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21st CENTURY CLIMATE BLUEPRINTS: PERSPECTIVES FROM THE RECENT HISTORY OF THE ATMOSPHERE

July 26th, 2009

by ANDREW GLIKSON Earth and Paleoclimate scientist

The Earth surface temperature reflects the net balance between incoming solar shortwave radiation and outgoing terrestrial long wave radiation Kiehl and Trenberth, 1997 [1]. The severe disturbance of the energy balance of the atmosphere ensuing from the emission of over 320 billion tons of carbon since 1750 threatens a shift in the state of the atmosphere/ocean system to ice free greenhouse Earth conditions. Based on the recent Copenhagen Synthesis Report [2], climate change trends at the top range of IPCC 2007 projections [2], and the identification of tipping points in the recent history of the atmosphere/ocean system i.e. at 14 - 11 and 8.2 thousand years-ago [3], the scale and pace of 21st Century climate changes [4] require re-consideration of mitigation and adaptation strategies.

  1. The combined CO2 and methane level in the atmosphere is fast tracking toward a level of 500 ppm, which defines the approximate onset of the East Antarctic ice sheet [5], the upper climate range which allowed the development of habitats where large mammals flourished from about 40, and in particular 34 million years ago, and hominids appeared from about 7 million years ago [6] Figure 1. Feedbacks from the carbon cycle, including release of methane from permafrost, polar sediments and bogs, and feedbacks from ice melt/warm water interaction dynamics, accelerate this process. In view of the cumulative nature of CO2 in the atmosphere, at current growth rates of about 2 ppm per-year, rising above the combined CO2 + methane level of 450 ppm [7], the atmosphere/ocean system is fast tracking toward conditions similar to those of an ice-free Earth.
  2. The scale of such greenhouse event may, or may not, bear an analogy to the PETM Paleocene-Eocene Thermal Maximum event about 55 million years ago [8], including release of large volumes of methane. Recent methane release from Siberian permafrost, lakes and shallow sediments [9].
  3. Due to hysteresis retardation of effect after cause, the effects of temperature rise, superposed ENSO El Nino Southern Oscillation cycles Figure 2, melting of Greenland and the west Antarctic ice sheets [10], sea level rise [11], possible collapse of the North Atlantic Thermohaline Circulation [12], and potential tipping points Figure 3, lag behind CO2 rise by as yet little-specified periods. A shift of the climate system through a transitional stage is occurring at present and is associated with extreme weather events [13].
  4. With a mean global temperature rise of about 0.8 degrees C since 1750, plus a rise of about 0.5 degrees C masked by sulfur aerosols emitted by industry [14], plus temperature rise due to ice albedo loss and infrared absorption by water [10], in particular the Arctic Sea, global warming is potentially near 1.5 degrees C. At this rate, conditions which existed on Earth about 2.8 million years ago mid-Pliocene +2 to 3 degrees C; Sea level rise of 25+/-12 meters [6] could be reached within time frames of a few decades.
  5. The unique nature of the "experiment" Homo sapiens is conducting with the atmosphere through the emission of 319 billion tons of carbon by 2007 [15], and the consequent extreme rise in atmospheric CO2 of about 2 ppm/year, two orders of magnitude faster than during the last glacial termination [16], counsels caution.

John Holdren, Obama's science advisor, compared global warming to “being in a car with bad brakes driving toward a cliff in the fog."

Should humanity choose to undertake all possible mitigation and adaptation efforts in an attempt at slowing global warming down, or even reversing it, steps need to include:

  1. Urgent deep reductions in carbon emissions, on the scale of at least 5 percent of emissions per year, relative to 1990 Anderson and Bows, 2008 [7].
  2. Global reforestation efforts in semi-arid and drought-effected regions, among other providing employment to millions of people.
  3. Construction of long-range water conduits from flood-affected to drought-stricken regions an even more important task than designing Broadband networks….
  4. Urgent development of atmospheric CO2 draw-down methods, including CO2-sequestering vegetation, soil carbon enrichment, sodium-based CO2 capture a technology no more complex than space projects technologies and financially not more expensive than military expenditure.
  5. Rapid transition to clean energy solar-thermal, hot-rock, hydrogen, wind, tide, photovoltaic and transport systems electric vehicles.

