PLS 147 Lecture Notes - Lecture 24: Global Warming Potential, Post Present Medium, Industrial Revolution
Greenhouse Gases in the troposphere
CO2
●pulled out of the air by photosynthesis
●respiration releases it back into the atmosphere
Two most abundant gases
●Nitrogen and Oxygen
○gaseous form not accessible to plants and animals
Greenhouse gases
●CO2, water vapor, CH4, N2O, O3
CO2 Global Warming Potential indicates 1 gram of equivalent to grams of CO2 over a 100 year time
frame
●each molecule of Nitrous Oxide is 300x CO2
●Methane 25x CO2
●steady increase in carbon dioxide since 1990
"Greenhouse effect"
●longwave radiation (heat) is absorbed and radiated from earth's surface where it then gets
absorbed and redistributed by GHG both up and down, keeping things warm
●land is heating up more than water (heat capacity is lower)
relationship between CO2 and temperature is strong
●suggest causativity
interglacials: the periods of higher CO2 and temp
●variation is normal
spike in CO2 since industrial revolution
●rising in an order of magnitude faster than previously
●over 400 ppm
●records before around 280 ppm
CO2 very high in early days of earth (Cambrian), dropped down, variatio
Global temperature shows steady increases with some small drops
●massive volcanic eruptions cooled temperatures
Last time CO2 was high?
●2-4.6 million years ago during the Pliocene, and much more slowly
How do we know?
●Ice cores
○taken from old glaciers in Antarctica
○shows trapped atmospheric gasses in ice
○look at stable isotope ratios of C, H, and N
■ratios differ with temp and other things so we know what the climate was
like
●lake sediments
●tree rings
○can only go back a few hundred years
○but matches info we get from other sources
●speleothems
○cave formations
■stalactites, stalagmites
●used like ice cores
So what does this mean for CA?
●higher temp → more evaporation → more precipitation
●snowpack disappearing up to a month earlier
●drought stress bc temperature, less stress bc more precipitation
●on average, increases in precipitation
○which will mitigate some warming effects
○rain is fewer but more intense
○more runoff
potential impacts to physical environment depend on our choices
●high emissions: 8-10.4 F, 90% loss snowpack,
●medium: 5.5-7.9 F
●lower: 3-5.4 F, 30-60% loss snowpack
Snowpack will continue to shrink
●just a little bit of warming, 40% remaining. Moderate warming, 20% remaining
○snowpack important for giving us moisture through Med dry season and plant
communities downstream
More winter runoff and flooding
●melting earlier
●rain more intense
○water washed away
●increased riparian erosion
●economic damage
●more summer drought stress bc lost snowpack, water too early
●more conflicts over water supply
●less water for water-dependent species and habitat
Document Summary
Pulled out of the air by photosynthesis. Respiration releases it back into the atmosphere. Gaseous form not accessible to plants and animals. Co2 global warming potential indicates 1 gram of equivalent to grams of co2 over a 100 year time frame. Each molecule of nitrous oxide is 300x co2. Steady increase in carbon dioxide since 1990. Longwave radiation (heat) is absorbed and radiated from earth"s surface where it then gets absorbed and redistributed by ghg both up and down, keeping things warm. Land is heating up more than water (heat capacity is lower) relationship between co2 and temperature is strong. Suggest causativity interglacials: the periods of higher co2 and temp. Variation is normal spike in co2 since industrial revolution. Rising in an order of magnitude faster than previously. Co2 very high in early days of earth (cambrian), dropped down, variatio. Global temperature shows steady increases with some small drops. 2-4. 6 million years ago during the pliocene, and much more slowly.
