Ref. 5: Chap. 17: Humans and climate change(Anthropogenic climate change)

Earth’s age 4.55 Byr1st human-like creatures (stone tools) 4 Myr agohomo sapiens 100,000 to 200,000 years ago1st civilizations 10,000 years agoIndustrial era last few hundred years

The Impact of climate on human evolution The Impact of climate on early civilizationEarly impacts of humans on climateThe impacts of humans on the atmosphere: the last 250 years

The Impact of climate on human evolution

FIGURE17-1FIGURE17-2

FIGURE17-3

Modern-day lemurs

FIGURE17-4

Hominid creature

3.6 Myr ago

FIGURE17-5

FIGURE17-6 Large-scale effects of uplift and seaway shrinkage Over the last 20 Myr, tectnic-scale trends gradually made North Africa drier. The uplift of Tibet caused a strong flow of hot, dry northeasterly winds out of the Asian interior and into North Africa in summer. Shrinkage of a large inland sea in west-central Asia further reduced the amount of moisture transported toward Africa. In addition, falling atmospheric CO2 levels reduced the amount of C3 (tree and shrub)vegetation in the Sahara and Arabian deserts.

FIGURE17-8FIGURE17-7

Impact of climate on early civilizations

Fertile Crescent:Syria, Iraq,

Jordan, Turkey

FIGURE17-9 The spread of agriculture

The first advanced civilizations of the early Egyptian dynasties 6000-5000 yr ago

Sea-level rise and the origin of flood legends

In the 18th–19th centuries, Diluvial Hypothesis: a great world-wide flood to explain the widespread deposits of unsorted debris strewn across the northern continents.

FIGURE17-10 Black Sea flood hypothesis Bill Ryan and Walter Pitman (1998) 7600 years ago

Little ice age → high northern latitude

A.D. 300-1300 → migration of cultures along streams and rivers in the S. Colorado Plateau

A.D. 1300 → Anasazi abondoned cave dwellings into the sides of cliffs

A.D. 860 → collapse of the Mayan centers on the Yucatan Peninsula in Mexico

Cause-and-effect links between climate change and human cultural dislocations ?

Other factors: war, disease, tree cutting, farming methods

Early impacts of humans on climate

Early impacts of humans on large mammals? No longer than 1000 year centered on 12500 years ago

Climate changes at the end of the glacial maximum

Overkill hypothesis

Impacts of land clearance on climate?

FIGURE17-11 Pulse of mammal extinctions near

The impacts of humans on the atmosphere: the last 250 years

FIGURE17-13 Human production of CO2

FIGURE17-12 Pre-industrial and anthropogenic CO2 The combined atmospheric CO2 record from bubbles in ice cores and from insttrumentmeasurements since 1958 shows an accelerating increase of CO2 in the last 200 years above the natural baseline of 280 ppm

FIGURE17-14 Where does the CO2 produced by humans go?

FIGURE17-15 Ocean sources and sinks of CO2

FIGURE17-15

FIGURE17-17FIGURE17-16

Estimated present-day sources of atmospheric methane [gigatons/year]

Natural: (30%)

Anthropogenic sources (70%):

BOX 17-1

FIGURE17-18

FIGURE17-20

FIGURE17-21