In the RT scenario, CO2 emissions from energy use by 2040 fall by around 45% relative to current levels. Although such a reduction represents considerable progress, it implies that a significant level of CO2 emissions (around 18 Gt) would still remain.
Looking beyond 2040, in order to meet the Paris climate goals, these remaining emissions would need to be greatly reduced in the second half of the century and offset with negative emissions.
These remaining emissions are concentrated in transport (7 Gt) and industry (5 Gt), with smaller contributions from power (3 Gt) and buildings (2 Gt).
In transport, the majority of the emissions stem from the continuing use of oil (45 Mb/d) in 2040. More than half of this consumption stems from the use of oil in cars and light and medium-duty trucks which can be gradually electrified overtime. But the remainder is concentrated in modes of transport which are harder to electrify: including elements of heavy-duty trucks, aviation, and marine.
In industry, much of the CO2 emitted stems from the continuing use of coal (2 Gt) and gas (2 Gt) in activities that are hard and/or expensive to abate, either because they require high temperatures or where carbon is inherently involved in the production process, such as iron and steel, chemicals and cement.
A further substantial reduction in net CO2 emissions from energy use beyond 2040 would likely require further improvements and changes across a number of fronts.
A key development would be an (almost) complete decarbonization of the power sector, together with greater electrification of end-use activities. Decarbonization of the power sector would require more renewables – supported by improvements in energy storage and demand-side-response to ease the issues associated with intermittency – plus more CCUS in conjunction with natural gas and coal.
But the IEA recently estimated that only around two-thirds of final energy use has the technical potential to be electrified, highlighting the need for other lower-carbon forms of energy (and energy carriers) for the remaining one-third. This includes hydrogen produced from decarbonized sources, bioenergy, and gas/coal/oil with CCUS.
Two other over-arching developments are also likely to be important: