Global Warming: we’re on thin ice!Global Warming: we’re on thin ice!

• Evidence of global warming

• Denial of global warming

• Convergence of evidence

Compton Tucker

NASA/Goddard Space Flight Center &

Climate Change Science Program Office

Measured Surface Temperature Measured Surface Temperature the past 150 yearsthe past 150 years

5 warmest years: 1998, 2002, 2003, 2004, 5 warmest years: 1998, 2002, 2003, 2004, 20052005

Warming Warming greatest at greatest at

high high latitudeslatitudes

Amplification of Amplification of warming due to warming due to

decrease of decrease of albedo (melting of albedo (melting of

snow and ice)snow and ice)

Mann, Bradley, & Hughes (1998):Mann, Bradley, & Hughes (1998):The “hockey stick” surface temperatureThe “hockey stick” surface temperature

Proxy data used by Mann et al. 1998Proxy data used by Mann et al. 1998

Tree Ring DendrochronologyTree Ring Dendrochronology

Tree Ring DendrochronologyTree Ring Dendrochronology

Tree Ring Temperature ReconstructionsTree Ring Temperature Reconstructions~40% tree ring variation is due to temperature~40% tree ring variation is due to temperature

Best tree ring chronology is bristlecone pine series from Best tree ring chronology is bristlecone pine series from US west that grows >3,000 m & extends >4,000 yearsUS west that grows >3,000 m & extends >4,000 years

Much of the Much of the controversy over controversy over

surface surface temperature temperature

reconstructions has reconstructions has been associated been associated with tree ring with tree ring

proxy temperatureproxy temperature

Some ring-width seriesSome ring-width series

Cook, 1989

Four red spruce ring-width series from the same stand – different Four red spruce ring-width series from the same stand – different trends related to competition and disturbance.trends related to competition and disturbance.

Coral 18O/16O TemperatureReconstruction

Proxy Surface Temperaturesfrom corals, sediments, and

ice cores using 18O/16O18O = (18O/16O)sample - (18O/16O)SMOW x 103 ‰ (18O/16O)SMOW

SMOW = Standard Mean Ocean Water

1818O: O: 0.20%0.20%

1717O: O: 0.04%0.04%

1616O: O: 99.76%99.76%

The vapor pressure of HH221616O is > than that of O is > than that of

HH221818O; converselyO; conversely HH22

1818OO passes into the liquid state more readily. Because condensation is the result of cooling, the greater the fall in

temperature the lower the 1818O concentration O concentration in Hin H22O will be. Isotope concentration can thus O will be. Isotope concentration can thus

be considered a function of temperature.be considered a function of temperature.

Greenland ice core: high resolution/distinct layers

Greenland ice core--yearly layers

McIntyre and McKitrick 2003McIntyre and McKitrick 2003a reanalysis with a subset of Mann et al. a reanalysis with a subset of Mann et al.

1998’s data1998’s data

15th century the warmest time 15th century the warmest time in the past 1000 to 2000 years?in the past 1000 to 2000 years?

Same result as Mann et al. 1998 when Same result as Mann et al. 1998 when 5 PCs are used for 15th century5 PCs are used for 15th century

Same result as Mann et al. 1998Same result as Mann et al. 1998

Proxy data used by Mann et al. 1998Proxy data used by Mann et al. 1998

Total Solar Irradiance

Arctic Sea Ice Trends

2005 summer minima

1979 summer minima

Warmer Earth Warmer Earth Greener NorthGreener North

Arctic Sea Ice Extent 1979 to 1999Arctic Sea Ice Extent 1979 to 1999

Claire Parkinson et al. 2002

Majority of Glaciers are recedingMajority of Glaciers are receding

Receding GlaciersReceding Glaciers

Holgate Glacier July 24, 1909Holgate Glacier July 24, 1909

Holgate Glacier August 13, 2004Holgate Glacier August 13, 2004

Sea Level Rise from thermal expansion Sea Level Rise from thermal expansion & input of water from melting glaciers& input of water from melting glaciers

20 cm (7 inches) in a century20 cm (7 inches) in a century

Bore Hole Temperature Reconstructions

Bore Hole LocationsBore Hole Locationsdifferent physics (different physics (thermal diffusivity) thermal diffusivity)

& 10s of years time steps& 10s of years time steps

Bore Hole Temp. ReconstructionsBore Hole Temp. Reconstructions

~500 years

Subsurface Annual TemperatureSubsurface Annual Temperature12.8 m depth @ North Dakota12.8 m depth @ North Dakota

Bore Hole Data for Eastern & Bore Hole Data for Eastern & Western North America Western North America

((Huang & Pollack)Huang & Pollack)

Pollack & Huang Pollack & Huang Bore Hole DataBore Hole Data

Bore Hole Cumulative Temperature

Figure 6 from pollack and huang p. 365

National Research Council’s National Research Council’s June 2006 ReportJune 2006 Report

Data density circa 1000 ADData density circa 1000 AD

Data density circa 1500 ADData density circa 1500 AD

Equilibrium Climate from Ice Core DataEquilibrium Climate from Ice Core Data

J. HansenJ. Hansen

• Estimate Estimate climate climate

forcing (W/mforcing (W/m22) ) from from

atmospheric atmospheric composition composition

changeschanges

• Regress Regress Temperature Temperature

anomalies anomalies against against climate climate forcing forcing

Data

c8 = ~ 10k year periodicity

c12 = ~ 400,000 year periodicity

modes 10 to 13 : 20k, 40k, 100k, & 400k yearsmodes 10 to 13 : 20k, 40k, 100k, & 400k years

Equilibrium Climate from Ice Core DataEquilibrium Climate from Ice Core Data

J. HansenJ. Hansen

• Estimate Estimate climate climate

forcing (W/mforcing (W/m22) ) from from

atmospheric atmospheric composition composition

changeschanges

• Regress Regress Temperature Temperature

anomalies anomalies against against climate climate forcing forcing

Atmospheric CO2 measurements

Atmospheric CO2 since 1740

Different dCO2/dtime slopes reflect

techno-economic conditions

Climate Forcing: expressed as a change in Climate Forcing: expressed as a change in radiative heating (W/mradiative heating (W/m22) at surface for a given ) at surface for a given

change in trace gas composition or other change change in trace gas composition or other change external to the climate systemexternal to the climate system

Where the Where the rubber hits the rubber hits the

roadroad

Surface melt on Greenland ice sheet

descending into moulin, a vertical shaft carrying the water to base of ice sheet.

Source: Roger Braithwaite

January 31, 2002

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Gravity Recovery & Gravity Recovery & Climate ExperimentClimate Experiment

500 km orbit500 km orbit

220 km separation220 km separation

Distance accuracy Distance accuracy 0.001 mm0.001 mm

Greenland Mass Loss from GRACEGreenland Mass Loss from GRACE

Satellite record melt of 2002 was exceeded in 2005

Surging Surging glaciers & glaciers &

meltingmelting

Greenland Ice: Greenland Ice: 70 m thinning in 5 years70 m thinning in 5 years

> Streaming, >Earthquakes> Streaming, >Earthquakes

It’s only a matter of time…

400 km3 ice = 1 mm sea level

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Business-as-Usual(2% annual growth until 50% depletion, then 2% annual decline)

What, me worry?

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Alternative Case: Coal Phaseout(+2%/yr to 2012; +1%/yr to 2022; linear shutdown between 2025-2050)

J. Hansen