When Mark Delaney and his wife Cathy packed their bags and left their Brisbane home in 1995, they didn't go looking for something more spacious or luxurious.

Instead, the couple moved to the slums of Delhi.

"We lived in a small place, no fridge, no washing machine, no running water," Mark says.

"We had electricity that was illegal — so yeah, it was pretty simple."

The trip was meant to last a few years, and teach them about the needs of the wider world.

But Mark and Cathy have been living on-and-off in India's slums ever since.

The pair — and their two sons Tom and Oscar, who were largely raised in Delhi's urban slums — switch up their time between India and Australia.

The Delaneys have lived in homes about the size of a standard Australian bedroom. ( Supplied )

Mark says he found it difficult to get used to some cultural differences, but he has come to understand the reasons behind them.

"The huge number of people competing for scarce resources — think queuing at the water tap or pushing to get on a crowded bus — means people can be pretty pushy," he says.

Then there's also the "very hierarchical nature of [Indian] society, based on caste, skin colour, language, gender [and] age".

Mark says this is very evident in slum areas, and it's difficult "seeing the 'little' people often treated badly by those higher up".

The Delaney family lived in this slum for a while. It has since been demolished and residents moved. ( Supplied )

Why would you do it?

Mark cites his Christian faith as one of the main reasons behind the radical change.

"I was studying law, and I came up to a point in my life where I thought, 'I've got a couple of paths in front of me here'," he says.

"I could go the normal path and be a lawyer... or I could look around me at the broader world and find out what are some of the needs out there.

"I chose to take that path."

Mark outside his home in Delhi. ( Supplied )

In India, Mark works for a non-government organisation, helping "poor people to attain their legal entitlements".

"Roughly speaking, I'd say Indian society is divided into about 20 per cent and 80 per cent," he says.

"Twenty percent are educated, English-speaking, can access all sorts of things.

"The 80 per cent are really struggling to survive."

Mark chose to give up not only an international salary, but an income altogether.

"I wasn't paid at all. I was a volunteer," he says.

"We were living off our own savings, and friends and family who would give us money to keep us there."

A cross-cultural life

Growing up between two cultures has had a profound impact on the couple's children.

Tom, the eldest of the boys, has vivid memories of the Islamic festival of Eid al-Adha, often known in India as Bakra Eid ("Goat Eid").

"[During] that festival … hundreds or thousands of goats are sacrificed in our community. [It] made a very powerful impression on me, as a 10 or 11-year-old," he explains.

"The goats were our family pets. I had patted the goats and played with them in the lead-up to this festival… and then on one day they're all slaughtered."

After that, Tom became a vegetarian.

Tom, who is 21 years old, teaching literacy skills in Lucknow, India. ( Supplied )

"In Australia, you don't really see where your meat is coming from, [so] it's quite possible to imagine that it wasn't actually an animal," he says.

"Whereas if you feed the animal and pat it, then you know where your meat is coming from."

Tom believes the positive parts of his upbringing far outweigh the negative.

"I'm just really privileged to have friends in both India and Australia, and to understand a bit more broadly and deeply about … different issues," he says.

"Wherever you are in the world, you're missing out on something somewhere else. I think the cross-cultural upbringing more than makes up for that."

After years of living between two worlds, father Mark says he feels neither "fully Australian or fully Indian".

"In India I have lots of good friends, and lovely networks and very fulfilling work," he says.

"But as soon as I walk out my door, I look different from my friends and neighbours, so I get all this attention, and as an introvert that's difficult."

Reverse culture-shock and climate action

Living in India cemented the Delaneys' philosophy of living sustainably.

When they returned to Australia for an extended period in 2014, they experienced a form of reverse culture-shock.

"We'd been reading a newspaper … and reading that climate change seems to be becoming a very, very serious issue; probably the issue of our generation," Mark says.

"We thought, 'Australians have one of the highest carbon footprints in the world, [but] they know science, they're educated, of course everybody will be working to reduce their carbon footprint'.

"We were shocked — flabbergasted — that it was hardly in the news. It was remarkable.

The Delaneys say Australians need to do more to combat climate change. ( Getty: John W Banagan )

According to Tom, this is a good example of the extreme inequality in resource distribution across the world.

"The world is a finite place, and we are enjoying lavish lifestyles in Australia," he says.

"I think Australians have got far more than the basic requirements, and that's actually taking away from other people's possibilities to achieve their basic requirements.

"The carbon budget is a very good example of that, we are contributing more than our fair share of it."

Sorry, this audio has expired Living the low carbon life in India

Based on figures from the Intergovernmental Panel on Climate Change, Mark and Tom calculated that a sustainable amount of carbon emissions is around 2 to 3 tonnes of per person each year.

The average Australian currently emits 22 tonnes of carbon, according to Climate Council statistics — seven times more than the sustainable average calculated by the Delaneys.

Mark and Tom are now working to convince Australians to reduce their carbon emissions.

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Mark says while it would be tempting for Australians to "throw their arms up" and think little can be done, that isn't the case.

And change doesn't have to be as extreme as packing up and moving to India.

One simple action, Mark says, involves taking a step back from "our busy-ness" and thinking about what's really important in life.

"Ordinary people would say, actually, the things that matter in life are relationships, being able to enjoy nature, creativity and so forth," Mark says.

He says "those things don't take a lot of carbon", so prioritising them over other activities would help reduce a person's carbon footprint, even just a little.

There are also small yet practical changes that can help reduce your carbon footprint over time.

"Maybe that goes from eating meat five times a week, to eating meat three times a week," Mark says.

"Maybe it means instead of driving your car to work five days a week, you do it four."