‘Net Zero’ climate goals: A cautionary note

15 fevereiro 2015

Recent support for the ‘net zero emissions’ target that has found its way into the negotiating text for a new global climate agreement should be reconsidered with greater understanding of the carbon cycle and with increased caution toward unproven technologies. Richard Branson and Unilever CEO Paul Polman are among those putting their names behind the net zero goal, which aims to reduce carbon emissions and to offset any surplus greenhouse gases with actions that absorb emissions, such as restoring or planting forests and other natural sinks.

Although ‘net zero’ supporters rightly emphasise reducing emissions, the goal of ‘net zero emissions’ perpetuates the false notion that land and forests can offset industrial emissions, maintaining the possibility for the continued consumption of fossil fuels. Tellingly, business proponents of the net zero approach fail to call for a swift phase-out of fossil fuels. Instead, they seem to suggest a reliance on Carbon Capture and Storage (CCS), the process of capturing the CO2produced through burning fossil fuels. This process has neither been proven at scale, nor resolved problems with capture efficiency, storage capacity and leakage.

To achieve net zero or negative emissions also requires other forms of geo-engineering, such as Bioenergy Carbon Capture and Storage (BECCS), which relies on vast tracts of land to plant biomass to burn under CCS conditions; many fear BECCS would entail even greater pressure on land and undermine food security, water availability, soil and biodiversity.

Calling for a ‘net zero’ target demonstrates a lack of understanding about the carbon cycle. Fossil carbon and terrestrial carbon are different sources of carbon that are not interchangeable. Emissions and removals of terrestrial carbon occur on different time scales than fossil carbon sequestration (which happens over millions of years). Due to the time scales involved, emissions from fossil carbon can be considered permanent, while sequestration of emissions in the land sector (forests and soils) is only temporary. Carbon dioxide is only slowly removed from the atmosphere, mainly by the oceans and forests, until it is dissolved on the ocean floor after thousands of years. For these reasons, the terrestrial carbon sink cannot be relied upon to offset industrial carbon emissions.

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