More on the UNIPCC report - Global Warming of 1.5C

Anyone who is interested in potential pathways to zero carbon should read the UNIPCC special report on the impacts of 1.5C of global warming. In addition to documenting the impacts of 1.5C vs 2.0C the report also looks at four “four illustrative .. pathways” to zero carbon

In plain language this section outlines four hypothetical scenarios that have global emissions decreasing from 45GT/year to zero. The scenarios rely on different contributions from 12 key decarbonisation mechanisms. Obviously there is a virtually unlimited number of hypothetical pathways so the 4 chosen scenarios highlight the more important changes needed and showcase the inherent tradeoffs and compromises that will need to be made if some mechanisms are ignored. One can also discern a nod to political orthodoxy in terms of potential strategies excluded from the discussion.

The scenarios share some fairly predictable features – all four have renewables becoming the major global source of electrical generation by 2050, totally displacing coal and also a large part of the natural gas generation fleet.

What is more interesting are the insights into what else has to happen if one assumes lots of renewables, no coal and a sharp reduction in natural gas is the new normal for electrical generation.

The first insight is the fundamental importance of total energy demand on the decarbonisation challenge. The primary point of difference between the four potential pathways is the trajectory for total global energy over the next 30 years. The first pathway has a 1% annual reduction with the other three pathways having energy demand ranging from remaining essentially flat to increasing annually by either 0.6% or 1.2%.

Over the past 10 years global energy demand has been increasing by 1.7% pa and while it has been basically flat in OECD countries it has been growing by 3.2% pa in non OECD nations. To see a decrease in energy demand growth to near the midpoint of the IPCC scenarios will require some major breakthroughs in energy efficiency, technology transfer and individual usage behaviour.

The slower the reduction energy demand the greater the reliance on nuclear energy but under all scenarios it remains a key technology growing by at least 100% and potentially up to 500%. Groups who have strong “no nuclear” policies may need to reconcile this with a clear IPCC position highlighting the inevitability of an ongoing and potentially major role for nuclear power plants.

The second key insight is that just like coal and natural gas, oil usage also needs to decline. Perhaps reflecting different assumptions on the rate at which the global transportation fleet is either electrified or converted to low carbon hydrogen the decline in oil usage is either a precipitous 87% or a still challenging 32% relative the current levels. The geopolitical implications to a major structural decline in the relative importance of oil (the use of which is still increasing) will be fascinating to watch.

A final insight is that if reduced global energy demand and the virtual elimination of oil don’t do the heavy lifting then the shortfall will need to be made up by major changes to land use and agriculture. This could be steep cuts in CH4 and N2O emissions from domesticated animals combined with a relatively higher reliance on renewables and afforestation. This might be called the “vegetarian option”- land currently used for livestock being converted back to forest and woodlands. If livestock remain a key part of our diet then it seems afforestation measures will need to be supplemented by the use of bioenergy and negative emission technologies based around Carbon Capture and Sequestration (CCS).

Bioenergy is based on the growth of biofuels – fast growing crops that can be harvested and used as feedstock to specifically design power generation facilities. A currently very niche activity will need to become mainstream as will negative emission technologies require that CO2 to be captured either from combustion processes (especially those based on biofuels) or via direct extraction of CO2 from the atmosphere. In all cases the stored CO2 is pressurised and stored – sequestered – in suitable porous geological formations. CCS has been part of the IPCC decarbonisation toolkits for a long time and once had reasonable political backing. Over recent years this backing has declining and it is not supported by many environmental groups. As a result progress on the development of CCS has stalled – this may need to change as we approach 2050

The bottom line is that not only do the obvious things like reduced fossil fuel usage and increased reliance on renewables need to happen. Lots of other changes are also needed – changes that will upset lots of new stakeholders such as opponents of nuclear power and farming communities. Greater awareness of the challenges and tradeoffs in decarbonisation will require recasting the current political debate and will no doubt create new bedfellows and opponents.

January 2019