climate changes effecting water and carbon cycles

human activities cause changes in water and carbon

population and economic growth, deforestation and urbanisation have modified size of water and carbon stores
human impacts on water cycle:
- rising demand for water has created shortages in aquifers, rivers, and surface supplies.
- quality of fresh water supplies have also dropped - overpumping of aquifers in coastal regions leading to incursions of salt water
- deforestation reduces evapotranspiration and therefore precipitation, increasing surafce runoff and decreasing throughflow, therefore lowering water tables
human impacts on carbon cycle:
- world relies on fossil fuels for 87% of primary energy consumption: releases billions of tonnes of carbon
- 8 billion tonnes of carbon transfered into atmosphere by burning fossil fuels
- land use changes add a further billion tonnes to atmosphere
- decline in carbon stored in biosphere - planet's forest cover declined by 50% from historic times
- acidification of oceans threatens phytoplankton (which absorb more than half of CO2 released from burning fossil fuels
- soil erosion also decreases carbon stored

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atmosphere: CO2 plays vital role in photosynthesis, stimulated growth. plants extract water from soil and transpire in the water cycle. water from oceans evaporated to enter atmosphere - CO2 also exchanged between these two stores
oceans: ocean acidity increases with excess CO2. solubility of CO2 in oceans also increases
vegetation and soil: water availability influences rates of photosynthesis, NPP and transpiration. water storage in soils increases with more organic matter. temperatures and rainfall effect decomposition rates and CO2 release in atmosphere
cryosphere (frozen part of earth's systems): CO2 levels increase greenhouse effect, causing rise in global temperatures whic melts icesheets and glaciers. melting permafrost releases carbon and methane. runoff, river flow and evaporation increase in warmer climate

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global warming increases evaporation rates, and therefore the amount of water vapour in the atmosphere
more vapour has positive feedback which raises global temps further
flood risks increase with more precipitation
more energy in atmosphere increases extreme weather events such as hurricanes
gloabl warming melts polar ice, ocean levels rise

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higher global temperatures increase rates of decomposition in the biosphere, releasing even more carbon into atmosphere
hotter weather may cause tropical forests to become arid, or at least turn forests into grasslands which decreases carbon stored, meaning more enters atmosphere
carbon frozen as permafrost is released
oceans become more acidic, reduces photosynthesis from phytoplankton, limits ocean's capacity to store carbon
increase in carbon stored in atmosphere, decrease in biosphere and oceans

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