Climate Changes and Anthropogenic Influences ATM 100

Introduction to Climate Changes and Anthropogenic Influences Brief 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 with the rest of Solar System approximately 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 H 2 O, Carbon Dioxide (CO 2 ), Sulfur Dioxide(SO 2,), Carbon Monoxide (CO), Sulfur (S 2,) Chlorine (Cl 2 ), Nitrogen (N 2 ), Hydrogen (H 2 ), Ammonia (NH 3 ), and Methane (CH 4 )

Early Climate Change Photosynthesizing cyanobacteria evolve 3 billion years bp. They start emitting a noxious and caustic gas – Oxygen! (O 2 ) 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 Oxygen As oxygen builds up in the atmosphere a layer of ozone (0 3 ) 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 Global Clock The Global Clock

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 bp Agricultural revolution occurs ~5000 years bp – civilization begins.

Human History 1640: Industrial revolution begins in England Mid–18 th century: industrial revolution spreads throughout Europe – eventually worldwide Mid-19 th century: Dickens describes the ‘fogs”of London in his novels – 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 – The Clean Air Act is passed in the United States (Revised in 1990) 1973 – USA bans CFCs 1987 – “Montreal Protocol” bans CFCs worldwide 1994 – US EPA implements “Cap and Trade” system for sulfur emissions.

Chemical Cycling (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 (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. CO 2 and SST) ◦ Negative feedbacks – As the process continues, the conditions favoring that process are counteracted. (e.g. DMS and clouds.)

Natural Releases of Sulfur and Nitrogen Volcanoes (Sulfur and Nitrogen) Lightening (Nitrogen) Bacteria (Nitrogen)

Fertilizer or Acid Rain? In naturally occurring concentrations, Sulfur and Nitrogen react with ammonium ion (NH 4 + ) 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 Atmosphere Burning fossil fuels both by industry and by vehicles also releases sulfur dioxide (SO 2 ) and nitrogen oxides (NO and NO 2 ) into the atmosphere. These gases are mixed into clouds, where they dissolve into water droplets and are oxidized: ◦ SO 2  H 2 SO 4 [Sulfuric Acid] ◦ NO 2  HNO 2 [Nitric Acid]

USA Sulfur Emissions

NADP Maps National Atmospheric Deposition Program: