2

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

observed overthe 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 anthropogenic

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 Gases

• Let sunlight in– short wavelengths

• Earth heats up and radiates heat– longer wavelengths

• GHGs– don’t let Earth’s heat out

Increased Greenhouse Gases

Earth’s “cooling” system is “clogged”

• Net effect:– Earth warms to a

temperaturewhere itsradiation isshorter wave-lengths and canescape

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

• Sea level rise• 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 GHGs

Signs that global warming is underway

•Globe 1°F warmer than 100 yrs ago

•Last glacial max. was only 5°F cooler

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

– Winter and night increasing fastest(~5 times faster)

•Weather becoming more variable and more severe

Some climate change facts

14

Arctic Sea Ice Melting

151980

-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

16

1941

2004

Melting of small glaciers and ice caps

17

McCarty Glacier, Alaska

18

Kilimanjaro

19

1970 2005

Kilimanjaro

20

1928 2004

Patagonia

Sea-level rise

Sea-level rise

• Fastest extinction rate in 65 M 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

24

Coral bleaching

25

Mass extinction

26

Habitat loss

27

Palmer Drought Severity Index 1900-2002

What can you do?

Reduce consumption

Plant trees

Drive less

Shop smart

Alternative energy

Be informed

Unplug

Improve insulation

Don’t remain happy in ignorance