Why are isotherms more irregular in the Northern Hemisphere than in Southern Hemisphere? Discuss. 

Isotherms are more irregular in the Northern Hemisphere than in the Southern Hemisphere because of the marked contrasts in the distribution pattern of land and water in two hemispheres.

Isotherms are generally parallel to the latitudes and the effect of altitude is well indicated. But deviation from this general trend is more pronounced in January than in July, and particularly in the Northern Hemisphere. Northern Hemisphere has larger landmass than the southern one.

In January isotherms deviate to the north over the ocean and to the south over the continent. The presence of warm oceanic currents, Gulf Stream and North Atlantic Drift, make the Northern Atlantic ocean warmer and the isotherms bend towards the north over the continents. They bend towards south making the isotherms more irregular.