Common Assumptions

These assumptions are shared throughout the GCAM model.

Regional Resolution

Geopolitical Regions

GCAM subdivides the world into 32 geopolitical regions, representing countries or collections of countries (see Table below).

GCAM Region	Countries
Africa_Eastern	Burundi, Comoros, Djibouti, Eritrea, Ethiopia, Kenya, Madagascar, Mauritius, Reunion, Rwanda, Sudan, Somalia, Uganda
Africa_Northern	Algeria, Egypt, Western Sahara, Libya, Morocco, Tunisia
Africa_Southern	Angola, Botswana, Lesotho, Mozambique, Malawi, Namibia, Swaziland, Tanzania, Zambia, Zimbabwe
Africa_Western	Benin, Burkina Faso, Central African Republic, Cote d’Ivoire, Cameroon, Democratic Republic of the Congo, Congo, Cape Verde, Gabon, Ghana, Guinea, Gambia, Guinea-Bissau, Equatorial Guinea, Liberia, Mali, Mauritania, Niger, Nigeria, Senegal, Sierra Leone, Sao Tome and Principe, Chad, Togo
Argentina	Argentina
Australia_NZ	Australia, New Zealand
Brazil	Brazil
Canada	Canada
Central America and the Caribbean	Aruba, Anguilla, Netherlands Antilles, Antigua & Barbuda, Bahamas, Belize, Bermuda, Barbados, Costa Rica, Cuba, Cayman Islands, Dominica, Dominican Republic, Guadeloupe, Grenada, Guatemala, Honduras, Haiti, Jamaica, Saint Kitts and Nevis, Saint Lucia, Montserrat, Martinique, Nicaragua, Panama, El Salvador, Trinidad and Tobago, Saint Vincent and the Grenadines
Central Asia	Armenia, Azerbaijan, Georgia, Kazakhstan, Kyrgyzstan, Mongolia, Tajikistan, Turkmenistan, Uzbekistan
China	China
Colombia	Colombia
EU-12	Bulgaria, Cyprus, Czech Republic, Estonia, Hungary, Lithuania, Latvia, Malta, Poland, Romania, Slovakia, Slovenia
EU-15	Andorra, Austria, Belgium, Denmark, Finland, France, Germany, Greece, Greenland, Ireland, Italy, Luxembourg, Monaco, Netherlands, Portugal, Sweden, Spain, United Kingdom
Europe_Eastern	Belarus, Moldova, Ukraine
European Free Trade Association	Iceland, Norway, Switzerland
Europe_Non_EU	Albania, Bosnia and Herzegovina, Croatia, Macedonia, Montenegro, Serbia, Turkey
India	India
Indonesia	Indonesia
Japan	Japan
Mexico	Mexico
Middle East	United Arab Emirates, Bahrain, Iran, Iraq, Israel, Jordan, Kuwait, Lebanon, Oman, Palestine, Qatar, Saudi Arabia, Syria, Yemen
Pakistan	Pakistan
Russia	Russia
South Africa	South Africa
South America_Northern	French Guiana, Guyana, Suriname, Venezuela
South America_Southern	Bolivia, Chile, Ecuador, Peru, Paraguay, Uruguay
South Asia	Afghanistan, Bangladesh, Bhutan, Sri Lanka, Maldives, Nepal
Southeast Asia	American Samoa, Brunei Darussalam, Cocos (Keeling) Islands, Cook Islands, Christmas Island, Fiji, Federated States of Micronesia, Guam, Cambodia, Kiribati, Lao Peoples Democratic Republic, Marshall Islands, Myanmar, Northern Mariana Islands, Malaysia, Mayotte, New Caledonia, Norfolk Island, Niue, Nauru, Pacific Islands Trust Territory, Pitcairn Islands, Philippines, Palau, Papua New Guinea, Democratic Peoples Republic of Korea, French Polynesia, Singapore, Solomon Islands, Seychelles, Thailand, Tokelau, Timor Leste, Tonga, Tuvalu, Viet Nam, Vanuatu, Samoa
South Korea	South Korea
Taiwan	Taiwan
USA	United States

Table: Mapping from GCAM region to country

Global River Basins

We have represented the water at the scale of major river basins. Currently 235 global river basins are represented in GCAM. The full list of major river basins included in GCAM is shown in Table 1. Each of the GCAM regions contains the river basins within its border. In many instances, river basins may overlap across multiple GCAM regions where water resources are shared. A few remote basins without water demand representations, such as Antarctica, are not actively modeled.

