Australian contributors to the first instalment of the Sixth Assessment Report (AR6) for the Intergovernmental Panel on Climate Change (IPCC) have said there is a long way to go to cap global warming to 1.5°C — but it’s not too late.
Associate Professor Shayne McGregor has described government inaction as the biggest threat to the world’s chances of decreasing greenhouse gas emissions.
The climate researcher from Monash University’s School of Earth, Atmosphere and Environment said the report ‘unequivocally’ pointed to human impact as being responsible for pre-industrial global warming. He said that human activity was directly linked to extremes in temperature and rainfall, and global sea level rise occurring today at three times the rate it was occurring pre 1971.
“The next two decades are particularly critical,” McGregor said.
“It will require sustained and concerted global efforts targeting rapid reductions in CO2, methane and other greenhouse gases to limit warming to 1.5°C in line with the Paris agreement.”
The landmark report, published in Geneva on Monday, is one of the most comprehensive documents summarising scientific understanding of climate change. It includes a new suite of climate models and scenarios that map possible future climate changes. The modelling also details the positive impact of future emissions reductions, to give decision-makers a guide about what to do.
McGregor worked on chapter three of the report assessing human impact on past climate changes. He warned that without sustained, rapid and large-scale cuts to greenhouse gas emissions, it would be impossible to meet the target of 191 signatories to the Paris Agreement to limit global warming to 1.5°C.
“Every small increase in warming leads to greater impacts.
“We are already seeing the consequence of human impacts on the climate with near global increases in heat and rainfall extremes, which have had severe impacts in many parts of the world, including Australia,” he said.
At home, McGregor pointed to Australian land areas warming by around 1.4°C in the more than 100 years from 1910 to 2020. This change was largely attributed to human influence, he said, with cold and heat extremes predicted to push further. Increased evidence relating to climate extremes will also apply to global marine systems, the report found.
Much of the climate change in Australia has led to more frequent and severe weather incidents such a heatwaves, bushfires and rainfall events. It has resulted in more droughts over some regions, and the more the effects of global warming take hold, the worse these extremes become.
Worldwide, the report showed that the Earth’s global surface temperature had warmed by 1.09°C in the same time. Since 1970 the global surface temperature has warmed faster than in any other 50-year period in the previous 2,000 years at least, and warming has affected ocean depths below 2,000 metres.
But Associate Professor McGregor added that he still had some hope world leaders would step up and act now to mitigate the effects of global warming.
“It’s time to play the long-game like it’s our last game. Every bit of warming we mitigate with greenhouse gas reductions will reduce the risk of dangerous, irreversible, climate changes occurring,” he said.
The report is the first major release from the IPCC since 2014.
ANU’s Professor Mark Howden, another contributor to the report and Vice Chair of the IPCC, described the document as a ‘clear and loud alarm bell’. He called for serious commitment before 2050 to reduce carbon emissions and to accelerate the transition to 100% renewable energy.
Action now is the only option to avoid global warming exceeding 2°C during the 21st Century.
“The choice of climate future is ours to make. Scenarios with lower levels of climate change are now only reachable with very rapid and substantial reductions in greenhouse gas emissions,” Howden said.
“Reducing emissions from the 2020s onwards and reaching net-zero before the 2050s is really our best chance at keeping temperature increases below 1.5°C.”
Failing to act will risk fewer but more intense cyclones in the Pacific, which coupled with the threat of sea-level rise would smash nations like Fiji and Vanuatu, he added.
“Despite a projected increase in rainfall with future climate change in the equatorial Pacific, many locations will likely face greater water scarcity due to saltwater intrusion from rising seas and higher rates of potential evaporation due to increased temperatures,” Howden said.
Professor Howden noted other opportunity areas Australia should be focusing its efforts such as decarbonising transport, reducing emissions from agriculture, and drawing down and storing atmospheric greenhouse gas emissions.