0349 GMT April 24, 2019
"We are using the sky as an open sewer, it's insane," the former US vice president, Al Gore, told the conference, noting that humanity belches 110 million tons of heat-trapping pollution into the atmosphere every day, AFP reported.
"Will we change? That's what the Global Climate Action Summit is all about."
Over three days, thousands of delegates from the private and public sectors showcased policies and innovations aimed at reducing that flow of greenhouse gases.
Cities are converting to all-electric vehicle fleets and setting deadlines for banishing gas-guzzling cars from their roads; companies have vowed to operate only with renewable energy, including a few smokestack multinationals in the developing world.
"Clean and green is profitable," Mahendra Singhi, the CEO of Dalmia Cement Ltd. in India told AFP.
Investors managing fortunes said they were purging coal, oil and gas from their portfolios; young entrepreneurs showed off energy-efficiency apps and inventions.
Provincial and state governors in tropical countries vowed to empower indigenous peoples who have been managing forests sustainably since before ‘sustainable’ was even a word.
But all these efforts may be in vain, the delegates warned, if national governments fail to do their part.
"Now is the time for all leaders to step up and take bold action," they said in an appeal framed as a Call to Action.
"We call on the national governments of the world to step up ambition now... and chart a clear path to your zero-carbon future."
"We have enough critical mass in the private sector now to help spur that political process," said Paul Polman, the CEO of Unilever, one of the world's largest consumer goods companies.
The 196-nation Paris Agreement, inked in 2015, enjoins nations to cap global warming this century at ‘well below’ 2°C (3.6°F), and to strive for a ceiling of 1.5°C if possible.
With only 1°C of warming so far, Earth has seen a crescendo of deadly heatwaves, droughts, floods and superstorms engorged by rising seas.
But UN talks to implement the treaty, which goes into effect in 2020, have stalled over disagreements on money to help poor countries green their economies and brace for unavoidable climate impacts.
More urgent still is the so-called ‘ambition gap’ between voluntary national commitments to curb carbon pollution, and what is needed to keep global temperature rises under 2°C.
Even if all nations honor current pledges — many of which depend on climate finance that does not yet exist — the world will heat up by an unbearable 3.5°C, scientists have calculated.
'Kick this monster's ass'
A climate summit convened by UN Secretary-General Antonio Guterres next fall "is what is going to determine whether we can save the Paris Agreement or not", said David Paul, the environment minister for the Marshall Islands.
The transition to a greener global economy has been hampered by US President Donald Trump, who opted out of the Paris pact months after taking office, saying it would pose a ‘burden’ on the US economy.
Trump has also taken a sledge hammer to the climate policies of his predecessor, Barack Obama, relaxing pollution rules for coal-fired power plants and rolling back car-mileage standards.
"Withdrawing American leadership from an issue that is life or death is one of the single greatest acts of irresponsibility of a president anywhere, anytime," the former US secretary of state and presidential candidate, John Kerry, told the plenary, to thunderous applause.
But the American people are ‘way smarter’, he added, pointing to the conference and climate change policies in dozens of states across the country.
"The zero-carbon economy is the growth story of the 21st century," Nicholas Stern, an economist at Grantham Research Institute on Climate Change and the Environment at the London School of Economics, told AFP.
"There is no long-run high carbon growth story."
The final verdict was delivered by Hollywood veteran Harrison Ford.
"Nature doesn't need people, people need Nature," he told the plenary.
"So let's turn off our phones, let's roll up our sleeves and let's kick this monster's ass."