It is possible that, in order to gain time, some governments may opt for geo-engineering efforts, including stratospheric injection of sulfur aerosols simulating volcanic eruptions [17], likely over polar regions, meant to temporarily raise the Earth albedo while other measures are undertaken.

The alternative to urgent fast tracked mitigation efforts does not bear contemplation.

_______________________________________________________

References

1. Kiehl, J. T. and Trenberth, K. E.: Earth’s annual global mean energy budget, B. Am. Meteorol. Soc., 78, 197–208, 1997.

2. Copenhagen Synthesis Report. Copenhagen Synthesis Report http://climatecongress.ku.dk/pdf/synthesisreport/. Rahmstorf, S.R. et al. 2007. Recent Climate Observations Compared to Projections, Science Express, http://www.sciencemag.org/cgi/content/abstract/sci;316/5825/709

3. Broecker W.S. 2000. Abrupt climate change: causal constraints provided by the paleoclimate record. Earth Science Reviews 51, 137–154; Alley, R.B., 2000. Ice-core evidence of abrupt climate changes.Proceedings of the Natural Academy of Science 97, 1331–1334; Alley, R.B. et al., 2003. Abrupt Climate Change, Science 299, 2005–2010; Kobashi, T., et al., 2008. 4±1.5 °C abrupt warming 11,270 years ago identified from trapped air in Greenland ice. Earth Planetary Science Letters, 268, 397–407; Steffensen, J.P., et al., 2008. High-resolution Greenland ice core data show abrupt climate change happens in few years. Science Express, 19.6.2008; Ganopolski, A., Rahmstorf, S., 2002. Abrupt glacial climate changes due to stochastic resonance. Physics Review Letters 88, 038501.

4. Lenton, T.M., et al., 2008. Tipping points in the Earth system. PNAS, 105, 1786–1793 _ www.pnas.org_cgi_doi_10.1073_pnas.0705414105; http://researchpages.net/ESMG/people/tim-lenton/tipping-points/. http://www.pnas.org/content/105/6/1786.abstract; Easterling and Wehner, 2009. Is the climate warming or cooling? Geophys. Res. Lett. 36, L08706 http://www.agu.org/pubs/crossref/2009/2009GL037810.shtml; Eby, M., et al., 2009. Lifetime of Anthropogenic Climate Change: Millennial Time Scales of Potential CO2 and Surface Temperature Perturbations, J. Climate, 22, 15 May 2009; Dakos, V., et al., 2008. Slowing down as an early warning signal for abrupt climate change. PNAS, 105, 14308–14312. www.pnas.org_cgi_doi_10.1073_pnas.0802430105. Slowing down as an early warning signal for abrupt climate change ; Stipp, D., 2004. The Pentagon’s Weather Nightmare: the climate could change radically, and fast. That would be the mother of all national security issues. Http://money.cnn.com/magazines/fortune/fortune_archive/2004/02/09/360120/index.htm.

5. Zachos, J.C, et al., 2008. An early Cenozoic perspective on greenhouse warming and carbon-cycle dynamics, Nature 451 7176: 279–83; Royer, D. L., 2006. CO2-forced climate thresholds during the Phanerozoic. Geochim. et Cosmochim. Acta, 70, 5665–5675; Royer, D.L. et al., 2004. CO2 as a primary driver of Phanerozoic climate. GSA Today, 14, 4–10; Royer, D.L., et al., 2007. Climate sensitivity constrained by CO2 concentrations over the past 420 million years. Nature, 446. doi:10.1038/nature 05699; Beerling, D.J., Berner R.A., 2005. Feedbacks and the coevolution of plants and atmospheric CO2. PNAS, 102, 1302–1305; Berner, R.A. 2004. The Phanerozoic Carbon Cycle: CO2 and O2, Oxford University Press, New York; Berner, R. A., 2006. GEOCARBSULF: A combined model for Phanerozoic atmospheric O2 and CO2. Geochim. et Cosmochim. Acta, 70, 5653–5664; Berner, R.A., Vandenbrook, J.M.,Ward, P.D. 2007. Oxygen and evolution. Science 316, 557–558.

