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Earth's Systems / Carbon cycling

Carbon cycling

How carbon moves between the air, oceans, living things, soil and rock, and how burning fossil fuels adds to the air.

Boundary: where this process starts

Starts with: Where does a unit of CO2 go?

Boundary: where it ends

Ends after: Fossil and geologic carbon exchange; CO2 accumulates in the atmosphere and traps heat

PARTICIPANTSRESOURCESOceanEarth systemAtmosphereSoil microbesLand biosphereCarbon dioxideSunlightWaterSeawaterFossil carbonImpact +3 of 5. Click for details and evidence.CO2 enters the carbon cycleImpact +4 of 5. Click for details and evidence.29% taken up by landImpact +4 of 5. Click for details and evidence.26% absorbed by oceanImpact +5 of 5. Click for details and evidence.45% stays airborneImpact +3 of 5. Click for details and evidence.warming effectImpact +3 of 5. Click for details and evidence.↻ reinforces · moderate · 0.15 weaker sinks Impact +1 of 5. Click for details and evidence.land carbon continues to geoImpact +2 of 5. Click for details and evidence.ocean carbon to carbonate buImpact 02 of 5. Click for details and evidence.cycle closes on geologic scaImpact 02 of 5. Click for details and evidence.atmospheric stock carried foWhere does a unit of CO2 go?: uses Carbon dioxideTerrestrial carbon uptake and release: uses Carbon dioxideTerrestrial carbon uptake and release: uses SunlightTerrestrial carbon uptake and release: uses WaterOcean carbon exchange and burial: uses Carbon dioxideOcean carbon exchange and burial: uses SeawaterFossil and geologic carbon exchange: uses Carbon dioxideFossil and geologic carbon exchange: uses Fossil carbonCO2 accumulates in the atmosphere and traps heat: uses Carbon dioxideWarming reduces ocean solubility and speeds soil respiration: makes Carbon dioxidemakestraced through thecarbon cycleCarbon dioxide: traced through the carbon cycleexchanged withterrestrial biosphereCarbon dioxide: exchanged with terrestrial biospherepowers terrestrialuptakeSunlight: powers terrestrial uptakemoves through plants andsoilWater: moves through plants and soildissolves into seawaterCarbon dioxide: dissolves into seawaterexchanges carbon withthe airSeawater: exchanges carbon with the airreleased by geologicprocessesCarbon dioxide: released by geologic processesslowly released byweatheringFossil carbon: slowly released by weatheringabsorbs outgoingradiationCarbon dioxide: absorbs outgoing radiationreleased from soils andoceansCarbon dioxide: released from soils and oceansStart: Carbon cyclingSTARTStart: Carbon cyclingEnd: Carbon cyclingENDEnd: Carbon cyclingWhere does a unit ofCO2 go?👍1 👎1📄1Where does a unit of CO2 go?Terrestrial carbonuptake and release↘📄1Terrestrial carbon uptake and releaseOcean carbon exchangeand burial↘👍1📄1Ocean carbon exchange and burialFossil and geologiccarbon exchange↘👍2📄1Fossil and geologic carbon exchangeCO2 accumulates in theatmosphere and trapsheat👍2📄1CO2 accumulates in the atmosphere and traps heatWarming reduces oceansolubility and speedssoil respiration 👎1📄1 ↗1Warming reduces ocean solubility and speeds soil respiration
Line thickness = size of impact (1 to 5)% on a line = chance a fork takes that branch📄 = pieces of evidence on a stepNegative effectLoops backHypothesisResource used up (arrow into the step)Resource used, not used upResource made or released (arrow out of the step)
What am I looking at? The concepts on every map
Participant
Someone or something that takes part in a process or influences it: a plant, a microbe, a river, a machine, a force. Participants are the rows of a map.
Resource
Something a step uses or uses up: water, oxygen, sunlight, a tool. Each step has an arrow down to the resources it uses.
Step
One thing that happens in a process. Every step has at least one participant and carries evidence.
Decision fork
A step where the process can go several ways. Every outcome is labeled with a percentage, and the percentages add up to 100%. It is not limited to yes or no.
Loop
A line that carries the process back to an earlier step. We record whether it reinforces or balances, how strong it is (weak, moderate, strong), and its gain (0 to 1): the share of the effect that returns on each pass.
Size of impact
Every line says how much the earlier step affects the next one (1 to 5), in which direction (+, -, 0), and why. Thicker lines mean bigger impact.
Evidence
The support for a claim: a source and what it shows. Every step, line, change and vote needs it. Click any step or line to read its evidence.
Boundary
Where a process starts and where it ends. Every process, and every subprocess, has a start and an end.
Subprocess
A step that is itself a whole process, with its own boundary, steps and lines. Click a step marked ↘ to open it. Subprocesses nest as deep as the evidence goes.
Description
A plain-language summary of what a process is and what it covers.
Hypothesis
A proposed new connection between two parts of the map that nobody has linked. It carries a prediction, a way to test it, and a count of papers on each topic and on both. It is an unverified idea until someone tests it.

