Two of the world's most influential environmentalists, US politician John Kerry and teenage activist Greta Thunberg, have poured cold water on hopes for success at this year's climate change summit in Glasgow.
The COP26 climate change conference, scheduled to start at the end of this month, is being billed as a make-or-break moment for the Earth's future, with those campaigning against global warming hoping they can convince other countries to join them.
Boris Johnson has previously told world leaders to "grow up" ahead of the summit and listen to scientists warnings about climate change, telling them the event must be a “turning point for humanity”.
But Mr Kerry, the US special presidential envoy for climate, has tempered expectations about the meeting, suggesting talks aimed at cutting emissions will fall short of the target.
He said that talks will likely end with nations still short of the target of cuts in coal and petroleum emissions that are needed to stave off increasingly devastating levels of global warming.
And 18-year-old Ms Thunberg, who inspired a generation of environmentalists with her school strikes, said she believes things will "remain the same" following the conference, although she expects "many nice speeches".
What is COP26?
As part of the Paris Climate Agreement almost every country in the world committed to limiting the global temperature from rising 1.5°C above the preindustrial average.
They then promised to track progress towards that target every five years.
Scheduled to take place in 2020 but postponed because of coronavirus, Glasgow is the first chance for countries to get together and track what progress has been made.
The global temperature is already 1.1°C higher than it was before the industrial revolution - meaning a lot more progress must be made in Glasgow if countries can stick to the 1.5°C commitment.
Those committed to protecting the planet are hoping more countries will forward their individual plans to reduce greenhouse gas emissions - known as their nationally determined contributions or NDC’s.
What did John Kerry say?
The former presidential candidate, who Joe Biden appointed as America's first special presidential envoy for climate, said it would be "wonderful" if every country committed to hit the 1.5°C mark "but some countries just don't have the energy mix yet that allows them to do that".
He praised the United States, Canada, Japan, the UK and the EU for putting "forward plans that do keep 1.5°C alive", but said "there are a number of other countries that have not yet submitted their plans".
He suggested he would like to see a new commitment from China, which he said accounts for 28% of global emissions.
He said he expects Mexico, Saudi Arabia and Russia to "step up and make an announcement", adding that following COP26 people will see "which countries have neglected to do what is responsible".
"There is time in the next weeks for countries to put in there their plans. But I am saying that by the time Glasgow is over, we're going to know who is doing their fair share and who isn't."
What did Greta Thunberg say?
The Swedish activist said in an interview with Reuters that the world is "so, so far behind what would be needed" to keep to the 1.5°C target, but added she hopes speakers will be honest about the task ahead.
"Maybe leaders being honest will create a sense of urgency that will make people wake up."
”My expectation is that we will hear many, many nice speeches, we will hear many pledges that - if you really look into the details - are more or less meaningless but they just say them in order to have something to say, in order for media to have something to report about," she said.
"And then I expect things to continue to remain the same...
"The COPs as they are now will not lead to anything unless there is big, massive pressure from the outside."