climate change and ELSS Flashcards
methods used to reconstruct past climates
Marine sediments-fossil shells called foraminifera reveal the temps in which they were formed.
Ice cores- cylinders of ice removed from ice sheets containing bubbles of gas(measure proportions of gas making climate changes)
Lake sediments-cores from lake beds contain pollen and algae showing which plant communities existed.
Tree rings- the width of each ring reveals how quickly the tree grew which reflects temperatures.
Fossils- plants and animals are sensitive to climate and fossils show what climate they lived in.
To reveal patterns - 100mil years ago temps 6-8 degrees higher, co2 levels 5x higher.
Helps see national variations
Greenhouse and ice house
Greenhouse - co2 is high and temps and sea lile els are high.
Icehouse - opposite conditions
Antarctica’s galciation
Fossils from Antarctica show sun tropical conditions 40mil yrs ago then rapid cooling which created ice sheets three factors were responsible:
-Antarctica moved towards South Pole stopping warm water coming south.
-submerging of volcanoes stopped warm water reaching Antarctica.
-co2 levels fell
Quaternary glaciation
Climate altered from interglacial (warm) to glacial (long cold periods)
4 interglacial and 4 glacial periods have happened in past 450,000 years making thick ice sheets leaving only the south regions free of ice.
The Holocene
coo and warm periods
little ice age -Europe had some of coldest winters.
I’ve rpast 200 years climate been driven by human activity and everything new period, the Anthropocene.
Natural forcing driving climate change - external
-milankowitch theorised cycles that show effects go solar radiation reaching earths surface .
1. Tilt of Earths Axis- between 22-24 degrees, closer to 22 fewer seasonal differences (summers cooler winters milder) snow and ice dont melt increasing radiation reflecting lowering temperatures.
2. Earths movement on the axis- earth spins on the axis this alters amount of solar radiation earth receives eg northern hemisphere winters are milder when earth is close to sun.
3. Earths orbit around the sun- varies from circular to elliptical, very elliptical means there’s significant difference (30%) in solar radiation received between summer and winter. Correlating to glacial periods.
Internal forcings
Plate tectonics- as Pangea began to break up continents drifted, the changing distribution of land altered balance of incoming and outgoing solar radiation.
Volcanic gases- after eruptions gas and ash in atmosphere, ash reflects solar radiation out to space, some of the gases act as greenhouse, the more material erupted the higher impact of climate change only for several years tho.
Natural greenhouse gases- include water vapour ,co2 ,methane. Lead to warmer conditions.
Solar output- sunspot evidence , less unsportsmanlike earth gets less energy from so cooler. Over 11yr cycle and too little to alter global climate significantly.
Evidence the world has warmed since 19th century
-increase in temps- global sea surface temps increased by 0.74 degrees.
-shrinking ice sheets , Antarctica Penisula ice sheet is melting.
Rising sea levels- increasing by 3mm/year by 2 factors; thermal expansion of water (as sea surface temps rise water density decreases and water expands in volume)
And transfer of land ice to the sea, ice melts and water flows back to the sea.
How have anthropogenic ghg emissions changed since ore industrial times?
Co2- 1800s- 280ppm , 2015- 400ppm .
Methane- 1800- 700ppb - now 1,750 ppb.
why have anthropogenic ghg emissions risen?
-Pop growth- 1800- global 1billion, 2016- passed 7.4billion, increase in carbon footprint and carbon output by rising standards of living.
-land use changes- deforestation
-energy demand- still rely on fossil fuels to supply 87% of energy.
how is the natural greenhouse effect enhanced?
-ghg allow radiation from the sun to pass through the atmosphere, however they act like greenhouse glass reflecting the sunlight, allowing more heating to occur, as ghg volume increases makes atmosphere warmer.
