Researchers and green groups pointed to a chasm between the radical response demanded by a growing mass movement around the world and the glacial pace of policy decisions by governments to speed efforts to keep global warming to agreed limits.
As negotiations ended on Thursday evening, U.N. climate chief Patricia Espinosa reminded states they must deliver on the 2015 Paris Agreement, now ratified by 185 nations.
"People are demanding results - whether that's online or in the streets - and we must show we are taking responsibility," she said in a statement.
Noting progress in "several important areas", she said outstanding issues on rules for implementing the Paris accord should be resolved by December, when the annual U.N. climate conference in Chile takes place.
That leap was needed "to live up to our collective responsibility and ensure that ambition is raised to the extent that the worst impacts of climate change can be avoided", she added.
Some development specialists at the Bonn talks highlighted how rising global temperatures are already super-charging water shortages in India, powerful storms hitting poor communities in Mozambique and other extremes.
"This (U.N.) process needs to be urgently rebooted in a way that responds to the terrifying reality facing those on the frontline of climate change," said Harjeet Singh, who leads international charity ActionAid's climate change work.
But there was little sign of government officials in Bonn heeding that plea, with advances restricted to technical issues.
They settled on a process for a December review of a key mechanism to address "loss and damage" caused by climate and weather extremes and rising seas.
And they inched forward on rules to put in place new markets for carbon credits, due to be finalised in Chile.
But a bitter dispute erupted over how to treat the scientific findings of a flagship report, requested by the talks, on limiting global warming to 1.5 degrees Celsius (2.7F), the lower goal set in the Paris pact.
A handful of countries, led by oil-rich Saudi Arabia, wanted to make note of uncertainties around the science in the report by the Intergovernmental Panel on Climate Change, which outlined potential harms if the 1.5C threshold was breached.
The world is already about 1C hotter than pre-industrial times.
Under a compromise, a Bonn decision praised the 1.5C report as "the best available science", but closed the door to further formal discussion of its findings in the U.N. climate process.
Alden Meyer, strategy director with the Union of Concerned Scientists, said Saudi Arabia's move "can't prevent scientific fact from continuing to drive the heightened awareness among governments, the business community and the public of the need for an urgent response to the climate crisis".
'ARSONISTS AT THE TABLE'
Lawyers and campaigners, meanwhile, decried the ongoing failure to introduce a "conflict of interest" policy at the negotiations, which they say is needed to stop business bodies and representatives of fossil fuel firms shaping discussions.
Burning of oil, coal and gas to produce energy by the power, industry and transport sectors is the main driver of the emissions heating up the planet.
Some developed countries, including the United States, Australia, the European Union and Norway, have consistently blocked creation of a conflict of interest policy.
That continued in Bonn, according to campaign group Corporate Accountability, despite a letter signed by 300 environmental, development and transparency organisations calling on the countries to shift their stance.
Data released during the talks by the Climate Investigations Center showed that nearly 6,500 delegates from fossil fuel companies or associations that lobby on their behalf attended U.N. climate talks as "observers" between 1995 and 2018.
"Everyone is running around talking about how the house is on fire, but the arsonists are still at the table," Nathan Thanki of the Global Campaign to Demand Climate Justice told journalists.
The next major opportunity for governments to make commitments to cut emissions further and faster, and put new money on the table to help developing nations cope with climate change, will be at a September summit organised by the U.N. secretary-general.
There, about 80 countries have signalled they may commit to more ambitious national climate action plans as a 2020 Paris Agreement deadline for strengthening those plans looms.
Campaigners are also raising pressure on wealthy countries to double their contributions to the international Green Climate Fund as part of a promise to provide $100 billion a year to poorer nations to develop cleanly and adapt to a warmer world.
Jean Su, energy director at the Center for Biological Diversity, said the main obstacle to "real climate action" was "the sheer lack of political will"."We urge world leaders to listen to the millions of people in the streets and act with humanity and courage to turn this crisis around," she said.