Bronwyn Hayward, Jim Salinger, James Renwick and other experts respond to a critical report from the International Panel on Climate Change 

The IPCC’s latest special report, Global Warming of 1.5C, has been released at a press conference in Incheon, South Korea. Its publication follows a week-long session in Incheon. It highlights a number of climate change impacts that could be avoided by limiting warming to 1.5C above pre-industrial levels, including offering some protection to coral reefs and preventing about 10 centimetres of sea-level rise.

The NZ Science Media Centre collected comment from a range of experts.

Bronwyn Hayward

In my view, this hard-hitting 1.5 degrees Global Warming Report marks the end of “magical thinking” about climate change. The report is unequivocal, our climate is changing now. These changes are already affecting human wellbeing through extreme weather events and sea level rise, and risking far-reaching losses including coral reefs and Arctic sea ice.

For the first time, this IPCC report also places climate change within a social context, it asks: how can we limit climate change and achieve other important related goals of sustainable development and reducing poverty?

The report makes clear that without unprecedented cuts to emissions now, we will have fewer opportunities to develop sustainably and will be required to rely increasingly on unproven, risky and possibly socially undesirable technologies to remove carbon from the atmosphere in the future.

But to avoid climate warming above 1.5C, we have to scale up action in unprecedented ways across all sectors of our economy and everyday life, over the next 10 years.

The report estimates that temperatures have already risen by 1C higher than pre-industrial averages and that our world is now warming at a rate of about 0.2C per decade.

This doesn’t sound like much but if we carry on like this, effectively the world will be warmed 50% more that it has already experienced, between 2040-50, and some regions will feel the effects of these changes even more severely and quickly.

The report is also clear that avoiding a warmer future above 1.5C will bring significant benefits for millions of people who will face significantly reduced risks of flooding, food insecurity and climate stress, including Pacific communities.

Avoiding a higher than 1.5C warmer future matters to New Zealand in many ways – I want to highlight three:

1. Implications for New Zealand’s coastal communities

If the world’s temperatures remain at or below 1.5C the report suggests we could avoid an additional 10 cm of sea level rise on average, over and above the trajectories we are already committed to by 2100. Here in New Zealand where many of our cities are coastal, this matters a great deal.

As Tim Naish’s work shows, 20cm to 30cm by 2060 is pretty much given already due to warming from carbon already accumulated in our atmosphere. This new IPCC report underscores that 1.5 to 2 degrees could trigger rapid melting of the Antarctic and Greenland with very significant impacts locally for much higher rates of sea level rise over time. At the very least a world warmed above 1.5 degrees has significant implications for New Zealand national adaptation planning.

2. Issues raised for New Zealand’s Farming Sector

The 1.5 report also states that if we want to limit global warming to 1.5 degrees and avoid ‘overshoot’ we need to make ‘deep reductions’ in methane – by 35% by 2050 relative to the rates of emission in 2010 and undertake targeted mitigation of nitrous oxide. Again, this presents New Zealand governments and the farming sector with difficult choices. We have some tremendous opportunities for reducing methane and nitrous oxide but the need for deep cuts in emissions raises far-reaching questions about stocking and land use, and signals that we might expect significant shifts in terms of changing consumer behaviours towards more sustainable diets.

3. New Zealand’s challenge to achieve climate resilient development

The report is also clear that current national commitments to emission cuts are insufficient to hold the world’s climate to below 2 degrees. The report calls for far-reaching transitions across all sectors including how we use energy, land, urban and infrastructure (transport and buildings), and industrial systems and notes the need for a wide portfolio of mitigation options that carefully manage development to help communities already struggling, to develop equitably.

The New Zealand government and opposition have already committed to debating a bill to create a New Zealand net carbon zero by 2050, but making this vision a reality presents tough challenges in a country which has historically relied predominantly on one policy tool – Emissions Trading – to address climate change.

The implications of the report are that systemic, sustainable changes are required, for a low carbon future. At the very least, this includes a wide range of life-altering actions across all sectors of our society and economy if New Zealand is to have a realistic shot at achieving climate-resilient development pathways which meet the needs of all the community in the future.

Bronwyn Hayward is associate professor at the University of Canterbury and a lead author on the IPCC special report.She would also like to acknowledge the efforts of Dr Andy Reisinger, the New Zealand Vice Chair of the IPCC, and Ministry of Environment officials, Dan Zwartz and Helen Plume who put in many long hours in the intergovernmental approval process for this Special Report.

Catherine Leining

For the past decade, we have kept hitting the “snooze” button on serious climate action. The latest IPCC report is a serious wake-up call about the environmental, social and economic costs of low and slow ambition. We do not face a simple binary choice between 1.5 or 2 degrees C when the world is on track for neither target and already experiencing serious climate change impacts.