Inside this process

Terrestrial carbon uptake and release

11 steps

Ocean carbon exchange and burial

10 steps

Fossil and geologic carbon exchange

7 steps

Every step, with its evidence

The same information as the map, as a list you can search and share. Click a participant or resource to see everywhere it appears.

⑂ Where does a unit of CO2 go?
AtmosphereLand biosphereOceanCarbon dioxide
Evidence (1) · added by Brook
  • Friedlingstein et al. 2022, Global Carbon Budget 2022, Earth System Science Data 14:4811-4900: Of anthropogenic CO2 emissions in 2012-2021, about 46% stayed in the atmosphere, 29% went to land and 26% to the ocean (rounded to 45/29/26 here). (confidence 0.85)
↘ Terrestrial carbon uptake and release
PlantsSoil microbesTerrestrial ecosystemCarbon dioxideSunlightWater
Evidence (1) · added by Brook
  • Falkowski et al. 2000, The global carbon cycle: a test of our knowledge of Earth as a system, Science 290:291-296: Land photosynthesis (~120 Pg C/yr gross) and respiration dominate fast carbon exchange with the atmosphere. (confidence 0.8)
↘ Ocean carbon exchange and burial
PhytoplanktonOceanThermohaline circulationCarbon dioxideSeawater
Evidence (1) · added by Brook
  • Sarmiento & Gruber 2006, Ocean Biogeochemical Dynamics, Princeton Univ. Press, chapter on the carbon cycle: The ocean holds ~38,000 Pg C of dissolved inorganic carbon and exchanges ~90 Pg C/yr with the atmosphere in each direction. (confidence 0.8)
↘ Fossil and geologic carbon exchange
HumansVolcanoesRocksOceanCarbon dioxideFossil carbonCalcium carbonate
Evidence (1) · added by Brook
  • Berner 2004, The Phanerozoic Carbon Cycle: CO2 and O2, Oxford Univ. Press: Slow geologic carbon cycle: silicate weathering and carbonate burial remove CO2, volcanic degassing returns it, on 10^5-10^7 yr scales. (confidence 0.8)
CO2 accumulates in the atmosphere and traps heat
AtmosphereGreenhouse gasesCarbon dioxideInfrared radiation
Evidence (1) · added by Brook
  • Friedlingstein et al. 2022, Global Carbon Budget 2022, Earth System Science Data 14:4811-4900: Atmospheric CO2 rose from about 278 ppm preindustrial to about 417 ppm in 2022. (confidence 0.85)
Warming reduces ocean solubility and speeds soil respiration
Climate systemOceanSoil microbesHeatCarbon dioxide
Evidence (1) · added by Brook
  • Davidson & Janssens 2006, Temperature sensitivity of soil carbon decomposition and feedbacks to climate change, Nature 440:165-173: Warming raises soil heterotrophic respiration (Q10 around 2) and lowers CO2 solubility in seawater, weakening both sinks. (confidence 0.75)