Global Climate Change

150 Authors 1,000 Contributing Authors 5 Years Work 130 Countries 1,000 Expert Reviewers The IPCC WGI Report

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 21 st century climate

Vostok Ice Core Looking Back in Time

Looking Back 650,000 Years N20N20 CH 4 CO 2 T Thousands years before 1950

Looking Back 130,000 Years

Looking Back 1,300 Years Year Little Ice Age Medieval Warm Period Temperature Change (°C)

Looking Back 150 Years Year ~1°C Temperature Change (°C)

SurfaceAbove Where is This Happening? 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

Oceans are Warming Year Heat Content Change

Photos: US Geological Service, via National Snow and Ice Data Centre 1909 Toboggan Glacier, Alaska 2000 Glaciers are Retreating Year Length Change (m)

Ice Sheets are Melting Elevation Change (cm/year)

Reconstructed sea level fields Tide gauges Satellites Sea Level is Rising ~20 cm Year Sea Level Change (mm)

Sea-ice is Melting Year Millions of square km

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 hurricanes floods What about extreme events?

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 21 st century climate

Global Climate Change