Simulations using a climate model are used to investigate the possible impact of increasing emissions of carbonaceous aerosols on near-surface temperature in the mid-20th century. The annual global mean near-surface temperature change from the mid-20th century onward is reasonably described by a model that is forced by changes in most of the known climate forcing agents including an increase in carbonaceous aerosols, though it can also be well reproduced without increases in carbonaceous aerosols. However, if we consider spatio-temporal structure of the changes in the near-surface temperature, an increase in carbonaceous aerosols is definitely required for the model to represent changes in the near-surface temperature in the mid-century, in particular, cooling trends in the tropical and subtropical continents. The significance of an increase in carbonaceous aerosols as an indispensable contributor to mid-20th century temperature changes is confirmed with the use of an optimal fingerprinting methodology.