Evolution of the Atmosphere

Review of last lecture

• • • The modern climatology (meteorology) was born in the 1940s (a very young science!), but has been growing very fast! Now we have a global observational network with many satellites, ships, radars and surface stations, as well as very comprehensive prediction models running on the world ’ s fastest supercomputers. The current status of weather and climate predictions: (1) weather prediction good to 10 days, (2) tropical cyclone prediction good in track but not in intensity, (3) climate prediction good to two seasons, (4) climate change projections have a 3-fold difference in magnitude.

The main reasons of the difficulties in weather and climate predictions: (1) Teleconnection problem, (2) Feedback problem, and (3) Subgrid-scale problem.

Some basic concepts

• Units of measurement • Scientific notation

Standard units of measurement SI (System International)

Quantity

Length Mass Time

Name

meter kilogram second Temperature Kelvin Density kilogram Speed Force Pressure Energy Power per cubic meter meter per second newton pascal joule watt

Units

m kg s K kg/m 3 m/s m.kg/s 2 N/m 2 N.m

J/s

Symbol

m kg s K kg/m 3 m/s N Pa J W

nano micro milli centi deci deka hecto kilo mega giga … yotta

Scientific Notation

one-billionth one-millionth one-thousandth one-hundredth one-tenth ten one hundred one thousand one million one billion 10 -9 10 -6 10 -3 10 -2 10 -1 10 1 10 2 10 3 10 6 10 9 10 24 0.000000001

0.000001

0.001

0.01

0.1

10 100 1000 1000000 1000000000

The Universe

Hubble (2012) view – each light speck is a galaxy – some of these are as old as 13.2 billion years – the Universe is estimated to contain 200 billion galaxies.

• The Universe is made up of voids and filaments, that can be broken down into superclusters, clusters, galaxy groups, galaxies, and subsequently into stars and their constituents (e.g. our Solar System).

Our Milky Way galaxy

Our solar system is in the Orion arm, and we are about 25,000 light years (2.5 X 10 17 miles) from the very center of the Galaxy.

Life cycle of the Sun and Earth

The earth will be inhabitable for another 0.5 billion years, if we protect it well enough.

After another 1 billion years, all oceans and rivers will have completely disappeared. The mean global temperature will reach 160 F.

Formation of the Earth

• 4.6 billion years ago, as part of the birth of the solar system

Earth’s first Atmosphere

• Topic of much debate • Probably H and He, no oxygen • No oceans • No magnetic field to deflect solar winds and cosmic rays

Differentiation of the Earth

• Cooled enough to form crust, heavily populated with volcanoes • Formation of magnetic field that deflects the solar wind and cosmic rays • Increasing volcano activity, releasing gases into atmosphere

Earth’s Second Atmosphere

• Around 4 - 3.8 billion years ago • Composition similar to gases released from volcanoes (CO2, water vapor, nitrogen) • Large concentration of gases in the atmosphere (100 times of today’s) • Greenhouse effect keeps the earth from freezing

Earth Begins to Cool

• Water condenses to form oceans • Carbon Dioxide dissolves into oceans eventually forming carbonates • Nitrogen becomes major component of the atmosphere

Life and oxygen

• Around 3.5 billion years ago cyanobateria were known to be carrying out photosynthesis CO2 + H2O + sunlight = organic compounds + O2 • Eukaryotes capable of respiration emerge around 2.5 billion years ago. Photosynthesis becomes more efficient • Increased oxygen concentration, around 1% of atmosphere, produced the ozone layer • Life emerges outside of the oceans . Formation of terrestrial plants lead to atmospheric saturation of oxygen

Earth’s third atmosphere (current) • Reached around 400 million years ago • Consisting of gases, water droplets (clouds/precipitation) and aerosols

Formation of the continents and ocean basins

• 225 million years ago from Pangaea (the super continent)

Permanent gases and variable gases

• Residence time: The amount of time a gas is in the atmosphere • The permanent gases: gases having long residence times (N 2 =42,000,000 y, O 2 =5,000 y), 99.999% of total atmosphere mass • The variable gases: Gases generally having shorter residence times (H 2 O=10 days, CO 2 =150 y).

Importance of the Variable Gases

• CO2 and water vapor are the major greenhouse gases • Water can exist in all three phases (vapor, liquid, ice) on Earth. The released latent heat during phase changes of water drives global atmospheric circulation and many weather systems (e.g. hurricanes).

Montreal Protocol to ban freon • O3 protects us against harmful ultraviolet radiation

Earth’s climate history

Temperature variation during the past 2.4 billion years - The ice ages • • • An ice age is a long interval of time (10 6 to 10 7 of years) when global temperatures are relatively cold and large areas of the Earth are covered by continental ice sheets and alpine glaciers. At least 5 ice ages have occurred throughout Earth ’s history. Currently, we are living in an ice age!

Typically develop slowly, but end more abruptly.

Variations within an ice age: – Abrupt climate change and tipping point

Some examples of tipping points

Variations within an ice age: The 100,000-year glacial cycle Possible causes: • Change in atmospheric composition (e.g. CO 2 , CH 4 ) • Change in earth’s orbit (e.g. Milankovitch cycles) • Motion of tectonic plates • Change in solar output

The little ice age (1350AD-1850AD)

Evolution of the atmosphere

– The standard units of measurements (SI) – Earth ’ s three atmospheres: 1st: 4.6 billion years ago , H, He Transition: formation of magnetic field, volcano activities 2nd: 4 billion years ago, CO 2 , H 2 O, N 2 Transition: emergence of life, formation of ocean 3rd: 400 million years ago, O 2 Important event: formation of seven continents – What is the residence time? What is the difference between the permanent and variable gases? Name 3 of each . What are the most and second most abundant gases?

– Given that variable gases are so rare, why are they considered at all? How are CO 2 and O 3 changing?

– Earth ’ s climate history: ice ages (at least 5 have occurred so far. We’re in an ice age!), 100,000-year cycle, little ice age (1350-1850AD)

Works cited

• • http://ase.tufts.edu/cosmos/view_picture.asp?id=850 http://www.waterconservation.co.za/2010/10/26/theres -never-been-a-better-time-to-start-harvesting rainwater/