Last week the world’s leading authority on climate science, the Intergovernmental Panel on Climate Change (IPCC) published its most detailed assessment yet of how humans are driving unprecedented change to our fast-warming world.
A total of 234 scientists representing 66 countries are behind the first chapter of the IPCC’s sixth assessment report, which draws on 14,000 research papers to come up with conclusions on how the Earth’s climate is changing as a result of human activity.
A 41-page summary of the report was released to the public. Below are 10 of the key takeaways from the landmark assessment, the first of its kind since 2013.
Compound extreme weather events on the rise
Compound extreme weather events, such as concurrent heatwaves and droughts, are on the rise as the result of human-induced warming, the report says.
Such compound extremes can greatly enhance the risk of severe wildfires occurring, scientists say.
Humans’ role in climate crisis ‘unequivocal’
The summary of the report begins with a stark opening message: “It is unequivocal that human influence has warmed the atmosphere, ocean and land.”
Humans have caused the world to heat up by around 1.1C since the period 1850-1900, the report says. Though this is the average figure, some parts of the world are heating up a lot faster than others, it adds. For example, the Arctic is heating up at a rate that is more than twice as fast as the global average.
‘Every region’ on Earth already affected
No region on Earth has escaped the impacts of the climate crisis, the new report confirms. It says that “human-induced climate change is already affecting many weather and climate extremes in every region across the globe”.
The report has uncovered stronger evidence than ever before that extreme weather events such as heatwaves, heavy rainfall, droughts and hurricanes are becoming more frequent and more likely as a result of the climate crisis.
CO2 levels at highest in ‘2 million years’
The report notes that levels of CO2, the primary driver of global heating, were higher in 2019 than at any time in “at least 2 million years”.
It adds that levels of methane and nitrous oxide, the second and third biggest drivers of warming respectively, were higher in 2019 than at any time in “at least 800,000 years”.
Climate goals of 1.5C and 2C slipping ‘beyond reach’
Under the historic Paris Agreement in 2015, countries agreed to limit global warming to 2C above pre-industrial levels, with an aspiration of keeping temperatures at 1.5C. The report finds that “it is more likely than not” that the world will reach 1.5C sometime between 2021 and 2040. Immediate, rapid and large-scale cuts to greenhouse gas emissions are needed to keep these climate goals within our grasp, the report says.
‘Strong and rapid’ cuts to methane needed
In addition to slashing CO2 emissions, the world must also deliver “strong, rapid and sustained reductions” in methane in order to get to grips with the climate crisis, the report says.
Human-caused methane emissions largely come from agriculture, particularly livestock rearing, as well as from the production of fossil fuels.
Humans ‘main driver’ of worsening heat
It is “virtually certain” that heatwaves have become more frequent and more intense since the 1950s, the report says, with human-caused warming being “the main driver” of these increases, according to the report.
Some of the heat extremes seen over the past decade would have been “extremely unlikely to occur” without the climate crisis, it adds.
Changes to ice, oceans and sea levels ‘irreversible for centuries’
The report notes that “many changes due to past and future greenhouse gas emissions are irreversible for centuries to millennia”.
This includes changes to global sea levels, oceans and ice sheets, it says. For example, the report says sea levels are “committed to rise for centuries to millennia” due to continuing ocean heating and the melting of ice sheets. It adds that sea levels “will remain elevated for thousands of years”.
Climate tipping points ‘can’t be ruled out’
Tipping points in Earth’s climate – thresholds where a small change could lead to dramatic change – “can’t be ruled out”, the report says. Such tipping points could include ice-sheet collapse or abrupt changes to ocean circulation patterns, it adds.
However, taking urgent action to address greenhouse gas emissions would minimise the likelihood of such tipping points occurring, the scientists say.
‘Every bit’ of action matters
The findings of the new report are unsettling. But it is important to note “we are not doomed”, says Dr Friederike Otto, a report author and associate director of the Environmental Change Institute at the University of Oxford. She and her fellow report authors urged the world to take note of the fact that every action the world takes to reduce greenhouse gas emissions will make a difference.
“Every bit of warming really does matter,” says Dr Helene Hewitt, a report author and scientist at the UK’s Met Office. “It’s only by limiting warming that we’ve got a chance of limiting the larger [risks] that we might see in the longer term.”
The remaining chapters of the IPCC’s sixth assessment report are due to be published in 2022.
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