6. de Menocal, P.B., 2004. African climate change and faunal evolution during the Pliocene-Pleistocene. Earth Planet. Sci. Lett., 220, 3–24; Dowsett, H.J., et al., 2005. Middle Pliocene sea surface temperature variability. Paleoceanography, 20, PA2014; Haywood, A., Williams, M., 2005. The climate of the future: clues from three million years ago. Geology Today, 21 4, 138–143.

7. Anderson, K., Bows, A., 2008. Reframing the climate change challenge in light of post-2000 emission trends. Phil. Trans. Roy. Soc. London, doi:10.1098/rsta.2008.0138; Global Carbon Project http://www.globalcarbonproject.org/. Hansen, J.R. et al., 2006, Global temperature change. Proc. Nat. Acad. Sci. 101, 16109–16114. Hansen, J.R., 2007. Climate change and trace gases. Philosophical Transactions Royalk Society London, 365A, 1925–1954; Hansen, J., et al., 2008. Target CO2: where should humanity aim? http://arxiv.org/abs/0804.1126.

8. Gingerich, P. D., 2006. Environment and evolution through the Paleocene — Eocene thermal maximum. Trends Ecol. Evolution 21, 246–253; Sluijs, A.,et al., 2007 Subtropical Arctic Ocean temperatures during the Palaeocene/ Eocene thermal maximum. Nature, 441, 610–613.

9. Walter, K.M., Smith, L.C., Chapin, F.S., 2005. Methane bubbling from Siberian thaw lakes as a positive feedback to climate warming. Nature, 443, 71–75.

10. Chen, J.L., Wilson, C.R., Blankenship. D.D., Tapley, B.D., 2006. Antarctic mass rates from GRACE. Geophysical Research Letters 33, L11502; Frederick, T.R. E., Krabill, S. Martin, C., 2006. Progressive increase in ice loss from Greenland. Geophysical Research Letters 33, L10503, doi:10.1029/2006GL026075; Hanna, H., Huybrechts, P., Janssens, I., Cappelen, J., Steffen, K., Stephens A., 2005. Runoff and mass balance of the Greenland ice sheet: 1958–2003. Journal Geophysical Research, 110, D13108; NASA 2006. Greenland ice loss doubles in past decade, raising sea level faster, news release, 16 Feb. http://earthobservatory.nasa.gov/Newsroom/ Nasa News/2006 /2006021621775.html; National Snow and Ice Data Centre [NSIDC], 2008. http://nsidc.org/NSIDC, 2008, http://nsidc.org/news/press/20080325_Wilkins.html; Steffen, K., Huff R., 2002. A record maximum melt extent on the Greenland ice sheet in 2002. Cooperative Institute for Research in Environmental Sciences CIRES, University of Colorado at Boulder, CO 80309-0216; Steffen, K., Nghiem, S.V., Huff, R., Neumann, G., 2004. The melt anomaly of 2002 on the Greenland Ice Sheet from active and passive microwave satellite observations. Geophysical Research Letters, 31 20, L2040210.1029/ 2004GL020444; Steffen, K. and Huff, R., 2002. A record maximum melt extent on the Greenland ice sheet in 2002. Cooperative Institute for Research in Environmental Sciences CIRES, University of Colorado at Boulder; Velicogna, I., Wahr, J. 2006. Measurements of Time-Variable Gravity Show Mass Loss in Antarctica, Science, 311.

