The world is set to cross 1.5°C global warming in the coming years, but we can still limit, adapt to and return from higher temperatures, according to a new UN report published this morning. 

The Limiting Overshoot report looks at what needs to be done to minimize the size and duration of this ‘climate overshoot’ and to try return to below 1.5°C as soon as possible.

The authors state that the impacts on extreme weather, sea level rise, human health, and ecosystem loss are already unavoidable and must be adapted to. However, returning below 1.5°C as quickly as possible and prioritising climate adaptation will reduce these risks.

The All Ireland Science Media Centre asked local experts to comment.

Dr Róisín Moriarty, Research Fellow in Climate Science and Policy at the Sustainability Institute, University College Cork, comments:

“The UNEP Limiting Overshoot report released today makes it clear, that now more than ever, ‘every fraction of a degree of warming matters’.

“When countries around the world signed up to the Paris Agreement, they agreed to do everything possible to limit climate change. Ireland, like all countries around the world, has an obligation to take action. So far action has been limited and not quick enough.

“The risks of overshoot are made clear in the report (severe damage to human health and security, nature, infrastructure and economies, alongside irreversible damage to ice sheets, the Atlantic Meridional Overturning Circulation and the Amazon rainforest) but so too are the actions that can be taken to keep 1.5 degrees in reach.

“We need to stop burning fossil fuels, cut methane emissions and protect nature and we need to do these things as quickly as possible. The faster we take action the more overshoot can be limited both in terms of peak warming and duration of exceedance.

“Reducing methane emissions is important, as unlike carbon dioxide that stays in the atmosphere and causes warming for a long time, methane, although a potent greenhouse gas, has a short atmospheric lifetime, so when methane emissions are reduced there is a reduction in warming. Substantial immediate reductions of methane (in parallel to rapid, deep and sustained reductions in carbon dioxide) can reduce peak warming.

“Ireland has high methane emissions from agriculture. Making a plan with farmers for how they can make big reductions in methane, in the next ten years, would contribute to limiting peak warming and limit some of the irreversible outcomes of overshoot. Action at national level can make a difference because ‘every fraction of a degree of warming matters’, no matter how small it is.”

Declaration of interest: “I declare no interests. I am funded my the Environmental Protection Agency.”

Dr Silvia Caldararu, Assistant Professor, Botany, Trinity College Dublin, comments: 

“The report sends a very strong and clear message of the urgent need for climate action and what our possible futures might look like.

“One thing that is very important to highlight is that the overshoot and return option is not at all certain and that we might be stuck with the overshoot part of it, without the possibility to return atmospheric CO2 concentrations to a level that would lead to temperatures below 1.5 degrees of warming. This is because CDR (carbon dioxide removal) methods are still very uncertain. The only one that we know works and is cost effective is afforestation and even then, efficiency of planting forests remains uncertain, especially as climate change gets worse and droughts, heatwaves and storms, as we have seen in the past year alone, affect forest stability and capacity to take up CO2 out of the air.

“What this means is that while the climate might stabilise as we reduce fossil fuel emissions, it will do so at a worse point than if we kept warming to below 1.5 degrees. The message of the report is not that we can keep on going way past any emission targets because we can always go back, but rather that we must urgently stop emissions and that the quicker we do so, the higher the chance that we can go back.”

Declaration of interest: “No declarations of interest. I have received national research funding from Research Ireland and the EPA.” 

Professor Iris Moeller, Professor of Geography and coastal geomorphologist, Trinity College Dublin, comments:

“This report is welcome as a reminder of what is at stake for generations to come; those who live and work in low-lying areas and small island states across the world will have no choice but to experience the impact of more intense or frequent coastal storms, often occurring at times when river levels are also high from intense rainfall. We saw this happening during storm Chandra last winter in Ireland, when Dublin experienced water levels that only narrowly missed overtopping sea defences – and there will be more and increasingly severe occurrences of this scenario as we overshoot the 1.5 C global temperature threshold.

“The global ocean heats up slowly and its waters mix over time scales of 1000s of years. So it will take many centuries for the ocean’s deep waters to warm and expand due to the rise in temperatures. On top of this, our ice sheets will continue to respond to warming that has taken place decades ago as the seasonal warming is gradually causing more ice to melt than to build up in the winter months. A rise in temperature takes time to translate into the release of meltwater but once it has formed, meltwater lubricates the base of the ice – so ultimately, we may be looking at a kind of ‘runaway’ effect; an acceleration of the process and a more rapid rise in sea level. The sooner we act to minimise our ‘overshoot’ above 1.5 C, the less likely we are to reach levels of catastrophic instability in our ice sheets.  

“As the report makes clear, we have to urgently curb our emissions, fast and globally. As to the impact of the damage already done, however, the good news is that nature itself has a way of counteracting and protecting itself from these impacts. We know now that our coastal fringes can absolutely protect us from the negative impacts, even where our coasts are ‘soft’ – offshore banks and shallow coastal waters, soft eroding cliffs, beaches, dunes, and salt marshes all contribute towards taking energy out of waves, reducing their height and reducing storm surge induced extreme water levels.

“But these nature-based solutions require space and we have gradually taken away this space. We have seen our cities’ urban and industrial areas, and, in more rural areas, our farmlands encroach seaward into and onto coastal ecosystems and are now locked into escalating costs to protect our new lands. Where we can, we have to urgently re-think the use of those spaces. There is a win-win-win situation here: Our EU-wide ‘REWRITE’ and Island of Ireland wide ‘CMAP’ projects show that allowing coastal nature to thrive not only protects us from the impacts of the 1.5 C ‘overshoot’ but at the same time enhances our health and well-being, counteracts widespread biodiversity loss, and leads to carbon removal from the atmosphere by coastal ecosystems such as seagrass, salt marsh and intertidal mudflats. If we work towards allowing space for coastal nature now, at scale and across the globe, there is no doubt that we will reduce the overshoot and accelerate the return to below 1.5 C. It requires government commitment, urgently, to do so.”

Declaration of interest: I have received EU research funding for NATURESCAPES, REWRITE and CMAP projects and I have also been receiving funding from the UK and Irish Governments in my role as lead of the ‘Risk and Opportunities’ Spoke of the Co-Centre for Climate, Biodiversity and Water.