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 the past 150 years 5 warmest years: 1998, 2002, 2003, 2004, 2005

Warming greatest at high latitudes Amplification of warming due to decrease of albedo (melting of snow and ice)

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

Proxy data used by Mann et al. 1998

Tree Ring Dendrochronology

Tree Ring Temperature Reconstructions ~40% tree ring variation is due to temperature Best tree ring chronology is bristlecone pine series from US west that grows >3,000 m & extends >4,000 years Much of the controversy over surface temperature reconstructions has been associated with tree ring proxy temperature

Some ring-width series Cook, 1989 Four red spruce ring-width series from the same stand – different trends related to competition and disturbance.

Coral  18 O/ 16 O Temperature Reconstruction

Proxy Surface Temperatures from corals, sediments, and ice cores using 18 O/ 16 O  18 O = ( 18 O/ 16 O)sample - ( 18 O/ 16 O)SMOW x 10 3 ‰ ( 18 O/ 16 O)SMOW SMOW = Standard Mean Ocean Water 18 O: 0.20% 17 O: 0.04% 16 O: 99.76% H 2 16 O is > than that of H 2 18 O; converselyH 2 18 O 18 O concentration in H 2 O will be. Isotope concentration can thus be considered a function of temperature. The vapor pressure of H 2 16 O is > than that of H 2 18 O; conversely H 2 18 O passes into the liquid state more readily. Because condensation is the result of cooling, the greater the fall in temperature the lower the 18 O concentration in H 2 O will be. Isotope concentration can thus be considered a function of temperature.

Greenland ice core: high resolution/distinct layers

Greenland ice core--yearly layers

McIntyre and McKitrick 2003 a reanalysis with a subset of Mann et al. 1998’s data 15th century the warmest time in the past 1000 to 2000 years? Same result as Mann et al when 5 PCs are used for 15th century Same result as Mann et al. 1998

Proxy data used by Mann et al. 1998

Total Solar Irradiance

Arctic Sea Ice Trends 2005 summer minima 1979 summer minima

Warmer Earth Greener North Arctic Sea Ice Extent 1979 to 1999 Claire Parkinson et al. 2002

Majority of Glaciers are receding

Receding Glaciers

Holgate Glacier July 24, 1909 Holgate Glacier August 13, 2004

Sea Level Rise from thermal expansion & input of water from melting glaciers 20 cm (7 inches) in a century

Bore Hole Temperature Reconstructions

Bore Hole Locations different physics ( thermal diffusivity) & 10s of years time steps

Bore Hole Temp. Reconstructions ~500 years

Subsurface Annual Temperature 12.8 m North Dakota

Bore Hole Data for Eastern & Western North America ( Huang & Pollack)

Pollack & Huang Bore Hole Data

Bore Hole Cumulative Temperature Figure 6 from pollack and huang p. 365

National Research Council’s June 2006 Report

Data density circa 1000 AD

Data density circa 1500 AD

Equilibrium Climate from Ice Core Data J. Hansen Estimate climate forcing (W/m 2 ) from atmospheric composition changesEstimate climate forcing (W/m 2 ) from atmospheric composition changes Regress Temperature anomalies against climate forcingRegress Temperature anomalies against climate forcing

Data

c8 = ~ 10k year periodicity

c12 = ~ 400,000 year periodicity

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

Equilibrium Climate from Ice Core Data J. Hansen Estimate climate forcing (W/m 2 ) from atmospheric composition changesEstimate climate forcing (W/m 2 ) from atmospheric composition changes Regress Temperature anomalies against climate forcingRegress Temperature anomalies against climate forcing

Atmospheric CO 2 measurements

Atmospheric CO 2 since 1740 Different dCO 2 /dtime slopes reflect techno-economic conditions

Climate Forcing: expressed as a change in radiative heating (W/m 2 ) at surface for a given change in trace gas composition or other change external to the climate system

Where the rubber hits the road 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, mi 20 km

March 7, mi 20 km

Gravity Recovery & Climate Experiment 500 km orbit 220 km separation Distance accuracy  mm

Greenland Mass Loss from GRACE

Satellite record melt of 2002 was exceeded in 2005 Surging glaciers & melting Greenland Ice: 70 m thinning in 5 years

> Streaming, >Earthquakes

It’s only a matter of time… 400 km 3 ice = 1 mm sea level

What, me worry?

J. Hansen