The election in November 2016 of Donald Trump as a populist, nationalist and unpredictable US President has upended many aspects of international relations and policy, and of American national policies, regulations and practices. Climate change is an ideological issue for Trump’s administration and political base, and so climate policy is under assault. US federal climate policies and institutions are being dismantled, climate science is questioned and its funding threatened, and the President has announced that the United States “will withdraw from” the Paris Agreement (White House, 2017), a signature achievement of his predecessor Barack Obama. A year and a half into Trump’s presidency, Climate Policy has published several papers on current US climate policy and its possible effects and trajectories, some of which are collated in a thematic section in this issue of the journal. More papers will no doubt follow in coming months and years. Contemporaneous, research-based analysis of this nature is one of the strengths of this journal. This editorial takes stock and introduces key themes discussed in the papers.

US President Donald Trump opposes efforts to limit climate change, in the United States as well as internationally. This stance apparently is rooted in his administration’s electoral populism and economic nationalism, a particular interpretation of individual liberty and a conviction that humanity has a right to exploit nature. Such convictions are shared by key players such as the head of the Environmental Protection Agency (EPA) Scott Pruitt. They are also echoed in deep traditions of US isolationism and rejection of multilateral institutions that could influence or constrain US actions, especially on economically important issues such as climate change. The latter was already evident in the US Senate’s unanimous rejection of the 1997 Kyoto Protocol before it was even finalized – on the basis that it might harm the American economy and that developing countries would be exempt from any new commitments. In the era of ‘making America great again’ as per Trump’s election slogan, collective action is not a favoured solution. As a challenge of the global commons, climate change thus sits uneasily with the Trump Administration’s worldview.

During his election campaign, Trump said he would ‘cancel the Paris Climate Agreement’.¹ Consistent with this pledge, in a 1 June 2017 speech in the White House Rose Garden, he announced that the US would withdraw from the Paris Agreement and ‘cease all implementation’ of it (White House, 2017). The US Ambassador to the UN later confirmed this intent to withdraw ‘unless the US identifies suitable terms for re-engagement’ (USA, 2017a). The rules of the Paris Agreement mean that the US cannot formally notify its withdrawal until 4 November 2019, and the withdrawal would only take effect a year later, ironically the day after the next US presidential election. As Kemp (2017a) points out, the Paris Agreement was designed for a US administration to be able to join by presidential executive action only, bypassing the need for Congressional approval, which has so often stymied US ratification of international treaties (Bang, Hovi, & Sprinz, 2012; Kemp, 2016). Although this legal device has made it easier for Trump to withdraw from the treaty, it would also make it easier for a post-Trump President to rejoin by administrative decision.

A key question is whether the US will indeed seek to identify ‘suitable terms for re-engagement’, and what this would mean in practice. Re-negotiation of the Paris Agreement itself is not a realistic prospect now that it has entered into force. However, the US Administration statement could be interpreted to say that the US may attempt to weaken its own Nationally Determined Contribution (NDC) under the Agreement. Although the Paris Agreement provides that parties ‘may at any time adjust’ their NDC, this should be ‘with a view to enhancing its level of ambition’ (Article 4.11), not to weaken it. Analysis by legal scholars indicates that, while not strictly violating its legal obligations, a Party would contravene the spirit of the Paris Agreement if it downgraded an existing NDC or presented a subsequent weaker NDC (e.g. see analysis in Center for Climate and Energy Solutions, 2017; Rajamani & Brunnée, 2017). Any downward adjustment would go against normative expectations established by the Agreement and is liable to draw criticism. The question for many then becomes, what price is too high to pay for the US to be on board the multilateral climate effort?

A year on, however, there are no signs that the US Administration is seeking to either renegotiate the Paris Agreement, nor has it put forward an alternative, weaker NDC. The President’s attention is evidently focussed on geopolitics and trade, while international climate change policy has taken a back seat. There are also few signs that other countries will follow the US lead, and themselves withdraw – or fail to ratify – the Paris Agreement. That the Russian Federation, a top emitter and longtime climate laggard (Martus, 2018), has not yet ratified the Agreement may ring some alarm bells. However, many more national leaders reacted to President Trump’s 1 June announcement by reaffirming their determination to implement the Paris Agreement (e.g. see Carbonbrief, 2017). In an unusually strong diplomatic move, all other G7 Environment Ministers meeting in Bologna soon after the US announcement expressed strong support for the Paris Agreement, with the lone opposing US view registered in a footnote to their communiqué (G7, 2017). At the June 2018 G7 meeting, the leaders of the G7 nations, excluding the US, re-affirmed their commitment to the Paris Agreement (G7, 2018). The horror scenario of the Paris Agreement unravelling as a result of US withdrawal now seems unlikely. But Trump’s rhetoric and actions clearly provide backing for opponents of climate change action in any country, and may have a ‘chilling’ effect on global climate action.