Historical evidence for global warming debate
Greenhouse effect discovered in 1824, found out co2 was being added to atmosphere increasing temperatures,
The global warming debate
- The nature of the data of global mean temperature-there was concern that the next ice age was beginning in 1970 but then paleoclimate research was found (study of past climates using ice cores, tree rings) for example the cooling in 1960s was found due to the sunspot cycle.
2.the lack of global environmental awareness- 1980s the environmental awareness occurred, the discovery of the hole in the ozone layer over Antarctica, and the Valdez oil spill made headlining news and global warming soon became a focus of concern.
the role of governments and international organisations
The UN- International treaty signed by 41 countries at Rio earth summit. Kyoto protocol sets targets to reduce ghg emissions 192 countries involved.
The EU-environmental leader, European climate change programme set 20% cut in ghg emission, 20% of electricity from renewables and 20%improvement in energy efficiency by 2050.
The UK-uk climate chnage act reduction in ghgs of at least 80% by 2050 strategies include:
Increasing energy efficient(building insulation and smart metres)investing in new renewables (solar and wind)
India- argued that ACs were responsible in increase in ghg emissions and that they shouldn’t have to pay. They are 1.7tonnes under global eversge if co2 and priorities are reducing poverty.but do aim to lower ghg emissions by 20% by 2020.
Role of the media and interest groups
Media-more access to climate change through media since 1980s, spreads awareness quickly however often reports don’t have time or space to provide any more detail abt research. Donald trump.
Interest groups- energy and mining industries have vested interests in maintaining the production of fossil fuels, focuses like on the environment of wildlife can help interest groups supports reducing ghg emission.eg dorest energy solutions who promote grants to help encourage use of renewable energy.
Carbon stores and pathways
Stores-oceans,carbonated rocks,soil and biosphere
Pathways-photosynthesis,respiration,decomposition and chemical weathering.
Carbon cycle
-life is carbon based
-carbon stores like carbonated rocks lock away carbon for millions of years.
-carbon is stored in the atmosphere,the oceans, soils and living organisms.
-green plants and phytoplankton convert co2 into carbohydrates , therefore beginning flow of carbon.
-decomposition and oxidisation maintain the flow until co2 is returned back to atmosphere.
Positive and negative feedback to rising co2 in the atmosphere
P- amplified change and increases disequilibrium.
N-restores balance in a system.
Positive feedback
-increased ocean acidity- acidity reduced the oceans capacity to absorb co2 leaving more co2 in atmosphere.
-declining forest cover- global temp increases, tropical forest trees die,releasing co2,higher temps.
-increased cloudiness- more water atmosphere , so more clouds, they retain heat from earth , temp increases and more evaporation.
Negative feedback effects
-Increased aerosols in atmosphere- burning fossil fuels, more smoke and dust in atmosphere, relict solar radiation back into space decreasing global temps.
-Expansion of forests-as temps increase, tree line advances polewards , the expansion of forests will absorb co2 from the atmosphere.
Mean global temp chambers and sea level changes
Temp-dw pending on ghg emissions temps will rise between 0.3 and 4.8 degrees Celsius by 2100.
Sea level- between 1990-2010 rose over 3mm a year . Prediction of sea level reaching 1m or over if Antarctica ice sheet melts.
Climate change impacts on marine ecosystems
The rise in ssts is more intense in tropical and subtropical regions, coral ecosystems are risk due to coral bleaching (loss of algae due to rising water temps algae gives colour.) which can lead to coral mortality and the loss of one of the most diverse ecosystems on earth.
Loss of sea ice affects the mammals living in the region: walrus, seals and polar bears all rely on being able to alone across the ice or use it to rest,give birth or raise the young.
Urbanisation on the carbon and water cycle
Converting land use to rural from urban.
CC- removing vegetation = reduced photosynthesis and development of factories and homes = more co2 release.
WC- natural surfaces (soil) replaced with concreate = impermeable little filtration , runoff into Sewars.
agriculture on water cycle
Can reduce vegetation and soil compaction from machinery, both reducing amount of water infiltrating into soil , increasing run off.
