Unit 6 - Environmental Implication Flashcards
UNFCCC definition of climate change
a change of climate which is attributed directly or indirectly to human activity that alters the composition of the global atmosphere and which is in addition to natural climate variability observed over comparable time periods.
UNFCCC distinction between CC and climate variability
CC = purely anthropogenic phenomenon caused by human activities altering the composition of the athmosphere
Climate Variability = attributed to natural causes
IPCC definition climate change
A change in the state of the climate that can be identified (using statistical tests) by changes in the mean and/or the variability of its properties, and that persists for an extended period, typically decades or longer. It refers to any change in climate over time, wether due to natural variability or as a result of human activity.
How are energy use and CC linked?
- about 70% of all GHG emissions worldwide come from energy related activities.
- energy use impacts are assumed to exceed the impact from other sources like land-use and other industrial activities.
What are the atmospheric concentrations of CO2
Pre-industrial level is 280 ppm
2005 - 380 ppm
2007 - 396 ppm
2013 - 400 ppm
Increased levels of: CO2 MH4 N2O Since pre-industrial times
CO2 = 40% MH4 = 150% N2O = 20%
(IPPC, 2014)
What is the greenhouse effect?
The athmosphere controls the heat budget of the earth
Incoming solar radiation has short wavelength, the outgoing terrestrial radiation (heat) has a longer wavelenght
Different gases absorp different wavelenghts: absorption spectrum
Little incoming solar radiation is absorbed but a lot of outgoing terrestrial radiation = heat is retained in the atmosphere
This depends on the composition of the atmosphere as some gasses absorb more than other gases.
This is a natural process that keeps the earth at around 20 degrees warmer as without.
Anthropogenic GHGes
CO2 CH4 N2O - nitrous oxide HFCs - hydrofluorocarbons PFCs - perfluorocarbons SF6 - sulfur hexafluoride
+ water vapour (not anthropogenic)
+ ozone (not anthropogenic)
The importance of different gases in promoting global warming depends upon:
1) their concentration in the atmosphere
2) the GH effect of each molecule as a result of their absorption of radiation, a consequence of their chemical structure
3) the length of time that the gases stay in the atmosphere
The global warming potential (GWP)
The estimate of the GWP compared with the same quantity of CO2 in CO2equivalent
- greenhouse effect of each molecule (absorption rate)
- length of time in the atmosphere
What is the anthropogenic green house effect?
An accumulation of heat-absorbing (or heat-trapping) GHGs in the atmosphere.
As long as the atmospheric concentrations of GHG remain constant, there is no imbalance in the radiative budget of the earth, and no radiateive forcing and no CC.
Reasons of accumulation of GHGs:
- as a result of human activities (especially the combustion of fossil fuels)
- Sinks are destroyed and degraded (as a result of human activity)
- release previously stored sinks
- loss of absorbtion
Explain the 2 degree target and its likelihood to be reached
The global mean surface temperature has risen by 0.85 +/- 0.2 degres C between 1880 and 2012.
2 degrees C is by 2100 threshold is between acceptable and daberous climate change.
For a 50% chance of achieving the 2 degree target, a global atmospheric CO2 equivalent concentration of 400-450ppm should not be exceeded which would require an immediate reduction of global GHG emissions of about 60-80 % by 2100.
Impacts of climate change:
- Temperature rise
- More extreme weather events
- irreversible changes to the earth’s ecosystem, especially the oceans, which are a large absorber of CO2 and become more acidified 4. Changes in cryosphere
- Sea level rise
The reasons for sea level rise
- thermal expansion of the ocean
- melting water
CC impact on oceans
Oceans have absorbed >80% of the heat added to the climate system.
Rise:
1901-2010 a rise of 1.7mm/year
1971-2010 a rise of 2.0mm/year
1993-2010 a rise of 3.2mm/year
CC impact on cryosphere
The
- greenland ice sheet
- antartic ice sheet
- worldwide glaciers
- artic sea ice
Have declines