Table 1. Major Water Basins in GCAM

id	name	id	name	id	name	id	name	id	name
1	Arctic Ocean Islands	51	Japan	101	Caribbean	151	Lake Chad	201	New Zealand
2	Northwest Territories	52	Caspian Sea-East Coast	102	Hamun-i-Mashkel	152	Senegal	202	Australia-South Coast
3	Siberia-North Coast	53	Don	103	Taiwan	153	Cauvery	203	Mar Chiquita
4	Siberia-West Coast	54	Danube	104	Arabian Sea Coast	154	Sri Lanka	204	South Africa-West Coast
5	Kara Sea Coast	55	Adriatic Sea-Greece-Black Sea Coast	105	North Gulf	155	India South Coast	205	Salinas Grandes
6	Lena	56	Ob	106	Yangtze	156	Orinoco	206	La Plata
7	Pacific and Arctic Coast	57	Po	107	Sabarmati	157	Colombia-Ecuador-Pacific Coast	207	North Chile-Pacific Coast
8	Scandinavia-North Coast	58	Amu Darya	108	Xun Jiang	158	Palau and East Indonesia	208	Murray-Darling
9	Russia-Barents Sea Coast	59	Italy-West Coast	109	Hong-Red River	159	North Borneo Coast	209	Pampas Region
10	Mackenzie	60	Spain-Portugal-Atlantic Coast	110	Ganges-Bramaputra	160	Volta	210	North Argentina-South Atlantic Coast
11	Iceland	61	France-South Coast	111	Yucatan Peninsula	161	Northeast South America-South Atlantic Coast	211	Tasmania
12	Sweden	62	Rhone	112	South China Sea Coast	162	Gulf of Guinea	212	South America-Colorado
13	Finland	63	Mediterranean Sea Islands	113	Mahi	163	Sumatra	213	Negro
14	Northern Dvina	64	Gironde	114	Mexico-Interior	164	Sulawesi	214	Central Patagonia Highlands
15	Hudson Bay Coast	65	North and South Korea	115	Pacific Central Coast	165	Kalimantan	215	South Argentina-South Atlantic Coast
16	Scotland	66	Bo Hai-Korean Bay-North Coast	116	Bay of Bengal-North East Coast	166	Magdalena	216	Antarctica
17	Neva	67	Spain-South and East Coast	117	Tapti	167	Irian Jaya Coast	217	California River
18	Volga	68	Lake Balkash	118	Yasai	168	Amazon	218	Upper Mississippi
19	Atlantic Ocean Seaboard	69	Tiber	119	Philippines	169	South Chile-Pacific Coast	219	Lower Mississippi River
20	Baltic Sea Coast	70	Black Sea-South Coast	120	Brahamani	170	Shebelli-Juba	220	Upper Colorado River
21	Denmark-Germany Coast	71	Tagus	121	North Marina Islands and Guam	171	Africa-East Central Coast	221	Lower Colorado River
22	Narva	72	Caspian Sea-South West Coast	122	Mahandi	172	North Brazil-South Atlantic Coast	222	Great
23	Saskatchewan-Nelson	73	Ebro	123	Godavari	173	Papua New Guinea Coast	223	Missouri River
24	Ireland	74	Douro	124	Hainan	174	Tocantins	224	Arkansas White Red
25	Daugava	75	Mediterranean Sea-East Coast	125	Mekong	175	Java-Timor	225	Texas Gulf Coast
26	England and Wales	76	Syr Darya	126	Viet Nam-Coast	176	Solomon Islands	226	South Atlantic Gulf
27	Fraser	77	Ziya He-Interior	127	Salween	177	Madasgacar	227	Great Lakes
28	Ems-Weser	78	China Coast	128	India North East Coast	178	Sepik	228	Ohio River
29	Oder	79	Huang He	129	India West Coast	179	Rift Valley	229	Pacific Northwest
30	Wisla	80	Mediterranean South Coast	130	Papaloapan	180	Peru-Pacific Coast	230	Tennessee River
31	Elbe	81	Guadiana	131	Rio Lerma	181	Fly	231	Rio Grande River
32	Rhine	82	Central Iran	132	Rio Verde	182	Angola-Coast	232	New England
33	Poland Coast	83	Guadalquivir	133	Grijalva-Usumacinta	183	Congo	233	Mid Atlantic
34	Churchill	84	Tigris-Euphrates	134	Rio Balsas	184	Australia-North Coast	234	Hawaii
35	Neman	85	Tarim Interior	135	Southern Central America	185	South Pacific Islands	235	Narmada
36	Scheldt	86	Africa-North West Coast	136	Isthmus of Tehuantepec	186	East Brazil-South Atlantic Coast
37	Russia-South East Coast	87	Nile	137	Irrawaddy	187	Parnaiba
38	Ural	88	Persian Gulf Coast	138	Sittang	188	Zambezi
39	Dnieper	89	Indus	139	Peninsula Malaysia	189	Australia-East Coast
40	St Lawrence	90	Farahrud	140	Krishna	190	Africa-Indian Ocean Coast
41	France-West Coast	91	Baja California	141	Andaman-Nicobar Islands	191	Australia-West Coast
42	Gobi Interior	92	Plateau of Tibet Interior	142	Africa-West Coast	192	Sao Francisco
43	Amur	93	Red Sea-East Coast	143	Caribbean Coast	193	Australia-Interior
44	Loire	94	Arabian Peninsula	144	Africa-North Interior	194	Orange
45	Caspian Sea Coast	95	Dead Sea	145	India East Coast	195	Uruguay-Brazil-South Atlantic Coast
46	Seine	96	Mexico-Northwest Coast	146	Chao Phraya	196	Namibia-Coast
47	Black Sea-North Coast	97	Helmand	147	Pennar	197	Africa-South Interior
48	Yenisey	98	Sinai Peninsula	148	Gulf of Thailand Coast	198	South Africa-South Coast
49	Dniester	99	Eastern Jordan-Syria	149	Niger	199	Limpopo
50	Italy-East Coast	100	Africa-Red Sea-Gulf of Aden Coast	150	Micronesia	200	La Puna Region

Global Land Units

For GCAM3.0 through GCAM4.4, the Agriculture and Land Use model subdivided the GCAM geopolitical regions into as many as 18 climatically defined agro-ecological zones (AEZs) developed by the GTAP group. GCAM5+ switches subregions to water basin-defined geographic land units (GLUs). The land data system files are produced by the Moirai, described in Di Vittorio et al. (2016).

Temporal Resolution

Historical Years

The GCAM data system can produce such data sets annually beginning in 1971. Currently, GCAM uses data from 1990, 2005, 2010, and 2015 to initialize the model, but could be initialized to any year beginning in 1971.

Future Years

Currently, GCAM models the future from 2020 to 2100 in 5 year time steps. The time step is variable and can be changed in the data system.

Economic Choice

GCAM represents choices among options using a logit function. For more information on economic choice, see choice.