A recent book and associated website discusses the steps necessary to address and even reverse the current warming of the climate system. The project, known as Drawdown, maps, measures, models, and describes the 100 most substantive solutions to global warming. For each solution, the Drawdown team describe its history, the carbon impact it provides, the relative cost and savings, the path to adoption, and how it works. Drawdown is that point in time when the concentration of greenhouse gases in the atmosphere begins to decline on a year-to-year basis.
Atmospheric carbon dioxide would likely stabilize before the world stops emitting (on a net basis) carbon dioxide from anthropogenic sources. This is because of the action of the oceans and the lag in carbon dioxide uptake that they exhibit. Net carbon dioxide emissions of 6-10 Gt per annum (currently 40 Gt per annum) are possible while atmospheric carbon dioxide plateaus, but emissions must eventually head to net-zero to see atmospheric carbon dioxide fall and for that trend to continue. Even then, the fall will be very slow given the quantity of carbon dioxide in the atmosphere and the rate at which the ocean can absorb it, at least until the surface layers are largely saturated. Further processes which involve fixing the carbon in ocean sediment and absorbing it through mineralization will play out over thousands of years.
‘Drawdown’ is a comprehensive piece of work and covers not just energy solutions such as replacing fossil fuel use with renewables, but also includes social changes such as the need for educating girls in developing countries. Education is linked to infant mortality, birth rates and therefore long term population trends, which in turn impacts energy use and therefore emissions. Within the website is a listing of the approaches, starting with Refrigerant Management at the top of the list. A change in this area is claimed to be the equivalent of 90 Gt CO2, but this is a more complex story as refrigerants are, for the most part, short lived climate pollutants (SLCP). I discussed this in a post last October, shortly after the Parties to the Montreal Protocol had agreed the Kigali Amendment which covers these refrigerants.
While the list covers areas such as electricity generation, land use change and transport, it has very little to offer for industrial processes, but seems to rely on them completely to deliver systemic change. Building wind turbines, developing mass transit, deploying nuclear power stations, manufacturing insulation and automating buildings will require large scale manufacturing and significant production of chemicals and materials. Today, these activities alone account for some 8 Gt of global carbon dioxide emissions, or nearly the same as transport. New activities such as building hundreds of TWhrs of battery storage are likely to exacerbate these emissions. Included within this there are significant emissions from the processes themselves, such as the carbon dioxide from the reduction of iron ore to make iron / steel and the calcination of limestone to make cement.
These activities are amongst the most difficult to decarbonise and lead to the need for carbon capture and storage (CCS). Capturing and geologically storing the emissions from cement manufacture may be far simpler than trying to find substitutes, developing alternative process routes or trying to offset the emissions through reforestation. The one hundred solutions offered on the Drawdown website make no specific mention of geological storage of carbon dioxide, yet venture into areas such as air capture of carbon dioxide. While the latter may provide a useful conduit towards synthetic fuels, it will make no difference at all to atmospheric carbon dioxide if there isn’t large scale storage involved.
‘Drawdown’ is an interesting piece of work, but it doesn’t tackle the real challenge associated with net-zero emissions, let alone actual drawdown of carbon from the atmosphere. These issues are tackled with much greater rigour in the recent Shell publication ‘A Better Life With a Healthy Planet: Pathways to Net-Zero Emissions’ and in my forthcoming book ‘Putting the Genie Back: Solving the Climate and Energy Dilemma’.