Some data suggest that the average global

temperature will increase by 1°C–2°C by the

year 2050. If this occurs, a major concern for

humans would most likely be that

(1) sea levels might rise enough to flood some

coastal areas

(2) long-term stability of the climate will benefit

ecosystems

(3) the availability of salt water for agricultural

use will increase

(4) the threat of extinction of land organisms will

decrease