The Atmosphere • A mixture of gases surrounding the Earth. • Nitrogen – 78.08% • Oxygen – 20.95% • Argon – 0.93% • Carbon dioxide – 0.4% • Helium, methane, nitrous oxide, hydrogen, carbon monoxide, ozone, nitrogen dioxide, ammonia, and sulfur dioxide – less than 0.01%
Ozone • Most oxygen molecules (O2) are diatomic – there are two oxygen atoms bonded together. • When UV light or lightening bolts strike an oxygen molecule (O2), it splits become two free oxygen atoms (O). • Some of the free atoms join with the diatomic oxygen to form O3 (ozone).
Ground Level Ozone • Not all ozone is good ozone…when it is in the lower atmosphere it is considered to be a pollutant. • Breathing ozone can cause chest pain, coughing, throat irritation, and congestion; worsen bronchitis, emphysema, and asthma; reduce lung function and inflame the linings of the lungs. Repeated exposure may permanently scar lung tissue. • San Antonio has ozone action days or ozone alert days to try to cut down on ground level ozone.
The Ozone Layer • Most of the earth’s ozone (90%) forms a protective shield within the stratosphere (10-25 miles above the earth’s surface). • Without the ozone layer…we would have serious problems.
Good Ozone Bad Ozone
Why do we need the ozone layer? • Ultraviolet radiation is harmful to our health and the health of various ecosystems…and the ozone layer blocks/filters UV light. • In other words, its like natural sunscreen!!!
Ultraviolet Radiation (UV rays) • There are three types of UV rays: • UV-A: mildly irritating to the skin, needed for vitamin D production, not absorbed by oxygen or ozone. • UV-B: harmful to most organisms; absorbed only by ozone. • UV-C: deadly; luckily it is absorbed by both oxygen and ozone before it reaches the earth’s surface.
UV-B • Can cause cancer because it can mutate DNA! • It can also kill phytoplankton (the basis of aquatic and marine food chains) and cause certain species to be more likely to get diseases.
Think About It • The tanning beds at most salons use bulbs that emit significant amounts of UV-B radiation!!!!
Ozone Destruction • Some ozone is naturally broken down…but it is also naturally forming. • Since it is being naturally broken down at about the same rate as it is being formed it is said to be in equilibrium. • There are several compounds that can further break down ozone…this throws the equilibrium out of whack…and the ozone layer thins.
Warning… • In 1974 scientists first proposed that certain human activities and compounds might be affecting the ozone layer. • In 1977 the UN Environmental Programme drew up a World Plan of Acton on the Ozone Layer; it led Canada and several European countries to ban the use of CFCs in aerosols.
Not Heeded… • In the US and other countries politicians and scientists wanted more evidence before restricting the use of these chemicals. • In 1985 a team scientists reported a 50% decrease in the concentration of ozone over Antarctica.
The Montreal Protocol • On September 16, 1987, 35 countries signed the Montreal Protocol on Substances that Deplete the Ozone Layer. • In 1999 it was amended to include stronger controls. • It bans or limits ODSs (Ozone Depleting Substances) • CFCs • Halons
Climate vs. Weather • Weather refers to the atmospheric conditions that result from interactions between temperature, moisture, winds, and clouds. • Climate refers to the average weather pattern of a location over a period of years. • The sun impacts temperature, moisture, wind, and clouds…so the sun influences both weather and climate.
Conduction, Convection, Radiation • As the sun shines…energy is being transported through space (the sunlight), this is known as radiation. • As water and air are heated by the sunlight they move heat through convection…the transfer of energy due to the movement of warmed matter. This causes wind, ocean currents and air currents (like the Jet Stream). • Conduction is the transfer of energy through direct contact…air is a poor conductor…but ice burgs melting in the ocean can be caused by warmer water…that would be conduction.
The Greenhouse Effect • In a greenhouse, short wavelengths of light pass through the glass of the house…but become trapped since it loses energy and becomes longer wavelengths (which cannot pass through).
The Good and the Bad • Without the greenhouse effect, the Earth would be too cold to support life as we know it. • Increasing greenhouse gases seems to have led to an increase in global temperatures…which is altering the planet in ways we cannot even predict…
Some Common Greenhouse Gases • Water vapor-most important…natural and not changing so not a cause of climate change. • Carbon dioxide-most important from a climate change perspective…naturally produced from cellular respiration…increased due to combustion (mostly fossil fuels). • Methane-also increasing…traps more heat than CO2…decomposition, livestock (gas), landfills, leaking natural gas pipelines. • CFCs-so stable that they are still around! • Nitrous oxide (N2O)-increasing, 310x more powerful than CO2. • Ground level ozone!
Possible Effects of Climate Change • Melting ice caps and glaciers • Increased sea level • Precipitation and evaporation are both predicted to increase…in some areas evaporation is predicted to exceed precipitation • Possible increased severity of storms and flooding
Movement of species • Soils might become drier • Increased fires • Crop yield altered • Changes in weather forecastibility • Increase in ground level ozone • Heat related illness and deaths could increase during summer months • Increase in insect borne diseases