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Nature rounds up reaction from researchers around the world to US President Donald Trump's decision to pull the United States out of the Paris climate agreement.

Jane Lubchenco, marine ecologist at Oregon State University in Corvallis and former administrator of the US National Oceanic and Atmospheric Administration:

Where to start? President Trump’s decision to withdraw from the Paris Agreement shows a blatant disregard for the wishes of most Americans and business leaders, an irresponsible and callous dismissal of the health, safety and economic well-being of Americans, a moral emptiness in ignoring impacts to the poorest people in the US and around the world, and gross ignorance about overwhelming scientific evidence. Far from “protecting America” as the president stated, withdrawing from Paris will make America more vulnerable and diminish its world leadership. It is terrifying that the individual who should be leading the rest of the world is so arrogant and irresponsible.

Our collective future and that of much of the rest of life on Earth depends in part on confronting climate change and ocean acidification. Doing so requires global collective action. It’s hard to imagine anyone consciously choosing to leave a legacy of impoverishment, economic disruption, increasingly bizarre weather, health impacts ranging from heat strokes to spread of diseases, rising sea levels and flooding — but that is just what the president has done. Moreover, the new path and the president’s proposed budget would forego significant economic opportunities.

Fortunately, mayors, governors, faith leaders, scientists and business executives understand what is at risk, respect the scientific evidence, and see the powerful economic potential and moral imperative in shifting to renewable energy, preparing to adapt to changes already under way, and investing in science and monitoring to guide future decisions. There is strong economic momentum to continue these actions, but they would have been accelerated and more effective with strong action and forceful leadership from the president. Alas, he has chosen instead to stick his head in the sand.

Jean-Pascal van Ypersele, climate scientist at the Catholic University of Louvain in Louvain-la-Neuve, Belgium, and former vice-chair of the Intergovernmental Panel on Climate Change (IPCC):

President Trump's decision to introduce a request to leave the Paris agreement in 2020 is regrettable. It negates both the results of (1) serious scientific analyses (many made by US scientists) about the urgency to address the climate change problem; and (2) the rigorous assessment made by the IPCC about the technical and socio-economic aspects of response options, including their significant co-benefits in other areas like air quality, energy security, health or job creation.

President Trump's speech attempting to justify his decision was an amazing concentrate of some of the worst climate confusers' and fossil lobbyists' arguments.

The United States has played a very important role over the years to foster and nurture quality scientific research about the causes and processes of climate change, the potential risks and the response options. It is a shame that this leadership by the US is temporarily lost. Others in Europe, Asia and emerging economies will most likely compensate for this loss, transforming a difficulty into an opportunity.

Almost 150 countries, representing close to 85% of greenhouse-gas emissions, have now ratified the Paris agreement. Removing the US contribution from this total still leaves almost two-thirds of the emissions covered by the remaining countries, which have confirmed their plans to honour the agreement. This means that the transition to a low-carbon economy, now seen as an opportunity by many, will continue unabated, with or without the US.

Susanne Dröge, climate-policy researcher at the German Institute for International and Security Affairs in Berlin:

The US pull-out is bad news for the international climate process. The United Nations negotiations need to focus on implementation. This will become more difficult, also because it is unclear how Trump wants to renegotiate the agreement. Political attention is absorbed due to the US move, attention that is needed for much more important issues such as bringing climate action forward.

Thomas Stocker, former co-chair of climate science for the IPCC, and climate and environmental physicist at the University of Bern, Switzerland:

Trump’s decision to ignore scientific facts of climate disruption and the high risks of climate-change impacts is irresponsible not only towards his own people but to all people and life on this planet. The US administration prefers old technology over innovation and transformation. It is rejecting the enormous benefits and returns that leadership in the next industrial revolution — decarbonization — has to offer.

The United States is the second-biggest emitter of carbon dioxide worldwide (and has contributed, with Europe, 52% of the share of cumulative carbon emissions since industrialization). It is withdrawing from its historical responsibility to reduce greenhouse-gas emissions and lead the way forward. Given the continuous commitment of most countries to reduce emissions, and the firm leadership of Europe, China and Russia in shaping the transformation towards a decarbonized economy, the United States runs the risk of being left behind and missing one of the greatest economic opportunities of our time.

Susan Lozier, oceanographer at Duke University in Durham, North Carolina:

Trump’s decision is as short-sighted as it is disheartening. The oceans already hold about 35% of the carbon dioxide that has been released to the atmosphere since the Industrial Revolution. Nothing good for the ocean and the life it contains comes from this storage. Whether you simply admire marine life or count on it for your livelihood, this decision shouldn’t sit well. An already fragile ocean is further imperilled.

