1. 11.1 Natural Climate Change Science 10 p.464-481

2. Climate  describes the average conditions of a region. is usually measured over 30 years or more. is usually measured over 30 years or more. Climate = clouds, precipitation, average temperature, humidity, atmospheric pressure, solar radiation, and wind. Climate = clouds, precipitation, average temperature, humidity, atmospheric pressure, solar radiation, and wind. BC’s climate zones Climate and geography combine to allow specific organisms to grow. –Biogeoclimatic zones have distinct plants, soil, geography, and climate. –British Columbia has 14 distinct biogeoclimatic zones.

3.  Paleoclimatologists study long-term patterns environment (using fossils)environment (using fossils) growing seasons (using tree rings)growing seasons (using tree rings) types of rainfall (using river sediments)types of rainfall (using river sediments) air condition and composition (using glacier ice cores)air condition and composition (using glacier ice cores) Gases trapped in the ice, specifically CO 2, Gases trapped in the ice, specifically CO 2, reveal long-term atmospheric levels. Fossils and sediment evidence show Earth’s climate has changed often and drastically Fossils and sediment evidence show Earth’s climate has changed often and drastically 21 000 years ago, much of Canada and northern Europe was under glaciers.21 000 years ago, much of Canada and northern Europe was under glaciers.

4.  Ice core data reveal CO 2 levels for the past 650 000 years. Scientists have tested the atmospheric CO 2 for the past 50 years Scientists have tested the atmospheric CO 2 for the past 50 years

5. Factors That Influence Climate: 1) Composition of Earth’s Atmosphere  Earth’s atmosphere is a boundary, so very little energy (except radiant energy) enters or leaves  The Earth’s “natural greenhouse effect” allows a narrow range of temperatures. Solar radiation comes in, is Solar radiation comes in, is absorbed, and is then emitted and trapped before being able to escape. trapped before being able to escape. Greenhouse gases in the Greenhouse gases in the atmosphere absorb thermal energy. This keeps Earth an average of 34ºCThis keeps Earth an average of 34ºC warmer than it would be otherwise. More greenhouse gases could make it too warm.More greenhouse gases could make it too warm.

6. 2) Earth’s Tilt, Rotation and Orbit  Earth’s tilt is responsible for the seasons In summer, we are tilted toward the Sun In summer, we are tilted toward the Sun In winter when we are tilted away from the Sun In winter when we are tilted away from the Sun Earth’s tilt varies slightly (currently 23.5º) –When tilt is largest, climate experiences the largest extremes

7.  Earth “wobbles” as it rotates on its axis. the axis changes so the angle of incidence of solar radiation also changes the axis changes so the angle of incidence of solar radiation also changes Earth’s revolution around the Sun is elliptical and changes shape. –On a 100 000 year cycle, Earth’s elliptical orbit becomes more circular. –When the orbit is most elliptical, Earth can be farther away from the Sun.

8. 3) The Water Cycle  describes the circulation of water on, above, and below Earth’s surface. water vapour = 70% of the greenhouse gasses in the atmosphere water vapour = 70% of the greenhouse gasses in the atmosphere When temperature increases, more water evaporates and causes When temperature increases, more water evaporates and causes 1) More solar energy absorbed by this greenhouse gas. by this greenhouse gas. 2) More solar energy reflected back out to space and never back out to space and never reachs Earth. reachs Earth. The water cycle stores and transfers large amounts of thermal energy.

9. 4) Ocean Currents  Convection currents in the oceans move large amounts of thermal energy all around Earth. Deep ocean currents flow based on density differences. Deep ocean currents flow based on density differences. They behave like massive convection currents, with warm water rising in the tropics and cold water from the higher latitudes replacing it.They behave like massive convection currents, with warm water rising in the tropics and cold water from the higher latitudes replacing it. Deep-ocean currents move cold, salty water below the surface and warm, less-salty water near the surface.

10.  Salinity and temperature change water density Cold water and salty water (found at the poles) are more dense than warm water and fresh water. Cold water and salty water (found at the poles) are more dense than warm water and fresh water.  Surface currents (0 - 200 m) are warmed by solar radiation. The thermocline is the The thermocline is the region separating surface region separating surface and deep ocean currents. and deep ocean currents. Upwelling occurs when Upwelling occurs when cold, deep water rises cold, deep water rises through the thermocline through the thermocline into surface currents. into surface currents.

11. La Niña is an example of upwelling. When this occurs, cool water at the surface of the Pacific Ocean causes warm winters in southeastern North America, and cool winters in the northwest. El NiñoEl Niño is the reverse: warmer water on the surface of the Pacific Ocean results in warm winters in the Pacific Northwest and in eastern Canada. El Niño

12. 5) The Carbon Cycle (remember this from chapter 2!)  Carbon dioxide is an important greenhouse gas 2 nd most prevalent greenhouse gas 2 nd most prevalent greenhouse gas Without CO 2 to trap infrared radiation from Earth’s surface, the average temperature of Earth would be below freezing.Without CO 2 to trap infrared radiation from Earth’s surface, the average temperature of Earth would be below freezing.

13. The carbon cycle maintains a balance of CO 2 in the atmosphere. The carbon cycle maintains a balance of CO 2 in the atmosphere. Deep oceans are carbon sinks.Deep oceans are carbon sinks. CO 2 in the ocean is converted to carbonates (CO 3 2- ), in shells. CO 2 in the ocean is converted to carbonates (CO 3 2- ), in shells. Phytoplankton use CO 2 for photosynthesis at the ocean’s surface. Phytoplankton use CO 2 for photosynthesis at the ocean’s surface. Weathering of rocks releases carbon.Weathering of rocks releases carbon. Carbonic acid is formed when water reacts with CO 2 in the atmosphere.Carbonic acid is formed when water reacts with CO 2 in the atmosphere. Forests are carbon sinksForests are carbon sinks take in CO 2 while growing but take in CO 2 while growing but release CO 2 when burned or release CO 2 when burned or when decaying. when decaying.

15.  Meteorites and comets are thought to have caused dramatic changes. cause large amounts of dust, debris and gases in the atmosphere. cause large amounts of dust, debris and gases in the atmosphere. Solar radiation is affected so much that it is thought that these events are responsible for some of Earth’s largest extinction events. (dinosaurs!) Solar radiation is affected so much that it is thought that these events are responsible for some of Earth’s largest extinction events. (dinosaurs!) Take the Section 11.1 Quiz Large comet and meteor collisions with Earth can cause debris to block solar radiation and cause changes all over the Earth.