Merkel and France's new President Emmanuel Macron knew what was coming this week after Trump failed to restate climate commitments with the other G7 leaders.
Trump's decision to withdraw from the Paris Agreement is a moment of clarity about the Trump Administration.
Even from Trump's standpoint, quitting Paris was unnecessary. Trump simply could have adjusted America's CO2 targets if he had wanted but still stayed in the circle. As it is, withdrawing takes four years and would come into effect just after the 2020 presidential election. A country can re-join immediately.
But staying in and leading on a globally-vital issue is important, as is maintaining collective pressure on countries to meet emissions goals. America, as one of the two worst carbon emitters, has a responsibility to pull its weight. And now Washington's clout and support is missing.
Battling climate change is also all about jobs and goods. Foreign Policy writes: "Action on climate and economic growth go hand in hand, and are mutually reinforcing. That is why twice as much money was invested worldwide in renewables last year as in fossil fuels."
This is now and future economic and political territory: from technological competitiveness and innovation to what programmes will be put in place to help workers retrain for required work, as automation rises and old ways are phased out.
Trump said: "I was elected by voters of Pittsburgh, not Paris". The Mayor of Pittsburgh, Bill Peduto, retorted: "I can assure you that we will follow the guidelines of the Paris Agreement for our people, our economy and future". According to a report last year by the Philadelphia-based Keystone Energy Efficiency Alliance, 66,000 people in Pennsylvania work in the renewable energy industry. The Washington Post reports that in total in the US "the coal industry employed 76,572 people in 2014, the latest year for which data is available".
This climate deal withdrawal, Trump's flag-waving pinnacle of his 'America First' approach, looks hugely self-destructive.
'America First' is about isolationism and nationalism, just as the world is at its globalised peak. There have been limits to it: Trump has antagonised Nato allies but hasn't taken it further. He canned the TPP but stuck with Nafta.
In a Wall Street Journal article on 'America First' this week, Trump advisers HR McMaster and Gary Cohn wrote: "The President embarked on his first foreign trip with a clear-eyed outlook that the world is not a 'global community' but an arena where nations, nongovernmental actors and businesses engage and compete for advantage. We bring to this forum unmatched military, political, economic, cultural and moral strength. Rather than deny this elemental nature of international affairs, we embrace it".
In his climate speech, Trump said that the US would negotiate the agreement or a new one that would put American workers first.
The existing agreement "disadvantages the United States, to the exclusive benefit of other countries, leaving American workers, who I love, and taxpayers to absorb the cost". He added: "This agreement is less about the climate and more about other countries gaining a financial advantage over the United States ... We don't want other leaders and other countries laughing at us anymore."
Atlantic writer James Fallows tweeted it was the "clearest-yet revelation that resentment, 'not being laughed at' not 'being taken advantage of' is dead-centre of DJT motivation".
Trump is acting on behalf of the 30-40 per cent of US voters who, polls say, approve of him rather than those who don't. Climate change is an issue of particular concern to Democrat voters but Republicans are more divided. Trump continues to hug his base rather than try to grow it. CFR analyst Micah Zenko tweeted: "Trump's deeply misleading positions on climate change are all GOP orthodoxy. This isn't him, it's his party."
Yet Gallup polling and Brookings Institution research show a majority of Americans are concerned about global warming and believe in the science of it.
Aside from the potential impact on the climate and the US economy, Trump has either knowingly or unknowingly undermined his Administration in the world and within the US. He has ceded power to lead on this issue to powerful US states, cities and companies.
Macron and Canada's Prime Minister Justin Trudeau effectively quarantined the Trump Administration in their reactions to his speech.
Macron, unusually speaking in English from the Elysee Palace - most likely to be understood by the US public - said: "The world believes in you. I know that you are a great nation". Trudeau pointedly said: "We are deeply disappointed that the United States federal government has decided to withdraw from the Paris Agreement". The government, not the people.
Trump felt the wet slap of waves of opposition from all corners.
Merkel said she would keep working to "save our planet".
Macron, who has stressed his determination not to be taken lightly with a handshake wrestle with Trump and a smackdown of Russian President Vladimir Putin, trolled the US President with: "We all share the same responsibility to make our planet great again".
He brought the implications home with: "If we do nothing, our children will know a world of migrations, of wars, of shortage. A dangerous world". He again suggested that any disgruntled US scientists would be welcomed in France. And he cut off any idea of renegotiation with: "We will not renegotiate a less ambitious deal ... There is no Plan B, there is no planet B".
To underline that, France, Germany and Italy issued a joint statement saying the accord cannot be renegotiated.
Tesla and SpaceX CEO Elon Musk said he would leave the President's advisory boards. General Electric CEO Jeff Immelt tweeted: "Disappointed with today's decision on the Paris Agreement. Climate change is real. Industry must now lead and not depend on government."
The governors of New York, California and Washington announced the formation of a climate alliance. Mayors of various US cities said they would uphold the Paris goals. California Governor Jerry Brown, who said "Trump is AWOL but California is on the field, ready for battle", spoke on CNN of holding talks in China on climate.
Trump is now forcing leaders at all levels to take stock and change strategy the way Merkel (supported by Macron) did.
Continuing to pretend that Trump could be handled by conventional diplomatic means and language would have eventually ended up creating a cavern between those leaders and the people they represent. With Trump hugely unpopular and regularly ridiculed, other leaders would look hypocritical not dealing with that reality.
Macron, especially, appears to understand this and his blunt talk has been refreshing so far. It is a pointer for opponents of Trump in the US.
It is also useful for Macron, who faces parliamentary elections this month, and Merkel, up for re-election in September, to define themselves against Trump. They know now that he isn't going to change. And they will see economic advantages in stepping into the sinkhole Trump has opened up. There's the possibility that a grouping of China, the EU, India and wealthy US states such as California and New York can limit the damage by stepping up efforts on climate change.
Josh Barro of Business Insider argues that Trump's climate exit could have a positive effect, increasing pressure "within other countries to act on climate change. This effect would be similar to the surprising way Trump seems to be strengthening the European Union and depressing support for Eurosceptic parties in Europe. Trump is globally unpopular, and he tends to bring discredit on the causes with which he associates himself."