Kevin Anderson, deputy director of the Tyndall Centre for Climate Change Research in Manchester, UK:

Beneath the veil of the low-carbon rhetoric of the Paris agreement, there is no evidence of a mitigation agenda even approaching the scale of our international obligations. Trump’s ostensibly reckless decision can be used either as a further excuse for continued apathy or as a catalyst for transforming our comfortable rhetoric into meaningful and timely action. In that regard, Trump’s ignorant blunderings can inadvertently be a force for good. Channelled positively, it could yet oblige the rest of us to forego our increasing reliance on speculative technologies and incremental carbon prices and begin to shape a mitigation agenda that is fit for purpose.

We need to take Trump at face value. If he is successful in returning the US to a coal-based economy (and that looks unlikely), then the European Union needs to borrow his ‘protectionist’ cloak and put in place carbon standards for imported goods.

Finally, let’s keep Trump in context. US states and cities have considerable devolved powers — and many of their leaders continue to favour climate science.

Joeri Rogelj, energy researcher at the International Institute for Applied Systems Analysis in Laxenburg, Austria:

The US withdrawing from the Paris agreement is damaging for international collaborative efforts to limit climate change, but will likely be most damaging to the US economy itself. The US has decided to sideline itself, internationally, diplomatically and morally — not to prepare itself for the future, but to gaze into the past for a few more years. Many other major economies, including China and the European Union, have indicated their strong commitment to implementing the climate agreement. This signal will spur innovation and business development in these regions. However, the US government refuses to give US businesses such a clear sense of direction and is disregarding the most robust scientific evidence by doing so. By setting research, innovation and business priorities based on misleading short-term political goals, the US will miss the boat and might become a laggard in the global technology and innovation landscape.

The climate issue is a global and a cumulative problem that was not solved in one go with the Paris agreement, but requires incremental updates and adjustments of climate action. To halt climate change, global carbon dioxide emissions need to be capped and annual emissions need to be brought to zero. One country failing on its commitments thus implies that deeper emissions cuts are required in other regions or later in the future. This makes the problem harder and less equitable to solve.

Oliver Geden, visiting research fellow at the Institute for Science, Innovation and Society, University of Oxford, UK:

The United States gave up climate leadership on the day of Trump's inauguration. In March, Trump announced his rollback of Obama-era climate regulations. So it’s been clear for some time that the US federal government is not going to act on climate change in the foreseeable future. Withdrawing from the Paris agreement is just another step, although a highly symbolic one.

For now, it seems that this step reunites the rest of the world, but only on the symbolic level. It is quite easy for a government to declare that it will stick to the Paris agreement. But in a regime of bottom-up climate policy that still aims to achieve top-down temperature targets, other governments would need to step up and declare that they increase their mitigation pledges — and act accordingly. That's obviously the harder thing to do.

Katharine Hayhoe, director of the Climate Science Center at Texas Tech University in Lubbock:

The biggest loser from the decision could be the United States itself. Why? Because although the Paris agreement is a climate treaty, a triumph for evidence-based decision-making, it’s also much more: a trade agreement, an investment blueprint and a strong incentive for innovation in the energy and the economy of the future.

Earlier this week, India broke its own record for the lowest bids for electricity from solar power. Last month, Ernst & Young listed its most attractive markets for renewables: the United States came third, behind China and India. And earlier this year, China announced a US$360-billion investment in clean energy to create 13 million new jobs. The US announcement shows that it will be doing its best to turn back the clock, while the rest of the world accelerates into the future.

It’s true that federal policy is only one piece of the pie, and not even the biggest one. Cities, states and private industry have arguably played an even more important role in shaping US technological innovation, energy mix and carbon emissions over the past ten years, even under proactive federal climate policy. But Trump’s announcement sends a strong message that the US would rather be one of only two nations in the world that is not interested in preventing “dangerous anthropogenic interference with the climate system”. That other nation? War-torn Syria. (Note that Nicaragua is also opting out of the agreement — but in that case it’s because it wants to do more, not less.)

Atte Korhola, climate-policy and environmental-change researcher at the University of Helsinki, Finland:

The US withdrawal from the Paris climate agreement is very disappointing and unfavourable for the United States and the rest of the world. Many climate scientists consider the Paris agreement insufficient for limiting warming to 2 °C, so the task will be all the harder now. However, international climate agreements have not been very effective so far in reducing emissions, so there is still hope that the United States will proceed on other fronts, such as through bilateral agreements, clean-tech development and investing in new ‘negative emissions’ technologies.