For the international climate negotiations, uncertainty over whether the US is ‘in or out’ of the Paris Agreement (see Kemp 2017b) poses a major challenge. For now, the US remains ‘in’, and can therefore participate fully in the negotiations on the Paris Agreement’s implementation details. There are fears that this could allow the US delegation to block the negotiations, or else impose unpopular options, before withdrawing altogether in 2020. So far, however, the US delegation has largely maintained long-held positions in the negotiations rather than seeking to obstruct or adopt any dramatically new stance. The US delegation appears to have a mandate to engage constructively on technical issues, with a strong focus on transparency that may well be beneficial for the implementation of the Paris Agreement. However, it is constrained by overarching Presidential political imperatives. These constraints were evident in its closing statement at the 23rd Conference of the Parties (COP 23) in November 2017 (USA, 2017b), which indicated that the US might not be bound by decisions taken, casting doubt on any technical progress achieved.

Many are concluding that the door to US participation needs to remain open, but that the Paris Agreement rulebook cannot be weakened to suit the US. This is different from the Paris Agreement itself, which was very significantly determined by what the US and China could agree.

It stands to reason that Trump’s impact on climate policy will remain strongest domestically. Although the US legally remains a party to the Paris Agreement, it has ceased all implementation of the treaty. Already, federal incentives for low-carbon investments have been scrapped, regulations changed to allow more high carbon developments especially in coal and oil production, motor vehicle emission standards are being rolled back, and the Clean Power Plan – the centre piece of the Obama Administration’s domestic climate policy – is being repealed (see Berardo & Holm, 2018).

The most lasting domestic damage of a Trump Administration may be in the erosion of institutions – both regulatory (e.g. the US EPA under Scott Pruitt) and those supporting climate science (National Oceanic and Atmospheric Administration (NOAA) and the National Aeronautics and Space Administration (NASA)), with funding to climate-change-related programmes cut. These actions could damage US institutions and capacity on climate policy and regulation for a long time to come.

What difference will this bonfire of climate regulations and institutions make to US greenhouse gas emissions? Galik, DeCarolis, and Fell (2017) provide quantitative estimates of potential emission pathways under the Trump Administration, in contrast to the Mid-Century Strategy for Deep Decarbonization (an 80% reduction in emissions by 2050) released under the Obama Administration. They find that federal US policy is unlikely to strongly influence continued reductions in emissions in the electricity sector. They estimate that near-term emissions trends will remain flat, no matter what the current US Administration does or does not do, and that President Trump’s impact on cumulative US emissions will be small if a subsequent administration gets back onto a trajectory towards an 80% reduction. However, Galik et al. find that there could be material and lasting impacts in the built environment and land use sectors, where investments have particularly long-term consequences and so may affect mid-century emissions outcomes. Decisions with large ‘lock-in potential’ (Kemp, 2017b) for future emissions also include the Keystone XL oil pipeline between the US and the oil sands in Alberta, Canada. As pointed out by several authors, the negative impact of one term of a Trump Presidency may be manageable and reversible, but two terms would be far more damaging.

Chen et al. (2018) undertake an analysis of the effect of current US climate policy on global emissions and costs of emissions reductions, as well as temperature outcomes, using a global model. They examine scenarios of US emissions levels staying constant for some time before declining, and also an extreme scenario where US emissions remain at their present level until the end of the century. Chen et al.’s simulations indicate that, if the US were to step outside of the global effort and remain a high emitting economy for a long time, then others – including developing countries – would need to mitigate significantly more to achieve the same temperature outcomes, at a significantly higher cost to the world economy overall. The equity implications of such a scenario would be profound. The decisive assumption in Chen et al.’s paper is that the US does not get back on track toward deep emissions reductions once Trump leaves office, as Galik et al. assume in their analysis.

In announcing withdrawal from the Paris Agreement, Trump also made it plain that all financial contributions to the Green Climate Fund (GCF) would stop. Before leaving office, Obama fast-tracked a $1 billion donation to the GCF, but the remaining $2 billion of the US pledge has now been scrapped. For Urpelainen and Van de Graaf (2018), climate finance is a key vulnerability for future climate cooperation: with the US pulling out of its commitments to provide funding for climate action in developing countries, trust in the UN-based multilateral system could be eroded. As Sharma (2017) points out, key provisions in the Paris Agreement on dealing with climate impacts – adaptation, loss and damage and finance – are already weak, even with full US participation. Under a Trump withdrawal, there is likely to be even less support – politically and financially – for adaptation, and loss and damage.

