CHAPTER 17 Weather and Climate - Mr. Barrow's Science Center

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El Niño and La NiñaEl Niño is a climatic event that involves the atmosphere andoceans. Normally, the trade winds blow warm surface waterwestward toward a low pressure area in the western Pacific. Thewarm surface water is replaced by cold, nutrient-rich water thatis upwelled from below the surface. When the tradewindsweaken, surface pressure patterns break down and the flow ofwarm water is reversed. Nutrient-rich cold water is no longerupwelled and warm, nutrient-poor water remains at the surface.Fewer fish and other marine life can be supported by thenutrient-poor water. Rainfall in the western Pacific decreases,where as heavy rain and flooding can occur on the normally drycoast of Peru. El Niño can dramatically alter global weather patterns.For example, a strong El Niño can lead to flooding andmudslides in California, as shown in Figure 21, and droughts inIndia, Australia, and parts of Africa.The opposite of El Niño is La Niña, which occurs whentradewinds in the Pacific are unusually strong and equatorialoceanic surface temperatures are colder than normal. La Niñacan cause drought in the southern United States and excess rainfallin the northwest.Figure 21 Parts of the PacificCoast Highway in California havebeen disrupted by erosion andmudslides caused by El Niño.SummarySeasonal•ChangesThe tilt of Earth’s axis changes the amount ofsolar radiation received by the northern andsouthern hemispheres throughout the year,causing the seasons.•Long-term Climate ChangesCycles of glaciation occur on the scale of tens•of thousands of years.Sunspots and volcanoes influence climate onshorter timescales.•The Human FactorHuman activities have increased theconcentration of trace gases and decreasedstratospheric ozone.•El Niño and La NiñaEl Niño is a warming of the Pacific Ocean withworldwide effects. La Niña is the opposite ofEl Niño.Self Check1. Identify ways that humans may be affecting climate.2. Explain why the contrast between land and waterchanges with the seasons.3. Explain why it is difficult to identify any single cause ofan observed climate change.4. Think Critically What can be done to stop globalwarming? What can you do to help?5. Use Percentages The eruption of Mount Pinatubo in1991 put large amounts of dust into the atmosphere.Scientists say this decreased the average global temperatureabout 0.8 percent during the next year. Howwould this affect an area with an average temperatureof 25°C before the eruption?6. Calculate Areas of the southeastern United States mayreceive 15 percent of their rain during hurricanes. Ifaverage rainfall for this area ranges from 100–200 cm,how much of this might be from hurricanes?More Section Review gpescience.comSECTION 4 Earth’s Changing Climates 539APF/Getty Images
Design Your OwnInvestigating MicroclimateGoals■ Investigate how environmentalvariablesrespond to variousmicroclimates.Possible Materialsdirectional compassthermometerrain gaugemeter sticksmall plastic cups*graduated cylinder*Alternate materialsSafety PrecautionsReal World ProblemWhile we can talk about global climate or regional climate, we alsocan discuss climate on the scale of a few meters. We call climate atthis scale a microclimate. For example, because cold, heavy air drainsdownhill, valley fog sometimes forms in moist, low-lying areas.Along the California coast, coastal fog collects on the needles ofredwood trees, drips to the ground, and is absorbed by the tree’sshallow root system. This microclimate helps the coastal redwoodssurvive, nestled in the fog belt along the California coast. In this lab,you will investigate local differences in microclimate.Form a HypothesisChoose an aspect of climate, such as precipitation, light, or temperature.Form a hypothesis to explain how this aspect influences localenvironments. Predict how these factors will vary in response to differencesin your microclimate variable.540 CHAPTER 17 Weather and ClimateBill Ross/CORBIS
Page 2 and 3: Start-Up ActivitiesAtmospheric Pres
Page 7 and 8: Figure 5 Earth’s continualcycling
Page 9 and 10: WeatherReading Guide■ Explain wha
Page 11 and 12: Figure 8 The symbols shownbelow eac
Page 13 and 14: Topic: Hurricane TrackingVisit gpes
Page 15 and 16: Topic: World ClimatesVisit gpescien
Page 17 and 18: Ocean and Land Influence Oceans and
Page 19 and 20: ColdAridColdDry winterWarmAridWarmS
Page 21 and 22: Dinosaur ExtinctionThe impact of a
Page 23: Trace Gases Today’s atmosphere co
Page 27 and 28: The Grapes of Wrathby John Steinbec
Page 29 and 30: iosphere p. 529continental climate
Page 31 and 32: Record your answers on the answer s

CHAPTER 17 Weather and Climate - Mr. Barrow's Science Center

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