Temperatures could rise by 1.5 degrees Celsius as soon as 2030 if global warming continues at its current pace and the world fails to take rapid and unprecedented measures to stem the increase, experts warned in a landmark United Nations report on Monday. It will be one of the main items discussed at a global conference in Poland in December, when governments will review the Paris Agreement (which the USA withdrew from in June 2017).
The report was a collaboration of over 90 scientists from 40 countries, who used over 6,000 scientific references.
The report, commissioned as part of the 2015 Paris climate agreement, presents a stark portrait of the future unless the world undertakes "rapid, fair-reaching and unprecedented changes in all aspects of society" in the next decade or so - changes that thus far have been hard for decision-makers to agree on.
The report called climate change "an urgent and potentially irreversible threat to human societies and the planet", and warned that delayed action would make it impossible to limit warming to 2.7º F.
We have just twelve years before a catastrophic environmental breakdown is inevitable, unless we radically change the way we live now. The new report explains why going that far is critical, based on a summary of recent research that shows that the impacts at 2 degrees are much worse than previously understood.
The report estimates that sea-level rise in the year 2100 would be around 10 centimeters lower in a 1.5°C world than a 2.0°C world.
Countries are already seeing an increase in extreme weather and rising sea levels as a result of the increase in average global temperatures of 1 degree above pre-industrial levels that has already occurred, the IPCC study said.
The report includes a wide array of possible scenarios that would draw down emissions and keep warming below 1.5°C, including bumping the share of renewables in electricity to 97 percent in the most aggressive forecast. When water heats up, it expands meaning when oceans likely continue to rise, the IPCC says, we can expect the oceans to rise between 28 to 98cm by 2100, enough to swamp numerous cities along the USA east coast. Scientists consider that temperature to be a tipping point at which many severe effects of global warming will be realized. "Even the scientists were surprised to see how much science was already there and how much they could really differentiate and how great are the benefits of limiting global warming at 1.5 compared to 2", Thelma Krug, vice-chair of the IPCC, told Reuters in an interview. Global net human-caused emissions of carbon dioxide would need to fall by about 45 percent from 2010 levels by 2030, reaching "net zero" around 2050.
"All options need to be exercised in order to achieve 1.5C", said Prof Jim Skea, an IPCC co-chair.
To have even a 50-50 chance of staying under 1.5C, the world has to be carbon neutral by 2050, with emissions of carbon dioxide falling sharply from 2020.
But the report warned such techniques were still unproven at a large scale and could carry significant risks for sustainable development. But Monday's report comes amid a reactionary political climate. Additionally, there must be renewed emphasis on adaptation, which, as the Report says, requires transformation and incremental shifts with more finance directed towards adaptation. Under the 2015 Paris accord, countries agreed to limit the average temperature increase to well below 2 degrees, with a goal of no more than 1.5 degrees.
The headlines about cutting emissions by 45% by 2030 and getting nearly all of our electricity from renewables by the middle of the century, are all very well but a key point of this report is that successfully limiting climate change to 1.5C is not just down to cutting emissions or making lifestyle changes or planting trees - it is all of that and then some, acting in concert at the same time. This will mean a lot for our ability to bring you news, perspectives and analysis from the ground so that we can make change together.
Global sea levels would rise 10 cm lower by 2100. IPCC assessments are a key input into the worldwide negotiations to tackle climate change.
RealClimateScience.com's Tony Heller ticked off past failed predictions of global-warming disaster, such as a 1989 U.N. warning that "entire nations could be wiped from the face of the earth" by rising seas unless global warming was reversed by 2000.