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Chapter 10Global Climate Systems

Geo210Introduction to Physical Geography

Michael Paluzzi, ABD

ClimateClimate is weather over time

Climatology is the study of climate

Climatic regions are areas with similar weather statistics

No two places have the exact same climate, but places with similar weather statistics are grouped together

Earth’s Climate System and Its Classification

Climate Components Insolation – solar radiation (varies by latitude)

Temperature – impacted by latitude, altitude, land/water heating differences and cloud cover)

Pressure – responsible for winds

Air masses – vast bodies of homogeneous air

Precipitation – patterns of average annual precipitation control climate types

Classification of Climatic RegionsGrouping similar climates into classes

Worldwide Average Precipitation

Figure 10.2

Wettest climates straddle the equatorAmazon in South America, Congo region of Africa, Indonesia and Southeast Asia

ClimatesEven though climate is a long term pattern

climates do change over extended time periods For example: such as the ice age that occurred the Pleistocene epoch

most recent Ice Age – 1.75 million to 11,000 years ago.

Climate ClassificationKöppen system – A standard scheme used to describe the world's diverse climates

It is based on the concept that native vegetation is the best expression of climate

thus, climate zone boundaries have been selected with vegetation distribution in mind.

It combines average annual and monthly temperatures and precipitation, and the seasonality of precipitation

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Climate ClassificationKöppen system

the A climates are tropical climatesTropical – equatorial and tropical latitudes

the B climates are dryDesertArid – tropical/midlatitudesSemi-arid – tropical/midlatitudes

the C climates are generally moderate and are found in the middle latitudes

Temperate – mid-latitudes, mild wintersthe D climates are associated with continental and high-latitude locations.

Continental/ – midlatitudes/high latitudes, cold winters

The E climates are polar High latitudes/polar regions

Highland climates – lower temps than similar latitudes (lapse rate)

Climate ClassificationThe first sub-classification show precipitation levels,

f - Moist with adequate precipitation in all months and no dry season. Goes usually with A, C, and D climates.

m - Rainforest climate in spite of short, dry season in monsoon type cycle. This letter only applies to A climates.

s - There is a dry season in the summer of the respective hemisphere (high-sun season).

w - There is a dry season in the winter of the respective hemisphere (low-sun season).

Climate Classificationthe second shows temperature.

a - Hot summers where the warmest month is over 22°C (72°F). These can be found in C and D climates.

b - Warm summer with the warmest month below 22°C (72°F). These can also be found in C and D climates.

c - Cool, short summers with less than four months over 10°C (50°F) in the C and D climates.

d - Very cold winters with the coldest month below -38°C (-36°F) in the D climate only.

h - Dry-hot with a mean annual temperature over 18°C (64°F) in B climates only.

k - Dry-cold with a mean annual temperature under 18°C (64°F) in B climates only.

Climate ClassificationGulf States = Cfa

C = mild mid-latitude

f = moist = no dry season

a = average temperature of the warmest month is above 72°F (22°C) = hot summer

Climatic Relationships

Figure 10.3

Generalized Climate Regions

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Tropical Climates

Tropical ClimatesTropical Rainforest (Af)

Temperature – near 80o F the year round.Precipitation – lots of rain – 75 to 100 inches per year

Location – equatorial zone either side of the equatorVegetation – broadleaf evergreen forest.

solid canopy of tree tops – only filtered light reaches groundSoils are nutrient poor and difficult for agriculture

Tropical ClimatesTropical Monsoon (Am) -

Temperature – near 80o for the yearPrecipitation - 20 to 30" per month during summer monsoon

but much drier during winter.

Location – usually located 5° - 20° N & S latitudeVegetation – mixed broadleaf deciduous and broadleaf evergreen forest - more shrubs and bushes.

Arid & Semiarid Climates

Dry ClimatesDeserts (BW)

Temperature - cooler annual average than tropical areas but hotter in the high sun period & cooler during low sun.

Nights are very cool (greatest daily temperature range)

Precipitation – is less than 10" per year.

Found in 3 main areas:1. on western side of continents

2. in rain-shadows of north-south mountain ranges

3. in the interior of large continental land mass.

Vegetation - drought resistant shrubs and cacti

barren sand dunes

Dry ClimatesSteppe (BS) - transition areas adjacent to deserts

Temperature:- hotter than tropical areas in summer - cooler in winter with a larger annual range.

Precipitation – 10-25" per year

The vegetation of steppe zones is primarily grasslands

Low-Latitude Hot Steppe

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Dry ClimatesThe location of steppe climates follow the location of deserts and are prone to desertification

Desertification: the expansion of desert-like conditionsCaused by poor agricultural practices, overgrazing, and the build-up of salts in soil from irrigation

UN estimates that 60% of the world’s rangelands are threatened by desertification

Humid Mid-latitude

Humid Subtropical (Ca)Temperature –As hot as tropical climates in summer average and between 32o & 64o in coldest month

Precipitation - annual rainfall 30-65” with greatest amounts in summer

Location - east side of continents - 20o & 40o.

Vegetation - broadleaf evergreen, deciduous forests, and needle-leaf evergreen pine forest found in the SE U.S.

Subtropical Climates

Humid Mid-latitude ClimatesMediterranean (Cs)

Temperature –mild winters average 40o - 55o , warm summers 70o - 80o

Precipitation – 15-25 inches mostly falling during the low sun season

Location - west sides of continents between 30o & 45o with thelargest area around the Mediterranean Sea.

