First Assessment Report - IPCC

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102 Validation of Climate Models 4 temperatures, also provides a useful test of climate models Finally for validation of the experiments on transient climate change discussed in Section 6, it is important to consider the validation of ocean and coupled oceanatmosphere models 4.2 Simulation of the Atmospheric Circulation In this section we consider a number of basic atmospheric variables for which validation data arc readily available and whose satisfactory simulation is a prerequisite for confidence in the models ability to portray climate change 4.2.1 Sea-Level Pressure The sea-level pressure pattern provides a uselul char dctcn/ation ol the atmospheric circulation near the surface and is closely related to many aspects of climate A simple but revealing measure of the pressuie pattern is the northsouth profile ol the zonal average (average around a latitude circle) (Figure 4 1) In both solstitial seasons the structure is rather similar, with a deep Antarctic trough subtropical ridges with a near-equatorial trough between and a rather weak and asymmetric pattern in northern middle and high latitudes The models approximate the observed pattern with varying degrees ol success all simulate to some extent the subtropical ridges and Antarctic tiough The ridges are in some cases displaced polewaid and theie is a consideiable range in then strength particulaily in the NH (Northern Hemisphere) In the lower iesolution models the Antarctic tiough is generally too weak and sometimes poorly located The dependence ot the simulation of the Antarctic trough on resolution evident here for the GFDL and UKMO models has been found in several pievious studies (Manabc et al 1978 Hansen et al 1981 Dyson 198^) While Manabc et al lound it to be maikcd in the GFDL spectial models only in July the similai GFDL model consideied heie shows it clearly in Januaiy also The earlier GFDL result is consistent with expenments with the CCC model by Boei and La/aie (1988) showing only a slight deepening of an alieady deep Antarctic trough as resolution was mcicased The important lesult in the present context is that the moie realistic models used in CO2 expenments aie those with higher resolution (CCC GFHI and UKHI) The NH winter subtropical ridge is too strong in most models while the decrease in pressure fiom this ridge to the mid-latitude trough is generally excessive this is associated with excessively deep oceanic lows in some models and with spurious westerlies ovei the Rockies in otheis The westerlies in high iesolution models are ver\ sensitive to the ^presentation of the diag associated with giaxitv waves induced by mountains without it a ring of strong westerlies extends around middle latitudes dining northern winter (Slingo and Pearson 1987) The models simulate the seasonal reversal from northern summer to winter (for example Figure 4 2) To some degree this reflects the dominance of thermal forcing of the pressure pattern and the fact that most of the models have ocean temperatures which are kept close to climatology Summer temperatures over land are strongly affected by the availability ol soil moisture (see Section 4 1 1), the absence of evaporative cooling generates higher surface temperatuie and lower pressure as in the "dry land" experiment ol Shukla and Mintz (1982) This effect is evident in some ot the models simulations of pressure over land in the summer A serious shortcoming of the lower resolution models in the northern summer is the tendency to develop too strong a ridge between the Azores high and the Arctic, this error shows up as the absence of a trough near 60°N in Figuie 4 1(b) and was also found in previous assessments (e g , Manabe et al 1978, Dyson, 1985) The variability of the pressure pattern can usefully be separated into the daily variance within a month and the interannual vailability of monthly means Both are simulated with some skill by models, especially the daily variance (e g Figure 4 3) in particular, the variability maxima over the eastern Atlantic and northeast Pacific are well simulated and in the Southern Hemisphere high values arc simulated near 60°S as observed These results indicate that the models can successfully simulate the major storm tracks in middle latitudes On smaller scales, however there are regionally important errors, associated for example with the displacements of the variability maxima in the Northern Hemisphere In summary the recent higher resolution models are capable of generally realistic simulations of the time averaged sea level pressure and of the temporal pressure variability 4.2 2 Temperature While models successfully simulate the major features of the observed tempciature structure of the atmosphere, all models contain systematic errors such as those shown in the simulated zonally averaged temperatures in Figure 4 4 Of eirors common to many models, the most notable is the general coldness of the simulated atmosphere, simulated tempeiatures in the polar upper troposphere and lower stratosphere are too low in summer by more than 10°C while the lower troposphere in tropical and middle latitudes is too cold in both summer and winter The latter error may in some cases be alleviated by increasing the hon/ontal resolution (Boer and Lazare 1988, Ingram, personal communication) The existence of such common deficiencies despite the considerable differences in the models resolution numerical treatments and physical parameten/ations implies that all models may be misrepiesenting (01 indeed omitting) some physical mechanisms In contrast in some regions of the
(a) DJF MEAN SEA LEVEL PRESSURE: OBSERVED (b) DJF MEAN SEA LEVEL PRESSURE: UKHl (c) JJA MEAN SEA LEVEL PRESSURE: OBSERVED (d) JJA MEAN SEA LEVEL PRESSURE: UKHl Figure 4.2: Sea-level pressure (hPa) for December-January-February (a.b) and June-July-August (c,d) for: (a,c) Observed (Schutz and Gates 1971, 1972) and (b,d) the UKHl model (No. 22, Table 3.2(a))
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INTERGOVERNMENTAL PANEL ON CLIMATE
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Contents 9 Sea Level Rise 257 R.A.
