Lecture 7 Air: Climate and Global Changes

Lecture 7
Air: Climate and Global Changes

The Atmosphere (1)

The atmosphere is composed of

Gases:

• 78.1% Nitrogen,

• 20.9% Oxygen,

• ~1% Argon,

• 0.035% Carbon dioxide,

• Trace amounts of Methane, Hydrogen, Ozone, Water vapor, Carbon monoxide, Sulfur dioxide, Nitrogen oxides.

The Atmosphere (2)

Particulates -solid and liquid particles found in the atmosphere: Natural:smoke from forest fires, volcanic ash, sand and salt particles. Antropogenic: industrial & car emissions, smoke / soot from fires.

Particulatesaffect weather and climate by:

• 1. Absorbing water and accumulating water, cloud formation.

• 2. Absorbing or reflecting sun light, so changing the portion of solar radiation that falls on Earth

The Atmosphere (3)

troposphere ~10 km
stratosphere ~10-50km
mesosphere ~50-80 km
thermosphere ~80-120 km

The troposphere extends from the Earth’s surface to about 10 km above the Earth.

The stratosphere extends from the top of the troposphere to about 50 km above the Earth.

Most ozone is located in a band between 15 and 30 km.

The mesosphere extends from 50-80 km above the Earth.

The thermosphere extends to about 300 km above the Earth.

Weather and Climate are defined by the atmosphere

Weather: atmospheric conditions (short-run) existing at a given time and location.

• immediate

Climate: weather conditions over a long period of time (years, decades, centuries).

• long-term and general

Weather & Climate Elements

• Temperature

• Pressure

• Wind

• Moisture content

Atmospheric Pressure, Temperature & Wind

Atmospheric pressure: force exerted by air molecules on the earth’s surface (per square unit)

– at Sea level: 1 atm or 760 mm Hg = 101.325 kPa ~ 1.03 kg/cm2

– more gas molecules at Sea level than on mountain peak à

higher pressure is at Sea level (NEXT SLIDE).

Temperature & Pressure (based on Gas Laws)

• very warm air has low pressure

• rising air produces low pressure

• very cold air has high pressure

• sharply descending air produces high pressure

Wind = horizontal air movement

Insolation → Unequal heating → Temperature gradients → Pressure gradients → WIND

• Air moves from high to low pressure area

• Wind levels off the uneven distribution of air pressure

• Main driving forces of the wind:

– Pressure gradient

– Coriolis Force

– Friction

Wind as the result of pressure gradients

Physical phenomena in atmosphere

• Evaporation:

phase transition “liquid à vapor”

• Latent heat:

heat absorbed (or released) during phase transition Latent heat for water is high: 540 cal/g

• Condensation

phase transition “liquid à vapor”

• Convection currents –

heat (energy) transfer in liquid or gas

Convection and Atmospheric Pressure

• Horse latitudes:

30 degrees N & S

• Trade winds, or passats:

NE winds in Northern hemisphere

SE winds in Southern hemisphere

• Air pressure

Hstory: sailors gave the region name "horse latitudes" because ships relying on wind power stalled; fearful of running out of food and water, sailors threw their horses and cattle overboard to save on provisions.

Blowing from horse latitudes toward the low pressure equator are TRADE WINDS. They quickly move (propel) trading ships across the ocean, the trade winds between about 30° latitude and the equator are steady and blow about 11-13 miles/ h. In the Northern Hemisphere, the trade winds blow from the northeast: NE Trade Winds; in the Southern Hemisphere they blow from the southeast: SE Trade Winds.

Movement of the atmosphere has a reproducible general pattern caused by earth spinning, and heating / cooling at the cooler N and S poles relative to the warmer equator. These conditions produce movement of air around the earth through convection: Hadley cells. Dominant winds: Trade Winds and Westerlies, occur within these convection cells. These forces dictate to a large extent the movement and dispersal of pollutants and other substances through the atmosphere.

Coriolis Force an artifact of the earth's rotation

Coriolis effect produces steady reliable wind patterns controlled by the earth’s spin:

Trade winds (passats) blowing from 30N to equator – bend right in N hemisphere à

They become NorthEast winds.

Object deflects:

- to the right in N Hemisphere

- To the left in S hemisphere

Global Winds & Storms

• Passats (trade winds): blow from 30’s latitudes to equator: NE wind in Northern hemisphere

SE wind in Southern hemisphere

• Monsoons – seasonal winds on ‘water-land’ boundaries:

– Summer: heavy rainfalls ‘wateràland’

– Winter: dry weather/winds ‘landàwater’

• Hurricane, typhoon, tropical cyclone – tropical revolving storms, originated above water (oceans/seas): à Katrina, Dennis, Rita, etc.

