Earth is likely to cross a critical threshold for global warming within the next decade, and nations will need to make an immediate and drastic shift away from fossil fuels to prevent the planet from overheating dangerously beyond that level, according to a major new report released on Monday.

The report, by the Intergovernmental Panel on Climate Change, a body of experts convened by the UN, offers the most comprehensive understanding to date of ways in which the planet is changing.

It says that global average temperatures are estimated to rise 1.5° Celsius above pre-industrial levels sometime around “the first half of the 2030s” as humans continue to burn coal, oil and natural gas.

That number holds a special significance in global climate politics: Under the 2015 Paris climate agreement, virtually every nation agreed to “pursue efforts” to hold global warming to 1.5° Celsius.

Beyond that point, scientists say, the impacts of catastrophic heat waves, flooding, drought, crop failures and species extinction become significantly harder for humanity to handle.

But Earth has already warmed an average of 1.1° Celsius since the industrial age, and, with global fossil-fuel emissions setting records last year, that goal is quickly slipping out of reach.

There is still one last chance to shift course, the new report says. But it would require industrialised nations to join together immediately to slash greenhouse gases roughly in half by 2030 and then stop adding carbon dioxide to the atmosphere altogether by the early 2050s.

If those two steps were taken, the world would have about a 50 per cent chance of limiting warming to 1.5° Celsius.

Delays of even a few years would most likely make that goal unattainable, guaranteeing a hotter, more perilous future.

The report comes as the world’s two biggest polluters, China and the US, continue to approve new fossil fuel projects.

Last year, China issued permits for 168 coal-fired power plants of various sizes, according to the Centre for Research on Energy and Clean Air in Finland.

Last week, the Biden administration approved an enormous oil drilling project known as Willow that will take place on pristine federal land in Alaska.

The report, which was approved by 195 governments, says that existing and currently planned fossil fuel infrastructure — coal-fired power plants, oil wells, factories, cars and trucks across the globe — will already produce enough carbon dioxide to warm the planet roughly 2° Celsius this century. To keep warming below that level, many of those projects would need to be cancelled, retired early or otherwise cleaned up.

“The 1.5° limit is achievable, but it will take a quantum leap in climate action,” António Guterres, the UN secretary-general, said. In response to the report, Guterres called on countries to stop building new coal plants and to stop approving new oil and gas projects.

“It’s not that if we go past 1.5° everything is lost,” said Joeri Rogelj, director of research at the Grantham Institute for Climate Change and the Environment at Imperial College London.

“But there’s clear evidence that 1.5 is better than 1.6, which is better than 1.7, and so on. The point is we need to do everything we can to keep warming as low as possible.”

Scientists say that warming will largely halt once humans stop adding heat-trapping gases to the atmosphere, a concept known as “net zero” emissions.

How quickly nations reach net zero will determine how hot the planet ultimately becomes. Under the current policies of national governments, Earth is on pace to heat up by 2.1 to 2.9° Celsius this century, analysts say.

The new report is a synthesis of six previous landmark reports on climate change issued by the UN panel since 2018, each one compiled by hundreds of experts across the globe, approved by 195 countries and based on thousands of scientific studies.

Taken together, the reports represent the most comprehensive look to date at the causes of global warming, the impacts that rising temperatures are having on people and ecosystems across the world and the strategies that countries can pursue to halt global warming.

The report makes clear that humanity’s actions today have the potential to fundamentally reshape the planet for thousands of years. Many of the direst climate scenarios once feared by scientists, such as those forecasting warming of 4° Celsius or more, now look unlikely, as nations have invested more heavily in clean energy.

At least 18 countries, including the US, have managed to reduce their emissions for more than a decade, the report finds, while the costs of solar panels, wind turbines and lithium-ion batteries for electric vehicles have plummeted.

Even modest increases in global temperature are now expected to be more disruptive than previously thought, the report concludes. At current levels of warming, for instance, food production is starting to come under strain.

The world is still producing more food each year, thanks to improvements in farming and crop technology, but climate change has slowed the rate of growth, the report says.

It’s an ominous trend that puts food security at risk as the world’s population soars past eight billion people.

Today, the world is seeing record-shattering storms in California and catastrophic droughts in places like East Africa. But by the 2030s, as temperatures rise, climate hazards are expected to increase all over the globe as different countries face more crippling heat waves, worsening coastal flooding and crop failures, the report says.

At the same time, mosquitoes carrying diseases like malaria and dengue will spread into new areas, it adds.

New York Times News Service