CLIMATEChapter 14

14.1 What is Climate?

Climatology is the study of Earth’s climate and the factors that affect past, present, and future climatic changes

Pertains to long-term weather patterns of an area More than average weather conditions Describes annual variations of temperature,

precipitation, wind, and other variables Details extreme fluctuations in these variables over time

Climatology

Data used to describe an area’s climate are compiled from meteorological records from thousands of locations around the world.

Data includes daily high and low temperatures, amounts of rainfall, wind speeds and direction, humidity, and air pressure.

Once gathered, data is averaged on a monthly or annual basis over a period of at least 30 years to determine the standard values (normals) for a location.

Normals

Factors that Influence Climate

Latitude

Based on solar radiation and how the Sun’s rays strike the Earth The tropics refers to the area between 23.5oS and 23.5o north of

the equator Receives the most solar radiation Temperatures are warm year-round

The temperate zones lie between 23.5o and 66.5o north and south of the equator Temperatures are moderate

The polar zones lie from 66.5o north and south of the equator to the poles Solar radiation strikes at a low angle Temperatures are almost always cold

Air Masses

Distinct origin due to difference in solar radiation Depends on where formed (land or water)

Topographic Effects Water heats and cools more slowly than land Coastal regions are warmer in winter and cooler in the summer months Temperatures in troposphere decrease with altitude, so mountain

climates are typically cooler than sea level In addition, climates differ on each side of the mountain due to the

rising and sinking of air

14.2 Climate Classification

Koeppen Classification System

Tropical Climates

Dry Climates

Mild Climates

Continental Climates

Polar Climates

Sometimes, the climate of a small area can be much different from that of the larger surrounding area.

A localized climate that differs from the surrounding regional climate is called a microclimate.

In mountainous areas, the climate becomes cooler with elevation.

In an urban area, the climate is warmer due to large areas of asphalt and concrete buildings.

Microclimates

Heat IslandArea where the climate is warmer than in surrounding rural areas

Large areas of asphalt and concrete radiate far more heat into the air than grasslands, wooded areas, and bodies of water

This causes greater changes in temperature with altitude, which causes convection currents that produce increased cloudiness and up to 15% more precipitation in cities

Heat Islands are examples of climatic change on a small scale

14.3 Climatic Changes

The Earth’s climate is in a constant state of change.Changes take place over both long and short periods of time.Geologic records show Earth was once colder or warmer than it is today.

Long-Term Climate Changes

Ice Age Period of time where much of Earth

was covered by sheets of ice The average global temperature

decreased by an estimated 5 oC Snowfalls increased throughout

Earth, which sparked the advance of existing ice sheets

Ice ages alternate with warm periods (interglacial intervals) in which we are currently experiencing

The most recent ice age ended only 10,000 years ago

Short-Term Climate Changes

Seasons Short-term periods caused by

regular variations in daylight, temperature, and weather patterns

During summer in the Northern Hemisphere, the North Pole is tilted toward Sun

During winter in the Northern Hemisphere, the North Pole is tilted away from Sun

The opposite is true of the Southern Hemisphere

A warm ocean current that occasionally develops off the western coast of South America

Brings wet weather to areas that are normally dry (excessive flooding)

Brings dry conditions to areas that are normally wet (extreme drought)

Leads to extensive property damage Most devastating to tropical regions Positively affects tropical disturbances from reaching

hurricane strength storms in the Atlantic Ocean

El Nino

14.4 The Human Factor

The retention of heat by the atmosphere results in the Greenhouse Effect, which is the natural heating of the Earth’s surface caused by greenhouse gases.

Without the Greenhouse Effect, life as we know it would NOT exist on Earth as our planet would be super cold! Meaning, we could not sustain life without it.

On the other hand, an increase in the greenhouse effect could cause our planet to be hot.

Scientists believe that it may be possible to increase or decrease the greenhouse effect by changing the amount of atmospheric gases… specifically carbon dioxide

Any Increase in the amount of these gases could result in the increased absorption of radiation.

Currently, levels of carbon dioxide in the atmosphere ARE increasing – which can lead to a rise in global temperatures.

The Greenhouse Effect

Global warming is a rise in global temperatures.

Over past 200 years, temperatures have increased globally, with the warmest years on record having occurred over the past two decades (20 years).

If this continues polar ice caps might melt and sea levels will rise, leading to flooding.

Global warming can also cause an increase in the frequency of severe storms.

Global Warming

Impact of Human Activities• Automobiles serve as the prime source of atmospheric CO2

• Burning of fossil fuels results in the release of CO2 and other gases into atmosphere

• Deforestation is the massive removal of trees, which increases the CO2 into atmosphere because vegetation removes carbon dioxide during photosynthesis

 Environmental Efforts• We can conserve energy, as individuals, to combat global

warming• Conservation of energy helps reduce the consumption of fossil

fuels• Easy ways to conserve energy include:

• Turning off appliances and lights• Turning down thermostats during the winter• Recycling• Riding bikes for transportation… or walking

Protecting our Planet