The Paris Agreement on climate change, reached in 2015 has a goal of limiting the worlds average temperature rise from global warming to ‘well below 2 degrees Celsius above pre-industrial levels’. But it also stretches its ambition in a slightly more precise manner than that, stating an aim to ‘pursue efforts to limit the temperature increase even further to 1.5 degrees.’. This outcome, not expected as negotiations in Paris began, was a surprise for many in the climate change community, but then led to questions of how, or perhaps if, the goal could be achieved.

The 1.5ᵒC window is narrow and to reach the target will be a daunting policy challenge – with emissions needing to peak in the next year or so and then rapidly decline year-on-year to reach zero by around 2050.

There is a relative lack of scientific analysis focusing on the mitigation efforts needed to stay below 1.5ᵒC compared to 2ᵒC, mainly as 1.5ᵒC has, until now, been something of a political impossibility. But what is clear is that remaining within the carbon budget for 1.5ᵒC will require rapid decarbonisation and a transformation of the energy system at a radical pace never seen before.

Emissions need to start declining rapidly right now. As well as the obvious – a phase out of fossil fuel power, increased renewable energy capacity, and a switch to low carbon electricity for heating and transport – many technologies will be necessary to get there. And, as analysis from Climate Analytics and the Climate Action Tracker consortium indicates, the next ten years will be critical.

Let’s start with the obvious – electricity grids will need to be further decarbonised, and this means that the electricity climate villain, coal power, will have to disappear from power systems entirely. Climate Analytics analysis indicates that coal will need to be phased out entirely world-wide by mid-century, and earlier in Europe, with countries having to retire existing coal plants early and stop building new capacity.

Energy efficiency is well known as one of the cheapest methods to reduce emissions from energy use and supply, and one with a great deal of potential. Todays new builds should be future-proofed in terms of efficiency, but tackling new buildings is not enough – retrofit rates for existing buildings will need to at least triple from the current level in order to transform the entire current building stock by 2050.

Electrifying the transport sector is a key element of 2ᵒC and 1.5ᵒC scenarios. There has been a spate of activity in this space recently, with car manufacturers announcing big electrification plans and governments announcing target dates to phase out fossil fuelled vehicles. But, regardless of these targets, Climate Action Tracker’s pathway says if we are serious about 1.5ᵒC, the worlds very last fossil fuelled car will need to be sold by 2035.

Electric vehicles powered by renewable electricity are the current favourite of zero-emission vehicle technology to replace these conventional cars. Freight transport is a whole different ball-game, and a tricky area. Land freight movement will have to shift as much as possible from road to rail, while trucks will need to tap onto low carbon electricity – either via overhead wires on highways, or through the use low carbon synthetic fuel produced using renewables. We will have to fly less, and for what air travel is deemed necessary the aviation sector will need to use efficient planes and biofuels to eventually get its emissions down to zero.

The bulk of future energy and climate scenarios bank on future technologies being developed that can directly reduce the atmospheric concentration of carbon dioxide. It is common in 2ᵒC scenarios that emissions ‘overshoot’ the total budget and then must be ‘sucked’ back in from the atmosphere at a later date. Cut to a 1.5ᵒC budget, and this becomes more important.

‘It is certainly the case that you cannot do 1.5ᵒC unless you are willing to take carbon dioxide out of the atmosphere,’ says Skea, ‘that has to be part of the set.’.

Carbon capture and storage (CCS) alone will be important if the worlds energy systems are to continue to rely on an extent on large, centralised fossil fuel generators. And it is also argued as one of the only ways to decarbonise industrial emissions in the future, as well as a route to low carbon heat through hydrogen production.

Could a reliance on future negative emissions technologies result in a less immediate mitigation efforts now, as some research suggests, due to complacency and holding out for a future magic solution?

There are no two ways about it – keeping to below a 1.5ᵒ temperature rise is going to be hard. But there will also be huge benefits to remaining below it, in terms of avoiding damaging climate change impacts, particularly to vulnerable nations like Fiji.

Article adapted from Energy World November 2017 – Magazine of the Energy Institute London