Meinshausen et al. (2009) provides the key scientific foundation for inferring a fixed ["forever"] global carbon budget from a given target global temperature rise constraint. Under the Paris Agreement (UNFCCC 2015) the parties to the United Nations Framework Convention on Climate Change have endorsed a collective global goal of keeping temperature rise “well below” +2°C over pre-industrial. However, almost all IPCC scenarios for achieving this goal currently assume that cumulative CO₂ emissions will, in fact, overshoot the corresponding available atmospheric budget within 20-40 years; but that it will become physically and economically practical to deploy “negative emissions technologies” (NETs) on a sufficiently large scale to “recapture” this excess CO₂, and store it securely enough, quickly enough, to still prevent the temperature limit being breached. Net negative emissions are achieved when more GHGs are sequestered or stored than are released to the atmosphere over a given time. Smith et al (2015) presents a review of current global scenario modelling for climate change mitigation. For cases meeting the ⪅+2°C temperature goal they find that current global mitigation scenarios almost all assume the achievement of global net negative emissions from approximately 2050 onward, with a sustained net negative emissions rate of the order of 3.3 GtC/yr (12 GtCO₂/yr). However, there are very large uncertainties in the technical feasibility of such rates, in costs (even if technically feasible), in cumulative storage/sequestration capacity, and in impacts on other critical global human systems, particularly food production.

While the sources of rising CO₂ and other greenhouse gases (GHGs) are many, primary energy supply is a major contributor. The grand challenge is to lower GHG emissions while providing energy to meet the continuing needs of human development (against a background of a still growing world population). Electricity generation alone accounts for approximately one third of global emissions. A sustainable energy future requires strategies to allow the use of energy while enabling the absolute reduction of GHG concentrations in the atmosphere.

Society needs to be informed of the potential risks and opportunities associated with the mitigation options in order to decide which are the best for dealing with climate change. Many NETs have been proposed but we need to be clear on their feasibility, cost and acceptability before recommendations can be made on their implementation. Probably the less well studied aspects of the application of these technologies have been the impacts that large-scale CO₂ removal could have on ecosystems and biodiversity.

A key question when considering the application of NETs is whether deployment of any proposed mechanism can be effectively achieved and most importantly sustained. Most of the NETs require the use of land and water, some use fertilizer, and many impact on albedo (Smith et al. 2015). NETs vary significantly in terms of their requirement for land, GHG emissions removed or emitted, water and nutrient use, energy produced or demanded, biophysical climate impacts (effects on albedo), and cost. All of these are strongly dependent on their scale of deployment. To inform society of the potential risks and opportunities afforded by NETs, more research is clearly required.

The overarching objective [of the ie-nets project] is to provide a detailed and rigorous assessment of the scale and speed of negative emissions technology deployment that is required by currently envisaged decarbonisation pathways (globally and nationally), consistent with the Paris agreement goal of limiting global temperature rise to “well below +2°C” over pre-industrial; to evaluate the options and capacity for Ireland itself to directly contribute to such deployment; and to provide an evidence base for assessing the risks attaching to reliance on such presumptive future technology deployment in designing current (5-15 year) decarbonisation policy measures. In particular, the project will focus on identifying early research or policy actions that could significantly reduce the uncertainties attaching to the feasibility and costs of negative emissions technology, both globally and nationally.