Perhaps the greatest threat presented by US disengagement with the Paris Agreement is that of demotivation, a danger cited by Pickering, McGee, Stephens, and Karlsson Vinkhuyzen (2018). Using an agent-based model, Sprinz, Sælen, Underdal, and Hovi (2018) also conclude that, if the US was an outsider to an international agreement, this may reduce participation by other countries in climate mitigation ‘clubs’, compared to a situation where the US is within a global agreement, but not leading the way (a ‘follower’). The next round of NDCs is to be adopted in 2020, and researchers are unanimous that these must significantly scale-up ambition if the window of opportunity of avoiding a 2-degree temperature rise (let alone 1.5) is not to be closed forever (Höhne et al., 2017). A US administration that is at best disinterested, at worst hostile, is the last thing the regime needs when ambition needs to be dramatically ramped up. As Pickering et al. point out, the greater urgency of global emissions reductions makes US non-participation relatively more problematic than it was during the 2000s under the Kyoto Protocol.

There is, however, room for cautious optimism, as several papers in this collection express. Sprinz et al.’s analysis shows that only in some scenarios does US recalcitrance lead to widespread defection, while in some other constellations it can lead to others joining the ‘club’. Both Pickering et al., and Urpelainen and Van de Graaf, find that the flexible design of the Paris Agreement, with its system of national pledges and actions, should be more resilient than that of the Kyoto Protocol. The economic and technological landscape is also very different from what it was in the 2000s. Urpelainen and Van de Graaf observe that cutting emissions is becoming easier with the cost of low-carbon technologies falling. The Trump Administration’s support for the coal and oil industry, as well as gas production, will not stop the transition to clean energy that is underway. The US coal industry has been in decline mostly because natural gas is the preferred fuel for new installations on economic grounds. Wind and solar power in many instances are already cheaper than fossil fuel alternatives, and they keep getting cheaper (Galik et al., 2017). The US Administration simply does not have the power to stem this tide, and if it did, it would impose economic damage on the country.

All this leads Urpelainen and Van de Graaf to agree with Galik et al. that US domestic emissions levels are unlikely to rise, even without favourable federal climate policies. Flatlining emissions, however, are not enough. The yardstick should, instead, be the targeted emissions reductions under the US NDC, and the far stronger reductions necessary to achieve the Paris Agreement’s long-term goals.

Sub-national actors, such as US states, cities, businesses and other stakeholders – many of which have long been leaders on clean energy policy – now have an even more important role to play in compensating for federal inaction (Chen et al., 2018; Galik et al., 2017; Pickering et al., 2018). Many US states already have instruments such as renewable portfolio standards in place, and several states have made strong commitments and achieved recent progress – for example California’s extension of its cap-and-trade programme, and the tightening of the cap under the North-Eastern Regional Greenhouse Gas Initiative carbon trading programme (Arroyo, 2017; Narassimhan, Gallagher, Koester, & Alejo, 2018). Many US States, cities and other stakeholders have also pledged to uphold the US NDC under the Paris Agreement within their own jurisdictions.²

At the international level, US abdication of any leadership role has opened up new opportunities for plurilateral collaboration. Urpelainen and Van de Graaf see scope for deeper engagement by Europe with China and India, emphasizing the co-benefits of national and internationally co-ordinated climate action. Some closer EU–China–India engagement is taking place, although European leaders’ attention has been predominantly on European issues including Brexit and other manifestations of the rise of populism. China meanwhile is pushing ahead with its transition to cleaner technologies, motivated by domestic environmental concerns and the prospect of industrial leadership in new technologies. India has begun implementing ambitious plans for rapid and large deployment of renewable energy. However, it remains to be seen to what extent individual countries or new coalitions proactively take on a leadership role in the international climate policy regime.

If the world is to achieve the Paris Agreement’s goal of remaining ‘well below’ a 2-degree temperature increase, and pursuing efforts to 1.5 degrees, there is no room for any country or region of the world to remain a high-carbon reservation. The remaining future global carbon budget is already small (Le Quéré et al., 2017), and any one nation spending it with profligacy would impose disproportionate – and most probably unacceptable – constraints on the others. Thankfully, such a scenario remains unlikely, even under the climate-sceptic Trump Presidency. Technological progress with low carbon energy technologies has been such that the economic and business case for them is becoming ever stronger. The calls by President Trump and like-minded politicians anywhere in the world to perpetuate a twentieth-century high polluting energy and industrial system now ring increasingly hollow in the face of mega-trends in the other direction. And whoever becomes the next President of the US will have a splendid opportunity to differentiate her or his climate policy from Trump’s backpedalling.