But the plans by the Trump administration to cut more than 30% from the Environmental Protection Agency’s budget and about 70% of the funding for renewable-energy research and development unfortunately don’t point in this direction. The situation in all respects is quite depressing. The only hope is that the US states, cities and companies will continue their effective work to cut emissions.

Benjamin Santer, climate scientist at Lawrence Livermore National Laboratory in California:

In Shakespeare's Julius Caesar, Brutus said these famous lines: "There is a tide in the affairs of men. Which, taken at the flood, leads on to fortune; Omitted, all the voyage of their life is bound in shallows and in miseries."

Today, the United States pulled out of the Paris climate agreement and missed the rising tide. Far from "Making America Great Again", this decision condemns the United States to becoming one of the 'has-beens' of history. We will become increasingly irrelevant to the rest of the world. They are going forward; we are going backward.

Hans Joachim Schellnhuber, director of the Potsdam Institute for Climate Impact Research in Potsdam, Germany:

It will not substantially hamper global climate progress if the US really quits the Paris agreement, but it will hurt the American economy and society alike. China and Europe have become world leaders on the path towards green development already and will strengthen their position if the US slips back at the national level. Innovative states such as California, the world's sixth-largest economy, will keep going for climate action, however. The Washington people around Trump hide in the trenches of the past instead of building the future. They fail to recognize that the climate wars are over, while the race for sustainable prosperity is on.

David Victor, climate-policy expert at the University of California, San Diego:

The odds of other countries renegotiating Paris are low to zero. The whole structure of the Paris agreement is to allow countries to set their own commitments. So there is nobody to negotiate with if a country needs to adjust. This claim that the problem with Paris is that the deal wasn’t struck properly is a disingenuous argument that is not informed by how Paris actually works, nor by any reality about how the world actually crafts big complex deals.

Glen Peters, climate-policy expert at the Center for International Climate and Environmental Research in Oslo:

It seems that Trump and his advisers have completely misconceived what the Paris agreement is. All his reasons for pulling out were basically the concessions that forged the path to the creation of the Paris agreement. Paris is the agreement that Trump desires!

The genius of Paris is to allow countries to put forward emission pledges that they feel they can meet (Nationally Determined Contributions). The US pledge was put forward by the US, alone. Countries are already enacting their emissions pledges, and — as could be expected by the design of the Paris agreement — most countries show signs of exceeding their conservative emissions pledges. China looks like it may peak its emissions a decade earlier than pledged. India has slowed down on coal consumption and sped up on solar deployment. Even the US has made great strides in the past decade, and was poised to make more.

The irony is that Paris is working, because it is designed to be flexible to the national circumstances that Trump himself champions!

Myles Allen, climate scientist at the University of Oxford, UK:

The Paris agreement is far from perfect, and one of its problems, as we are seeing now, is the lack of any real penalty for pulling out. Talk of trade sanctions is pure hyperbole and the last thing the world needs right now. But perhaps it is time to think about a simple product label: “Made in and sourced from regions that support the Paris climate agreement.” With California and Oregon insisting they will abide by the terms of the Paris agreement anyway, we could then have an interesting discussion about whether and how this could be stuck on Californian orange juice — or computers containing Intel chips.

Painful though it may be for the agreement’s supporters, acknowledging that it isn’t perfect must also be part of the response to this proposal to renegotiate the US terms of participation. Some, no doubt, will see this as just a distraction tactic. Others would argue that even to begin to negotiate would be to deliver Trump an ill-deserved political “win”. But thinking beyond 2020, we will eventually need to work out how to make the agreement both more effective and more acceptable to nations, companies and individuals that own substantial fossil-fuel reserves — or the US won’t be the last to leave.

Benjamin Sanderson, climate modeller at the National Center for Atmospheric Research in Boulder, Colorado:

Today's announcement that the US will depart from the Paris agreement is unfortunate, but it is no time for fatalism. From this point forward, there are now large uncertainties in global mitigation efforts over the coming years. The long-term evolution of the climate hinges on what other countries, and agents both within and outside of the US, do in response to the US departure from the agreement.

A complete failure of the agreement at this point, with business-as-usual growth for another decade, would almost certainly commit the planet to significantly more warming than the Paris goals, and the human consequences of this would be catastrophic. However, some major remaining signatories have expressed a commitment to increasing mitigation goals, and within the US, many states, cities and some of the country's largest companies are committed to mitigation irrespective of the US participation in the agreement.

Decisions made today are made in the context of confident projections of future warming with continued emissions, but clearly there is more to do to better characterize the human and economic consequences of delaying action on climate change and how to frame these issues in the context of other concerns. The role of the scientific community is more important than ever, both to continue to provide the best possible research to inform decisions, and to communicate any risks associated with further emissions in a publicly accessible fashion.