The Earth’s climate system is changing across the planet, and its “widespread, rapid and intense” effects are exacerbated by human activities, according to the latest report of the Intergovernmental Panel on Climate Change (IPCC).
The report by eminent climate scientists, published Monday, provides evidence that “unless there are immediate, rapid and widespread reductions in greenhouse gas emissions, limiting the rise in temperature to approximately 1.5 degrees or even two degrees will be out of reach.”
The report’s authors warned that such a scenario would bring inevitable catastrophic effects over the coming decades for humans, particularly in the form of extreme weather events and rising sea levels.
Many of the changes observed are “unprecedented in thousands, if not hundreds of thousands of years, and some changes that have already begun – such as continued sea-level rise – are irreversible” in a future time frame of hundreds to thousands of years.
On a positive note, the scientists emphasized that strong and sustained cuts immediately followed in emissions of carbon dioxide and other greenhouse gases – particularly methane – will curb climate change. The report shows that human actions still have the power to determine the future course of Earth’s climate.
While the benefits from air quality will materialize quickly, it could take 20 to 30 years for global temperatures to stabilize, according to the report of the Intergovernmental Panel on Climate Change Working Group 1 (WG1).
Drawing on more than 14,000 scientific papers, the review provides the latest knowledge about past and possible future warming; How humans alter climate and how it increases extreme weather events and leads to sea level rise.
It was approved by the 195 member governments of the Intergovernmental Panel on Climate Change – signatories to the Paris Agreement – through a virtual approval session held over the past two weeks. Its findings provide a stark backdrop for the upcoming United Nations climate summit, COP26, in Glasgow next November.
However, the report decisively concludes that halving emissions by 2030 and achieving net-zero emissions by 2050 is the right path for countries to enable collective containment of temperature rise to within 1.5 degrees above pre-industrial levels – a key Paris goal.
The WG1 report is the first batch of the Sixth Global Assessment Report of the Intergovernmental Panel on Climate Change (AR6), which will be completed in 2022.
“This report reflects extraordinary efforts under exceptional circumstances,” said Hosung Lee, chair of the Intergovernmental Panel on Climate Change. “The innovations presented in this report, and the advances in climate science they reflect, provide invaluable input into climate negotiations and decision-making.”
Professor Peter Thorne of the University of Maynooth was lead author of a group of 230 climate specialists who prepared the report. After it was agreed late last week, he tweeted: “THIS IS NOT AN EXERCISE: We have an IPCC WGI Certified! Great. Words are lost now.”
On its importance, he told The Irish Times: “It is the first time that the IPCC has found that human impact on the climate system is unambiguous. This now also goes beyond long-term changes, to find human impact in many extreme heat waves, and the extreme precipitation and drought events that we are increasingly seeing around the world.”
The report provides new estimates of the chances of exceeding the 1.5 degree level of global warming, and finds that emissions from human activities are responsible for approximately 1.1 degrees of warming since 1850-1900. Global temperature is projected to reach or exceed 1.5 degrees of warming, averaging over the next 20 years.
This assessment builds on improved observational data to assess historical warming, as well as advances in scientific understanding of the climate system’s response to human-caused emissions and more reliable climate modeling techniques to predict future possibilities.
“This report is a reality check,” said Valerie Mason Delmott, co-chair of the Intergovernmental Panel on Climate Change. “We now have a much clearer picture of past, present and future climate, which is essential to understanding where we are heading, what can be done, and how we can prepare.”
She added that many characteristics of climate change depend directly on the level of global warming, but what people experience is often very different from the global average. “For example, the warming over land is greater than the global average, and it is twice as high in the Arctic.”
“Climate change is already affecting every region on Earth in multiple ways. The changes we are experiencing will only increase with increasing warming,” said Panmao Chai, co-chair of the Intergovernmental Panel on Climate Change WG1.
The report predicts that “climate changes will increase in all regions.” For 1.5 degrees of global warming, there will be increased heat waves, longer warm seasons and shorter cold seasons. The study shows that at two degrees of global warming, temperature extremes will “often reach critical tolerance thresholds for agriculture and health.”
Contributing author Dr Michael Byrne, an Irish climate scientist based at the University of St Andrews and Oxford University, said the report “almost certainly repeats what we have known for more than a decade: the climate is warming, human activities are the main driver, and it will only get worse” .
“What is different now… is that the effects of global warming no longer exist in the distant future or in remote parts of the world. Climate change has reached our daily lives and is here to stay.”
The evidence is unequivocal: the world has warmed by 1.1 degrees since the 19th century (land areas by 1.6 degrees), each of the past four decades has been warmer than any decade since 1850, and Arctic sea ice has shrunk in late summer By 40 percent in 30 years, the sea level has risen by 20 centimeters since 1901 and is accelerating…the list goes on.”
Dr Byrne noted that extreme weather events – from the thermal dome in Canada to flash floods in Germany to wildfires in Greece – “now carry the hallmarks of climate change, wreaking havoc around the world week after week.”
“The report is particularly important because it is the first to provide clear evidence linking these extreme events to human activities. This evidence was inconclusive in 2013, at the time of the previous IPCC report; now it is irrefutable.”
Climate change is causing multiple changes beyond warming – all of which will increase with more warming.
The report lists the following examples:
– it “intensifies the water cycle”, which leads to heavy rains and associated floods, as well as an increase in drought in many areas;
– At higher latitudes, precipitation is likely to increase while in subtropical regions it is expected to decrease;
Coastal areas will experience continuous sea level rise throughout the twenty-first century, contributing to frequent and severe coastal flooding in low-lying areas and coastal erosion. Previously severe sea level events that occurred once every 100 years could occur every year by 2100;
Additional warming will amplify the thawing of permafrost, the loss of seasonal snow cover, the melting of glaciers and ice sheets, and the loss of summer sea ice in the Arctic;
Changes in the oceans, including warming, more frequent marine heat waves, ocean acidification, and lower oxygen levels, have been clearly associated with human influence. These changes affect both the ocean ecosystems and the people who depend on them, and will continue for at least the remainder of this century;
For cities, the effects of climate change can be amplified, including heat (because urban areas are usually warmer than surrounding areas), flooding from heavy rainfall events and sea level rise in coastal cities.
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