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

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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 mitiating 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 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

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

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 from 9 to

88cm

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

Clean Air Act (1990)

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