4a- effective human response relies on knowing what the future may hold Flashcards
importance on the carbon cycle
-All living organisms depend on carbon, which is a fundamental building block of life.
-Green plants and phytoplankton extract carbon from the atmosphere in the process of photosynthesis. They are primary producers in ecosystems, supporting all consumer organisms, including humans.
-Carbon stores such as ocean sediments and carbonate rocks lock away carbon for millions of years, helping to maintain atmospheric CO₂ at levels conducive to life.
-Decomposition and oxidation ensure that CO₂ is recycled rapidly, replenishing stores of CO₂ in the atmosphere for photosynthesis.
influence of positive feedback cycles in carbon cycle
increase temp-more evap-more water vapour-more warming
melting-less albedo-more radiation absorbed- more melting
melting-CO2 and CH4 relseased- GHG-warming-melting
high temp-stresses trees-die-CO2 released from store-higher temps
high temp-more water vapour-clouds-retain radiated heat from earth-temp rises
influence of negative feedback loop in the carbon cycle
temp rise-trees head polewards-expansion of forestes-more PS- less CO2 in atmosphere
high temp-more evap-more water vapour-clowds-reflect radiation coming in-cools
aerosols of smoke dust and sulphur on the atmosphere reflect solar radiation so temps decreases- global dimming
RCP 8.5
CO2 emissions continue to rise beyond 2100, 4-5C rise in the next 100 years in places like Aus and S America, arctic free of ice in September by 2080s
RCP 6
CO2 emissions rise until 2100. Temperature rises greater than 5C in the arctic over next 100 years.
RCP 4.5
CO2 emissions continue to rise until 2070. Artic will have a 3-4 degree rise. Artic sea ice 60% reduced area in september
RCP 2.6
CO2 emissions are at a peak now. Arctic may warm 2C over next 100 years.
what RCP is the world at now
currently past all RCP pathways and even if we get down to RCP 8.5 there will still be global impacts
what are the future emission scenarios
Because of uncertainties about future emissions of GHGs and the complexity of the Earth-atmosphere system, the IPCC provides a range of forecasts of global temperature and sea level rises during the 21st century. Range from worst to best-case scenarios.
impact on mean global temperatures
All of the IPCC projections for the next 70-80 years show significant rises in mean global temperatures during the 21st century. Depending on the trajectory of GHG emissions, temperature increases range from 0.3°C to 4.8°C. However, a mean global temperature rise of around 2°C is the most likely scenario.
the impacts on global sea levels
Rising sea level is the result of the thermal expansion of the oceans due to warming, and the loss of ice by ice sheets and glaciers on land. Ice losses are caused by surface melting and increased rates of glacier flow. Sea level has been rising since industrialisation in the mid-nineteenth century.
Between 1901 and 1990 mean global sea level rose by 1.5 mm/year. However, between 1990 and 2010 it rose over 3.0 mm/year. After 2100 it is almost certain that global sea level will continue to rise for several centuries.
forecasts of global sea level rise are subject to uncertainty, depending on the future trend of GHG emissions. Current projections suggest a minimum rise (RCP 2.6) of 0.28 m by the end of the century, and a maximum of 0.98 m (RCP 8.5).
However, the most pessimistic forecast does not include the possible collapse of marine-based sections of the West Antarctic ice sheet, which could increase the 0.98 m figure substantially.
