Climate and Change
Why has climate changed in the past? There are 3 main theories: 1) The eruption theory 2) The sunspot theory 3) The orbital theory The eruption theory: When a volcano erupts it throws out large volumes of sulphur dioxide (SO 2 ), water vapour, dust, and ash into the atmosphere. Although the volcanic activity may last only a few days, yet the large volumes of gases and ash can influence climatic patterns for years. Millions of tonnes of sulphur dioxide gas can reach the upper levels of the atmosphere from a major eruption. The gases and dust particles partially block the incoming rays of the sun, leading to cooling. The sunspot theory: The number of dark spots (known as sun spots) visible on the disc of the sun varies over roughly an 11-year period. When there are many spots, the sun's magnetic activity increases and the sun radiates more heat. These changes in total irradiance are very slight, and represent only a tiny percentage of the sun's total output, but even these small changes can produce a significant change in the earth's heat balance. The orbital theory: 1) The Earth s orbit is sometimes circular and sometimes more of an eclipse (oval). 2) The Earth s axis tilts. Sometimes it is more upright and sometimes more on its side. 3) The Earth s axis wobbles, like a spinning top about to fall over. These three changes alter the amount of light that the Earth receives from the sun. They also affect where light falls on the Earth s surface. It would be enough to start or finish an ice age.
Climate change may have made the megafauna weaker than normal. The Little Ice Age: This cooler period lasted from approximately 1315 to 1860. Impacts: Wheat and Oat crops did not ripen The Great Famine started in 1317 and lasted until 1325. In some areas 10-20% of peasant farmers may have died of hunger. The numbers that died during the Black Death in 1349 in Europe was made worse by the cooler climate and bad farming conditions. Sea ice stopped trade with Iceland and Norway. Cattle and sheep had less food in winter so animals did not survive. Fighting between local people may have increased as food ran short. In the Alps valley glaciers advanced down valleys destroying villages and farmland. People in Europe had to adapt. They did this by farming new crops, abandoning farms in higher altitudes, and enjoying the colder climate by having frost fairs on rivers! The impact of climate change on megafauna: Megafauna refers to big animals that weighed over 40kg e.g. the Woolly mammoth. As the last ice age ended and the climate warmed by 6 degrees many animals had to move. The impacts were: They migrated to areas where the climate better suited them. But finding food to eat was hard as many plants were not suitable. This would have disrupted food chains leaving some animals short of food. As the climate warmed back up people also migrated to different areas and hunted some of the megafauna, this meant less prey for carnivores. Some herbivores were hunted to extinction leaving carnivores with nothing to eat.
Enhanced Greenhouse effect - A warming of the Earth s temperature due to human interference.
Scientists do not fully know what will happen to future climate. The estimates are that temperatures will rise between 1.1 and 6.4 degrees centigrade. Sea level is predicted to rise by 30cm to 1 meter by 2100. So what might be in store for the UK?
Case Study: Bangladesh (LEDC)
Climate and Change Question Checklist make sure you can answer these using this guide and your exercise books! 1. What is climate? 2. Using the graph in this guide, describe what has happened to the earth s temperature during the period shown. 3. Explain the three natural causes of climate change. 4. What evidence is there that the earth s climate has changed in the past? Battle for the How reliable is this evidence? 5. What could have caused the little Ice Age? 6. Describe one advantage and one disadvantage of the little ice age for people alive at the time. 7. What does megafauna mean? Biosphere 8. What is an ecosystem? 9. Using examples describe how ecosystems were affected by climate change in the past. 10.What are the main greenhouse gases? 11.Draw a diagram to explain how the greenhouse effect works. 12.How can human activities add greenhouse gases into the atmosphere? List as many examples as you can. 13.Why do people in the developing world produce only a small amount of greenhouse gases? 14.The greenhouse effect can occur naturally, what is the enhanced greenhouse effect? 15.Using examples, explain how global warming could have both costs and benefits for the UK. 16.How could sea level changes caused by global warming affect other countries in the world such as Bangladesh, the Maldives and Tuvalu?