World leaders will converge on New York on Monday for the United Nations' Climate Action Summit in the latest effort to tackle an issue increasingly viewed as a global crisis.
The spectre of climate change - and its stark consequences - has hung over the world for years and arguments over how it should be addressed continue to rage.
Just who or what is to blame, and whether it should even be a cause of such widespread concern to begin with, has sparked fierce debate.
It is decades since researchers first began discussing the idea that human-made carbon emissions were causing climate change.
Few scientific theories have proved as controversial, with global warming having faced resistance from researchers, the media, strands of political opinion and business interests.
As decision-makers prepare to debate the issue once more, acceptance among researchers and the mainstream press, at least, is now almost universal.
Few have followed the debate more closely than Professor Christoph Schär, of the Institute for Atmospheric and Climate Science at the Swiss Federal Institute of Technology in Zurich, Switzerland. Prof Schär has been publishing scientific papers about the climate since the 1980s.
“The first report with broad impact was 1978. Many scientists didn’t believe in climate change; they had valid concerns and questions,” he said.
“One question was that the observed data series was short and, for 1880 to 1950, good observations were sparse. The data had never been taken to detect climate change, but to observe the weather, so there were open questions.
“There were quite a large number of critical papers. If somebody raises objections, these objections have to be followed up. This has happened with hundreds of papers.”
Among the most significant scientific doubters was Professor Richard Lindzen who published a paper in 1990 entitled, “Some Coolness Concerning Global Warming” and became a prominent critic of the received wisdom. The Massachusetts Institute of Technology meteorology professor, who retired in 2013, nevertheless worked on Intergovernmental Panel on Climate Change (IPCC) reports.
Particular controversy developed in 2009, when emails from the Climatic Research Unit (CRU) at the University of East Anglia (UEA) in Norwich, United Kingdom, were accessed by hackers and made public.
In a scandal dubbed “Climategate”, some commentators argued that these emails showed that efforts were being made by scientists to suppress results that cast doubt on the extent of climate change.
Asher Minns, executive director of the Tyndall Centre for Climate Change Research at the UEA, said the episode may, ultimately, have been positive.
“It focused even more scrutiny on the science by multiple interested panels in the UK and US and it also showed how robust the science was,” he said.
This increased scrutiny, he suggested, could have increased political efforts to combat climate change and paved the way for the 2015 Paris agreement, which aims to intensify international efforts to combat climate change so that temperature rises can, ideally, be limited to 1.5°C.
The scientific evidence is now “pretty much bulletproof”, says Mr Minns, and the question of whether human-induced climate change is happening is “a debate that’s done with”.
Echoing this, Prof Schär says that, for the past decade or so, climate change has become “an accepted issue” among climate researchers.
“The range of opinions has become much narrower among scientists, because the evidence generated by a large number of studies is convincing,” he said.
“We’ve seen the planet has indeed become much warmer. There’s no doubt about the warming itself anymore.”
The Arabian Gulf is one area, he says, that has been shown to be warming and, globally, observed data is largely following the predictions of climate-change models.
Nevertheless, outside the world of climate research, there remain voices sceptical of the idea that the world faces a climate emergency.
In a survey of public opinion in 23 countries published in May, 18 percent of respondents in Indonesia agreed with the idea that human activity “is not responsible at all” for climate change, the highest figure of any country. Saudi Arabia was second, at 16 percent, and the United States third, at 13 percent.
Indeed Republicanism in the United States “remains shot through with climate change denial”, according to Bob Ward, policy and communications director at the London School of Economics’ Grantham Research Institute on Climate Change and the Environment.
In some western countries, he says an “alliance of private sector fossil fuel interests and a strand of conservative ideology opposed to business regulation” has given climate change denial a significant presence in public debate.
Recent news reports have said that lobbyists, researchers and lawmakers opposed to efforts to clamp down on carbon emissions have targeted UN and European Union leaders to argue against the idea that the world faces significant consequences because of climate change.
Among the groups variously described as climate change deniers or sceptics is the UK-based Global Warming Policy Foundation, which includes British politicians and academics on its board of governors.
Dr Benny Peiser, the group’s director, says that the “real divide from a scientific point of view” today is between “Doomsday prophets” and people who think that global warming is “much slower than predicted and isn’t a disaster in the foreseeable future”.
“There’s perhaps a scientific consensus that carbon dioxide emissions are contributing to global warming. There’s no scientific consensus that we’re facing Armageddon,” he said.
People who hold this view – that climate change is happening, but that it is less harmful than often said – “cherry pick the evidence”, according to Mr Ward.
“This is a cynical tactic by climate change deniers who previously denied that the Earth was warming. They realise that’s simply untenable, so they’ve shifted to a different argument – the so-called lukewarmer argument,” he said.
“They ignore the evidence that impacts are mounting and growing. They’re not honest assessments of the science.”