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Global Warming: we’re on thin ice! Evidence of global warming Denial of global warming Convergence of evidence Compton Tucker NASA/Goddard Space Flight.

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Presentation on theme: "Global Warming: we’re on thin ice! Evidence of global warming Denial of global warming Convergence of evidence Compton Tucker NASA/Goddard Space Flight."— Presentation transcript:

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2 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

3 Measured Surface Temperature the past 150 years 5 warmest years: 1998, 2002, 2003, 2004, 2005

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

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

6 Proxy data used by Mann et al. 1998

7 Tree Ring Dendrochronology

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9 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

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

11 Coral  18 O/ 16 O Temperature Reconstruction

12 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.

13 Greenland ice core: high resolution/distinct layers

14 Greenland ice core--yearly layers

15 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

16 Proxy data used by Mann et al. 1998

17 Total Solar Irradiance

18 Arctic Sea Ice Trends 2005 summer minima 1979 summer minima

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

20 Majority of Glaciers are receding

21 Receding Glaciers

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

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

24 Bore Hole Temperature Reconstructions

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

26 Bore Hole Temp. Reconstructions ~500 years

27 Subsurface Annual Temperature 12.8 m North Dakota

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

29 Pollack & Huang Bore Hole Data

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

31 National Research Council’s June 2006 Report

32 Data density circa 1000 AD

33 Data density circa 1500 AD

34 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

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38 Data

39 c8 = ~ 10k year periodicity

40 c12 = ~ 400,000 year periodicity

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

42 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

43 Atmospheric CO 2 measurements

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

45 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

46 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

47 January 31, mi 20 km

48 March 7, mi 20 km

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

51 Greenland Mass Loss from GRACE

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

53 > Streaming, >Earthquakes

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

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56 What, me worry?

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59 J. Hansen

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