Global Climate Change
150Authors
1,000Contributing Authors
5 Years Work130 Countries
1,000 Expert Reviewers
The Famous “IPCC Report”
VostokIce Core
Looking Back in Time
Temperature From 650,000 Years Ago
N20
CH4
CO2
T
Thousands years before 1950
Temperature From 1,300 Years Ago
Year
Little Ice Age
Medieval Warm Period
Tem
pera
ture
Cha
nge
(°C
)
Temperature From 150 Years Ago
Year
~1°C
Tem
pera
ture
Cha
nge
(°C
)
Surface Above
Where is This Happening?
An Explosion of New Data
• Oceans are warming
• Glaciers are retreating
• Ice sheets are melting
• Sea level is rising
• Sea-ice is melting
Oceans are Warming
Year
Hea
t C
onte
nt C
hang
e
Photos: US Geological Service, via National Snow and Ice DataCentre
1909
Toboggan Glacier, Alaska
2000
Glaciers are Retreating
Year
Leng
th C
hang
e (m
)
Ice Sheets are Melting
Elevation Change (cm/year)
Reconstructedsea level fields
Tide gauges
Satellites
Sea Level is Rising
~20 cm
Year
Sea
Lev
el C
hang
e (m
m)
Sea-ice is Melting
Year
Mill
ions
of
squa
re k
m
Why is This Happening?
• Climate models used to understand and predict climate change
• Based on physical principles, and subject to extensive validation
ObservationsClimate Models
ObservationsClimate Models
What About the Next 20 Years?
0.5°C
What About the Next 90 Years?
1-4°C
And the Next 300 Years?
Expect Sea Level Rise ~ 0.5 m
Sea Level Change Anomalies
Expect Large Warming Over Land
Temperature Change (°C)
Expect Regional Precipitation Change
Precipitation Change
Heavier Precipitation
Longer Growing SeasonMore Heat Waves
More Drought
Winners and Losers
Key Messages
• The climate has warmed, will continue to warm, and humans are the cause
• Mitigation will not substantially affect the climate over the next few decades
• But, choices made now will have a big impact on the late 21st century climate
Global Climate Change