(CNN) Governments around the world must take "rapid, far-reaching and unprecedented changes in all aspects of society" to avoid disastrous levels of global warming, says a stark new report from the global scientific authority on climate change.
The report issued Monday by the UN Intergovernmental Panel on Climate Change (IPCC), says the planet will reach the crucial threshold of 1.5 degrees Celsius (2.7 degrees Fahrenheit) above pre-industrial levels by as early as 2030, precipitating the risk of extreme drought, wildfires, floods and food shortages for hundreds of millions of people.
The date, which falls well within the lifetime of many people alive today, is based on current levels of greenhouse gas emissions.
The planet is already two-thirds of the way there, with global temperatures having warmed about 1 degree C. Avoiding going even higher will require significant action in the next few years.
"This is concerning because we know there are so many more problems if we exceed 1.5 degrees C global warming, including more heatwaves and hot summers, greater sea level rise, and, for many parts of the world, worse droughts and rainfall extremes," Andrew King, a lecturer in climate science at the University of Melbourne, said in a statement.
Global net emissions of carbon dioxide would need to fall by 45% from 2010 levels by 2030 and reach "net zero" around 2050 in order to keep the warming around 1.5 degrees C.
Lowering emissions to this degree, while technically possible, would require widespread changes in energy, industry, buildings, transportation and cities, the report says.
"The window on keeping global warming below 1.5 degrees C is closing rapidly and the current emissions pledges made by signatories to the Paris Agreement do not add up to us achieving that goal," added King.
Consequences of past inaction
The report makes it clear that climate change is already happening -- and what comes next could be even worse, unless urgent international political action is taken.
"One of the key messages that comes out very strongly from this report is that we are already seeing the consequences of 1 degree C of global warming through more extreme weather, rising sea levels and diminishing Arctic sea ice, among other changes," said Panmao Zhai, co-chair of IPCC Working Group I.