• Tornado – twister, forming funnel in thundercloud: destructive, high speed: 65-500 km/h, low pressure inside.

• Tsunami – underground earthquakes as predecessors of ‘Tsunami’ storms

• Sirocco – Mediterranian hurricane coming from Sahara

Storm ‘Katrina

Hurricane Katrina will be the most costly disaster in US history, though the loss of life was not as high as some other disasters

Seasonal Winds and Monsoons

The seasonality of weather is also a very important aspect of how weather influences the environment and people. For instance, in India, Society has depended on the timing and degree of monsoon rains that occur when warm, wet air from the Indian Ocean is drawn into the Indian subcontinent and releases rainfall as it rises and cools over the Himalayan mountains. Lack of monsoon rain due to different weather patterns sometimes causes drought, starvation, and death to people living in the region as well as to their animals, crops, and other organisms that depend on seasonal rainfall.

Tornadoes

Tornadoes are local cyclonic storms caused by rapid mixing of cold, dry air and warm, wet air

Unfortunately, pressure differentials can create extremely powerful forces that are destructive in nature. For instance, tornadoes and cyclones are extremely powerful local winds generated by rapid mixing of cold, dry air and warm, wet air. They powerful forces can cause high levels of destruction including loss of life.

Greenhouse Effect”

Another extremely important aspect of the atmosphere is what is called the 'greenhouse effect". Of the energy that comes from the sun, and impacts on the top of the earth's atmosphere, only about half of the energy reaches the surface of the earth. The energy that is absorbed by the surface of the earth is changed to a lower quality heat energy, and most of that energy is re-emitted as infrared energy. Much of this energy is reflected back to the earth to be absorbed and re-emitted again, particularly when there is high cloud cover. Trapping of the energy with in the earth's atmosphere causes the earth to be warmer than it otherwise would be...like a greenhouse. Notice that the presence of cloud cover greatly changes the reflectivity and absorptivity of the earth, called the albedo. One of the major variables in the greenhouse effect is the presence of cloud cover.

2 slaida est’ na kompe posmotri!

Spectrum of Solar Radiation

Radiation from the sun - source of E. Electromagnetic spectrum that includes light encompasses a wide range of frequencies, and what we can actually see as visible light is a very narrow band within that range. Photosynthesis of plants is driven by the narrow range of visible light, ranging from about 0.4 - 0.7 micrometers.

Other wavelengths can have effects on the environment; for instance, x-rays and gamma rays can be deadly, ultraviolet radiation gives us a sun tan, and also, potentially, skin cancer. Infrared energy heats us, and we use microwaves and radio waves to transmit energy. Microwave E heats lunch.

Climate Change

• The Earth's climate changes, often in short or long cycles.

• Ice ages, droughts

• Orbital shifts, sunspot cycles, ocean currents

• Climate does not necessarily change gradually - meteor impacts, methane releases?

Climate = general pattern of weather for a region over time. F i, in Astana in Jan we expect it to be cold and snowy. Weather is the short-time expression of climate which can vary significantly from day-to-day. Throughout the history of the Earth, climate has changed constantly on a long time scale. This is due partially to the movement of crustal plates and the interaction of weather with changing continent structure. Over the last 2 mln yrs, the earth has experienced Ice Ages that occur on a regular basis, along with smaller patterns of change in weather. Evidence of climate change is abundant in the Earth's record. It is thought that climate change normally follows long term cycles caused by shifts in the orbit of the earth, sunspot cycles, and possibly changes and ocean currents due to the movement of the continents. Certain catastrophic events such as a large asteroid or comet slamming into the earth could cause major climate change in a relatively short period of time. The possibility that a major impact such as this did in the dinosaurs about 65 mln yrs ago is highly likely.

CO2 level and Temperature: history

F.I, these figures show the variation in temp-re during 400,000 years. Note that there were relatively large fluctuations in the average T-re of the earth including warmer periods and cooler periods than the present that lasted thousands of years. Note that large decreases and increases in temperatures are part of the climate record.

Human-Caused Global Climate Change

• Global surface temperatures increased by ~0.74 degrees C over the past 100 yrs

(1906-2005)

• Much of this change is a result from human activities, primarily the burning of oil, gas, and coal.

