Seldom can the great and the good of the world have been so united in such a chorus of condemnation. And seldom can their hypocrisy and self-righteous self-interest been so nakedly displayed.

On Thursday, President Donald Trump announced he would withdraw the US from the Paris Agreement, the 2015 international accord under which the world’s nations proclaimed their intention to limit global warming. Speaking – with a nice touch of irony – in the White House rose garden, Trump complained that the Paris accord was “very unfair” to the US. “So we’re getting out,” the president declared, promising that he would seek to negotiate a better deal.

The denunciations followed thick and fast. In a leaked joint European Union-China statement, Chinese premier Li Keqiang joined with EU leaders to say that combating climate change is “more important than ever”. Li pledged that China would not shirk its “international responsibility” and would work with the EU to uphold the Paris Agreement.

In the US, Trump’s predecessor Barack Obama, on whose watch the Paris deal was signed, said the new administration had aligned itself with those who “reject the future”. And a whole parade of business leaders lined up to slam the president’s stance, among them the heads of corporate giants Apple, Google, Amazon and Facebook.

Even Lloyd Blankfein, chief executive of Goldman Sachs, took to Twitter for the first time ever to criticise Trump’s abrogation of the Paris accord, calling it “a setback for the environment and for the US’s leadership position in the world”.

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Blankfein, one of the most reviled figures in global business, who is widely regarded as a symbol of everything that is worst in the banking industry, clearly figured this was a neat opportunity to burnish his own muddied reputation at zero cost.

Doubtless, many of Trump’s critics were motivated by similar considerations. Trump’s withdrawal from the Paris Agreement was an easy target. Denouncing it allowed them to signal their own high moral virtues simply by contrasting their professed concern for the environment to the president’s narrow economic nationalism.

But here’s the rub. While Trump’s decision to pull out of Paris may well have far-reaching consequences for international diplomacy and on shifting global alliances, one thing on which it will have little or no effect is the earth’s climate.

The most obvious reason Trump’s announcement will have no discernible impact on the environment is that the Paris accord was never legally binding. Compliance with the self-determined targets for greenhouse gas emissions was entirely voluntary. As a result, US withdrawal from the agreement was a wholly symbolic gesture. The Trump administration had no need to pull out of Paris in order to begin to push back against environmental standards introduced under Obama. Indeed, Trump signed an executive order in March ordering precisely such a roll-back.

US withdrawal will not mean the death of the Paris climate accord

But if the US withdrawal from Paris was a symbolic step, it is also true that the Paris Agreement was itself largely symbolic, and that the accord has had, would have had, and will have little effect on constraining carbon emissions.

That might seem at first like an outrageous statement, especially since global emissions appear to have reached a plateau over the last few years since the world’s big polluters converged on the agreement. But on closer inspection, it becomes apparent that the declines in the greenhouse gases pumped out by the US, EU and even China, the world’s biggest emitter, have much less to do with environmental policy than with cold hard economics.

Take the US. Over the last 10 years, annual US carbon emissions have fallen by around 10 per cent. But the reason for this decline was not Obama’s Clean Power Plan, or anything to do with the Paris accord. The cause of the initial fall in carbon output was the economic slump that followed the 2008 financial crisis; a slower economy, and especially one building fewer houses, required less energy, which in turn meant fewer emissions.

And the subsequent fall in the amount of carbon released into the atmosphere even as the US economy recovered was caused by the discovery and exploitation of vast resources of cheap shale gas, first in the Marcellus formation of the US northeast, now in the Permian basin of Texas. Because of its cost advantages, gas overtook coal as the main fuel for US electricity generation last year. And because burning gas releases less carbon than burning coal for the same energy output, US greenhouse gas emissions are falling.

World leaders renew vow to fight climate change after Trump pulls US out of Paris agreement

That is not going to change. No one is going to rush out and dig new coal mines simply because Trump has pulled out of the Paris accord – not when new gas discoveries are rendering coal-fired electricity generation less and less competitive each year. In short, US emissions are falling regardless of the environmental policies of either Obama or Trump.

Similarly in China, economic realities are proving far more effective at constraining emissions than environmental policies. As China reaches the end of its development phase driven largely by investment in housing and infrastructure, growth in highly energy-intensive heavy industrial sectors has slowed and even gone into reverse.

As a result, energy demand growth has dropped steeply. In turn that has allowed energy producers to close down their most inefficient generators, which also tend to be their most carbon-intensive. China passed its peak coal use two years ago. Since then, carbon emissions have been flat to a touch lower.

In a nutshell, the emissions targets proclaimed in the Paris Agreement simply reflected reductions that were already happening, and would happen anyway, because of deeper economic forces. That means Trump’s withdrawal from the Paris accord will have little effect on either emissions or the world’s climate.

And it also means the condemnations of Trump’s announcement are just meaningless virtue-signalling; nothing but hot air.