Scientists have delivered a stark warning to the world about the impacts of climate change, saying that extreme heat, flooding, and drought are being observed in every region of the world and that these will increase in their intensity extreme unless rapid action is taken to reduce emissions.
On Monday, the Intergovernmental Panel on Climate Change delivered the first of three major reports being prepared as part of its sixth assessment of climate change, providing an authoritative statement on the current understandings of climate science.
The report – the first of its kind in eight years – “unequivocally” confirms that global warming is occurring, attributed to human-caused increases in atmospheric greenhouse gases.
The IPCC report confirms that global temperatures have already increased 1.09°C compared to pre-industrial temperatures – an increase more significant than anything that has occurred for more than 100,00 years – and that over the next 20 years, average global temperatures are expected to reach or exceed 1.5°C of warming.
“Global surface temperature will continue to increase until at least the mid-century under all emissions scenarios considered,” the report says.
“Global warming of 1.5°C and 2°C will be exceeded during the 21st century unless deep reductions in CO2 and other greenhouse gas emissions occur in the coming decades.”
The shocking news for Australia – already criticised for doing little on climate change – is that average temperatures have already risen 1.4°C.
The authors say that the current and future impacts of global warming are now well understood with unprecedented levels of certainty thanks to improved climate observations and advances in the scientific understanding of the human influence on the world’s climate.
“This report is a reality check,” IPCC Working Group I co-chair Valérie Masson-Delmotte said. “We now have a much clearer picture of the past, present and future climate, which is essential for understanding where we are headed, what can be done, and how we can prepare.”
The report was authored by 234 leading climate scientists, drawn from 66 countries, who cited more than 14,000 pieces of research in preparing the authoritative statement. Its publication had been delayed by the impact of the Covid-19 pandemic.
“This report reflects extraordinary efforts under exceptional circumstances,” chair of the IPCC, Hoesung Lee added. “The innovations in this report, and advances in climate science that it reflects, provide an invaluable input into climate negotiations and decision-making.”
The key message from the scientists is that “every faction of a degree matters” – a warning to the world about the worsening consequences of global warming, including more extreme weather events, higher temperature extremes and higher risk of fire, droughts and flooding.
But it is also a message about the need to act – the faster action is taken and the greater the emissions cuts that can be achieved, the greater the chance of avoiding the worst impacts of climate change.
“With every additional increment of global warming, changes in extremes continue to become larger,” the report says.
“For example, every additional 0.5°C of global warming causes clearly discernible increases in the intensity and frequency of hot extremes, including heatwaves (very likely), and heavy precipitation (high confidence), as well as agricultural and ecological droughts in some regions.
“There will be an increasing occurrence of some extreme events unprecedented in the observational record with additional global warming, even at 1.5°C of global warming,” it adds.
The report’s authors said the report should serve as a message to governments that the severe impacts of climate change can be limited by early and ambitious action to reduce emissions and that delays will lead to irreversible changes to the Earth’s climate.
“The climate we and the young generations will experience depends on future emissions,” the report says. “Reducing emissions rapidly will limit further changes, but continued emissions will trigger larger, faster changes that will increasingly affect all regions. Some changes will persist for hundreds or thousands of years, so today’s choices will have long-lasting consequences.”
The IPCC report compares five different potential futures – based on differing levels of expected global warming – finding that limiting global warming to below 2°C will almost certainly require negative emissions to be achieved by the second half the century.
For Australia, the IPCC found that it had already warmed by 1.4°C above pre-industrial levels and could expect higher heat extremes and an increase to the frequency and severity of both extreme fire events and heavy rainfall and river flooding.
The report added that these impacts were expected to get more extreme with each incremental increase in global warming.
“Heat extremes have increased, cold extremes have decreased, and these trends are projected to continue (high confidence),” the IPCC’s regional report on Australasia says.
“Frequency of extreme fire weather days has increased, and the fire season has become longer since 1950 at many locations (medium confidence). The intensity, frequency and duration of fire weather events are projected to increase throughout Australia (high confidence) and New Zealand (medium confidence).
“Changes in several climatic impact-drivers (e.g., heatwaves, droughts, floods) would be more widespread at 2°C compared to 1.5°C global warming and even more widespread and/or pronounced for higher warming levels,” the report adds.
Scientists have also attempted to give an indication of the very long term impacts of global warming, giving a stark warning that even modest increases in global temperatures continue to irreversibly impact global climate systems for thousands of years into the future.
“In the longer term, sea level is committed to rise for centuries to millennia due to continuing deep ocean warming and ice sheet melt, and will remain elevated for thousands of years,” the IPCC report says.
“Over the next 2000 years, global mean sea level will rise by about 2 to 3 m if warming is limited to 1.5°C, 2 to 6 m if limited to 2°C and 19 to 22 m with 5°C of warming, and it will continue to rise over subsequent millennia.”
The report is the first of three major reports to be published by the IPCC over the coming year. A report detailing the “impacts, adaptation and vulnerability” triggered by climate change will be published in February 2022. The third report on possible approaches to mitigating the causes of climate change will follow in March 2022.