1

Changing Earth’s Climate

`The balance of evidence suggests that there is a

discernible human influence on global

climate '

Intergovernmental Panel on Climate Change (United Nations), Second Assessment Report, 1996

`There is new and stronger evidence that most of the warming observed over

the last 50 years is attributable to human

activity'

Intergovernmental Panel on Climate Change (United Nations), Third Assessment Report, 2001

`Most of the observed increase in globally averaged

temperatures since the mid-20th century is very likely due to the

observed increase in greenhouse gas concentrations.'

Intergovernmental Panel on Climate Change (United Nations), Fourth Assessment Report, 2007

`Warming of the climate system is unequivocal, as is now evident

from observations of increases in global average air and ocean

temperatures, widespread melting of snow and ice, and rising global

mean sea level.'

Intergovernmental Panel on Climate Change (United Nations), Fourth Assessment Report, 2007

Greenhouse Gasses

• Sunlight heats up Earth’s surface

• Earth radiates heat back into the air

• Greenhouse gasses absorb this heat and don’t let Earth’s heat out

Increased Greenhouse Gases

Earth’s “cooling” system is “clogged”

Evidence from the Earth

9

Global mean temperature

Global averagesea level

Northern hemispheresnow cover

Observations of recent climate change

10

Global Instrumental Temperature Record

10 warmest years

1960 1970 1980 1990 2000310

320

340

360

370

380

Car

bon

Dio

xide

Con

cent

ratio

n (p

pmv)

2007

330

350

390

Carbon Dioxide Concentration

12

How we get data from the past

– Deep ocean cores

– Tree rings

– Historical documents

– Coral cores

– Ice cores

Reconstructing past climates

Reconstructed Surface Temperatures

270

290

360

370

380

Car

bon

Dio

xide

Con

cent

ratio

n (p

pmv)

280

300

310

320

330

340

350

1750 1800 1850 1900 1950 2000

Mauna Loa, Hawaii (1958 - present)

Siple Station (1750 - )

Past CO2 concentrations

800 600 400 200 0

CO

2 (

ppm

v)

Thousands of Years Before Present

Present CO2 concentration (383 ppmv)

CO2 concentration after 50 years of unrestricted fossil fuel burning (600 ppmv)

240

300

270

210

180

Petit et al., 1999; Siegenthaler et al., 2005; EPICA Community members, 2004

Tem

p.P

roxy

• Sea level rising• by thermal expansion AND ice melt

• Sea ice melting (Arctic and Antarctic)

• Glaciers melting worldwide

• Arctic and Antarctic Peninsula heating up fastest

• Melting on ice sheets is accelerating

• More severe weather (droughts, floods, storms, heat waves, hard freezes, etc.)

• Bottom line:• These changes do not fit the natural patterns unless we

add the effects of increased Greenhouse gasses

Signs that global warming is underway

•Earth is 1°F warmer than 100 years ago

•Not equally distributed– Some areas have warmed 11°F

•Weather becoming more variable and more severe

Some climate change facts

18

Scientists have no doubt

Glaciers fluctuate with climate

Glacier ice

Sea ice

18,000 years ago Present

•For over 30 years, scientists have predicted increased greenhouse gasses will cause unnatural changes

•By 2000 we have seen: Antarctic sea ice break-ups Antarctic Peninsula warming Arctic sea ice melting Faster Arctic warming (11°F!) Melting of small glaciers and ice caps Sea level rise

Predicted changes of human climate change

21

Antarctic Sea Ice Break-ups

22

Antarctic Sea Ice Melting

23

24

Arctic Sea Ice Melting

251980

-0.2

0.4

Ice

Ext

ent A

nom

aly

(106

km2 )

0.0

0.2

1985 1990 1995 2000 2005

-0.4

-0.8

-0.6

Arctic sea ice extent

26

1941

2004

Melting of small glaciers and ice caps

27

Carroll Glacier

1906 2004

28

McCarty Glacier, Alaska

29

Muir and Riggs Glaciers

1993

2000

31

1970 2005

Kilimanjaro

32

Qori Kalis

1978 2002

33

1928 2004

Patagonia

• ~80% of world’s water supply

• Rapidly retreating worldwide

• Glaciers and ice caps gone by 2100 or sooner

• Major ice sheets also retreating

1941 2004

Who cares about glaciers?

Sea-level rising

• Thermal expansion (warmer water expands and needs more space)

• Addition of water from melting ice

• Melting ice sheets– Greenland: 7.4 m (25’) potential– Antarctica: 74 m (250’) potential

36

1992 2005

Greenland satellite melt record

1 year of melt!

R. Huff, J. Box, S. Starkweather, T. Albert

This is how much ice

melted in just one year.

38

Sea Level Rise

• Areas in red will be under water if all Greenland melts.

39

Earth if Antarctica melts

Sea-level rise

• Fastest extinction rate of life on Earth in 65 Million years (1000x normal rate)

• Increased disease (e.g. asthma, malaria)

• Increased poverty and hunger

• Sea level rise

• More extreme weather– Droughts

– Flooding

– Heat-waves

– Storms

Additional consequences