Euro 30 per tonne for carbon - enough to avert catastrophic climate change?

An interesting opinion piece in today's Guardian arguing that there should be a far higher global carbon price to avoid apocalyptic rises in temperature.

And certainly there's a good point here in that most carbon pricing mechanisms were established prior to the global financial crisis and, consequently, the price of carbon is low, relative to what people thought it would be by 2018. Similarly, it seems that coal-fired power has remained a major part of the energy mix, notably in developing economies, but also in Germany too.

Thus, a higher carbon price would reduce coal's appeal. However, how what's the economics behind the 30 euros per kg price? This isn't touched upon, and that leaves a number of questions unanswered.