70% of radiation, so must lose 70% to remain stable (GHGs cause an imbalance) |
| What drives the Earth's climate system | heating imbalance between the poles + equator higher light intensity @ poles -> radiation spread over large area, hotter @ equator as radiation is focused on a small area less reflective surfaces @ equator, so radiation is absorbed more |
| Seasonal Changes in Solar Radiation | earth's tilt and rotation (changing position from the sun) Differential heating (water heats up less than land because of mixing) |
| Heat Transfer | Sensible: heat you can feel/sense (solar radiation warms surface, air molecules move faster when warmed which creates fast rising thermals) Latent heat: water (evaporation of, storage of heat in water vapour + release by condensation and precipitation) |
| atmospheric circulation | hadley cells: tropical circulation patterns (transfer of heat from the equator -> poles) Monsoons: seasonal heat transfers (tropical ocean -> land). build up of moisture = heavy rain |
| Surface ocean circulation | currents out of tropics to poles = heat polewards currents away from poles = cold water to the equator |
| Why wasn't earth frozen when sun was 30% weaker? | more volcanos + hot springs = more CO2 less chemical weathering = more CO2 earth had less O2, so more CH4 more volatile sun + higher frequency of solar flares |
| Thermostat Effect | Warmer climate -> higher temperature, precipitation, vegetation -> higher chemical weathering -> more CO2 removal -> reduction of initial warming (reversed if cooler climate) |
| Cause of glaciations in the last 500 million years | 1. Polar position: glaciation when continents were at poles 2. seafloor spreading + volcanism: rates were faster which changed the amount of CO2 put into the atmosphere 3. Uplift weathering ("fresh" rock to be weathered) |
| Major Cause of Ice Ages in the past 55 million years | Earth has been cooling for the past 55 million years (India bumped into Asia, increasing chemical weathering, decreasing CO2) |
| Milankovitch Cycles (1) | 1. Earth's Tilt Cycle (causes our seasons) -> varies between 22.1 and 24.5 degrees every 41,000 years (more tilt = higher solar radiation at poles in summer) |
| Milankovitch Cycles (2) | 2. Eccentricity Cycle (shape of earth's orbit) -> larger level of "ellipticalness". when earth is closer to the sun, stronger radiation = hotter (~100,000) |
| Milankovitch Cycles (3) | 3. Precession of the Equinoxes Cycles: "wobble" (axial precession), date when closer to the sun changes (23,000 years) |
| Insolation | radiation arriving at the top of earth's atmosphere (influenced by tilt, precession and eccentricity) Insolation controls monsoons |
| Milankovitch Theory | ice sheets grow in the N. Hemisphere when summer insolation is low (tilt is small, Earth is further from the sun). Ice melts when summer insolation is high |
| Lag | Peaks lag in all cycles because land and oceans take time to store and release the suns heat |
| Why 100,000 year cycles now? | Further tectonic cooling meant Earth reached the glaciation threshold more often. This overall cooling world meant ice-sheets could only partially melt during solar maxima (therefore, build-up further beyond 41,000 year cycles (>albedo, <CO2) |
| The Last Glacial Maximum | 20,000 years ago, sea level was 120m lower, ice cover was 25% compared to 10% now Deglaciation occurred due to higher solar summer radiation in the N. Hemisphere, loss of ice-sheets and higher CO2 (due to humans and agriculture) |
| The Last 1000 years | Medieval warm period + little ice age (no development of icesheets) Short term oscillations - El Niño (interrupts pacific circulation due to no strong S winds. Ocean stays warm, no upwelling, no nutrients, more evaporation, more rain) |
| Present + Future CC | should be heading towards another ice age, but instead is warming. CO2, CH4, volatile organic compounds, halogenated gases (cause warming in troposphere) |
Created by:
mishm
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