Biophysical and economic limits to negative CO2 emissions

Scenario analyses suggest that negative emissions technologies (NETs) are necessary to limit dangerous warming. Here the authors assess the biophysical limits to, and economic costs of, the widespread application of NETs. To have a >50% chance of limiting warming below 2 °C, most recent scenarios from integrated assessment models (IAMs) require large-scale deployment of negative emissions technologies (NETs). These are technologies that result in the net removal of greenhouse gases from the atmosphere. We quantify potential global impacts of the different NETs on various factors (such as land, greenhouse gas emissions, water, albedo, nutrients and energy) to determine the biophysical limits to, and economic costs of, their widespread application. Resource implications vary between technologies and need to be satisfactorily addressed if NETs are to have a significant role in achieving climate goals.