D4.3 Climate Change

greenhouse effect

• short-wave radiation/ultraviolet light/visible light/electromagnetic radiation from the sun can penetrate the atmosphere

• some radiation is reflected back into space, most absorbed the the earth and re-emitted as low wave radiation/heat/infrared

• gases in atmosphere retain heat

  • greehouse gases like CO2 and methane

  • oxygen and nitrogen are not greenhouse gases, do not absorb longer-wave radiation

• picture*

changes in heat have effects on the weather

temperature, humidity, precipitation, visibility, wind, atmospheric pressure

• water vapor formed by evaporation from the ocean, transpiration in plants, accelerated by global heating

• water vapor removed from atmosphere by rain or snow

• water continues to retain heat after being condensed to form droplets of liquid in clouds, water as a heat sink; atmospheric water absorbs heat energy, radiates back to earth’s surface as well as reflecting it back to earth

albedo

amount of radiation a substance reflects into space, high in light-colored matter such as snow.ice, reflect solar radiation

polar and sea ice melting effects

• open water (higher albedo exposed)

• absorbs more radiation than white ice

• more infrared radiation emitted at poles

• further acceleration of polar ice melting

permafrost

ground that remains frozen all year round, some containing frozen detritus

• global heating acceleration

• permafrost melting

• decay of waterlogged detritus

• release of methane

• further acceleration of global heating

solubility of gas in water decreases with temperature

• CO2 levels rise

• average global temperature increases

• ocean temperature increases

• ocean releases more CO2 in the atmosphere

• further increased global temperature

frozen hydrated methane

forms caps over store of methane, prevents escape into ocean and atmosphere

• warming ocean

• increased temperature may dissolve hydrate caps

• release of large volumes of methane

droughts and forest fires

• increased temperatures

• drier, fire-prone conditions

• forest fires

• more emissions from burning vegetation

• reduced carbon capture by destroyed or damaged forest

boreal forests as an example of a tipping point

• cold temperatures in boreal forest → reduced rate of cellular respiration → rate of decomposition of detritus is less than rate at which detritus collects

• photosynthesis by boreal forests captures CO2 in tree biomass; climate change → droughts and fires, release of CO2 stored in centuries of detritus, undermines forest’s ability to store carbon

• widespread fires may cause boreal forest transition from carbon sink to carbon source

antarctic landfast ice

pack ice that does not move with wind or down ocean currents, “fastened to shore”

• emperor penguins*

walruses and pack ice

used to give birth, rest, expand access to feeding sites

ocean stratification as a positive feedback cycle

• warmer, less salty water floats on top of denser, colder, saltier water; mixing between layers occurs more with lower density difference

• warming climate after increased stratification: surface ocean is less dense, water warming → expanded volume, melting ice → added freshwater, decreased salinity of surface water

• inhibited transfer of heat, O2, CO2, from surface into deeper ocean

• increased stratification further drives global warming: warmer water on surface →less CO2 absorbed from atmosphere

• coral reef bleaching

• deep ocean current forced upward → upwelling of nutrients, nutrient cycling of productive surface biological communities decreasing primary production and energy flow through marine food chains

climate change and montane species

• climate change → warmer temperature at each elevation

• montane species migrate upslope, tracking optimal climate

• combined with competitive exclusion, will cause species to seek marginal niches to escape competition

• tropical montane species more sensitive, shifts of latitude range

effects of increased carbon dioxide concentration on carbonate concentration in water

carbonate concentration lowered due to interrelated chemical reactions

• CO2 + H2O reacts to form H2CO3 (carbonic acid) dissociates into H+ + HCO3- (hydrogen carbonate ion)

• H+ + CO3^2- → HCO3-

effects of lower carbonate concentration

• difficult for reef-building corals to make skeletons

• decreasing concentration of carbonate in seawater causes existing calcium carbonate to dissolve

coral bleaching

coral ejects zooxanthellae algae due to water surrounding corals becoming too warm

afforestation

planting trees where they do not currently exist

forest regeneration

restocking depleted forests, forestry practices and clearcutting

restoring peatlands

restoration of water levels, blocking drainage, re-establishing native species