The Earth s Atmosphere Composition of the Atmosphere Keeping Earth warm List of primary gasses in Earth s Atmosphere 1 Water Vapor 2 Nitrogen Methane Ozone BUT Carbon Dioxide Oxygen Argon Atmosphere composed on O2 and N2 only Composition of the Atmosphere Avg global surface air temperature without GHG Avg global surface air temperature with GHG Atmosphere composed on O2 and N2 and greenhouse gasses The human thermometer Definition of Temperature Liquid Solid Gas can t see Measuring Temperature Device used to measure temperature Figure 1 1 Vostok Antarctica The relationship between Temperature and Density The higher the air temperature the faster the air molecules move The faster the molecules move the more space they will need to move around Warming the air will cause it to expand Cooling the air will cause it to contract General Temperature Variations Uneven surface heating drives atmospheric circulations Caused by 1 1 Avg Surface Air Temperature Key Idea Mother nature constantly tries to get to equilibrium NH spring Seasonal Variations in Temperature Summer Solstice 23 5 June 21st Sun s rays are direct on the Tropic of Cancer 23 5 N Most daylight hours closer Autumnal Equinox September 21st Sun s rays are direct on the Equator 12 hrs of daylight and 12 hrs of night Winter Solstice Dec 21st Sun s rays are direct on the Tropic of Capricorn 23 5 S Least daylight hours Vernal Equinox March 21st Sun s rays are direct on the Equator 12 hrs of daylight and 12 hrs of night NH winter NH summer NH autumn The tilt of the Earth on its axis causes the Sun s rays to become more or less direct which concentrates or disperses the Sun s energy throughout the year Seasons The effects of latitude Why Winter Summer Top of atmosphere Arctic Circle 66 5 N Tropic of Cancer 23 5 N Equator 0 12 N Nyala Sudan Africa Jan July 40 N Urbana Illinois USA Jan July 66 N Verkhoyansk Russia Jan July Proximity to large bodies of water D U na a rb IL D r e ov E warmest time of year west coast warmest time of year mid continent highest sun and greatest insolation CA ncisco a r F n a S Vertical Temperature Variations Aurora Borealis Meteor showers Lid