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Describe how the Earth's geography affects weather and climate.

Geography

a gif of the Earth spinning on a black background — **Earth's geography, rotation, and tilt help determine its climate.**

Geography plays an important role in shaping the climate on Earth. Geography is defined by Merriam-Webster as “the description, distribution, and interaction of the diverse physical, biological, and cultural features of the earth's surface.” When we think of geographic features of the earth in this course, we think about the exterior features of the planet including, but not limited to, mountain ranges, valleys, volcanoes, oceans, rivers, glaciers, ice caps, and any other physical feature that may impact climate.

Climate

A graphic explaining the difference between weather and climate. There is an image of rain falling on a tree on the weather side and an image of a tropical environment on the climate side. There is a graph for each, weather shows temperature fluctuations on the scale of days. The climate graph shows temperature fluctuations on the scale of years. The bottom of the graphic shows a clock and the words "Weather can change within minutes or hours" and "Climate is the average weather over many years in one specific place" — **"Climate is what you expect, weather is what you get." - Mark Twain**

Mark Twain once said, “Climate is what you expect, weather is what you get.” Twain was referring to the difference between climate and weather. Many people are confused about the difference between the two, but it’s important to know the difference between the two.

Climate is defined by the National Oceanic and Atmospheric Association (NOAA) as “long-term averages and variations in weather measured over a period of several decades.” As such, climate is what happens in the Earth’s climate system over many years. Earth’s climate system includes the atmosphere, the oceans, the land surface, and ice.

Weather, on the other hand, is defined by NOAA as “the state of the atmosphere at a particular location over the short-term.” Weather is basically what you experience when you step outside.

In his statement, Twain was saying that we might expect snow in the winter in colder areas because climate tells us that it usually snows there in the winter. However, on any given day it may or may not be snowing and it could actually be a very warm, clear day even in the winter!

The Geography-Climate Connection

As Garrett Hardin once said, “You can never do merely one thing.” This clearly applies to the connection between geography, weather, and climate because features and changes in any of these impact the others.

Each of the physical features of the Earth may potentially impact the weather (and climate over the long-term) in a given area.

For example, mountains and mountain ranges can force warm air to rise as the winds are forced upward as they pass over the mountain or range. This orographic lifting results in copious amounts of rainfall or snowfall on the windward side of the mountain. The leeward side of the mountain becomes an area with little moisture known as a rain shadow. In the rain shadow, plants and animals have to adapt to dry conditions.

A photo depicts snowy mountains with an upward-pointing orange arrow, illustrating the formation of a rain shadow: 1) Wind forces air to rise against mountains, called orographic lift. 2) Rising air cools, causing water vapor to condense into clouds and precipitation. 3) This leads to more snow on the windward side of the mountain in winter. — **Mountains can cause increased precipitation on the windward side of the mountain.**

Essential Knowledge

A rain shadow is a region of land that has become drier because a higher elevation area blocks precipitation from reaching the land.

Another example of the connection between geography and weather/climate can be seen with lake-effect snow that occurs near the Great Lakes.

Lake-effect snow occurs when cold air moves over warm lake water. The cold air picks up large amounts of moisture and clouds form. Eventually, the warm, moist air cools below the freezing point and the moisture drops out of the air as snow downwind from the lake.

A graphic depicts a lake, mountains, and a house, illustrating the lake-snow effect. Pink arrows show cold air moving from land to lake. Arrows from the lake, labeled "heat and moisture," lead to cloud formation. Larger clouds form, leading to snowfall. Finally, heavy snow bands form downwind of the lake, illustrated by snow falling on the house across the lake. — **The lake-snow effect can cause increased snow downwind from the lake.**

A photo of a volcanic eruption. In the cloud of soot and smoke, there are labels: Ash, SO2, HCl, CO2, HF, and H2SO4, indicating that the cloud is made up of those compounds. Rain is falling from the cloud and it is labeled "acid rain" — **Volcanic eruptions can cause acid rain when the erupted material mixes with air, making sulfuric acid. Eruptions can also include hydrochloric acid.**

Volcanic eruptions can also impact weather and climate for many years. Many scientists believe that such an eruption or multiple eruptions may have caused the mass extinction of dinosaurs. The particulate matter that is emitted by a volcano can block sunlight, lowering the temperature of the Earth and reducing the amount of photosynthesis that can take place.

The gases from the eruption may react or combine with normal atmospheric gases, resulting in acid deposition or other problems.

The connection between geography and climate is clear. The more we learn about each of these, the better prepared we become to deal with weather and climate changes in the future.

Essential Knowledge

Weather and climate are affected not only by the sun's energy but also by geologic and geographic factors, such as mountains and ocean temperatures.

AP Exam Tip

You should know that geography helps determine the Earth's climate.

Weather is what we get on a day-to-day basis while climate is the overall average of weather conditions over many years or decades.

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