causes Associate Professor Department of Meteorology The Pennsylvania State University

Transcription

1 Recent climate change and its causes Raymond Najjar Associate Professor Department of Meteorology The Pennsylvania State University Presentation for: Erie County Climate Adaptation Workshop September 1,

2 Outline Documentation of recent climate change Causes of recent climate change 2

3 Observed climate change Global average temperature Global average sea level ~1.5 F ~8 8inches Northern hemisphere snow cover ~1 million square miles IPCC (2007) IPCC (2007) Year 3

4 May, June & July extratropical Northern Hemisphere land temperature (departure from average) ) re ( C) Hottest July was in 2010 Temper rature departu Impact of Mt. Pinatubo, June 1991 Source: ECMWF (2010) 4

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6 Glacier retreat in Glacier Bay National Park, WA Glacier retreated 12 kilometers (8 miles) and thinned by 800 m (900 yards) Image Credit: National Snow and Ice Data Center, W. O. Field, B. F. Molnia 6

7 Small glaciers have decreased in volume by 9000 cubic kilometers and in thickness by 12 m (on average) Source: M. Dyurgerov, Inst. of Arctic and Alpine Res., Univ. of Colorado, Boulder 7

8 Courtesy: NASA Similar trends are found for the Antarctic Ice Sheet 8 Rignot & Cazenave (2009)

9 Arctic sea ice two days ago 9

10 arctic.atmos.uiuc.edu/cryosphere/ 10

11 Arctic sea ice is also thinning Kwok and Rothrock (2009) 11

12 arctic.atmos.uiuc.edu/cryosphere/ 12

13 Heat content of the global ocean 13

14 Conclusion from the data: Multiple lines of evidence show that the earth has warmed over the past century, and particularly over the last several decades. But is this warming unusual? 14

15 Northern Hemisphere temperature reconstructions Mann et al. (2008) 15

16 Sea level change over the last millenium ~2 mm yr -1 ~0 mm yr -1 The rate of sea-level l rise abruptly increased about a century ago Source: Church et al. (2008) 16

17 Source: NOAA 17

18 Trends in atmospheric CO 2 18

19 Ice ages as recorded in the Vostok ice core, Antarctica Petit et al. (1999) 19

20 Solar output over the past three decades Source: World Radiation Center ( 20

21 Solar activity it (sunspot number) Source: Solar Influences Data Analysis Center

22 Change in radiative forcing since 1750 IPCC (2007) 22

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24 Annual precipitation Simulated multi-model average observed IPCC (2007) 24

25 Observed and simulated global temperature t change Shading indicates 5-95% range of models IPCC (2007) 25

26 Observed and simulated (multi-model mean) temperature change ALL = all forcings NAT = only natural forcings Source: IPCC Fourth IPCC Assessment (2007) Report 26

27 Conclusions Warming of the climate system over the past century is unequivocal Human activity, through the burning of fossil fuels and subsequent CO 2 increase, has very likely caused this warming 27

28 Thank you Questions? 28

29 References Church, J.A., White, N.J., Aarup, T., Wilson, W.S., Woodworth, P.L., Domingues, C.M., Hunter, J.R., Lambeck, K., Understanding global sea levels: past, present and future. Sustainability Science 3, ECMWF, European Center for Medium-range Weather Forecasting, Kwok, R., and D.A. Rothrock Decline in Arctic sea ice thickness from submarine and ICESat records: Geophysical Research Letters. 36, L doi: /2009gl /2009GL IPCC (2007) Summary for Policymakers. In: Solomon S, Qin D, Manning M, Chen Z, Marquis M, Averyt KB, Tignor M, Miller HL (eds) Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA Mann ME, Zhang Z, Hughes MK, Bradley RS, Miller SK, Rutherford S, Ni F (2008) Proxybased reconstructions of hemispheric and global surface temperature variations over the past two millennia. Proceedings of the National Academy of Sciences 105: Petit JR, Jouzel J, Raynaud D, Barkov NI, Barnola JM, Basile I, Bender M, Chappellaz J, Davis M, Delaygue G (1999) Climate and atmospheric history of the past 420,000 years from the Vostok ice core, Antarctica. Nature 399: Rignot, E. and A. Cazenave Ice sheets and sea-level rise feedbacks. In Sommerkorn, M. and S. J. Hassol (eds.) : Arctic Climate Feedbacks: Global Implications. WWF International Arctic Programme, Oslo, Norway 29