1. Arizona Western College BIO 181 USDA-NIFA (ACIS)
Climate Change
Arizona Western College
BIO 181
USDA-NIFA (ACIS)

2. Climate Change
Climate change is a change in the typical or average weather of a region or city.
Earth's climate is the average of all the world's regional climates.
Global warming is a type of climate change that our Earth is experiencing now; in the past Earth has also experienced global cooling.
When global warming or cooling take place, the drastic changes in climate and weather has major and long-lasting impacts on Earth’s inhabitants.
This could be a change in a region's average annual rainfall, for example. Or it could be a change in a city's average temperature for a given month or season.
Climate change at a global scale means a change in Earth’s average temperature or a change in precipitation patterns.
Our Earth is warming. Earth's average temperature has risen by 1.5°F over the past century, and is projected to rise another 0.5 to 8.6°F over the next hundred years. Small changes in the average temperature of the planet can translate to large and potentially dangerous shifts in climate and weather.
NASA Logo linked to climate change page

3. Earth’s Climate is Dynamic
Changes in the energy and movement of the sun and Earth
Surface reflectivity
Season
Axial rotation and tilt
Milankovitch cycles
Chemicals ultimately drive Earth’s climate
The Greenhouse Effect
Release of chemical by-products from burning fossil fuels by humans
Sun’s energy is transmitted through atmospheric gasses
Earth’s temperature is a balancing act
The Earth is about 33OC warmer than expected if we consider only the amount of solar energy received and reflected.
Trace atmospheric gases, H2O and CO2, trap infrared radiation that would otherwise be re-emitted into space.
This effect is known as the Greenhouse Effect - the mechanism that keeps greenhouses hotter than we might expect.

4. Radiation Interacting with Molecules
Greenhouse gasses, such as CO2, N2O, and CH4 absorb energy by causing vibrations in the molecular bonds.
Vibrations cause the molecule to break, stretch, or bend.
Energy associated with the molecular movement generates heat.
Earth’s atmosphere absorbs some of the sun’s light and heat radiation which creates a relatively stable climate on Earth’s surface that facilitates life.

5. Some Atmospheric Gasses Absorb Infrared Radiation
Some of the sun’s energy that reaches Earth’s surface is reflected back into the atmosphere as infrared heat, which greenhouse gasses further absorb.
What is the term for this phenomenon?
Excess infrared energy absorbed by greenhouse gasses is then transferred to other atmospheric gasses that do not absorb infrared radiation, such as oxygen and nitrogen
What are examples of oxygen- and nitrogen-containing molecules in the atmosphere?

6. The infrared absorption spectrum of CO2 [wavenumber (cm-1) = 10,000/wavelength (µm)]
IR spectrum is the specific energy at certain wavelengths that the molecule absorbs.
Radiation that is 100% transmittance = heat that travels through (hence 0 absorption) the molecule.
Line dips are energy absorption, and thus reducing the percent of transmittance. δ- δ+ δ-

7. The Infrared Absorption Spectrum of Major Greenhouse Gasses
Sun TOA: sun’s radiation received at the top of Earth’s atmosphere
Earth: radiant heat emitted by Earth’s surface
What wavelength of light is most transmitted (= least absorbed) by the atmosphere?
What are the sources of IR heat absorption by each of the greenhouse gasses?
Do all gas molecules absorb and therefore transmit infrared heat energy equally?

8. Global Warming Potential
The amount of heat a greenhouse gas molecule traps
More complicated molecules with more polar bonds have more and stronger infrared radiation absorption bands, and thus higher GWP.
Calculate the total global warming contribution of each greenhouse gas above (=GWP * tropospheric abundance). What is the relative impact of each molecule?
What are the major sources of each molecule above?

9. GWP of More Greenhouse Gasses
The impact of human activities is evident

10. Global Atmospheric Lifetime
An important measure of a molecule’s residence time in the atmosphere
Can be used to improve model predictions of how long the effects of human activities will affect Earth’s climate
What are some other uses of knowing how long a molecule persists in the atmosphere?

11. Global CO2 Emissions are Increasing
How have sources of CO2 emissions expected to change among countries from 1995 to 2035?
How do you expect emissions of other greenhouse gasses to change among countries over this same time period?
What factors might contribute to these changes?

12. Global Warming is Unequivocal
Although climate change, such as global warming and global cooling, is a naturally-occurring phenomenon, the global warming we are experiencing over the last 200+ years is not.
Climate change naturally occurs over geologic time: hundreds of thousands to millions of years.
Current climate change is unnaturally occurring over the human time scale: decades.
This creates a problem because Earth and its inhabitants are unable to adapt over this relatively short time period.

13. What factors might cause the average temperature not change equally across Earth’s surface?
What impacts does uneven warming at the north pole have on the rest of Earth?

14. Evidence of Global Warming
Rates of surface warming have increased, with 11 of the past 12 years being the warmest since 1850.
Water vapor content has increased.
Ocean temperatures have increased to depths of at least 3 km; oceans absorb 80% of added heat.
Mountain glaciers and snow cover have declined in both hemispheres
…Although these shifts may seem minor, their consequences are major: species become extinct, ecosystems are degraded, ecosystem services are lost, disease spread increases, among many others.

15. LAB After reviewing metabolic processes: Photosynthesis
Aerobic respiration
Proceed to lab

16. References http://climate.nasa.gov