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It's "a clearly unacceptable level as it will definitely undermine any reductions achieved from other (greenhouse gas) emissions sources," the researchers wrote in the paper, which appeared in the Journal of Cleaner Production .

While the entire sector accounted for just 1 to 1.6 per cent of global carbon emissions in 2007, by 2040, it will account for 14 per cent of emissions, the researchers projected. That's the equivalent of half the transportation sector's emissions.

In a research paper published earlier this year, McMaster University associate professor Lotfi Belkhir, along with recent graduate Ahmed Elmeligi of the faculty of engineering concluded that the global information and communications tech sector — including consumer devices — is in the midst of a rapid explosion in its carbon footprint.

The common practice of buying a new smartphone every two years is taking a toll on the planet and threatens to undermine efforts to reduce greenhouse gas emissions, Canadian researchers have found.

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Data centres and communications networks will be the largest contributors to tech's carbon footprint, but smartphones will be the most damaging of all communications devices, they predict.

The number of smartphones in the world will hit 8.7 billion by 2040, equivalent to 95 per cent of the world's population by that time. Notably, other research shows that about a quarter of smartphone users have more than one phone, and the share is rising.

Using a smartphone is not particularly carbon-intensive; rather, it's the extraction of rare metals used in smartphones, and the manufacturing process, that are the culprits.

Over the course of a phone's lifetime, 85 per cent of the carbon emissions it causes will take place before a consumer even buys the product, the McMaster researchers found.

Which is why the habit of buying a new smartphone every two years, a habit created by telecom providers and their two-year contracts that come with subsidized phones, is so damaging to the environment.

"Clearly this business model, while highly profitable to smartphone manufacturers and the telecom industry, is unsustainable and quite detrimental to the global efforts in (greenhouse gas) reductions," they wrote.

...The technology is fine. It's the business model that's driving the very frequent changes and upgrades."Lotfi Belkhir, McMaster University

In a phone interview with HuffPost Canada, Belkhir said he suspected phone manufacturers may be intentionally slowing down their older models to convince consumers to buy new ones.

"You have a lot of people saying 'I've upgraded because my phone has become too slow,'" he said. "But you don't hear people using tablets and saying the same thing about them — even though it's still running the latest software."

Though tablets are very similar technology to smartphones, the McMaster researchers found tablets have a shelf life of seven years, compared to just 1.8 years for smartphones.

"This proves that really the technology is fine," Belkhir said. "It's the business model that's driving the very frequent changes and upgrades."

Keep your phone longer ... and recycle

Belkhir says the life of smartphones should be extended to four or more years, though in the research paper he concedes that the idea "could face strong resistance from the phone manufacturers for whom the accelerated obsolescence of their cell phones is central to their business model."

Also important: "People need to ensure that their phone is recycled, that they don't throw it away," Belkhir said.

Those phones contain significant amounts of precious metals (including some 0.03 grams of gold, or 10 times as much as in desktop or laptop computers) and recycling this material would mean less environmentally harmful mining of rare minerals.

The industry should be aiming for "cyclical manufacturing," where all the elements in a smartphone are successfully recovered and reused in new phones, Belkhir said.

"This would save a lot of money for manufacturers and have a significant environmental impact," he said.

CORRECTION: An earlier version of this article stated that smartphones contain 300 grams of gold. They actually contain approximately 0.03 grams of gold.