| A | B |
|---|
| Ice age | time period when northern ares were covered by ice |
| Pollen | spores made by plants |
| tree rings | indicate the quality of growing season |
| Volcanic activity | May cause sunlight to be blocked, cooler |
| Earth's position | distance from the sun |
| Last ice age | 10,500 years ago |
| solar energy | Amount of energy given off from the Sun |
| El Nino | Water warmer than normal brings severe droughts or heavy rain |
| La Nina | Cooler water, brings severe storms to northwest |
| Global Warming | average temperatures of the earth increase |
| Greenhouse gas | trap heat from sun in the atmosphere |
| Chloroflouracabon CFC has Chlorine atoms | these break down ozone into oxygen |
| Ozone depleton | loss of ozone |
| Antarctica | has an ozone hole |
| Principle used to determine past climates | organisms from the past needed similar conditions to live in the past as now |
| Ice age extended to | Nebraska and Iowa and northern Pa |
| Sea level during an Ice Age | Lowers |
| Level of carbon dioxide in the past 200 years | increased steadily |
| Ozone | filters harmful ultraviolet radiation |
