When you return to Ireland after many years abroad you notice small differences that end up becoming large ones.

The first thing that hits you is the unmatchable air quality. Once they open the plane it floods the cabin in great palefuls, that wonderfully hydrated Irish air.

It's the gift of the rain and the wide Atlantic and it never fails to wake you up, bring you to your senses, or raise your I.Q. by double digits. It's colder, richer and more reviving than even the brightest day where you live now.

Then you hear the ground staffs' Dublin or Shannon accents. That says you're home, or at least you're in the country that was once your home, and there's a little tug that goes with it, a twitch on a thread.

Out you go into the usually foggy morning. It's June but it looks like December under an ash grey sky.

Where has the sun gone? How does anyone live like this? It'll take you days to find the rhythm that you long ago left behind.

Everything on the road into the city has a slightly used look. Houses need work or a lick of paint.

Sheds look like they're in their last decade. Even the newly built roads are succumbing to the odd pothole. Nature seems to be always in the process of quietly reclaiming what has been built.

And there's an air of almost imperceptible neglect that covers the houses, the road works, the buses and trains with their hurriedly scrawled graffiti and their slightly worn chairs. Irish people barely notice it, but having arrived from somewhere else you can see what they've missed because you live differently now.

You don't mention any of this to the locals because you're from here and you know how they'd react. Instead you just look out the window at the epic fallout from the Celtic Tiger years.

Countless houses have sprouted “For Sale” signs. Many of them look like they haven't been inhabited in years.

That's when it strikes you -- the clearances, the disappearances, the mass emigration. It's actually worse now than in the decade when you left.

The sense of absence you have picked up on is an undeniable physical reality. Tens of thousands have walked away from their Irish lives. They will never return to them.

Later you'll reach the more salubrious suburbs of South Dublin, and in those leafy lanes you'll see a district that's been impervious to every economic shock or downturn since the foundation of the state. Here are the homes of Ireland's ruling classes and they can weather out every change of fortune, having the means and the connections. They hate Sinn Fein here but Sinn Fein (ourselves alone) has always been their unspoken motto.

Depending on where you're from you will fan out north, south or west. I travel north. That long artery allows me to see the scale of the devastation.

Old homes have been abandoned. For long stretches of the road I barely see a soul. The scale of the recession and its legacy are apparent in each town and village.

Teenagers and pensioners often seem to be the main occupants. All the missing generations between them are conspicuous mostly by their absence.

Telephone services have changed again. Some towns still don't have reliable broadband in 2015.

In north Donegal they shrug their shoulders, having experienced this governmental neglect since the foundation of the Republic. Ach, they say, ach.

Walking around your old town, you see ghosts everywhere. Here come the bright faces of your teenage years, the ghosts of you and your fellow desperadoes as you geared up to take on the world. How innocent you look, how unprepared for what's really out there.

There was a time when these streets were the whole world to you. That time has long passed. Now these streets look like lines on your palm, so familiar that you have to focus to even see them.

But what you never expected was to feel so ill at ease here. Worse, you feel like a tourist in your own town.

Your old gang reached Dublin Airport before or after you but they all departed to a man and woman, gone in search of a new life. You won't hear your name spoken or see their flashing smiles now.

What's left are echoes and hauntings, and no one can live on those.

When you all left you took the future with you. It belongs overseas now with you.

The writing's on the walls of small town rural Ireland. The economic collapse has left its scars.iStock