It is the first part of a global assessment of climate science by the Intergovernmental Panel on Climate Change (IPCC), the sixth such assessment the UN body has conducted, with the most recent one back in 2013/14. Further reports on impacts and adapting to global warming, and solutions to the crisis set to be published next year.
It is the UN body for assessing the science related to climate change. It was established in 1988 to provide political leaders with scientific assessments on climate change, to help them make policy. Some 195 countries are members of the IPCC.
It references more than 14,000 scientific papers, and has involved 234 authors from around the world – including Maynooth University's professor in physical geography (climate change) Peter Thorne – who have received tens of thousands of comments on earlier drafts from scientists and governments.
The 41-page summary has been subject to a line-by-line approval process involving scientists and representatives of the 195 governments before it is published.
It concludes it is “unequivocal” that human activity is warming the planet, causing rapid and widespread changes to land, atmosphere and oceans that are unprecedented for many centuries or even many thousands of years.
It highlights that human-caused climate change, which has pushed up global temperatures by 1.1C, is driving weather and climate extremes in every region across the world.
It also says global warming of 1.5C and 2C – limits countries have committed to in order to avoid the most dangerous impacts of climate change – will be exceeded in the 21st century unless deep reductions in CO2 and other greenhouse gas emissions occur in the coming decades.
The report is being released less than 100 days before world leaders gather in Glasgow for a crucial UN climate summit, known as Cop26.
The summit has been billed as the last best chance of keeping global warming to 1.5C above pre-industrial levels, seen as a threshold beyond which the worst impacts of climate change will be felt. It will ramp up the pressure on governments to provide clear action plans for how they will cut their country’s emissions in the next decade and beyond in the run-up to the talks, as the world is currently well off track to meet the 1.5C goal.
When the Paris Agreement – the global treaty on climate change – was negotiated in 2015, there was a strong push by countries, such as low-lying islands, to include the 1.5C target in the deal because they felt that letting temperatures go any higher would threaten their survival.
Dr Paul Deane, a research fellow at the MaREI Centre for Marine and Renewable Energy and the Environmental Research Institute (ERI) at UCC, told the: "Humans are the main cause of recent climate change and if unchecked it is going to lead to more extreme and dangerous weather. While the report doesn’t present specific information for Ireland, it is clear that many of the global centres of energy, commodity, and food production that we rely on in Ireland are now more exposed to extreme weather and climate impacts."
Yes, according to a special report by the IPPC in 2018, which found a 2C rise would lead to more heatwaves, extreme rainstorms, water shortages and drought, greater economic losses and lower crop yields, higher sea levels and greater damage to coral reefs than a 1.5C rise.
The latest report also warns that every additional 0.5C temperature rise leads to clear increases in the intensity of heatwaves, rainstorms and flooding, and droughts in some regions.
Dr Tara Shine, environmental scientist, policy adviser, and director of Change By Degrees, said: "At one degree warmer, look at the impact it is having already. Things we thought were farther off weren’t, they are already here.
"The window of time that we set in Paris has become smaller. All that means is that we have to act more and act faster."