Table 3. Forecast of future Mexican emigration at the national level under different climate scenarios

``

Scenario
CO2 effect	Adaptation*	Change in crop yields, %	Change in emigrants as percent of population, %	Change in no. of adult emigrants, millions†
Rosenzweig	and Iglesias (38): GISS‡
No	No	−46	9.2	6.4
Yes	No	−35	7.0	4.9
Yes	Level 1	−27	5.4	3.8
Yes	Level 2	−13	2.6	1.8
Rosenzweig	and Iglesias (38): GFDL‡
No	No	−39	7.8	5.5
Yes	No	−28	5.6	3.9
Yes	Level 1	−20	4.0	2.8
Yes	Level 2	−10	2.0	1.4
Rosenzweig	and Iglesias (38): UKMO‡
No	No	−48	9.6	6.7
Yes	No	−37	7.4	5.2
Yes	Level 1	−31	6.2	4.3
Yes	Level 2	−15	3.0	2.1
Cline preferred	estimates§
No	Not Clear	−35	7.1	5.0
Yes	Not Clear	−26	5.1	3.6

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*Level 1 adaptation includes changes that imply small additional cost to the farmers and not necessary policy

changes, such as shifts in planting dates, variety and crop, and increases in water application to irrigated crops.

Level 2 adaptation includes higher order adaptations that imply significant additional costs to the farmers, such

as large shifts in crop production timing, increased fertilizer application, installation of irrigation systems, development

of new varieties, and/or changes in policy.

†Assuming that the population aged 15–65 y is 70 million in Mexico.

‡The equilibrium scenarios for three major General Circulation Models were used by Rosenzweig and Iglesias

(38): the Goddard Institute for Space Studies (GISS), the GFDL, and the UKMO.

§The Cline estimates (23) give equal weights to estimates from Mendelsohn-Schlesinger Ricardian model and

Rosenzweig and Iglesias (38) crop model. Both assume some levels of adaptation. ''
 Taken from PNAS.