The Atmosphere Did you know we are on our 3 atmosphere on Earth? • Earth’s original atmosphere was probably just hydrogen and helium, because these were the main gases in the dusty, gassy disk around the Sun from which the planets formed. • And in second place we have… • Earth’s “second atmosphere” came from Earth itself. There were lots of volcanoes, many more than today, because Earth’s crust was still forming. Currently….. • Current Earth: Plants and animals thrive in balance. Plants take in carbon dioxide (CO2) and give off oxygen (O2). Animals take in oxygen (O2) and give off CO2. Burning stuff also gives off CO2. The atmosphere upon which life depends was created by life itself. • Now we have Earth’s “third atmosphere,” the one we all know and love—an atmosphere containing enough oxygen for animals, including ourselves, to evolve. • So plants and some bacteria use carbon dioxide and give off oxygen, and animals use oxygen and give off carbon-dioxide—how convenient! • The atmosphere has 4 layers: • the troposphere that we live in near the surface of the earth; • the stratosphere that houses the ozone layer; • the mesosphere, a colder and lower density layer with about 0.1% of the atmosphere; • and the thermosphere, the top layer, where the air is hot but very thin. Why do I care? The structure of the atmosphere dictates the way the atmosphere behaves and controls how weather develops near the surface of the earth. Temperature decreases with height in the troposphere. • This is true for a couple different reasons. First, even though the sun's energy comes down from the sky, it is mostly absorbed by the ground. • The ground is constantly releasing this energy, as heat in infrared light, so the troposphere is actually heated from the ground up, causing it to be warmer near the surface and cooler higher up. • Another reason is the decreasing air pressure with height. If the warm air at the surface gets blown upward into the cooler air above it, the surface air will continue to rise • The constantly decreasing air pressure in conjunction with the ground-up heating keeps the temperature in the troposphere decreasing with height. • In the real atmosphere, the actual vertical temperature structure depends on air masses with specific properties of temperature and humidity being blown into the area as well as effects of daytime heating. • If you have a layer of air with warm temperatures above the surface, we call that an "inversion". That layer can act as a cap which prevents clouds and sometimes severe weather from forming. Weather……………. As the popular saying goes, "Climate is what you expect, and weather is what you get!". • Weather is considered to be the atmospheric conditions that are happening now or within a few days. • On the other hand, Climate represents the long term atmospheric patterns within which weather occurs. Causes of Climate Change • The climate of the earth fluctuates, and there are many things that affect it. Volcanoes, changes in the orbit and the sun, greenhouse gases and the properties of the earth itself have influence over the climate. • Why do I care? • The climate of the earth is constantly changing and one should understand all the reasons why and how these changes impact the surrounding environment. • The earth has only had its current atmosphere for about 400 million years. In that time, Earth has had climates ranging from being almost completely covered in ice to times when even the poles were subtropical • The current global average temperature is 59°F (15°C, 288K), but it is not staying constant. • A few main factors and feedbacks are the driving forces for climate change. • These include volcanoes, the Earth’s orbit around the sun, solar output, green house gas concentrations, and feedbacks Why are there different climate regions? • Because of the tilt of the Earth and it’s orbit, different regions have different climates. • Therefore the number of hours of daylight and amount of solar radiation varies in differing locations on the planet. How does temperature affect precipitation? • What do you think the temperature will do to the type of precipitation that is present? • If it is very cold, what are the possibilities? • Temperature will determine if it will be rain, snow, sleet, fog, or hail Some questions to think about • Can you compare and contrast weather and climate? • How many layers does the atmosphere have? • How many atmospheres has the Earth had so far? • What kind of climate do we live in? • How did the Earth acquire it’s atmosphere? • What are climate regions? • Why do different regions have different climates?