The scene in GlasgowA Violence Reduction Unit was set up in the city in 2005. It now works across Scotland. on Sunday promises to be chaotic. Rubbish piled high, trains going nowhere: it could be a metaphor for the Earth's future as world leaders, experts and demonstrators converge on the city. The strike by cleaners and railway workers could yet be called off - but the problems facing Cop26 delegates will not be solved so easily.

The new Emissions Gap report from the UN Environment Programme (UNEP) brings sobering news. It looks at the carbon-cutting plans submitted by countries attending Cop26 - which are supposed to be a step up from those set in Paris six years ago - and concludes that they are not nearly ambitious enough.

As they stand, they would cut emissions by 7.5% by 2030Scientist say that if a 45% reduction is not achieved by then, it will not be possible to achieve net zero by 2050.. But scientists say that a 45% reduction is needed if global temperature rises are to be limited to 1.5% above pre-industrial levels.

"If we don't act now, it'll be too late," says David Attenborough. "Every day that goes by in which we don't do something about it is a day wasted."

The EU and 49 separate countries have pledged to achieve net zeroWhen the gases going into the atmosphere are balanced by those being taken out of it. emissions by 2050. They account for half the world's emissions.

But according to the UNEP, many countries' plans are vague, while those submitted by Russia, Brazil, Australia and Mexico are no improvement on ones they put forward in 2016. China and India, two of the biggest emitters, have not even published their plans yet.

According to one expert, "There is an ambition gap between country pledges and the cuts needed to limit temperature rise... and even more troubling is an implementation gap. Many large emitters are not even on track to meet their existing pledges."

The secretary-general of the UN Antonio Guterres, called the report a "thundering wake-up call": "The emissions gap is the result of a leadership gap," he said yesterday. "But leaders can still make this a turning point to a greener future instead of a tipping point to climate catastrophe."

Greta Thunberg, who will lead a march through Glasgow on Friday week, is sceptical. Her message to world leaders is: "Be honest about where you are, how you have been failing, how you're still failing us."

In her view, the problem can only be solved by the public pressure: "We're going to need to uproot the system, because that's where the change is going to come."

Yet while increasing numbers of people recognise the dangers of climate change, persuading them to make the sacrifices that cutting emissions demands is a huge challenge. Switching to clean energy is likely to make heating your home, driving a car and using electricity more expensiveNew Zealand's government estimates that the switch would cost developed countries 16% of their gross national product.. And politicians worry that would cost them crucial votes.

But UNEP's executive director, Inger Andersen, insists that we have no choice. "We have eight years to almost halve greenhouse gas emissions: eight years to make the plans, put in place the policies, implement them and ultimately deliver the cuts. The clock is ticking loudly."

Some say, no. Most governments are only elected for a few years, and their priority is always to get elected again - so they seldom make long-term plans. They are certainly not going to risk losing office by introducing drastic carbon-cutting measures which could push up prices.

Others point out that just over half the world's population is under 30. These are key voters today and will be the leaders of tomorrow, and they want drastic change. People have put up with austerity in times of war, and most would certainly do so in order to save the planet.