A bleak new report which the United Nations calls a "code red for humanity," warns that time is running out to save the planet as climate change is accelerating and intensifying. "Unless there are immediate, rapid and large-scale reductions in greenhouse gas emissions, limiting warming to 1.5°C will be beyond reach," scientist Valérie Masson-Delmotte told reporters as the Intergovernmental Panel on Climate Change (IPCC) released its report on Monday. Under the 2015 Paris climate agreement, world leaders committed to trying to limit warming to 1.5 degrees Celsius since the late 19th century because problems mount quickly after that. "The world listened but it did not hear. The world listened but it did not act strongly enough," deplored United Nations Environment Program Executive Director Inger Andersen, noting that scientists had issued this message for three decades. More than 200 scientists reviewed over 14,000 studies for the report, which is the culmination of a marathon five-year assessment. Getting worse' "Many of the changes observed in the climate are unprecedented in thousands, if not hundreds of thousands of years, and some of the changes already set in motion—such as continued sea-level rise—are irreversible over hundreds to thousands of years," the IPCC said. Shrinking ice and heatwaves, droughts, floods and storms are already visible impacts of climate change. All of these trends will get worse, the report predicted. For example, the kind of heatwave that used to happen only once every 50 years now happens once a decade. If the world warms another degree Celsius, it will happen twice every seven years, the report said. "It's just guaranteed that it's going to get worse," said report co-author Linda Mearns, a senior climate scientist at the US National Centre for Atmospheric Research. "I don't see any area that is safe ... Nowhere to run, nowhere to hide." IPCC scientists say "the role of human influence on the climate system is undisputed." Five scenarios of global warming The report outlines five different future scenarios based on how much the world reduces carbon emissions: * a future with sweeping and quick pollution cuts; * intense pollution cuts but not quite as massive; * a scenario with moderate emissions; * a scenario where current plans to make small pollution reductions continue; * a continued increase in carbon pollution. Under each scenario, the report said, the world will cross the 1.5 degrees Celsius warming mark in the 2030s, earlier than some past predictions. Warming has accelerated in recent years, data shows. In three scenarios, the world will also likely exceed 2 degrees Celsius over pre-industrial times with far worse heat waves, droughts and flood-inducing downpours. "The only way to limit global warming is net-zero CO2 emissions," Masson-Delmotte said. "It's all in our hands." World leaders pledge 'real action' World leaders and activists from all over the world were prompt to react to the alarming report. European Commission Vice President Frans Timmermans tweeted that the report "shows the immense urgency of acting now to tackle the climate crisis. It's not too late to stem the tide and prevent runaway climate change, but only if we act decisively now and all act together." Several major heatwaves over the summer led to large wildfires, including ones that continue to spread in southern Europe. "The report confirms in an impressive way the connection between man-made climate change and weather extremes. Floods after heavy rains, as we have just experienced, are increasing, as are heatwaves and forest fires, which have plagued us in recent years," said German Environment Minister Svenja Schulze, whose country was last month hit by deadly flooding. "We know what must be done to limit global warming — consign coal to history and shift to clean energy sources, protect nature and provide climate finance for countries on the frontline," said British Prime Minister Boris Johnson, whose country will host the next global climate conference in just a few months. "The impacts of the climate crisis, from extreme heat to wildfires to intense rainfall and flooding, will only continue to intensify unless we choose another course for ourselves and generations to come. What the world requires now is real action. All major economies must commit to aggressive climate action during this critical decade," said John Kerry, US special presidential envoy for the climate. — Euronews But for teenage environmental activist Greta Thunberg, the report "contains no real surprises." "It confirms what we already know from thousands of previous studies and reports — that we are in an emergency. ... It is up to us to be brave and take decisions based on the scientific evidence provided in these reports. We can still avoid the worst consequences, but not if we continue like today, and not without treating the crisis like a crisis," Thunberg said. Environmental NGO Greenpeace, meanwhile, said it was planning on taking the report's findings to the court. "Dear fossil fuel industry, we'll see you in court," the group tweeted.