Long and Short Term Changes in Climate

Natural events such as volcanic eruptions Long Term Changes Movement of Earth’s Crust Cyclical changes from warmer to colder climates due to variations in Earth’s orbit Short Term Changes Natural events such as volcanic eruptions

Long-Term Changes Due to Continental Drift According to the theory of Plate Tectonics, Earth’s continents have moved over the surface of the globe for hundreds of millions of years  called continental drift There use to be a supercontinent called Pangaea

Continental Drift Video Questions What mountain ranges formed from the collision of India and Asia? How do you think Antarctica’s change in position affected its climate? Which ocean formed in the division between North America and Europe?

Long-Term Changes Due to Continental Drift When continents move, the effect on climate includes: Ocean and wind patterns change, affecting heat transfer Distribution of land mass changes Example: Canada (Northern Hemisphere with fewer large bodies of water)  coldest winters and warmest summers) Uplifts new mountain ranges affects local and regional climate

Long-Term Cycles in Climate It is believed that the earth’s climate cycles between ices ages and interglacial periods Ice Age: a time in Earth’s history when Earth was colder and much of the planet is covered in ice Interglacial period: time between ice ages, when the Earth warms up

Interglacial Period About 20,000 years ago, the earth experienced its last ice age. The average temperature was 10°C lower than today. Ice sheets about 3 km thick covered much of Canada. Today, we are in an interglacial (warming) period. Frequency of warm interglacial periods: about every 100,000 years

Why do Interglacial and Ice Ages happen? The earth’s orbit around the sun changes in 3 main ways: 1. Eccentricity: shape of orbit around the Sun Varies from being circular to being more elliptical Influenced by Jupiter’s and Saturn’s gravities Cycles every 100,000 years 

Why do Interglacial and Ice Ages happen? 2. Tilt (Affects seasons) Varies from 22.1° to 24.5° Cycles every 41,000 years Currently the tilt is 23.5° and slowly decreasing

Why do Interglacial and Ice Ages happen? 3. Precession of Tilt As Earth spins on its axis, it slowly wobbles in a cycle over 26,000 years

Short-Term Variations in Climate Small variations in climate over tens of years to hundreds of years Caused by volcanic eruptions, changes in the Sun’s radiation, and changes in the circulation of air and ocean currents

Short-Term Variations in Climate Volcanic Eruptions Spew rocks, dust and gases into the atmosphere Sulfur dioxide (SO2) reflects the sun and earth temporarily cools down

Mt. Tambora Eruption Questions How many years ago did Mt. Tambora erupt? Where did it erupt? Which gas released from volcanic eruptions forms a reflective veil in the atmosphere? What effect did the eruption of Mt. Tambora have on the Earth’s climate in the years following?

Short-Term Variations in Climate Small Changes in the Sun’s radiation The amount of solar radiation changes in small amounts over about 11 year cycles We are currently in a solar minimum

Short-term Variations in Climate Air and Ocean Currents Changes in the ocean’s thermohaline circulation may cause abrupt changes in climate  phenomenon is not fully understood

Short-term Variations in Climate Air and Ocean Currents Changes in the ocean’s thermohaline circulation may cause abrupt changes in climate  phenomenon is not fully understood

Short-Term Changes in Climate A dramatic change takes place in the Pacific Ocean every three to seven years El Nino: periodic shift in Pacific winds and ocean currents; west coast of South America receives warmer, wetter weather

Homework Note #10: Page 353 #1, 3, 4, 5, 8