Lecture 2: Atmospheric CO2 Flashcards
Anthropocene:
humans have created a new era due to their change on climate
climate change and global warming =
NOT always warming!
- not globally uniform, colder in some places, warmer in other
modelling climate change:
V V complex,
- CO2 effect on future of planet predicted by looking at the past
CO2 conc= last 800 thousand years
pretty steady, never above 300 ppm until last 50 years or so
- humans never had to deal w higher then 300ppm
CO2 conc = last 500 mill years
- Much more range
- has been much higher
- BUT HUMANS HAVE NO EXPERIENCE AT THESE HIGH CONC, ANIMALS AND PLANTS W SURIVE, HUMANS WONT
The inorganic Geochemical carbon cycle: would occur =
happen EVEN if everything on the planet died
- geochemical = long term
The inorganic Geochemical carbon cycle:
- Carbon cycle between atmosphere & Lithosphere
- rainfall & silicate rocks (weathering of silicate rocks)
- Run off from rocks, limestone & HCO3- ions and are buried (long term storage)
- metamorphism of carbonate rocks = CO2 pressure
- volcanic (degassing) activity and CO2 is released
AND REPEAT
The inorganic Geochemical carbon cycle: Atmosphere and lithosphere carbon
Atmosphere = 700-800gt lithosphere = 75 million gt
lithosphere =
earth crust & earth soil
carbon leaves the atmosphere in 2 ways
- rainfall, dissolved in rainwater to form carbonic acid (I precip, D C in atmos)
- direct removal by silicate rocks
- -> Both lead to weather if silicate rocks == formation of limestone (28% of earths crust = silicate rocks)
Organic carbon cycle =
- CO2 taken up by plants
- photosynthesis & respiration (&decomposition)
- CO2 + H2O <==> CO2 + H2O
- ## short term-photosynthesis takes up 120gt,
-respiration releases 60gt, biomass absorbs 60gt - agricultural farming removes 3gt
- microbial respiration & decomposition releases 60gt
SO BALANCED, W US REMOVING EXTRA 3GT BUT
industrial processes, concrete production and land use change by humans adds 9gt
= loss of 6gt / year into atmosphere
carbon store in soil
2300gt
plant biomass carbon
550gt
human activity effect ___ & ___ carbon
natural flux (deforestation) long term storage (degrading wetlands, soils etc)
global CO2 atmospheric conc throughout the year
more in winter, less in summer due to photosynthesis ESP in upper latitudes (where most boreal forests are)
transpiration =
- Water is a ghg
- as temp increases, more water can be stored in atmosphere
evolution of plants impact on inorganic carbon cycle
increases weathering (more carbon taken up by plants and by rocks of earths crust) - more important role they play in carbon cycle
5 effects of plants on weathering:
- respiration and evapotranspiration increases global rainfall
- plant roots, break into soil and hold it together, stabilising soil particles whilst rain washes past it
- mycorrhiza interactions & plant roots secrete organic acids into soil, decreasing pH
- roots respire = CO2, dissolves in water = carbonic acid, lowers pH
- plants die & are decomposed by fungi & microbes = organic acids released
ALL INCREASE WEATHERING
ATMOSPHERE & PLANT INTERACTION: The evolution of leaves: megaphyll vs microphyll leaves
microphyll = simple, single vein, no leaf gap, limited size (simple vasculature)
megaphyll = leaf gap, branching veins, often larger (complex vasculature)
ATMOSPHERE & PLANT INTERACTION: The evolution of leaves. Earliest land plants =
- 415Mya Cooksonia
- similar to mosses or liverworts today
- single, simple upright stems
when did woody shrubs evolve =
385 Mya
STILL NO LEAVES, tiny tiny microphyll leaves
megaphyll leaves evolution?
365 Mya in Late Devonian
(50Mya of evolution of plants)
– very very long time? WHY
why did microphyll –> megaphyll take so long?
lost of theories debunked,
—> Hao et al 2002
SUN (light)? probably!!
- plant evolution in late Palaeozoic = HUGE CO2 decline (no fungi /microbes able to decompose dead plants, = coal today we burn)
- drop in CO2 relate to increase stomatal density as plants having to work hard to get CO2 in
- DEVELOPED TO BIGGER LEAVES
limited CO2 leading to leaf evolution: Erect axis vs laminate leaf
- flat leaf (laminate) can absorb more solar energy throughout the day
- BUT if they have small stomata, then energy/heat cannot escape and they overheat
- early devonian (HIGH CO2) erect axis leaves benefit as low stomata and don’t want leaves to over heat
- late devoniana (LOW CO2) megaphyll leaves benefit as more stomata due to lacking CO2, allowing heat energy to leave
Recent increases in CO2 led to _____ in number of stomata
DECREASES
Gray et al 2000
megaphyll leaves evolved __
separately in FOUR groups
– such an advantage, so evolved separately across multiple groups
leaves evolved because of ___
the atmospheric carbon levels
leaf evolution had huge effects ON the long-term carbon cycle
1) increased photosynthesis (led to huge diversity)
2) root and shoot co-evolution (big leaves, more roots required)
3) carbon burial (more microbes, more fungi so increased decomposition and burial)