Environment – Human-induced climate change already affecting weather and climate extremes

Climate change is happening, faster than we thought, and humans have caused it. That’s the stark message behind the new IPCC physical science climate report.

Human-induced climate change is already affecting weather and climate extremes across the globe, according to the latest report from Working Group 1 of the Intergovernmental Panel on Climate Change (IPCC).

The evidence has strengthened – not only in the observed changes in heatwaves, heavy rains, and drought extremes – but also in their attribution to human influence, since the last report was published in 2013.

The Science Media Centre asked independent experts to comment, as well as the report’s NZ-based authors.

Professor Bronwyn Hayward, Professor of Political Science and International Relations, University of Canterbury, comments:

Note: Professor Hayward is a member of the IPCC core writing team and Co-lead of the Cities & Infrastructure chapter of AR6 Working group 2 report. She was also a lead author on Special Report 1.5°C. These views are her own expert assessment and do not reflect those of the IPCC.

“Climate change is happening, faster than we thought, and humans have caused it.

“That’s the stark message behind the new IPCC physical science climate report.

“In this first of three major research reviews, scientists tell us human activity is ‘unequivocally’ driving the warming of atmosphere, ocean and land. Unequivocal is the strongest term the IPCC can use.

“The report is frank and blunt. It says our climate is changing faster than we anticipated even in 2018. The IPCC says human activity has warmed the climate by 1.1 degrees since the pre-industrial era.

“The report doesn’t put a precise date on when we know we have crossed the dangerous threshold of 1.5 degrees Celsius of warming, but says unless we make far reaching change, this will occur over the next 20 years using average temperatures. This will expose many more people and our natural environment to even more devastating consequences including intense flooding, storms and unprecedented droughts and fires.

“While we need more regional data for New Zealand, cities get a special mention, as hotspots where the experience of localised heat and flooding will be more intense than global averages. This matters because cities in New Zealand are already home to nearly 90 per cent of our population.”

No conflicts of interest.

Professor Iain White, Professor of Environmental Planning, University of Waikato, comments:

“The latest IPCC report lays out a sobering and authoritative assessment of climate change and what the near future might hold. I’ve read all the Assessment Reports on the physical science and implications over the years. I thought I might get desensitized, but I actually felt a little sick at a couple of paragraphs. I feel for the scientists who have to put this together.

“But it’s important to note that while it is new science, it is an old message. The physical science basis of climate change has been largely accepted since I was at school, and each periodic IPCC report only serves to increase the certainty and amplify the risk. To be honest, politicians already know what needs to be done and why. The persistent problem we have failed to grapple with is how and who?

“These difficult conversations about economic and societal transition are decades overdue, but an Emissions Reduction Plan is due by the end of the year. This will be vitally important. We need to change how we live, how we move, and the structure of our economy. We need to use all the levers of government, from incentives and signals to shape markets, to policies and budgets relating to housing, transport, and the wider economy to ensure actions are effective and equitable.

“The hidden challenge is integrating this at scale and pace across government. For example, at the same time as politicians in Wellington react to this report with concern, climate advocacy groups are suing Auckland Transport and Auckland Council over a long-term Land Transport Plan that fails to reduce emissions. It’s a sign that our institutions helped create the current situation, and action may involve new governance structures or fundamental changes to leadership, budgets, or sectors. Otherwise the biggest risk the government has in implementing the plan may be other arms of government.

“We also need to avoid falling into the trap of techno-optimism, which masks that significant changes are required that will be resisted. If anyone is in doubt at the scale of the challenge, reflect on how hard it was to reorient just a few individual streets towards walking and cycling during the Innovating Streets trial. Now do that to a city. Or a sector.

“Science has done its job. It did it decades ago, frankly. Now it’s time for politics and related professions to do their job. Only now they have less time than previous generations of politicians and the implications are ever more certain.”

No conflict of interest

Dr Sara Mikaloff-Fletcher, Principal Scientist – Carbon, Chemistry and Climate, NIWA, comments:

“Climate change is no longer a problem of the future. It has already affected weather and climate extremes in every inhabited region on earth, and these changes will continue for decades to come. The most recent report from the Intergovernmental Panel on Climate Change (IPCC) presents overwhelming evidence that greenhouse gas emissions have already affected every part of the climate system and shows that even with rapid emissions reductions, it will take 20 to 30 years for global temperatures to stabilise. Some other changes, such as melting of ice sheets, are irreversible on human timescales.

“It is still possible to limit the impacts of climate change. Every action we take to reduce our net emissions of carbon dioxide, methane, and other greenhouse gases will help us towards a brighter future. However, the IPCC report shows that the longer we wait to stabilise climate, the harder it will be. Models predict extreme temperatures and droughts brought on by climate change will weaken the ability of forests and other green spaces to absorb carbon dioxide. This is particularly significant for Aotearoa New Zealand, because our forests and land use offsets roughly a third of our total greenhouse gas emissions. We must begin to come to terms with how changes in climate impact our forests and their ability to absorb and store carbon.

“IPCC reports are the climate science community speaking in our most measured collective voice. Each word in this report has been carefully weighed and considered by the authors, and the document has been assessed by nearly eighty thousand experts worldwide. There are no surprises in this report for most climate scientists, only well supported facts. Strong, rapid, sustained reductions in our emissions are the only way to stabilise the earth’s climate.”

No conflicts of interest.

Professor Adrian McDonald, Director of Gateway Antarctica, School of Physical and Chemical Sciences, University of Canterbury, comments:

“The Working Group 1 sixth assessment report from the IPCC represents a vast amount of work from the authors, which must be congratulated. This report summarises the recent work of thousands of climate scientists and represents the most authoritative summary of the current state and possible futures of the Earth’s climate ever created.

“This report continues to confirm that human influences are impacting most aspects of our climate system. Temperatures have continued to increase, precipitation has changed, the oceans have warmed and sea level has continued to rise. The largest leap forward, in my view, is that the attribution of observed changes in the frequency and intensity of heat waves, heavy precipitation and flooding, and droughts to human influences is now much more certain. Basically, we have already changed our climate in dangerous ways based on robust scientific analysis.

“This report also identifies that climate model skill continues to improve. Meaning that the projections of a progressively worse climate state in the future are now even more certain.

“Simply put, this report tells us that the observed impacts of climate change are increasingly worrying. The improved and updated projections of the future in this report also show that efforts to reduce greenhouse gas emissions and prepare our societies for further change must be accelerated to safeguard the climate for future generations.”

No conflicts of interest.