Climate Changes and Anthropogenic Influences

ATM 100

Introduction to Climate Changes and Anthropogenic InfluencesBrief history of climate change on

Earth and air pollution

Chemical cycling in the environment

Introduction to Acid deposition

A Brief History of the Earth

Earth forms along withthe rest of Solar Systemapproximately 4.6 billion years bp (before present).

Earliest life appears 4 billion years bp in the oceans.

◦ At this time the atmosphere is mostly composed of H2O, Carbon Dioxide (CO2), Sulfur Dioxide(SO2,),

Carbon Monoxide (CO), Sulfur (S2,) Chlorine (Cl2), Nitrogen (N2), Hydrogen (H2), Ammonia (NH3),

and Methane (CH4)

Early Climate ChangeEarly Climate ChangePhotosynthesizing cyanobacteria

evolve 3 billion years bp. They start emitting a noxious and caustic gas – Oxygen! (O2) By 2.6 billion years bp this “pollution” results in the Oxygen Catastrophe. The fossil records indicate that at least 90% of all species then in existence were wiped out.

The rise of OxygenAs oxygen builds up in the

atmosphere a layer of ozone (03) forms in what becomes the Stratosphere. Ozone is highly absorptive of the deadly frequencies of solar short wave radiation.

Eventually, the ozone layer stops (nearly) all deadly sw radiation from reaching the Earth’s surface, allowing life to emerge from the oceans and colonize the land.

The The

GlobGlobalal

ClockClock

The Dawn of Humanity

Earliest hominids appear ~23.6 million years bp.

“Humans” first appear ~2 million years bp.“Modern” Humans appear 100,000 years bpAgricultural revolution occurs ~5000 years

bp – civilization begins.

Human History1640: Industrial revolution begins in

EnglandMid–18th century: industrial revolution

spreads throughout Europe – eventually worldwide

Mid-19th century: Dickens describes the ‘fogs”of London in his novels.

1884 – John Ruskin gives lecture on the “Storm cloud of the Nineteenth Century”. Today, we would call this “Acid Rain”.

History Concluded 1928 – Researchers at Dupont Labs develop

Chlorofluorocarbons (CFCs).1950s-60s – Researchers in Sweden note that

many of their lakes are acidifying causing widespread fish kills. Later this problem is confirmed in North America and Asia as well.

1970 – The Clean Air Act is passed in the United States (Revised in 1990)

1973 – USA bans CFCs 1987 – “Montreal Protocol” bans CFCs

worldwide1994 – US EPA implements “Cap and Trade”

system for sulfur emissions.

Chemical Cycling Chemical Cycling (definitions)(definitions)

Source – a mechanism that supplies a gas or other material into the atmosphere.

Sink -- a mechanism that removes a gas or other material into the atmosphere.

Residence time – how long the gas or material stays in the atmosphere. Items with long residence times will become uniformly distributed. The shorter the time the more regional or local the distribution will be.

Chemical Cycling Chemical Cycling (definitions) (2)(definitions) (2)Feedback – As a mechanism proceeds,

it affects the processing of other atmospheric (or environmental) mechanisms◦Positive feedbacks – As the process

continues, the conditions favoring that process are reinforced. (e.g. CO2 and SST)

◦Negative feedbacks – As the process continues, the conditions favoring that process are counteracted. (e.g. DMS and clouds.)

Natural Releases of Sulfur Natural Releases of Sulfur and Nitrogenand NitrogenVolcanoes (Sulfur and Nitrogen)

Lightening (Nitrogen)

Bacteria (Nitrogen)

Fertilizer or Acid Rain?Fertilizer or Acid Rain?In naturally occurring concentrations,

Sulfur and Nitrogen react with ammonium ion (NH4

+) forming ◦Ammonium sulfate ◦Ammonium nitrate ◦Which are fertilizers

However, once the ammonium and other buffers are exhausted, something different occurs…..

How Acid forms in the How Acid forms in the AtmosphereAtmosphereBurning fossil fuels both by industry

and by vehicles also releases sulfur dioxide (SO2) and nitrogen oxides (NO and NO2) into the atmosphere.

These gases are mixed into clouds, where they dissolve into water droplets and are oxidized:◦SO2 H2SO4 [Sulfuric Acid]

◦NO2 HNO2 [Nitric Acid]

USA Sulfur Emissions 1980 - USA Sulfur Emissions 1980 - 20062006

NADP MapsNADP MapsNational Atmospheric Deposition

Program:http://nadp.sws.uiuc.edu/

isopleths/