«DIRECT TESTIMONY OF JAMES E. HANSEN Q. Please state your name and business address. A. My name is James E. Hansen. My business address is 2880 ...»
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34 Figure 1. (a) Global surface temperature relative to 1951-1980 base period mean, based on surface air measurements at meteorological stations and ship and satellite SST (sea surface temperature) measurements, (b) temperature anomaly for first six years of the 21st century relative to 1951-1980 base period (update of figures of Hansen et al., Proc. Natl. Acad. Sci. 103, 14288-14293, 2006). Green vertical bars in (a) are estimated 2σ error (95% confidence) of annual global mean temperature anomaly.
Figure 2. Temperature change in Antarctica over the past 420,000 as inferred from the isotopic composition of snow preserved in the ice sheet and extracted in the Vostok ice core (Vimeux et al.
, Earth Planet. Sci. Lett. 203, 829-843, 2002).
Figure 3. Temperature, CO2, and sea level.
See Hansen et al. (2007) for original data sources.
Figure 4. Distribution of early urban societies.
Coastal mangroves and salt marshes shown by dark and light shades. (after Day, J.W. et al., EOS Trans. AGU, 88, 169-170, 2007).
Figure 5. CO2, CH4, and temperature from the Vostok Antarctic ice core (Vimeux et al.
Figure 6. (a) sea level records from three sources, (b) climate forcings due to greenhouse gases (CO2, CH4 and N2O) and surface albedo from the Siddall et al.
sea level record, (c) calculated and observed paleo temperature change. Calculated temperature is the product of the sum of the two forcings in (b) and ¾°C per W/m2. Observed temperature is the Vostok temperature (Figure 2) divided by two.
Figure 7. (a) Antarctic temperature from Vostok ice core (Vimeux et al.
2002) and global climate forcing (right scale) due to CO2, CH4 and N2O. (b) Correlation (%) diagram showing lead of temperature over greenhouse forcing.
Figure 8. Extension of Antarctic CO2, CH4 and temperature records of Figure 5 into modern era.
Antarctic temperature is divided by two to make it comparable to global temperature extension.
Figure 9. Continental positions at four times (adapted from Keller and Pinter 1996).
Figure 10. (a) Global compilation of deep-sea benthic foraminifera 18O isotope records from Deep Sea Drilling Program and Ocean Drilling Program sites (Zachos et al 2001), temperatures applying only to ice-free conditions, thus to times earlier than ~35 My BP.
The blue bar shows estimated times with ice present, dark blue being times when ice was equal or greater than at present. (b) Expansion of 18O data for past 3.5 My. (Lisiecki and Raymo 2005) (c) Temperature data based on Vostok ice core (Vimeux et al 2002).
Figure 11. Principal inferences from Cenozoic Era relevant to present-day climate.
Figure 12. Increased tilt of Earth’s spin axis exposes both poles to greater melt of high latitude ice.
Figure 13. Principal inferences from Pleistocene climate variations.
Figure 14. (A) Estimates of CO2 in the Phanerozoic based on proxy CO2 data and GEOCARB-III model of Berner and Kothavala (2001), (B) Intervals of glacial (dark) or cool (light) climates, (C) Latitudinal distribution of direct glacial records (tillites, striated bedrock, etc.
, from Crowley 1998). Figure is from Royer at al. (2004).
Figure 15. (A) Climate forcings since 1880, relative to the forcings in 1880.
The largest forcing is the positive (warming) forcing due to greenhouse gases, but human-made aerosols and occasional volcanoes provide significant negative forcings. (B) Observed global temperature and temperature simulated with the GISS global climate model, which has climate sensitivity 2.8°C for doubled CO2, using the forcings in (A). (C) Climate response function (% of equilibrium response) obtained with GISS atmosphere modelE connected to the Russell ocean model (from Hansen et al. 2007b) Figure 16. Extension of climate simulations through the 21st century. A1B (dark blue line) is a typical “business-as-usual” scenario for future greenhouse gas amounts. The “alternative scenario” has CO2 peaking near 450 ppm, thus keeping additional warming beyond that in 2000 less than 1°C.
Figure 17. Practically all nations in the world, including the United States, have signed the Framework Convention on Climate Change.
The problem is that “dangerous anthropogenic interference” in not defined.
Figure 18. Suggested principal metrics for defining the “dangerous” level of climate change.
Figure 19. Area on Greenland with summer surface melt fluctuates from year to year, but has been increasing during the period of satellite observations.
Recent years, not shown, have broken the record set in 2002.
Figure 20. Summer surface melt-water on Greenland burrows a hole in the ice sheet, more than a mile thick, that carries water to the base of the ice sheet.
There it serves as lubrication between the ice sheet and the ground beneath the ice sheet.
Figure 21. The rate of discharge of giant icebergs from Greenland has doubled in the past decade.
Figure 22. The GRACE satellite mission measures the Earth’s gravitational field with such high precision that changes of the mass of the Greenland and Antarctic ice sheets can be measured.
The ice sheet mass grows with winter snowfall and decreases during the melt season. Overall Greenland and West Antarctica are each now losing mass at rates of the order of 150 cubic kilometers of ice per year.
Figure 23. A majority of the world’s 100 largest cities are located on coast lines.
Figure 24. A sea level rise of 25 meters would displace about 1 billion people.
Even a 5-7 meter sea level rise would affect a few hundred million people, more than 1000 greater than the number of people in New Orleans affected by the Katrina hurricane disaster.
Paleo and Modern Temperatures in Critical Global Regions
Figure 25. Temperatures in the Pacific Warm Pool (a) and Indian Ocean (b), regions of special significance for global climate.
Warm Pool temperature affects the transport of heat to much of the world via ocean and atmosphere;
the Indian Ocean has the highest correlation with global mean temperature. In both regions warming of recent decades has brought the temperature within less than 1°C of the temperature during the warmest interglacial periods.
Figure 26. Unchecked global warming will, in effect, push polar species off the planet.
Mt. Graham Red Squirrel
Figure 27. Alpine species can also be pushed to extinction as global warming causes isotherms to move up the mountains.
The Mt. Graham red squirrel is an example of a threatened species. Impacts of climate change occur in bursts; forest fires in the lower reaches of the forested region cause permanent change, as the forests are unable to recover.
Figure 28. The millions of species on the planet are being stressed in several ways, as humans have taken over much of the planet.
Based on prior global warmings in the Earth’s history, much slower than the present humaninduced climate change, it is expected that the added stress from the large global climate change under business-asusual scenarios would lead to eventual extinction of at least several tens of percent of extant species.
Figure 29. Critical carbon cycle facts.
(a) A pulse of CO2 added to the atmosphere by burning fossil fuels decays rapidly at first, with about half of the CO2 taken up by sinks, principally the ocean, within the first quarter century. However, uptake slows as the CO2 added to the ocean exerts a back-pressure on the atmosphere. Even after 1000 years almost one-fifth of the increase due to the initial pulse is still in the atmosphere. (b) Fossil fuel reservoirs are finite. Oil and gas proven and estimated reserves are sufficient to take atmospheric CO2 to the neighborhood of 450 ppm. Coal and unconventional fossil fuels, if exploited without carbon capture, have the potential to at least double or triple the pre-industrial atmospheric CO2 amount of 280 ppm.
Figure 30. CO2 can be kept below 450 ppm only if coal and unconventional fossil fuels are used only where the CO2 is captured and sequestered.