204 Journal of Human Rights and the Environment, Vol. 8 No. 2 even to hold the temperature increase below 3°C.1 The United States federal government committed itself to doing only what could possibly be slipped past a legislature controlled tightly by fossil fuel interests; Russia committed itself to doing nothing meaningful; Poland forced the EU to scale back its ambition in order to keep burning Polish coal; many national commitments – some reasonably and some unreasonably – are to make only relative, not absolute, reductions in emissions, and so on. On the other hand, ‘a Party may at any time adjust its existing nationally determined contribution with a view to enhancing its level of ambition …’ (Article 4(11)). What are needed now are mechanisms to lock in prompt and regular sharply progressive enhancements of ambition. However, the Paris Agreement faces an even deeper political problem than the political issue of the distinctly un-ambitious levels of ‘ambition’ displayed so far in the NDCs. The Integrated Assessment Models (IAMs) that the Intergovernmental Panel on Climate Change (IPCC) uses to show how it is possible to hold global temperature rise to 2°C, not to mention 1.5°C, depend heavily on extensive ‘negative emissions’, that is, the removal of substantial amounts of carbon from the atmosphere to reverse the effects of carbon emitted. In an extensive assessment of the prospects for negative emissions technologies (NETs), Pete Smith and a large number of collaborators make the following observations: ‘The Fifth Assessment Report (AR5) by the Intergovernmental Panel on Climate Change (IPCC) database includes 116 scenarios that are consistent with a >66% probability of limiting warming below 2°C (that is, with atmospheric concentration levels of 430–480 ppm CO2eq in 2100). Of these, 101 (87%) apply global NETs in the second half of this century’.2 So 87% of the IPCC’s scenarios that allow the target of 2°C to be achieved rely on NETs. This dependence on NETs is not widely appreciated. In their subsequent penetrating and highly accessible two-pager, Kevin Anderson and Glen Peters make a similar observation about preponderant reliance on negative emissions, using a somewhat different reference point: The IPCC has assessed 900 mitigation scenarios from about 30 IAMs. Of these, 76 scenarios from five IAMs had sufficient data to estimate the carbon budget for a likely chance of not exceeding 2°C … Using the 76 scenarios consistent with a likely chance of not exceeding 2°C … two key features are immediately striking. First, the scenarios assume that the large-scale rollout of negative-emission technologies is technically, economically, and socially viable. In many scenarios, the level of negative emissions is comparable in size with the remaining carbon budget … Second, there is a large and growing deviation between actual emission trends and emission scenarios.3 1. J Rogelj, M den Elzen, N Höhne et al., ‘Paris Agreement Climate Proposals Need a Boost to Keep Warming Well Below 2°C’ (2016) 534 Nature 631–9. doi:10.1038/nature18307. For a reading of this article accessible to non-scientists, see C Mooney, ‘The World has the Right Climate Goals – but the Wrong Ambition Levels to Achieve Them’ (2016) Washington Post, 29 June, <https://www.washingtonpost.com/news/energy-environment/wp/2016/06/29/asweeping-new-analysis-shows-why-our-planetary-carbon-math-is-still-falling-short/?utm_ term=.b0a0796ac2e3> accessed 29 April 2017. 2. P Smith, S Davis, F Creutzig et al., ‘Biophysical and Economic Limits to Negative CO2 Emissions’ (2016) 6 Nature Climate Change 42–50, at 43. doi:10.1038/nclimate2870. 3. K Anderson and G Peters, ‘The Trouble with Negative Emissions’ (2016) 354(6309) Science 182–3, at 182. doi:10.1126/science.aah4567. This article is highly accessible to nonscientists, but for a perceptive interpretation of its significance see C Harvey, ‘We’re Placing Far Too Much Hope in Pulling Carbon Dioxide Out of the Air, Scientists Warn’ (2016) © 2017 The Author Journal compilation © 2017 Edward Elgar Publishing Ltd