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Foreword Many previous reports have
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Policymakers Summary Prepared by IP
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EXECUTIVE SUMMARY We are certain of
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Policymaket s Summary \m Introducti
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XVI Policymakei s Summaiy Table 1:
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\w// Policymakers Summaiy Table 2:
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Policymakers Summary 1120 560 280 1
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Wll predictions of climate change,
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XXIV Policymakers Summary ESTIMATES
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uw Polu \makei s Summai \ EQUILIBRI
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\X\lll Policymakeis Summaiy CONFIDE
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\w Policymakers Summaiy o, 120 LU S
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\\\ll Pohcymakeis Summaiy DEFORESTA
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\\\n Policymakeis Summaiy Annex EMI
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Intioduttion WWII Surface Pressure
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Inti oduttion sophisticated numeric
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CONTENTS Executive Summary 1.1 Intr
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EXECUTIVE SUMMARY The Earth's clima
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1 Gi eenhouse Gases and Aeiosols 7
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1 Gi eenhouse Gases and Aerosols 9
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7 Gi eenhouse Gases and Aei osoli 1
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1 Gi eenhouse Gast"; and Aei osols
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lb atmosphenc CO2 The climate chang
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1 G>eenhouse Gases and Aeiosols 19
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I Gi eenhouse Gases and Aei owls 21
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Gi eenhouse Gases and Aei osols 25
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1 Gi eenhouse Gases and Aeiosoh 27
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w Gi eenhouse Gases and Aei osols 1
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32 Gi eenhouse Gases and Aei osols
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34 Gi eenhouse Gases and Aeiosols 1
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36 Gi eenhouse Gases and Act osols
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2 Radiative Forcing of Climate K.P.
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EXECUTIVE SUMMARY 1 The climate of
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2 Radiali\ e Foicinq of Climate 47
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2 Radiative Foicing of Climate 49 a
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Page 101 and 102: 2 Radiatn e Fo> c im> of Climate 53
Page 103 and 104: 2 Radiative Foi c ing of Climate 55
Page 105 and 106: 2 Radiatne Foi cinq of Climate 57 T
Page 107 and 108: 2 Radiatn e Foi c mq of Climate 59
Page 109 and 110: 2 Radiatn e Foi c mg of Climate 61
Page 111 and 112: 2 Radunn e h01 c uiv, of Climate 63
Page 113 and 114: 2 Radiatn c Foi c im> of Climate 65
Page 115: 2 Radiatne Foicin of Climate 67 eru
Page 119: CONTENTS Executive Summary 73 3.1 I
Page 123 and 124: 3 Pi ocesses and Modelling 75 3.1 I
Page 125 and 126: 3 Pioc esses and Modelling 77 away
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Page 129 and 130: Table 3.2(a): Summai\ of tesults po
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Page 133 and 134: 3 Pi ocesses and Modelling 85 many
Page 135 and 136: 3 Pi oc esses and Modelling 87 glob
Page 137 and 138: 3 Pi OC esses and Modelling 89 from
Page 139: 3 Pi OC esses and Modellm ? 91 Rava
Page 145: Executive Summary 1 The validation
Page 148 and 149: 100 Validation of Climate Models 4
Page 156 and 157: I OH Validation of Climate Models 4
Page 158: (a) DJF PRECIPITATION: OBSERVED (b)
Page 163 and 164: 4 Validation of Climate Models IIS
Page 179: 5 Equilibrium Climate Change - and
Page 183: EXECUTIVE SUMMARY 1. All models sho
Page 186 and 187: nx Equihbi mm Climate Change 5 temp
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Page 198: 150 Ec/uilibi mm Climate Change 5 1
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H4 Ec/uilibiiiim Climate Clninqe 5
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756 Equilibi mm Climate Change 5 Ta
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1SS Ec/mlibi nun Climate Change 5 S
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160 Eqmlibnum Climate Chcuis,e 5 im
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162 Equilibrium Climate Change 5 Or
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164 Cquilibi mm Climate Change 5 Sc
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CONTENTS Executive Summary 177 6.1
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6 Time-Dependent Gi eenhoute-Gas In
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6 Time Dependent Gi eenhouse Gas-In
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6 Time Dependent Gi eenhouse Gas In
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6 Time-Dependent Gi eenhouse Gas-In
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6 Time-Dependent Gieenhouse Gas-Ind
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6 Time-Dependent Gieenhouse Gas Ind
