Why southern hemisphere is hotter than northern hemisphere?
The Southern Hemisphere is the half of Earth that is south of the Equator. It contains all or parts of five continents such as Antarctica, Australia, about 90% of South America, the southern third of Africa, and several southern islands off the continental mainland of Asia, four oceans such as Indian, South Atlantic, Southern, and South Pacific, and most of the Pacific Islands in Oceania.
Southern Hemisphere climates tend to be slightly milder than those at similar latitudes in the Northern Hemisphere, except in the Antarctic which is colder than the Arctic.
So, why southern hemisphere is hotter than northern hemisphere?
This is because the Southern Hemisphere has significantly more ocean and much less land; water heats up and cools down more slowly than land. The differences are also attributed to oceanic heat transfer (OHT) and differing extents of greenhouse trapping.
In the Southern Hemisphere, the sun passes from east to west through the north, although north of the Tropic of Capricorn the mean sun can be directly overhead or due south at midday. The southern temperate zone, a subsection of the Southern Hemisphere, is nearly all oceanic. This zone includes the southern tip of Uruguay and South Africa; the southern half of Chile and Argentina; parts of Australia, going south from Adelaide, and all of New Zealand.
The seasons are caused by the Earth being tilted on its axis by 23.5 degrees.
It is the fact that the southern hemisphere has more area of the ocean than the northern hemisphere, thus when the Earth is closer to the sun the southern oceans absorb that extra energy more than the in the northern hemisphere where there is more land area.
There is more land in the Northern Hemisphere, and more water bodies in the Southern Hemisphere. Now, the land has a much lower specific heat capacity than water; in other words, water can hold a lot of heat while land cannot.
Most of the landmass of the earth is concentrated in the northern hemisphere. The southern hemisphere, by contrast, is 80% covered by water. Water has the ability to absorb large amounts of heat. So, summer in the southern hemisphere, which occurs at perihelion, is warmer than summer in the northern hemisphere. The additional solar energy supplied by the sun at perihelion is absorbed by the large bodies of water in the southern hemisphere. The result is that temperatures are actually more moderate during summers in the southern hemisphere.
The Earth is at perihelion around 3 January and at aphelion around 3 July. The heat retained in the southern hemisphere oceans makes the average temperature of the Earth a few degrees higher in July when Earth is furthest from the Sun than it is in January when it is its closest.