Is global warming global?

Global warming since 1978 has been about 0.6 degrees centigrade in the Northern hemisphere. It has been about 0.3 degrees in the Southern hemisphere.  The global average has been between these two extremes. Why is global warming not global? Could it relate to the fact that it takes much less energy to heat land than water? Note that the Northern hemisphere is about  39.3% land, whereas the Southern hemisphere is only about 19.1% land. So the land mass is almost exactly twice as large in the Northern hemisphere as it is in the Southern hemisphere. Hmmm. The temperature increase in the Northern hemisphere is twice as large as that in the Southern hemisphere AND the land mass is twice as large too. This is kind of suggestive, isn’t it?

An alternative hypothesis is that global warming is related to something that humans are doing? But the distribution of population is even more extreme.  The Southern hemisphere population is only about 10 to 12 % of the global population. Wouldn’t this lead to even greater warming differences if human activity is the cause? It seems to me that the order of magnitude of the differential warming effects is way off if global warming is due to human activity, unless the humans in the Southern hemisphere are much worse behaved than those in the Northern hemisphere. However, it is the conventional wisdom that the industrial processes of the Northern hemisphere are the culprit. That is, Northerners are worse behaved than Southerners.

Does the fact that global warming is not global provide us with any information as to what causes global warming?