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THE ATMOSPHERE: CLIMATE, CLIMATE CHANGE AND OZONE DEPLETIONChapter 20
El niño and la niña
Atmosphere and weather
The atmosphere and weather atmospheric structure
The atmosphere and weather atmospheric structure
Troposphere Stratosphere
Extent: Ground level to 10 miles (16km)
Extent: 10 miles to 40 miles (16km to 65km)
Temperature normally decreases with altitude, down to -70oF (-59oC)
Temperature increases with altitude, up to +32oF (0oC)
Much vertical mixing, turbulence Little vertical mixing, slow exchange of gases with troposphere, via diffusion
Substances entering may we washed back to Earth
Substances entering remain unless attacked by sunlight or other chemicals
All weather and climate take place here
Isolated from the troposphere by the tropopause
Weather Solar
radiation
Weather Flowing air and
convection currents West to east
Jet streams, Earth’s rotations and air pressure gradients Polar jet stream
Fronts Regions of rapid
weather change
Climate
Climate Average temperature and
precipitation expected throughout a typical year in a given region
Major changes in climate are a major threat to the structure and function of ecosystems
Climates in the past Annual mean
global surface atmospheric temperature Periods of
cooling and warming
General increase in temperature
Climates in the past Proxies
Tree rings Pollen deposits Changes in landscapes Marine sediments Corals Ice cores
Thickness Gas content (CO2, CH4) Isotopes
Milankovitch cycles Rapid changes
Younger Dryas
Oceans and Atmosphere Oceans have an innate
heat capacity
Thermohaline circulation Conveyor system
Affect the density of seawater
One cycle is competed in 1000 years
Heinrich events Fresh water in the oceans
can change climate
Global climate change
Global climate change Factors that influence the climate include:
Internal components Oceans, the atmosphere, snow cover, sea ice
External factors Solar radiation, Earth’s rotation, slow changes in our
planet’s orbit, and the gaseous makeup of our atmosphere
Radiative forcing: the influence a particular factor has on the energy balance of the atmosphere – ocean – land system.
Factors can either be positive (warming) or negative (cooling)
Warming processes Infrared radiation and the greenhouse
effect
Warming processes Greenhouse
gases (GHGs) Water vapor Carbon
dioxide Methane Nitrous
oxides Ozone CFCs
Cooling processes The planetary
albedo Clouds Snow and ice Volcanoes Sulphate
aerosols Ozone
depletion Solar variability
(11 year cycle)
So… Global atmospheric
temperatures are a balance between positive and negative forcing from natural causes (volcanoes, clouds, natural GHGs, solar radiation) and anthropogenic causes (sulfate aerosols, soot, ozone depletion, increases in GHGs)
The greenhouse gases Carbon dioxide
Svante Arrhenius: “differences in CO2 levels in the atmosphere could greatly affect Earth’s energy budget”; he believed this change would be beneficial.
Charles Keeling, 1958, first measures of CO2 levels in Hawaii.
The greenhouse gases
Carbon dioxide Sources:
Fossil fuels Burning of forest trees Industrial processes
Sinks Oceans Terrestrial ecosystems
Sources of CO2 emissions from fossil fuel burning
Global carbon cycle
Atmospheric CO2750
Terrestrial biosphere
Living – 600 – 1000Dead - 1200
Oceanic dissolved inorganic carbonSurface – 1020Depths - 38100
Fossil fuel carbon
4130
Atmosphere – ocean exchange
92 (+/-0,6)90
62,4
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thesis
61
Resp
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6,6
Combustion
The greenhouse gases Water vapor
Absorbs infrared energy
Most abundant GHG Increases the
sensitivity of climate to increased anthropogenic GHG
The greenhouse gases Methane
Sources Microbial fermentation (wetlands, landfills,
cattle, manure) Coal and oil deposits Natural gas pipelines
The greenhouse gases Nitrous oxide
Sources Agriculture Burning of biomass Fossil fuels
It has a long resistance time (114 years) Also contributes to the destruction of
stratospheric ozone
The greenhouse gases Ozone
Short lived Source
Reactions of sunlight with pollutants from automobiles, burning forests and agricultural wastes
The greenhouse gases CFCs and other halocarbons
Long lived (50 – 100 years) Used as refrigerants, solvents and fire
retardants Montreal Accord (1987) prohibited the use
of CFCs
Evidence of Climate Change 1988, the UN Environmental Program and the
World Meteorologial Society established the Intergovernmental Panel on Climate Change (IPCC)
3 working groups were established Working group I: to asses scientific issues Working group II: to evaluate the impact on
global climate change and prospects for adapting to it
Working group III: to investigate ways of mitigating the effects
Evidence of Climate Change
The work of the IPCC has been guided on two basic questions: Risk assessment: is the climate system changing, and what is the
impact on society and ecosystems? Risk management: how can we manage the systems through
adaptation and mitigation?
