Class #37: Friday, April 10

Class #37: Friday, April 10 1

Class #37: Friday, April 10

Climate Types (D,E, and H)

Past Climates: Proxy Data


The 6 major climate groups

• A: Tropical moist• B: Dry (can be subtropical or mid latitude)• C: Moist with mild winters (mid latitude)• D: Moist with severe winters (mid latitude)• E: Polar (high latitude)• H: Highland (rapid climate change with

elevation)• 2nd letter: usually latitude (except B)• 3rd letter: differences in temperature


D Climate typeSevere (winter) Midlatitude

• Similar to C but severely cold winter

• Average temperature of coldest month <27ºF

• Snow on ground for extended periods

• Average temperature of warmest month >50ºF

• Overall, large change in temperature with season


D climate subtypes

• 2nd letter – “f” no dry season– “w” winter dry season

• 3rd letter– “a” hot summer– “b” warm summer– “c” cool summer– “d” extremely severe winter


D Climate Subtypes (continued)

• Humid continental– Dfa, Dfb, Dwa, Dwb– Dfa, for example, Chicago

• Subarctic– Dfc, Dfd, Dwc, Dwd– Long winter– Brief cool summer


E climate type

• Polar climate, very dry and cold

• Poleward of Arctic/Antarctic Circle, latitude 66.5º

• E climate subtypes– ET Tundra: mosses, lichens, flowering plants,

woody shrubs, small trees, permafrost– EF Ice caps: no vegetation; Greenland,

Antarctic Plateau


H climate type: Highland

• Large variation of temperature and precipitation over small horizontal distances

• Large diurnal temperature variation

• Can be dry or moist, depending on orientation, humidity, and whether prevailing winds are upslope or downslope


Have today’s climates always been the same?

• This question leads to the study of past climates.

• So do the questions: Can we predict future climates? What is the impact of humans on climate?

• Two kinds of past climate:– Historical, past few thousand years– Paleoclimate, ancient, back billions of years


Historical Climate

• Humans have kept records• Instrumental record

– Since about 1600

• Historical data: proxy data– Humans have kept some sort of record of

climate conditions– Examples: dates of freezes of lakes and rivers,

farmers’ logs, animals in cave paintings, other documents


Another source of data for the historical period is trees

• Tree rings are rings of growth in tree trunks in regions with distinct growing seasons.

• A wider tree ring means more growth.• Growth varies with temperature and precipitation,

depending on the species.• Information from various species is most helpful.• The study of tree rings is dendrochronology, and is

done by dendrochronologists.• Figure shows dry periods in Iowa in 1700, 1740,

1820, 1820, 1890, and 1930 from tree rings.


Proxy measurements of precipitation from tree rings

• Dry periods: 1930s, the “Dust Bowl”

around 1700

1740 1820 1890


Pollen for proxy information

• Pollen degrade slowly, distinctive shapes for each species

• Oldest sediments are deepest

• Spruce need a cool climate• Decline of spruce during

warming• Pine need a warm and moist

climate• Oak need it drier than pine

Class #37: Friday, April 10

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