Following up on last year's question of "What's the carbon footprint of sending a text message?", The Guardian has now asked "What's the carbon footprint of making a mobile phone call?"

Climate change expert Mike Berners-Lee has considered rather more than the earlier article, factoring in phone manufacture and network administration alongside power consumption. His answer is that a minute's mobile-to-mobile call will generate 57g of carbon.

Juniper Research has calculated that the revenue generated by mobile applications will treble in the next five years, from just under $10 billion in 2009 to $32 billion (£22 billion) in 2015. That figure includes the cost of buying apps ('pay-per-download'), value-added services (including subscription charges) and advertising.

Nokia Siemens Networks says it's been working to remove bottlenecks from O2’s mobile broadband coverage in London, helping the network meet the demands of its smartphone users.

By analysing the activity of smart devices on the O2 network and combining this with traffic growth forecasts, NSN says it's upgraded the network elements and modules identified as current and potential future bottlenecks. Adding new base stations to existing sites has helped O2 increase coverage and capacity while also conserving smartphone battery life.

This week's edition of The Fonecast is now online, taking its usual look at the latest mobile news headlines – from the new Apple iPhone 4 to Orange's welly-powered charger.

There's also an interview with Ben Whitaker, who's CEO of Masabi. His company recently announced a deal that'll soon see train tickets for the UK's national rail network available to order from your mobile phone.

Apple announces the iPhone 4, Iridium prepares 72 new satellites and Orange reveals a phone charger powered by hot feet. In addition there's a conversation with Ben Whitaker of Masabi about his company's plans to introduce rail tickets on mobile phones across the UK.