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Climate Change (Evidence of Climate Change (Rising Sea Levels Rose by >…
Climate Change
Natural Causes
Changes to Milankovitch Theory
- Cyclical recurrence
- Earth's eccentricity, axial tilt and precession of equinoxes has resulted in climate change
- Over the last 0.74mil yrs, 8 major glacial & interglacial cycles have occured each lasting 100k years but beginning and ending in sudden jumps in temperature
- Last glacial was 20k ya and since then, Earth has warmed
Volcanic Eruption
- Episodic Recurrence
- Explosive eruptions can throw vast quantities of gases (sulphate aerosols) into the atmo causing short term global warming
- Sulphate aerosols circulating in the stratosphere may cause globally lowered temperatures for several months or years
- When sulphur dioxide is emitted to high altitudes (>12km), it enters the stratosphere and forms acid droplets that partially scatter and reflect sunlight away from Earth, causing surface cooling
- During the eruption of Mount Pinatubo in Philippines in 1991, a cloud 1100km wide and 35km high formed over the volcano, carrying about 17 megatons of sulfur dioxide into the stratosphere
- Resulted in large parts of the world cooling by 0.4°C
from 1992-1993, where the tiny droplets remained suspended for 1-3 years
-
Greenhouse Gases
Water Vapour: H2O
- Most abundant ghg on Earth
- ↑ water vapor leads to warmer temps, causing more water vapor to be absorbed into the air, increasing rate of warming as its a strong absorber of infrared radiation (+ve feedback)
- Shortest lifespan of all ghgs on trapping heat energy
Methane: CH4
- Second-ranked contributor to global warming, with an annual increase of 1%
- 12 years lifespan
- Emitted from production and transport of fossil fuels for energy, industry, agriculture (livestock, wet rice padi fields) and waste management activities (decay of organic waste in landfills)
- Domestic livestock like cattle and sheep produce methane as part of their normal digestive processes
- Cattle convert 10% of the food they eat into methane, emitting 100million tonnes of methane into the atmosphere annually
- Animal's manure stored or managed in lagoons or holding tanks, methane is produced
- 50-65% of total methane emissions originate from human activities (where humans raise animals for food and products, emissions are human-related)
Carbon Dioxide: CO2
- Second largest share of GHG
- 100 years lifespan
- Integral in ensuring Earth remains habitable by absorbing longwave radiation from Earth, warming the Earth
- Absorbed CO2 is emitted naturally as part of the carbon cycle (atmo, oceans, soil, living things)
- Movement of Carbon into and out of the atmo is large where a fifth of total carbon emissions is cycled in and out each year
- Land & Reservoirs Carbon > Atmo
- CO2 is the principal anthropogenic ghg & is largely emitted by burning of fossil fuels, alterations to the carbon cycle influences atmospheric carbon
Nitrous Oxide: N2O
- Long lifespan of 120 years
- Occurs naturally through many sources in the nitrogen cycle (natural circulation of nitrogen among the atmosphere, plants, animals and microorganisms that live in soil and water)
- 40% of total N2O emissions come from human activities
- Agriculture: Use of synthetic and organic fertilizer
- Industrial Production: By-product during production of chemicals used to make synthetic fertilizer and fibres
- Wastewater Management: Treatment of wastewater during nitrification/denitrification of the nitrogen present in urea, ammonia and proteins
Anthropogenic Influence
Addition of GHG: Burning of Fossil Fuels for Energy
- Fossil Fuels are organic matter from the remains of flora and fauna subjected to immense pressure and heat deep within the Earth over millions of years
- 1750s to 2015, atmospheric CO2 concentration rose from 280 parts per million (ppm) to >400ppm
- The burning of carbon rich fossil fuels derived from coal, oil and natural gas (human-induced) for energy causes large carbon emissions mainly in the form of CO2 and methane that enhances the already existing ghg effect, causing global warming and fundamental changes in climate
- Bulk of usage of fossil fuels are industries and residential buildings to provide energy for populations
- Cement manufacturing contributes 3-4% of total global industrial CO2 emissions
- These emissions exceed the absorption capacity of the biosphere so carbon accumulates in the atmosphere, resulting in climate change
Addition of GHG: Agricultural Activities
- Agriculture is responsible for 18% of total ghg emissions (methane,Co2)
- Largely in CLLDs w agriculture as main econ activity due to expansion of total agricultural outputs
- Livestock Breeding: Major emitter of CH4 are ruminant animals like cattle due to their unique digestive system that undergoes enteric fermentation to produce lots of CH4
- Accounts for 30% of total anthropogenic methane released in 2012, of which 70% comes from beef cattle and 25% from dairy cattle
- Rice cultivation: When rice is grown in flooded paddies, the anaerobic conditions facilitate microbial methane-generation
- Accounts for 11% of total anthropogenic methane emissions in 2012
- Third major source is loss of methane from organic matter in manures
- Agricultural emissions from crop and livestock grew from 4.7 billion tonnes to 5.3 from 2001-2011, 14% increase
NOT a cause of climate change but influences/ contributes to it
(can influence CC positively thru use of AE altho short-term emits ghg + removes carbon sinks)
Criteria:
- Scale
- Time (as CC worsens over time)
Removal of Carbon Sinks: Landuse Change & Deforestation
- Deforestation and popn growth rates tend to increase during periods of economic development
- Causes: Forests are cleared for expansion of agricultural production and for raw materials and fuels
Impacts:
- Releases CO2 through the breakdown of forest biomass and increased rate of breakdown in organic content in soils
- Reduction of forest cover ↓ amt of CO2 taken out of the atmosphere by photosynthesis
- Human alter ecosystem patterns and processes, affecting amt of carbon stored in vegetation and soils
- Land use change results in net carbon losses into the atmosphere from long-accumulated aboveground or belowground carbon stores in vegetation and soils, resulting in large carbon flows from soils to the atmosphere
- Changes in surface albedo affects amt of solar energy absorbed and released by the surface, in turn affecting convection & rainfall (higher albedo = cooler surface, ↓ convection & rainfall)
- Results in Positive feedback
- Sea warms, more H2O in atmo, more warming
- Warming melts snow/ice, albedo ↓ , more warming that melts even more
-
Shrinking Ice Sheets
- Evidence for rising temperatures
- Ice sheets are maintained or expanded when cold season is long enough for ice to accumulate
- Rising temps & warming means that cold seasons are shortened → warm season is longer → addition of ice < melting so ice sheets shrink
(not just melting thus shrink!)
- Greenland lost avg 286 billion tons of ice/yr and Antarctica lost 127 bilion tons of ice/yr between 1993-2016
- Melting valley glaciers and ice sheets contribute towards global rising sea levels
Ocean Acidification
- Acidity of surface ocean waters increased by 30% (a rate not observed in 300mil years) due to humans emitting more CO2 into the atmosphere and more absorbed into oceans
- Amount of CO2 absorbed into upper layer of oceans is increasing by 2bil tons/yr
- Oceans are carbon sinks that absorb 25% of the CO2 produced by humans every year
- When CO2 is absorbed into the ocean, it dissolves to form carbonic acid resulting in more acidic oceans and disruption of pH balance that marine organisms and people dependent on the ocean rely on
- Change in climate of a region or place, reflected by its mean annual temps or ppt
- A natural phenomenon resulting in both global warming and global dimming, attributed to human activity
- From 1880-2012, temp rose by 0.85°C
- Humans emissions and activities have caused around 100% of the warming observed since 1950, according to the Intergovernmental Panel on Climate Change’s (IPCC)
Criteria:
- Ways it contributes to GW
- Lifespan
- Sources
- Proportion / Amount in Atmo