• CO2 levels are increasing ~0.5% a year.

• 1990s atmosphere over time that carbon dioxide levels all are increasing at a rate of about 0.5% per year. was the hottest decade on record

A major controversy regarding the atmosphere and climate is whether or not, and the degree to which human activity is changing climate. For instance, the surface temperatures of the earth have been increasing, although the high degree of variability of temperature may mask any changes and can make their measurements controversial. Many scientists believe that the burning of fossil fuels and emissions of carbon dioxide from land clearing have added to the greenhouse effect that we already know greatly increases relative temperatures of the Earth. For instance, it is a matter of simply measuring the levels of carbon dioxide in the

2 slaida!

Carbon dioxide levels are increasing

This figure, for instance, shows the measurement of carbon dioxide at the Mauna Loa observatory in Hawaii. The amount of carbon dioxide has been increasing steadily. Note also the annual changes in carbon dioxide that give the curve a saw tooth appearance. These seasonal changes are due to the difference between respiration in the Spring and Summer in northern temperate areas, which has a much larger land surface area than the southern temperate areas. When Rob took Botany 101 at the University of Maryland in 1974, he was taught that carbon dioxide was 330 ppm, and it is now over 370 ppm on the average.

Greenhouse Gases (GHG)

H2O – main GHG

CO2

CH4

CFCs

Ozone

NOx

Increases in carbon dioxide are considered to be the major contributor to global warming potentially caused by human activity, accounting for nearly two-thirds of global warming. Methane, a much more potent but rarer component of the Earth's atmosphere, accounts for about 19%, with chlorofluorocarbons, nitrous oxides and Sulfur hexaflourides showing smaller relative impacts.

Ozone depletion - result of human activities

CFCs (chlorofluorocarbons)

used widely as refrigerants, sprays

catalyze the destruction of

OZONE O3, a chemical that

protects life on earth from harmful radiation.

10% loss of ozone

worldwide causes more

skin cancer and cataracts

In 1985: discovered a significant thinning of the ozone layer over the Antarctic in Southern Hemisphere:

“ozone hole.”

Ozone in stratosphere shields the Earth from harmful UV radiation.

Chlorofluorocarbons are strongly implicated in the ozone reduction in the upper atmosphere.

CFC production

The figure above shows the reduction in production of chlorofluorocarbons since the Helsinki convention, which largely banned their production, was passed in 1989. Notice that some developing countries continue to produce increasing levels of chlorofluorocarbons, though not nearly at the rate that the industrialized countries of the world produced 15 years ago

Global warming facts

Potentially able to damage life on Earth

Natural fluctuations in weather/climate - ice ages

- warm periods

1. Thinning Ice

a. Antarctica 2. Hotter times

90 yrs – hottest decade

3. Wild weather

a. Heavy Rains

b. Fires

c. Floods

d. Hurricanes

b. Mt. Kilimanjaro

c. Lake Baikal

d. Montana

e. Venezuela

Global warming facts (2)

4. Nature’s pain

d. Massive Seal death in Caspian Sea

~10,000 seals

1. Pacific salmon death (West Canada)

sea lice = fish parasites

b. Polar bears – habitat loss

c. Coral reefs: cyanide & explosive fishing, global warming

5. Rising sea levels

a. Caspian Sea by ~2.25 m 1978 – 1996

b. Florida, Maryland

c. North Sea, Baltic Sea

d. Brazil

Environmental disaster: open net-cage salmon farming industry, and associated proliferation of billions of lethal sea lice, that blight the coast of British Columbia, west Canada.

Outlook

Little chance of halting global warming (even if every country in the world adheres to Kyoto protocol tomorrow).

How to ward off disaster

1. Storing Carbon (CO2)

a. Planting trees

b. No-till agriculture

c. Sequestration –

fixation of CO2

d. Silicate rocks

eating CO2 -> carbonates

2. Alternate energy

a. Wind power

b. Solar power

c. Nuclear power

d. Fuel cells

Sequestration – different methods to capture and store CO2:

Coal burning plants: flue gases are condensed, water separated and CO2 is stored.

Mixing ocean, Peat formation

No-till - нулевая обработка почвы, гербицидная обработка почвы (без вспашки)

In no-till agriculture, farmers plant seeds without using a plow to turn the soil. Soil loses most of it carbon content during plowing, which releases carbon dioxide gas into the atmosphere. Increased levels of CO2 in the atmosphere are associated with global climate change.

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