The US quitting the Paris climate agreement will only make things worse

US President Donald Trump has announced that he will decide this week whether to follow through on his threat to pull out of the Paris climate agreement. Some news outlets are already reporting that he has decided to leave. But would the world be better off if the US stays or goes?

An array of environmental groups, businesses and leaders of other countries are calling for the US to stay. While their reasons vary, a common theme is that the US has both a moral obligation to play its part in global climate policy, and an economic interest in doing so.

Many of these arguments rely on the US taking strong domestic climate action. But Trump has already begun dismantling a raft of Obama-era climate policies. Unless reversed, these moves will ruin any chance of the US meeting its current target of reducing emissions by 26-28% below 2005 levels by 2025. Trump’s draft budget would also drastically cut US climate aid to developing nations.

With this in mind, the question becomes: is global climate policy better served if a recalcitrant major power stays on board or if it goes its own way?

Considered this way, the arguments for leaving become harder to dismiss. In two thought-provoking commentaries, climate policy experts Luke Kemp of the Australian National University and Matthew Hoffmann of the University of Toronto argue that the world would actually better off if the US pulls out. Two reasons loom large in these analyses: the US would be prevented from white-anting further UN negotiations, and the backlash to its withdrawal would spur on China, Europe and other nations to greater action.

But if we look closely at each argument, it’s far from clear that leaving is the lesser evil.

Sidelining US obstruction?

It is not a foregone conclusion that the US, if it stayed, would be able to hold the talks hostage or successfully water down rules aimed at preventing countries from backsliding on their targets. Granted, the UN’s consensus-based model makes this a real danger, but climate negotiations have reached decisions even in the face of opposition from a major power, as happened when Russia was overridden in 2012.

What’s more, withdrawing wouldn’t necessarily stop the US trying to play spoiler anyway. Formal withdrawal from Paris could take until late 2020. Even then (assuming a more progressive president isn’t elected shortly after that), the US could still cause trouble by remaining within the Agreement’s parent treaty, the United Nations Framework Convention on Climate Change (UNFCCC).

The “nuclear option” of withdrawing from the UNFCCC itself would create further problems. Rejoining it would be likely to require the approval of the US Senate (which, given its current makeup, seems highly doubtful), whereas a new administration could rejoin Paris through a Presidential-executive agreement.

Will other countries do more?

Major economies like China and India have their own domestic reasons for cutting emissions, not least local air pollution and energy security. Both China and India plan to stick with the agreement regardless of what the US does. There are signs that they will exceed their current climate targets, thus more than outweighing the increase in emissions resulting from US climate policy rollbacks. We can’t be confident that US withdrawal would encourage China and India to do any more than they are already doing now.

The Kyoto Protocol provides a sobering precedent: while those countries that stayed in the protocol complied with their targets, none of them raised their targets to take up the slack when the US withdrew.

Writing in The Conversation, Luke Kemp suggests that US withdrawal could trigger countries to slap carbon tariffs on US imports. Large economies such as the European Union and China could attempt to do so outside the Paris framework, but few (if any) major trading partners will be eager for a trade war with the US.

US withdrawal is just as likely to demotivate other countries as energise them. Nations with less domestic momentum on climate policy may likewise pull out, water down their current or future targets, or fail to ratify Paris. For now, Australia plans to stay in, regardless of what the US does. A greater risk is Russia, the world’s fifth-largest emitter, which doesn’t plan to ratify the Paris Agreement until at least 2019. Other reluctant countries whose stance may be influenced by what the US does include Saudi Arabia and the Philippines (which have ratified Paris) and Iran and Turkey (which have not).

Fallout for multilateralism

Neither of the two arguments I’ve discussed so far amounts to a solid case for leaving. Meanwhile, there is another key reason for the US to stay: the risk that its withdrawal would strike a broader blow to the principle of multilateralism – the idea that tough global problems need to be solved through inclusive cooperation, not unilateral action or a spaghetti bowl of bilateral deals.

The UN climate talks are firmly integrated into the bigger picture of global diplomacy, and the Paris deal itself was seen as a huge achievement for multilateralism. Both the US and Australia previously suffered significant diplomatic fallout for deciding to stay out of Kyoto.

The international reaction to withdrawal from Paris would be even harsher. US participation was a prerequisite for China and India to sign up, and key elements of the treaty were designed to enable the US to join. To pull out after all that would be an egregious violation of trust and goodwill.

Some might welcome the resulting diminution of Trump’s ability to push through his agenda globally. But ultimately the erosion of multilateralism – already damaged by Brexit and Trump’s abrasive trip to Europe – is in no country’s interest if it undermines international trust and cooperation on issues like trade, public health and security.

Treaty withdrawal is uncommon in international diplomacy, arguably much more so than non-compliance. One of the few studies on this issue found that only 3.5% of multilateral treaties had any withdrawals. As most treaty exits are concentrated in a small number of treaties, the risk of knock-on effects is a real concern. When Canada withdrew from Kyoto, for example, it cited US non-participation as a justification.

Given how badly the US is behaving on climate policy, it is tempting to argue that it needs some time out from Paris until it’s ready to play nicely with the other kids again. But the fallout from US withdrawal could last far longer than a one- or two-term Republican presidency.

Withdrawal from Paris would signal, more emphatically than domestic inaction alone, that a major polluter is ready to turn its back on the international consensus that a 2℃ warmer world should be avoided. That would be bad, not just for international cooperation on climate change, but also for the broader project of multilateralism.

Thanks to Christian Downie, John Dryzek, Mark Howden, Luke Kemp (whom the author debated at an event held by the ANU Climate Change Institute), Peter Lawrence and Jeff McGee for insightful and lively discussions on this topic.