Greenhouse Effect and Climate Change

The enhanced greenhouse effect, sometimes referred to as climate change or global warming, is the impact on the climate from the additional heat retained due to the increased amounts of carbon dioxide and other greenhouse gases that humans have released into the earths atmosphere since the industrial revolution.

The enhanced greenhouse effect, sometimes referred to as climate change or global warming, is the impact on the climate from the additional heat retained due to the increased amounts of carbon dioxide and other greenhouse gases that humans have released into the earths atmosphere since the industrial revolution.

Greenhouse effect

  • The natural greenhouse effect is where various gases in the atmosphere, primarily
    Source: IPCC Temperature Change

    Source: IPCC Temperature Change

    water vapour and carbon dioxide are transparent to shortwave incoming radiation, but absorbs outgoing long wave radiation. This occurs because molecules resonate at certain at certain frequencies absorbing and releasing heat

  • Temperatures were stable up to 1900 followed by a warming period up to 1940, a brief cooling, and then continuing to increase since 1950.
    • Sea level rise – gradual increase in early 20th century, accelerating after 1950
    • Snow cover decreasing but with large amounts of variability
    • Average temperature increasing
  • Carbon 12, 13 and 14 in the atmosphere (Carbon 12 is dominant). Plants take up C12 so ff has higher C12 concentrations than the modern atmosphere. When burnt, C13 is depleted and ratio of C13:C12 decreases
  • 5.5 GtC emitted from ff and 1.6GtC from deforestation, with 2 GtC absorbed by oceans and 1.8 GtC going into the biosphere, a net atmospheric sink of 3.3 GtC.
    • When mixed in atmosphere this equals 1.7 ppm

Global emissions

  • IPCC (2007) – Global annual emissions of anthropogenic GHGs in 2004 is 49 GtCO2-eq/yr
    • 29 GtCO2-eq/yr from fossil fuel use and other sources
    • 10 GtCO2-eq/yr fromCH4 from agriculture, waste and energy
    • 5 GtCO2-eq/yr from CO2 deforestation, decay and peat
    • 3 GtCO2-eq/yr from N2O agriculture and others
  • IEA – reports we currently burn 12 Gt oil equivalent per year  = 30
  • SOTC – ff CO2 emissions increased by more than 3% per year from 2000 to 2010
  • SOTC – Australia contributes 1.3 % of global CO2 emissions
Emissions by fuel and Region

Emissions by fuel and Region

Drivers in climate change

Global atmospheric concentrations of CO2, CH4 and N2O have increased as a result of human activities since 1750 and now far exceed pre-industrial values

Impacts of climate change4.

  • Increase in extremes (heat waves, flooding)
  • Increase in intensity of tropical cyclones
  • Increase in intensity and duration of droughts
  • Phenology changes (timing of spring, disruption to natural cycles)
  • Drying in mid-latitudes, increase in river runoff in high latitudes
  • 20-30% plant and animal species under threat
  • Coral bleaching and mortality  (ocean acidification)

Future impact of climate change

  • Ecosystem
  • Food
  • Coasts
  • Industry, settlements and society (poor communities, those living on coastal and river flood plains and those dependent on climate sensitive resources)
  • Health
  • Water

IPCC Model

  • Scenarios
    • B1 has emissions halving by 2100, same population and rapid eco structures toward a service and information economy
    • B2 emissions plateaus at 2050, intermediate population and economic growth with local solutions to eco, social and environmental sustainability
    • A1 very rapid eco growth and intro of new/efficient technologies
    • A1F1 has the highest emissions
    • A2 triples emissions, from high population, slow eco development, slow tech change
  • Key uncertainty
    • Difficulties remain in reliably simulating and attributing observed temperature changes to natural or human causes at smaller than continental scales
    • Uncertainty in equilibrium climate sensitivity creates uncertainty in the expected warming for a given CO2 –eq stabilisation scenario
    • Understanding of how development planners incorporate information about climate variability and change into their decisions is limited
    • Assumptions regarding the drivers of technology diffusion and the potential of long term technology performance and cost improvements
  • Climate change sceptics argue
    • Natural variation
    • The sun
    • Cooling since (1998)
    • CO2 is good for plants
    • Warming in the first half of 20th Century before CO2 started really increasing
    • Climate scientists are running a conspiracy
  • Report states
    • “Warming of the system is unequivocal”
    • Most of the observed increase in global average temperature… is very likely due to GHG concentrations
    • Even if GHG emissions dropped warming would continue
    • For next two decades a warming of about 0.2⁰C per decade is predicted
    • After 2050, projections diverge with amount of emission dominating the uncertainty in climate change
    • “Continued GHG emissions at or above current rates would cause further warming and induce many changes in the global climate system during the 21st Century that would very likely be larger than those observed into the 21st Century”
    • “Anthropogenic warming could lead to some impacts that are abrupt or irreversible, depending upon the rate and magnitude of the climate change.

Who are the IPCC

  • 195 member states (countries)
  • Scientists nominated by home country who contribute their expertise
  • Working groups review the current state of the art of peer review literature on
    • The physical basis
    • Climate change impacts adaptation and vulnerability
    • Mitigation
  • Summarises for report go before a Plenary and are debated for validity
  • Final product is a mix of scientific expertise and political diplomacy
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