Working group I third assessment (2001)
An increasing body of observations gives a collective picture of a warming world and other changes in climate system Correlation CO2 / global atmospheric temperatures Heat content in oceans increased dramatically (pp.552)
Retreat of glaciers Thinning of polar ice Global temperature has increased 1oF Increase in precipitation, greater frequency of El Niño events More frequent and intense droughts, heat waves, rainfall and
tornadoes Rise in sea level between 0,1 and 0,2 mts (2mm/year)
Working group I third assessment (2001)
Emissions of GHGs and aerosols due to human activities continue to alter the atmosphere in ways that are expected to affect the climate. GHGs and aerosols continue to increase in the
atmosphere
Working group I third assessment (2001)
Confidence in the ability of models to project future climate has increased Forecasts are more accurate Coupled general circulation models
(CGCM) are capable of simulating long-term climatic conditions
The main purpose of the models is to project the future global climate.
Working group I third assessment (2001)
There is new and stronger evidence that most of the warming observed over the last 50 years is attributable to human activities (pp. 554)
Working group I third assessment (2001)
Human influences will continue to change atmospheric composition throughout the 21st century Different scenarios project a rise in CO2
levels as a consequence of burning fossil fuels (pp. 557)
The scenarios demonstrate the crucial importance of our energy choices.
Scenario
A1B Balance across all energy sources
A1T Shifts to non fossil energy sources
A1Fl Fossil fuel intensive society
A2 Independent countries going their own way, increased population and varied economic growth and technological change
B1 Population developments with rapid changes in economies and effective global cooperation to reach sustainability
B2 Increasing populations, regional adaptations, significant efforts to achieve sustainability
Working group I third assessment (2001)
Global average temperature and sea level are projected to rise under all IPCC scenarios The global averaged surface temperature is
projected to increase by 1.4 to 5.8oC over the period 1990 to 2100.
Climate will be seriously affected Sea level is projected to increase (pp. 558)
Working group I third assessment (2001)
Anthropogenic climate change will persist for many centuries Once atmospheric greenhouse gas levels
are stabilized, temperatures and sea levels will continue to rise for hundreds of years because of the slow response time of the oceans.
Working group I third assessment (2001)
Further action is required to address remaining gaps in information and understanding More research is needed on current climate
variables such as: Occurrence and impacts of clouds Changes in glaciers and sea ice Functioning of the carbon cycle Natural variability of climate Impacts of aerosols
Response to climate change
Response to climate change Mitigation: take action to reduce
emissions Adaptation: anticipate some harm and
plan adaptive responses
Why should we take action? Precautionary principle: “the lack of full
scientific certainty shall not be used as a reason for postponing cost-effective measures to prevent environmental degradation”
Polluter pays principle: polluters should pay for the damage their pollution causes
Equity principle: the rich and privileged should care about those generations which follow
Mitigation: taking steps towards sustainability What has been done?
Framework convention on climate change (FCCC) Goal to stabilize greenhouse gas levels in the
atmosphere, starting by reducing greenhouse gas emissions to 1990 levels by the year 2000
Kyoto protocol Goal to reduce emissions of six GHGs to 5,2% below
1990 levels to be achieved by 2012
Mitigation What has been done?
U.S Policy Opposed to the Kyoto protocol
Compromised to protect the environment by reducing CO2 emissions and other GHGs
Global climate change initiative 18% cut in emissions intensity over the next 10 years
U.S climate change science program (CCSP) Seeks to address several issues on climate science
States and corporations Fourteen states are adopting renewable portfolio standards to
regulate CO2 emissions
Adaptation Climate change is already
happening? Crop yields are likely to be reduced in
tropical and subtropical regions as warming and droughts become more severe
Water is more scarce in many regions Increased heat and moisture will lead
to an increase in infectious disease Increased intensity and frequency of
storm events
Adaptation What is being done?
New funds Least Developed Countries
Fund: to advice countries on adaptation strategies
Special Climate Change Fund: to provide additional financial assistance to developing countries affected by climate change
Adaptation Specific adaptation
strategies: Improved governance Vulnerability assessments Access to accurate
information on climate change
Integration of impacts into economic processes.
Depletion of the ozone layer
Radiation and importance of the shield
Shorter wavelengths are more energetic and therefore can cause more damage
Formation and breakdown of the shield
O2 + UVB O + O
O + O2 O3
O + O3 O2 + O2
O3 + UVB O + O2
Halogens in the atmosphere
CFCl3 + UV Cl + CFCl2
Cl + O3 ClO + O2
Chlorine catalytic cycle
ClO + ClO 2Cl + O2
The ozone hole
Public policy regarding ozone depletion
Montreal protocol (1987) 184 countries signed for the reduction of 50% of
CFCs by year 2000 Later target was changed to a phase-out of CFCs
by1996 U.S. action
Du Pont Chemical Company phase out CFC’s production
Clean Air Act (1990)
Final thoughts… The world can respond collectively and
effectively to a clearly perceived threat Scientists continue to influence the
political response to threats. Similar actions will be taken during the
21st century to prevent catastrophic global climate change.
http://changeiness.com/el-nino-more-dangerous-than-la-nina.html
http://soficp-english2.blogspot.com/2010/12/climate-change.html
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