One clear finding from the report is that significant and accelerated emission reductions are needed across the economy, including methane and nitrous oxide from agriculture. A clear implication is that we will need a predictable and responsive policy framework for adjusting our course, speed and distribution of costs as we progress. Policy uncertainty is toxic for low-emission investment.

For New Zealand, effective emission pricing must be a key part – but not the only part – of that framework. We also need policies to support those sectors and communities who will find it most difficult to adjust, as well as durable processes and institutions for cross-sector engagement and independent advice. Above all, we will need to sustain social and cross-party consensus on how much we stand to gain, and how we choose to spread the costs, from bolder, faster action.

Catherine Leining is policy fellow, Motu Economic and Public Policy Research

Jonny Williams

The IPCC special report on the effects of increasing average world temperatures by 1.5ᵒC above pre-industrial levels is realistic, with the authors recognising that maintaining temperatures below 1.5 degrees will be challenging, but certainly not impossible.

For this reason, the report also considers the differences between the effects of climate change at 1.5 and 2 degrees of warming as well as the potential need to actively remove greenhouse gases from the atmosphere to reduce their warming effects.

It’s important to emphasise here that although many people are familiar with global warming, this rising air temperature is just one example of climate change’s effects on our planet. Other effects which are explored in the report include ocean acidification and the impact of rising ocean temperatures on coral reefs and fisheries, and sea level rise.

When it comes to the risks to humans from climate change, sadly it is often the people who are least able to take action who will be affected the most. These groups include those who are dependent on the above-mentioned fisheries for their livelihoods and those who may be displaced from their homes due to sea level rise.

The report has gone through an extensive and lengthy peer review process and represents the current state of scientific understanding of where we are now and where we might be going in the future. It does not lose sight of the human side of the equation however and makes frequent reference to the UN’s Sustainable Development Goals which were highlighted frequently by former Prime Minister Helen Clark during her time as Administrator of the United Nations Development Programme.

Dr Jonny Williams is a climate scientist at NIWA. Conflict of interest statement: Dr Williams was a peer reviewer of the report.

James Renwick

The report says roughly what I expected it to, but it still makes for sobering reading. We are currently living with 1C of global warming and we’re seeing effects already in extreme events and impacts on ecosystems and societies worldwide. More warming, even half a degree, means more and bigger impacts, but it is clear that a 1.5C world would be a lot more manageable and recognisable than a 2C world.

This report makes a compelling case for rapid decarbonisation, starting now. If we want to save even a fraction of unique ecosystems such as the Great Barrier Reef, we cannot afford two degrees of global warming.

However, while stopping at 1.5C is still physically possible, it would require huge political and social commitment from all countries. The world would need to reach zero carbon by 2050, with a 50% reduction between now and 2030. Given the past trajectory of global emissions of greenhouse gases (nearly a doubling in the past 30 years), this represents a truly heroic and unprecedented effort to turn the global economy around. Are the governments, the businesses, and the people of the world up to it?

Professor James Renwick is a climate scientist at Victoria University of Wellington

Jim Salinger

The latest IPCC report is the most significant of all those to date because the difference between the impacts of 1.5°C and 2.0°C is earth-shattering. For example, coral reefs would decline by 70-90 per cent with global warming of 1.5°C, whereas virtually all (> 99 per cent) would be lost with 2ºC. Species loss and extinction are projected to be significantly lower at 1.5°C of global warming compared to 2°C.

The report notes globally, human activities are estimated to have caused approximately 1.0°C of global warming above pre-industrial levels, with a likely range of 0.8°C to 1.2°C. Global warming is likely to reach 1.5°C between 2030 and 2052 if it continues to increase at the current rate.

For New Zealand, temperatures have increased by 1.2°C between 1867 and 2018 as shown in the diagram below with this year heading to be one of the warmest ever.

With a global average temperature rise by 2ºC above pre-industrial values, then around 400,000 of the species that we know could go extinct, the numbers for 1.5°C would probably be about a third to half this number.

There are also substantial implications for New Zealand’s future greenhouse gas (GHG) emissions reductions, especially methane (CH4) to keep warming at about 1.5°C. Carbon dioxide emissions reductions must commence at 2020 and reduce by about half by 2030. For 2.0°C, this must be achieved by 2040.

For 1.5°C starting at 2020, methane must be halved by 2040 to keep warming at about 1.5°C, when carbon dioxide must be about a quarter of its 2020 emissions. Thus the 1.5°C requires immediate reductions in all greenhouse gas emissions. New Zealand does not have the luxury in delaying its agricultural methane emissions to play its part to achieve the 1.5°C target.

Dr Jim Salinger is deputy editor, Climatic Change Journal, and former IPCC lead author