Net-zero greenhouse gas emissions target year: information and analysis

Section 4: The scale of the challenge

Transformational changes and extremely ambitious policy choices will be needed to achieve a 90% target by 2050.

At present, it is estimated that Scotland emits around 55 million tonnes of carbon dioxide equivalent (MtCO2e, or megatonnes) to the atmosphere each year. Around 7 megatonnes are absorbed back out of the atmosphere by the natural forestry sink, so Scotland’s net emissions are currently estimated to be around 48 megatonnes per year. Global emissions are around 49,000 megatonnes per year, meaning Scotland’s emissions are approximately 0.1% of the global total.

Scotland’s targets are set as percentage reductions from the 1990 baseline, which the most recent estimates suggest was around 77 megatonnes per year. A 90% reduction target currently means that net Scottish emissions will be around 8 megatonnes by 2050. However, frequent technical revisions to the data means that this may change (see box).

Frequent changes to estimates of emissions

The science of how greenhouse gas emissions are measured is continuously evolving. This results in the estimates of Scottish emissions, for both the present day and all previous years including the baseline year, changing frequently. The changes are overseen by a UK-level steering committee, in line with UN guidelines.

Past data have been revised in every set of Scottish emissions estimates published to date. One of the most significant changes that has occurred so far is an upwards revision of around 3 megatonnes per year to estimates of forestry emissions. In other words, 3 megatonnes of emissions were added to Scotland’s inventory to reflect a better understanding of the science, but without any actual change in emissions taking place.

Very large data revisions can affect the appropriateness of emissions reduction targets: targets can become either harder or easier to meet. Implementation of the UN guidelines on wetland emissions is expected to mean a large revision to the data. It is likely to mean that the estimate of past Scottish emissions levels will increase far more significantly than any changes seen to date. In this event, a 90% target by 2050, and the proposed interim and annual targets between now and then, would become substantially more challenging and achieving it will require additional technological developments and social and economic changes.

In the CCC’s scenario for Scotland achieving a 90% reduction by 2050, based on current estimates, about 17 megatonnes would continue to be emitted, with around 9 megatonnes being removed from the atmosphere by forestry and substantial deployment of new negative emissions technologies, namely bioenergy with carbon capture and storage. Of the 17 megatonnes still being emitted, over a third would come from the agriculture sector, with the only other substantial contributions being from industry, aviation and maritime transport. All other sectors, such as surface transport, energy supply, waste, and buildings, would be either fully, or near-fully decarbonised.

The changes needed to deliver a 90% reduction will take place in every home and community across Scotland. In many cases this will have a positive impact, benefiting health, creating new economic opportunities, producing cost savings, supporting new industries and providing international opportunities for Scottish businesses.

The way in which people heat their homes, for example, will be very different by 2050. The technology is currently being piloted so it is not possible to be sure at this time exactly which technology will prove to be the most effective. It is important that a decision on the best technology is not made prematurely, which could result in sub-optimal technology being installed in people’s homes. In addition, changes in areas such as home energy must ensure there are no negative consequences in other priority policy areas such as tackling fuel poverty.

The CCC have said:

“we need that steer [on low carbon heat] in the first half of the 2020s — by 2025, and the earlier the better. However, that decision cannot be made now. There has to be a learning phase where things are demonstrated in a way that enables us to understand them better and understand more about their costs.”