Transcript Fourth IPCC Assessment Report

Global Climate Change
The IPCC WGI Report
150
Authors
1,000
Contributing Authors
5 Years Work
130 Countries
1,000 Expert Reviewers
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
Looking Back in Time
Vostok
Ice Core
Looking Back 650,000 Years
N20
CO2
CH4
T
Thousands years before 1950
Looking Back 130,000 Years
Temperature Change (°C)
Looking Back 1,300 Years
Medieval Warm
Period
Little Ice Age
Year
Temperature Change (°C)
Looking Back 150 Years
~1°C
Year
Where is This Happening?
Surface
Above
Global temperature trends from 1979 to 2005
An “Explosion” of New Data
•
•
•
•
•
Oceans are warming
Glaciers are retreating
Ice sheets are melting
Sea level is rising
Sea-ice is melting
Heat Content Change
Oceans are Warming
Year
Length Change (m)
Glaciers are Retreating
Toboggan Glacier, Alaska
1909
2000
Year
Photos: US Geological Service,
via National Snow and Ice Data
Centre
Ice Sheets are Melting
Elevation Change (cm/year)
Sea Level Change (mm)
Sea Level is Rising
Satellites
Reconstructed
sea level fields
~20 cm
Tide gauges
Year
Millions of square km
Sea-ice is Melting
Year
2008
2007
Why is This Happening?
• Climate models are used
to understand and predict
climate change
• Based on sound physical
principles, and subject
to extensive validation
Observations
Climate Models
Observations
Climate Models
What About the Next 20 Years?
0.5°C
What About the Next 90 Years?
1-4°C
Expect Large Warming Over Land
Surface temperature change (ºC) out to 2050
Expect Regional Precipitation Change
Precipitation change (mm/day) out to 2090
Expect Sea Level Rise ~ 0.5 m
Local sea level change (m) out to 2090
droughts
floods
What about extreme events?
hurricanes
Trend towards more extreme temperatures
Very warm nights
Very warm days
Trends (days per decade) in the frequency of extreme temperatures
Trend towards more very wet days
Trend 1951 – 2003 contribution from very wet days
“Likely trend since 1970 towards more
intense tropical storms in some regions”
Wind energy index for named tropical storms
Expect heavier precipitation
Expect more heat waves
Expect more drought
Expect more frost days
Key Messages Once Again
• 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