Yesterday was World Humanitarian Day.

For those unfamiliar with its significance, it's a day designated to celebrate the spirit that inspires humanitarian work around the globe and the dangers faced by those aid workers who try to help others.

And goodness, the world right now needs those committed to such work. Iraq, Syria, Gaza and Ukraine are only a few of the places facing overwhelming humanitarian crises.

As if these were not enough, creeping like a spectre on the humanitarian radar is the possibility of famine in South Sudan.

Some time in the coming weeks I fully expect to find myself reporting from that country and images of starving South Sudanese joining those of traumatised people in the Middle East and Ukraine on our television news broadcasts.

Already I can hear the clamour of anger and outrage from some quarters when such suffering intrudes into our comparatively comfortable lives.

Did no one see this coming? Have we not learned any lessons from the past? Could it not have been prevented? It's only right that people want answers to such questions. But the simple and sad fact is that yes, we did see it coming.

From the start of this year, aid organisations warned that South Sudan was potentially facing a famine. Those fears took hold shortly after my last visit in the spring when local farmers were forced to flee their homes due to fighting between Dinka and Nuer ethnic groups at a time when they would usually have been tilling their fields.

As recently as July, the United Nations Security Council expressed "grave concern" and described it as "currently ... the worst food insecurity situation in the world". Like other organisations, however, the UN fell short, just, of calling it a famine.

The bottom line in all this famine prediction process is that specific criteria have to be met before aid organisations can use the dreaded F-word and declare existing mass hunger an officially designated famine. Often they use what is known as the five-point Integrated Food Security Phase Classification (IPC) scale. As a set of tools for classifying the severity and magnitude of food insecurity, IPC phase 4 constitutes an "emergency", but not IPC phase 5, "famine". Right now South Sudan sits on the edge of the abyss as a "phase 4."

So until it is called a famine, there will not be a famine-type response, but by not reacting now a famine is all but certain. Put another way, early warning signs do not necessarily lead to early reactions, meaning help only really arrives when it is too late.

This is the terrible Catch 22 aid organisations and, indeed, reporters face when confronted by situations like South Sudan. Highlight a potential catastrophe in the making and you can be called alarmist and ignored. Report on the fully blown situation when people are dying like flies, and shrill voices demand answers as to why there was no warning. In this short column, I'm giving that warning. But don't be surprised if soon it is followed by accounts of human misery - famine - on a mass scale.