89 The Greenhouse and Other Effects

Earth’s temperature depends on three things:

  • Amount of sunlight received

    • Most is ultraviolet with short wavelength

    • About 2/3 is absorbed to warm the atmosphere

  • Amount of sunlight reflected

    • Mostly reflected as infrared radiation

  • Degree to which the atmosphere retains heat

    • •Water vapor, carbon dioxide, methane, nitrous oxides, and halocarbons absorb IR radiation

    • Gasses act as “blanket” to retain heat in troposphere

 

Three important greenhouse gases are shown symbolically in the image below: water vaporcarbon dioxide and methane.

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  • Greenhouse effect is a natural and necessary process.

    • Earth would be 33o colder without it.

    • All surface water would be frozen.

    • Little life would exist.

    • Natural effect is from water vapor.

  • Absorption (trapping) of reflected energy by greenhouse gasses (carbon dioxide, methane, nitrous oxide, halocarbons)

    • Enhances the greenhouse effect

Carbon dioxide accounts for most of the anthropogenic greenhouse effect. It is the most studied.

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Source: https://en.wikipedia.org/wiki/Greenhouse_gas#/media/File:Physical_Drivers_of_climate_change.svg

Volcanic Eruptions:

Ash from eruptions becomes suspended in the atmosphere, reflects sunlight having a cooling effect.
Mount Tambora, 1815 eruption contributed to cooling in North America and Europe.
Mount Pinatubo eruption in 1991 (June 12 – 16) counterbalanced global warming during 1991 and 1992.
Global Effects of Mount Pinatubo

11 major volcanic (flood basalt) events that affected Earth climate over 350 million years:

image

Source: Vincent E Courtillot, Paul R Renne, On the ages of flood basalt events, Comptes Rendus Geoscience, Volume 335, Issue 1, 2003, Pages 113-140. https://doi.org/10.1016/S1631-0713(03)00006-3

 

Human Impact: considered the most influential (primarily fossil fuels, deforestation, etc.)

  • Mathematical models of climate can isolate human causes from solar and volcanic forcing of climate change.

  • Models found that present warming greatly exceeds natural variability.

  • Models agree with climate change predicted from greenhouse gas forcing.

image

Source: https://en.wikipedia.org/wiki/Scientific_consensus_on_climate_change#/media/File:20200324_Global_average_temperature_-_NASA-GISS_HadCrut_NOAA_Japan_BerkeleyE.svg

 

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Geology 101 for Lehman College (CUNY) Copyright © by Yuri Gorokhovich and Lumen Learning is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License, except where otherwise noted.

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