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6 Time-Dependent Greenhouse Gas-Ind
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CONTENTS Executive Summary 199 7.1
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7 ObseivedClimate Variation andChan
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7 Obsei ved Climate Vai tation and
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7 Observed Climate Variation and Ch
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7 Obsei \ eel Climate Vai iation an
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7 Obsei \ed Climate Vailatum and Ch
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7 Obsei \ ed Climate Vai lation and
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7 Obsei ved Climate Va> mtion and C
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7 Obsencd Climate Vernation and Cha
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7 Obsened Climate Vai lation and Ch
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2M) Obsenid Climate Vaimtion and Ch
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7 Obsened Climate Van at ion and Ch
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7 Obsei i ed Climate Vai lation and
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7 Obsei \ ed Climate Vai wtion and
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8 Detection of the Greenhouse Effec
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EXECUTIVE SUMMARY Global-mean tempe
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246 Detec tion of the Gi eenhouse E
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248 Dctec tion of the Gieenhouse Ef
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250 Detec turn of the Gieenhouse Ef
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252 Detec tion of the Gi eenhouse E
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2S4 Detec tion of the Gi eenhouse E
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9 Sea Level Rise R. WARRICK, J. OER
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EXECUTIVE SUMMARY This Section addr
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264 Sea Level Rise 9 In addition, s
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266 Sea Le\ el Rise 9 meteoiologica
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270 Sea Level Rise 9 Table 9.4 Esti
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272 Sea Level Rise 9 Table 9.6 Anta
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274 Sea Level Rise 9 Table 9.8 Esti
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276 Sea Le\ el Rise 9 each scenario
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278 Sea Level Rise 9 O 50 Stop chan
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2S0 Sea Level Rise 9 Gornit/, V and
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10 Effects on Ecosystems J.M. MELIL
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EXECUTIVE SUMMARY Ecosystem Metabol
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10 Effects on Ecosystems 289 10.0 I
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7 0 Effec ts on Eco system s 291 in
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10 Effects on Ecosystems 293 Table
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296 Effects on Ecosystems 10 will h
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29h Effet ts on Ecosys'ems 10 10 2
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mo Effec ti on Ec osystem s 10 Tabl
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302 Effects on Ecosystems 10 (N2O)
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M)4 Effec ts on Ecosystems 10 poten
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106 Effects on Ecosystems 10 38,000
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308 Effects on Ecosystems 10 Hardy,
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11 Narrowing the Uncertainties: A S
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EXECUTIVE SUMMARY The IPCC has the
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?/ the Unt ei tamties 11 Analysis o
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uo 11.2 3 Precipitation and Evapora
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322 Narr owing the Uncertainties 11
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U4 Nai i cm ing the Unc ei tamties
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Narrowing the Uncertainties 327 199
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Annex 331 A.l Introduction Modellin
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Annex 333 900 Ball 4000 .-• 3500
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Annex 335 the current atmospheric b
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Annex 337 E UJ w ui > UJ < ui u BaU
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Appendix 1 EMISSIONS SCENARIOS FROM
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Appendix 3 CONTRIBUTORS TO IPCC WG1
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Appendix 3 347 Contributors: P.A. A
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Appendix 3 P Ya Groisman A Gruber S
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Appendix 3 351 J.P. Grime R. Giffor
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354 Appendix 4 H. Kenway M. Manton
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356 Appendix 4 JAPAN H. Akimoto H.
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358 Appendix 4 B. Flannery M.Ghil I
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Appendix 6 ACRONYMS: PROGRAMMES & M
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364 Appendix 7 Special Names and Sy
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