Climate

1. Climate • Climate is the average weather conditions of an area over a long period of time. • Climate is described by rainfall and temperature.

2. Factors that influence climate • Latitude—equatorial areas receive most of the vertical rays of the Sun and are warmest. Polar areas receive less and are colder.

3. Factors that influence climate • Global wind patterns—low pressure exists at the equator and 600 north and south. High pressure at 300 north and south. • High pressure indicates sinking air, no clouds, no rain. • Low pressure indicates rising air, clouds, and rain.

4. Factors that influence climate • Global wind patterns

5. Factors that influence climate • Presence of surface water—Waters heats more slowly than land but holds heat longer. • Areas near water, especially oceans, have temperatures more stable year round.

6. Factors that influence climate

7. Ocean currents • Ocean currents—can bring cold or warm water to areas and heat the up or cool them down. • Gulf Stream current brings warm water to Ireland and England and keeps them warm.

8. Ocean currents

9. Mountains • High mountains like our Sierra Nevada mountains create a barrier for clouds coming from the ocean. • As warm, moist air from the Pacific hit these, it rises and produces rainfall. The air coming down the other side is warm and dry. This is rain shadow.

10. Rain shadows

11. Q and A • What 2 factors determine the climate of an area? • What effect does an areas latitude have on its temperature? • Describe the types of weather that exist in the following areas: Equator to 30 degrees north, 30 degrees north to 60 degrees north, 60 degrees north to the north pole.

12. Q and A • Eureka, CA and Des Moines, IA are at roughly the same latitude. Des Moines averages 25 degrees cooler in winter and 10 degrees hotter in summer. Explain why. • What effect do mountains have on climate?

13. Tropical climates • Rain forests—near equator. Lots of rain and lush jungles. • Savannah—further from equator gets less rain and is grassland. • Deserts—near 300 latitude and gets little rain, but very hot.

14. Middle latitude climates • Marine west coast—west coast of US and Europe has near constant temperatures and lots of rainfall. • Mediterranean—inland west coast of US and Southern Europe and North Africa has warm winters with some rain and hot dry summers.

15. Middle latitude climates • Steppe—cold and dry winters and warm and wet summers. • Humid continental—most of mid west US. Warm summer, cold winter, rains any time of year. • Humid subtropical—narrow range of warm temperatures and much rain.

16. Polar climates • Subarctic—short summers and long winters. Some rain and snow. • Tundra—Most of year below freezing. Not much rain. • Ice cap—permanent ice cover, no plants, very cold.

17. World climate map

18. US climate map

19. Studying past climate • Ice cores obtained from glaciers show times when carbon dioxide was more plentiful. • Sea floor sediments show differences in organisms that lived in the past. • Tree rings indicate periods of good growth.

20. Global warming • Greenhouse effect caused by carbon dioxide may cause Earth to warm. • This may cause ice to melt and raise sea levels causing shoreline flooding. • Has not happened yet. • May lead to climate change.