Is hope still realistic? A major report on climate change published yesterday contains a terrifying warning - but insists that all is not yet lost if governments act now.

The fires which swept through Greece last week, even threatening the city of Athens, were a horrific illustration of the effects of climate change. In recent months there have been still worse fires in the US, and devastating floods in EuropeThe second-smallest of the world's continents. It has a population of 746 million. and ChinaA country in East Asia, home to 1.4 billion people.. And yesterday's report by the Intergovernmental Panel on Climate Change warned that there is worse to come.

Rises in sea levels of almost two metres by the end of the century could not be ruled out, it said. By 2150, they could rise by as much as five metres. Oceans will continue to grow warmer, and glaciers will continue to melt for decades - or perhaps centuries.

"We will see even more intense and more frequent heatwavesIn June Canada's highest ever temperature, 49.6C, was recorded in British Columbia.," says one of the report's authors, Dr Friederike Otto of Oxford University. "And we will also see an increase in heavy rainfall events on a global scale, and also increases in some types of droughts in some regions of the world."

Organised by the UN, the report is the largest ever on climate change. It involved scientists and government officials from 195 countries, and drew on over 14,000 scientific papers. "Urgent climate action was needed decades ago," commented Doug Parr, a director of GreenpeaceAn international campaigning organisation based in Amsterdam. Its aim is to  "ensure the ability of the Earth to nurture life in all its diversity".. "Now we're almost out of time."

But the report also contains what another of its authors, Professor Piers Forster of Leeds University, calls "nuggetsSmall lumps. The word is particularly used for precious metals such as gold. of optimism". The latest research shows that if the increase in global temperature since pre-industrial times can be limited to 1.5C, the worst effects can still be avoided. So far they have increased by 1.2C.

Scientists are also hopeful that if global carbon emissions can be halved by 2030 and reach net zero by 2050, global warming can be halted.

Heated debate

"The thought before was that we could get increasing temperatures even after net zero," says Professor Forster. "But we now expect nature to be kind to us, and if we are able to achieve net zero, we hopefully won't get any further temperature increase. And if we are able to achieve net zero greenhouse gases, we should eventually be able to reverse some of that temperature increase and get some cooling."

Professor Otto agrees that this would minimise the chances of reaching a tipping point. "We are not doomed," he says.

Nevertheless, the report is a "code red for humanity", according to the secretary-general of the UN, Antonio Guterres. "If we combine forces now, we can avert climate catastrophe. But, as today's report makes clear, there is no time for delay and no room for excuses."

Is hope still realistic?

Some say, no. The planet can only be saved if we all make major changes to our lifestyles, and all the industrial nations of the world co-operate. But nobody wants to give up their comforts, and - as the pandemic has shown - governments are bad at working together even in a global emergency. Some - such as Brazil's, with its disrespect for the rainforest - are making the situation even worse.

Others argue that people do change their habits when the situation demands it: we used not to recycle at all, but now everybody does it. The recent weather disasters have finally woken the world to the perils of climate change, and governments and businesses are responding to pressure to behave responsibly. Clean technology is making enormous strides.