Executive Summary

2.1 Introduction

2.2 How Much is the World Warming?

2.2.1 Background
2.2.2 Temperature in the Instrumental Record for Land and Oceans
2.2.2.1 Land-surface air temperature
2.2.2.2 Sea surface temperature and ocean air temperature
2.2.2.3 Land and sea combined
2.2.2.4 Are the land and ocean surface temperature changes mutually consistent?
2.2.2.5 Sub-surface ocean temperatures and salinities
2.2.3 Temperature of the Upper Air
2.2.4 How do Surface and Upper Air Temperature Variations Compare?
2.2.5 Changes in the Cryosphere
2.2.5.1 Snow cover, including snowfall
2.2.5.2 Sea-ice extent and thickness
2.2.5.3 Permafrost
2.2.5.4 Mountain glaciers
2.2.5.5 Lake and river ice
2.2.6 Are the Retreat of Glaciers, Sea Ice, and Snow Cover Consistent with the Surface Temperature Trends?
2.2.7 Summary

2.3 Is the Recent Warming Unusual?

2.3.1 Background
2.3.2 Temperature of the Past 1,000 Years
2.3.2.1 Palaeoclimate proxy indicators
2.3.2.2 Multi-proxy synthesis of recent temperature change
2.3.3 Was there a “Little Ice Age” and a “Medieval Warm Period”?
2.3.4 Volcanic and Solar Effects in the Recent Record
2.3.5 Summary

2.4 How Rapidly did Climate Change in the Distant Past?

2.4.1 Background
2.4.2 How Stable was the Holocene Climate?
2.4.3 How Fast did Climate Change during the Glacial Period?
2.4.4 How Stable was the Previous Inter-glacial?
2.4.5 Summary

2.5 How have Precipitation and Atmospheric Moisture Changed?

2.5.1 Background
2.5.2 Changes in Precipitation and Related Variables
2.5.2.1 Land
2.5.2.2 Palaeo-drought
2.5.2.3 Ocean
2.5.3 Water Vapour
2.5.3.1 Surface water vapour
2.5.3.2 Lower-tropospheric water vapour
2.5.3.3 Upper-tropospheric and lower-stratospheric water vapour
2.5.4 Evaporation
2.5.4.1 Land
2.5.5 Clouds
2.5.5.1 Land
2.5.5.2 Ocean
2.5.5.3 Global
2.5.6 Summary

2.6 Are the Atmospheric/Oceanic Circulations Changing?

2.6.1 Background
2.6.2 El Niño-Southern Oscillation and Tropical/Extra-tropical Interaction
2.6.3 Decadal to Inter-decadal Pacific Oscillation, and the North Pacific Oscillation
2.6.4 Monsoons
2.6.5 The Northern Hemisphere, excluding the North Pacific Ocean
2.6.6 The Southern Hemisphere
2.6.7 Summary

2.7 Has Climate Variability, or have Climate Extremes, Changed?

2.7.1 Background
2.7.2 Is There Evidence for Changes in Variability or Extremes?
2.7.2.1 Temperature
2.7.2.2 Precipitation
2.7.3 Is There Evidence for Changes in Extreme Weather or Climate Events?
2.7.3.1 Tropical cyclones
2.7.3.2 Extra-tropical cyclones
2.7.3.3 Droughts and wet spells
2.7.3.4 Tornadoes, hail and other severe local weather
2.7.4 Summary

2.8 Are the Observed Trends Internally Consistent?

References

Co-ordinating Lead Author
C.K. Folland, T.R. Karl

Lead Authors
J.R. Christy, R.A. Clarke, G.V. Gruza, J. Jouzel, M.E. Mann, J. Oerlemans, M.J. Salinger, S.-W. Wang

Contributing Authors
J. Bates, M. Burgess, M. Crowe, P. Frich, P. Groisman, J. Hurrell, P. Jones, D. Parker, T. Peterson, D. Robinson, J. Walsh,
M. Abbott, L. Alexander, H. Alexandersson, R. Allan, R. Alley, P. Ambenje, P. Arkin, L. Bajuk, R. Balling,
M.Y. Bardin, R. Bradley, R. Brázdil, K.R. Briffa, H. Brooks, R.D. Brown, S. Brown, M. Brunet-India,
M. Cane, D. Changnon, S. Changnon, J. Cole, D. Collins, E. Cook, A. Dai, A. Douglas, B. Douglas,
J.C. Duplessy, D. Easterling, P. Englehart, R.E. Eskridge, D. Etheridge, D. Fisher, D. Gaffen, K. Gallo,
E. Genikhovich, D. Gong, G. Gutman, W. Haeberli, J. Haigh, J. Hansen, D. Hardy, S. Harrison, R. Heino,
K. Hennessy, W. Hogg, S. Huang, K. Hughen, M.K. Hughes, M. Hulme, H. Iskenderian, O.M. Johannessen,
D. Kaiser, D. Karoly, D. Kley, R. Knight, K. K. Kumar, K. Kunkel, M. Lal, C. Landsea, J. Lawrimore,
J. Lean, C. Leovy, S. Levitus, H. Lins, R. Livezey, K.M. Lugina, I. Macadam, J.A. Majorowicz, B. Manighetti,
J. Marengo, E. Mekis, M.W. Miles, A. Moberg, I. Mokhov, V. Morgan, L. Mysak, M. New, J. Norris,
L. Ogallo, J. Overpeck, T. Owen, D. Paillard, T. Palmer, C. Parkinson, C.R. Pfister, N. Plummer, H. Pollack,
C. Prentice, R. Quayle, E.Y. Rankova, N. Rayner, V.N. Razuvaev, G. Ren, J. Renwick, R. Reynolds,
D. Rind, A. Robock, R. Rosen, S. Rösner, R. Ross, D. Rothrock, J.M. Russell, M. Serreze, W.R. Skinner,
J. Slack, D.M. Smith, S. Smith, D. Stahle, M. Stendel, A. Sterin, T. Stocker, B. Sun, V. Swail, V. Thapliyal,
L. Thompson, W.J. Thompson, A. Timmermann, R. Toumi, K. Trenberth, H. Tuomenvirta, T. van Ommen,
D. Vaughan, K.Y. Vinnikov, U. von Grafenstein, H. von Storch, M. Vuille, P. Wadhams, J.M. Wallace,
S. Warren, W. White, P. Xie, P. Zhai

Review Editors
R. Hallgren, B. Nyenzi

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