SASS EGeog Weather & Climate Gateway 2

Subject: Geography Topic: Variable Weather and Changing Climate Gateway 2: What is happening to the Earth’s climate? _____________________________________________________________________________________ A. How has global climate changed? B. What are some natural causes of climate change? C. What is the greenhouse effect? D. How do human activities lead to enhanced greenhouse effect? E. How does climate change affect people? F. What are the responses to climate change? A. How has global climate changed? - Global Climate Change: variation in the global climate or climatic patterns in the long term. • Changes in global climate since 1881. - Earth warmed up by 0.74°C in 100 years. - Greatest increase after 1980s - Some places recorded much higher temperature increases. - For example: Arctic, Asia and Africa (1.2° C to 1.4 ° C) B. What are some natural causes of climate change? 1. Variations in solar output 2. Volcanic eruptions 1. Variations in solar output - The magnetic activity of the sun has a cycle that lasts about 11 years. - An increase in solar radiation is due to an increase in sun spots. • Areas surrounding the sunspots radiate more energy to make up for the cooler sunspot areas. - With higher solar radiation, earth’s temperatures will increase. Sunspots represented by the dark spots on surface of the sun.

2. Volcanic eruptions - Global dimming: Gradual reduction in the amount of sunlight reaching the earth’s surface. Temporarily cools the earth for months or years. - Dust particles from eruption form condensation nuclei, creating more cloud cover. - Dust and ash also reflect away incoming solar radiation. - For example, Mount Pinatubo eruption lowered temperatures by as much as 0.6°C for as long as two years. C. What is the greenhouse effect? • Greenhouse effect: Natural process in which the gases in the Earth’s atmosphere trap longwave radiation emitted from the Earth’s surface, warming the atmosphere. • Water vapour, carbon dioxide, methane, nitrous oxide ozone and halocarbons such as chlorofluorocarbons (CFCs) are good absorbers of longwave radiation. - They are known as greenhouse gases and are found in the atmosphere. • Enhanced greenhouse effect: Increase in the concentration of greenhouse gases in the atmosphere, leading to a rise in global temperatures. - Generally due to human activities that release an increased amount of greenhouse gases, most notably carbon dioxide. D. How do human activities lead to enhanced greenhouse effect? Proportion of greenhouse gases in atmosphere Carbon Dioxide (72%) Methane (10%) Nitrous Oxide (5%) CFCs (13%)

Human activities - Burning fossil fuels - Deforestation - Changing land use - Agriculture - Industries - Urbanisation Burning fossil fuels - Fossil fuels: formed from decomposition of dead organic matter over millions of years. For example, petroleum, coal and natural gas. - Powers 80% of the world’s en