Vegetation - scattered broadleaf evergreen trees & shrubs called chaparral –

drought-resistant shrubs

Marine West Coast (Cb)Temperature - mild winters for the high latitude; average near or above freezing- cool summers approx. 60o F.

Precipitation - 25 to 40 inches on low coast to 100-200 inches on windward slopes facing sea; heavy mountain snows

Location - west side of continents (largest area found in Western Europe)

Vegetation - broadleaf deciduous in Europe, needle-leaf in Pacific Northwest , and broadleaf evergreen in Southern Chile.

Marine West Coast Climate

Humid Continentalfasd

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Humid Continental ClimateHumid Continental – Hot Summer (Da)

NY is an example

Temperature - cold winter, warm summer

Precipitation - 20-50" per year; heavy snowfalls

Location - Northern Hemisphere only

Vegetation –tall to medium grass in drier areas (prairie) to broadleaf deciduous forests mixed with evergreens.

Humid Continental ClimateHumid Continental – Mild Summer (Db)

Moscow, Russia is an example

Temperature - cold winter, mild summer

Precipitation - 20-50" per year - most in summer; heavy snowfalls frequent in winter

Location - Northern Hemisphere only

Vegetation – tall to medium grass in drier areas (prairie) to broadleaf deciduous forestsmixed with evergreens.

Sub-Arctic ClimateSubarctic (Dc)

Average 50o F in summerPrecipitation - 15-30" per year - heaviest in summer –

7-8 months of continuous snow cover.

Location - Northern Hemisphere only 45o - 70o.

Vegetation –coniferous forests known as the taiga

Polar and Highland Climates Tundra Climate

Ice Cap and Ice Sheet Climates

Polar Marine Climate

Polar ClimatesTundra (Et)

Temperature - warmest month between 32o & 50o, winter very cold

Precipitation - 10-12" per year

Location - northern edge of N.A. and Eurasia & outer tip of Antarctica.

Vegetation is primarily low plants, many wild flowers in summer & also bare rock.

Polar ClimatesIce Cap (Ef)

Temperature - extremely cold winter, average summer below freezing.

Precipitation - less than 5”the driest climate but experiences continuous accumulation of snow and permanent glaciers.

Location – interior Greenland, Antarctica.

Vegetation – None

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Polar ClimateHighland (H)

Climates change rapidly on mountains, becoming colder the higher the altitude gets.

Closely related to the climate of the surrounding climate. The highlands have the same seasons and wet and dry periods as the climate zone

Mountain climates are very important to mid-latitude climates. Snow is kept back until spring and summer when it is released slowly as water through melting

Highland Climates (H)

Highland ClimateHighland (H)

Climates change rapidly on mountains, becoming colder the higher the altitude gets.

Closely related to the climate of the surrounding climate. The highlands have the same seasons and wet and dry periods as the climate zone

Mountain climates are very important to mid-latitude climates. Snow is kept back until spring and summer when it is released slowly as water through melting

Global Climate ChangeGlobal Warming - the increase in the average temperature of the Earth's near-surface air and oceans in recent decades

1880-20031.4° average increasein global temperatures

Majority in the last 30 years

Causes:Debated among scientists

Consensus: increase in greenhouse gases related tohuman activity

Global Climate ChangeGreenhouse gases – absorbs solar radiation and emits longer wavelengths energy which warms the lower atmosphere

water vapor, carbon dioxide, methane, nitrous oxide, and ozone

The majority of greenhouse gases come from natural sources – also contributed to by human activity.

Global Climate ChangeMethane & Global Warming

Increased dramatically (0.7 ppm to 1.8 ppm) over last 500 years

Caused by bacterial action in livestock and organic activity of rice fields

Burning vegetation – contributes 20% of the excess

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Global Climate ChangeCarbon Dioxide & Global Warming

Responsible for 64% of global warming

increases highest in the last 20,000 years

Developing countries will be largest contributors in the coming years - as they industrialize

Global Climate ChangeConsequences of Global Warming

Dryer conditions in midlatitudesRequiring more energy, water and resources to be used

Climatic shift in crops – crops shift to preferred temperature regions

Melting glaciers and Ice sheetsKilimanjaro, Andes, Himalayas, Alaska

Led to worldwide rising sea levels

Global Climate Change

Climatic ChangeLong-term climatic change

Significant variations over geologic timeIce ages

Medieval warm period and “little ice age”

May be due to variations in: shape of Earth’s orbit, tilt of the axis, gyration of the rotation axis

Short-term climatic changeNatural processes

Volcanic eruptions, oceanic circulation, sunspot activity

Human processesEnhanced greenhouse effect

Climatic ChangeGreenhouse effect

Certain gases in the atmosphere function as an insulating barrier, trapping infrared radiation

Global warmingCaused by human activities that have increased the amount of greenhouse gases in the atmosphere

Carbon dioxide: burning fossil fuels, deforestation

Methane: natural gas and coal mining, agriculture and livestock, swamps, landfills

Nitrous oxides: motor vehicles, industry, fertilizers

Chlorofluorocarbons: industrial chemicals

Climatic ChangeEvidence of global warming

20th century was the warmest in 600 yearsAverage surface temp rose over 1° F during the century

Winter temps in the Arctic have risen about 7° F since the 1950s

Loss of Arctic ice cap

Glaciers are thinning and retreating

Consequences of global warming include:Rising sea levels

Changes in temperature and precipitation patternsImpact on soils, vegetation, agriculture