11. Rahmstorf, S.R., 2006. A Semi-Empirical Approach to Projecting Future Sea-Level Rise. Science, 315, 368–370; Church, J.A., White, N., 2006. A 20th century acceleration in global sea-level rise. Geophys. Res. Lett., 33, L01602, doi:10.1029/2005GL024826, 2006. http://www.pol.ac.uk/psmsl/author_archive/church_white/GRL_Church_White_2006_024826.pdf;

12. Bryden, H.L., et al., 2005. Slowing of the Atlantic meridional overturning circulation at 25N. Nature 438, 655–657.

13. Rising natural disasters and insurance costs between 1950 and 2006: Values in $billion. Source: http://www.draeger-stiftung.de/HG/internet/SD/pdf/charts_hoeppe.pdf; Webster, P.J., Holland, G.J., Curry, J.A., Chang, H.R., 2005. Changes in Tropical Cyclone Number, Duration, and Intensity in a Warming Environment, Science, 309, 1844–1846.

14. IPCC 2007 SPM-2. http://ipcc-wg1.ucar.edu/wg1/Report/AR4WG1_Print_SPM.pdf; http://www.realclimate.org/index.php/archives/2008/07/aerosols-chemistry-and-climate/;

15. Raupach et al., 2007. Global and regional drivers of accelerating CO2 emissions. PNAS June 12, 2007 vol. 104 no. 24 10288-10293. http://www.pnas.org/content/104/24/10288/suppl/DC1;

16. Glikson, A.Y., 2008. Milestones in the evolution of the atmosphere with reference to climate change. Aust. Journal Australia Earth Science, 55, 125–140

17. http://www.breitbart.com/article.php?id=d97echlg1&show_article=1 http://en.wikipedia.org/wiki/Carbon_dioxide_air_capture; Lenton, T. M., N. E. Vaughan, N.E., 2009. The radiative forcing potential of different climate geoengineering options. http://www.atmos-chem-phys-discuss.net/9/2559/2009/acpd-9-2559-2009.pdf

Figure 1. Top: Atmospheric CO2 and continental glaciation 400 Ma to present. Vertical bars mark the timing and palaeo-latitudinal extent of ice sheets. Plotted CO2 records represent five-point running averages from each of the four major proxies: stomata leaf pores, phytoplankton, Boron, pedogenic carbonates.

Middle: Global compilation of deep-sea benthic foraminifera 18O isotope records from 40 Deep Sea Drilling Program and Ocean Drilling Program sites updated with high-resolution records for the Eocene through Miocene interval.

Bottom: Detailed record of CO2 for the last 65 Myr. The range of error for each CO2 proxy varies considerably, with estimates based on soil nodules yielding the greatest uncertainty. Also plotted are the plausible ranges of CO2 from three geochemical carbon cycle models. After figure 6, http://ipcc-wg1.ucar.edu/wg1/Report/ AR4WG1_Print_Ch06.pdf

Figure 2. One realization of the globally averaged surface air temperature from the ECHAM5 coupled climate model forced with the SRES A2 greenhouse gas increase scenario for the 21st century. Easterling and Wehner 2009. Geophys. Res. Lett. 36, L08706 http://www.agu.org/pubs/crossref/2009/2009GL037810.shtml

Figure 3. Map of potential policy-relevant tipping elements in the climate system, overlain on global population density. Subsystems indicated could exhibit threshold-type behavior in response to anthropogenic climate forcing, where a small perturbation at a critical point qualitatively alters the future fate of the system. They could be triggered this century and would undergo a qualitative change within this millennium We exclude from the map systems in which any threshold appears inaccessible this century e.g., East Antarctic Ice Sheet or the qualitative change would appear beyond this millennium e.g., marine methane hydrates. Question marks indicate systems whose status as tipping elements is particularly uncertain. Lenton, T.M., et al., 2008. Tipping points in the Earth system. PNAS, 105, 1786–1793 _ www.pnas.org_cgi_doi_10.1073_pnas.0705414105

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ANDREW GLIKSON
Earth and Paleoclimate scientist
Australian National University

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