Carbon 1.5 - 1.7 Flashcards
What is paleoclimatology?
we use different sources to look into the recent, historical and long-term past. We reconstruct a record of climate variability using these sources
Ice cores
Can help determine the amount of co2, which reflects glacials or interglacials.they also show layers of ash from volcanos
Tree rings
- as trees grow they produce rings
- greater thickness of rings indicate better growing periods, and higher temperatures
- fossilised trees can also be used
Fossil records
Fossils from animals which no longer in a certain area can suggest higher or lower temperatures in the past
U shaped valleys
Evidence of previous glaciation
Historical sources
Paintings and diary entries tell us about unusual climate events, e.e. Frost fairs on the Thames, or difficult growing conditions
- e.g. little ice age
Between 1550 and 1800, winter temperatures in the UK were low enough for the river Thames to freeze - thick enough for people to walk on the river.
Siberia permafrost
Thawing starts after global temp rise of 1.5C
- globally, permafrost contains 1700bn tonnes of organic matter
- carbon is sequestrated - and there is 4x that released into the atmosphere
Solar radiation pathways
- 31% reflected by clouds
- 69% absorbed - 50% at earths surface, with the remaining re eradicated and trapped
- Increased veg = darker surfaces = more solar absorption
- But - increased clouds, increased reflection
Negative feedback cycles
- Evidence: tree leaf fossils in the arctic - suggesting plants and animals had to migrate towards the poles because of warming temperatures
- BUT: tectonics caused growth of the mountains, making rate of weathering faster as co2 dissolved in rain reacted with rock minerals
- Solution carried to sea, absorbed by phytoplankton and sea creatures = die = sinks = locking carbon away in rock store
- Carbon seqeustrain cooled planet
Positive feedback cycles
- Melting snow and ice = lower albedo, more surface absorption, more LW radiation trapped, higher temp
- Permafrost melt, methane release, more LW radiation trapped = higher temperature
- Microbe activity = more NOX released
Oceanic productivity 1
- Light availability for photosynthesis decreases exponentially with depth - only available for 200m
- But you also need nutrients and these vary with location: as cold water holds more nutrients (carbon)
- the most productivity occurs 50-75m in depth
Oceanic productivity 2 - ocean capacity to store carbon
- Coastal estuaries have the greatest concentration of productivity due to them being shallow and nutrient rich from coastal erosion
- But open ocean still accounts for greater share, owing to greater size
Terrestrial Productivity 1 - soil capacity to store carbon
- Latitude = temperature + precipitation patterns = productivity
- Depends on decomposition and weathering rates as well as biota content of soil - which respire
- Tropical rainforests have larger biomass, but high decomposition rates and instant nutrient uptake limit litter and soil storage
Terrestrial productivity 2
- Temperate grasslands have organic matter content in soils = increases capacity to store carbon
- Taiga biome has very slow decomposition rates, and frozen upper soil
- Clay rich soils protect carbon from decomposition by biota
- Soil erosion is a major threat to carbon = removal from active surface layer
Atmospheric Composition
- Carbon only accounts for 0.038% of the earths atmospheric composition
- BUT it plays a very important role in trapping the long wave radiation from the earths surface
- Without carbon dioxide and methane, the average temperature of the earth would be 20C lower
Natural controls
Balance between photosynthesis and respiration in ecosystems
Where?
Either on land (terrestrial) or within the ocean
How much?
- Depends on size of ecosystem and it’s productivity level
- Ecosystem productivity NPP is the rate of generation of biomass (acts as a carbon sink)
Measured in grams per metre squared a day
What controls this?
Soil health, I.e the availability of carbon and other nutrients such as nitrogen and phosphorus
What is soil health depend on
Soil health depends on amount of organic carbon stored in soil
Capacity of soil to store carbon is determined by:
- Climate (latitude ,continentality, altitude)
- Soil type (grain size and permeability)
- Land use (natural or altered?)
Anthropogenic pertubation
- Humans have removed lots of carbon from its natural stores in a slow geological cycles
- Only half of this carbon is being removed by the faster carbon cycle
- Half of the increase remains
- At the same time deforestation has slowed down the biological cycle
- Carbon has been transferred from fossil stores into the atmosphere, so slow exchange has become fast change
Pre industrial revolution
• A mixture of a fast carbon cycle (biological) and slow carbon cycle (geological)
Fairly fast fluxes / exchanges of carbon removed CO2 – a balanced carbon cycle
Anthropogenic CC
• Carbon has been transferred from fossil stores into the atmosphere
Slow exchange becomes fast change
Implications of carbon change on Climate system
- Co2 causes about 20% of climate forcing, water vapour -> 50%
- Co2 provides initial GHG heating = water vapour formation
- When co2 drops, earth cools, water vapour condensates out of atmosphere, which limits further greenhouse warming
- All bonds have capacity to absorb energy, so as number of water molecules increase in air will hold more energy, increasing air temperature
- Water molecules absorb infrared radiation from the sun, leading to it being trapped in the earths atmosphere- i.e. a positive feedback loop
