Holding global warming to a critical limit would require "rapid, far-reaching and unprecedented changes in all aspects of society," says a key report from the global scientific authority on climate change.
The Intergovernmental Panel on Climate Change (IPCC) report was released Monday at the 48th Session of the IPCC in Incheon, South Korea.
It focuses on the impacts of global warming reaching 1.5 degrees Celsius (2.7 degrees Fahrenheit) above pre-industrial levels. The planet is already two-thirds of the way there, with global temperatures having warmed about 1 degree C.
According to the report, the planet will reach this crucial threshold as early as 2030 based on our current levels of greenhouse gas emissions -- and avoiding going even higher will require significant action in the next few years.
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 Celsius.
Lowering emissions to this degree would require widespread changes in energy, industry, buildings, transportation and cities, the report says.
But even if warming is able to be kept to 1.5 degrees Celsius, the impacts would be widespread and significant.
Temperatures during summer heatwaves, such as those just experienced across Europe this summer, can be expected to increase by 3 degrees Celsius, according to the report.
More frequent or intense droughts, such as the one that nearly ran the taps in Cape Town, South Africa, dry, as well as more frequent extreme rainfall events such as hurricanes Harvey and Florence in the United States, are also pointed to as expectations as we reach the warming threshold.
Monday's report is three years in the making and is a direct result of the 2015 Paris Climate Agreement. In the Paris accord, 197 countries agreed to the goal of holding global temperatures "well below" 2 degrees C above pre-industrial levels and to pursue efforts to limit it to 1.5 degrees C.
The United States was initially in the agreement. But President Donald Trump pulled the country out a year and half later, claiming it was unfair to the country.
'Possible with the laws of chemistry and physics'
To limit global warming to 1.5 degree C is "possible within the laws of chemistry and physics," said Jim Skea, co-chair of IPCC Working Group III. "But doing so would require unprecedented changes."
In Paris, the world's governments tasked the IPCC with preparing this special report to detail the impacts that climate change of 1.5 degree C will bring, what will be required to prevent further warming and what mitigation and adaptation options are available for countries to deal with these impacts.
More than 90 authors from 40 countries were involved in leading the report, helped by 133 contributing authors. The report pulls together the current understanding of the scientific community on climate change and includes citations of more than 6,000 peer-reviewed scientific articles and studies.
"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.
The report cites specific examples of how impacts of global warming would be lessened with the 1.5 degrees C increase, compared to the 2 degees C increase:
- Global sea levels would rise 10 cm lower by 2100
- The likelihood of an Arctic Ocean free of sea ice in summer would be once per century, instead of at least once per decade
- Coral reefs would decline by 70% to 90% instead of being almost completely wiped out.
"Every extra bit of warming matters, especially since warming of 1.5 degrees C or higher increases the risk associated with long-lasting or irreversible changes, such as the loss of some ecosystems," said Hans-Otto Pörtner, Co-Chair of IPCC Working Group II.