The Synthesis Report acts as a concise summary of the most important science on climate change presented in the underlying 4 volumes. Selected findings that are deemed of the highest policy and societal relevance from each underlying volume are integrated into the report.  The reports include the work of 23 Irish climate and energy experts.  See original publication at bit.ly/44l54op (2023).

Key findings

A.  A changing climate

Human activity has resulted in widespread and rapid changes in climate which are already impacting us all today.

A.1   Human activity has led to widespread and rapid changes in all components of the global climate system, which are unprecedented over many centuries to many thousands of years. Atmospheric greenhouse gas concentrations are higher than at any point in millions of years. Globally, the most recent decade was likely warmer than any sustained period in at least the last 100,000 years. Global sea level has risen by 0.2m since 1900, and the rate of global sea level rise is accelerating.

A.2   The best estimate of human-caused global warming from 1850–1900 to 2013–2022 (1.14°C) matches almost exactly the best estimate of observed global warming (1.15°C). This warming is mainly due to increased atmospheric greenhouse gas concentrations, partly masked by cooling due to short-lived atmospheric aerosols (small particulates) co-emitted with fossil fuel combustion. Human-induced climate change is also modifying climatic extremes globally, with robust evidence in particular that it is increasing the frequency and intensity of heatwaves and extreme precipitation events.

A.3   Over Ireland, annual average temperatures are now approximately 1°C higher than the early 20th century with 16

of the 20 warmest years occurring since 1990, and 2022 being the hottest year on record to date. Overall, when aggregated, there has been an increase in heavy precipitation extremes over Ireland across a range of indicators. Recent studies have highlighted higher rates of sea level rise than the global average since the late 20th century in Cork and Dublin.

A.4   Recent extreme events in Ireland highlight the vulnerability of individuals, communities, sectors and ecosystems to climate change and indicate an adaptation deficit.

B.  Climate futures and their impacts

The future climate is in our collective hands. To halt warming globally and in Ireland requires rapidly reaching at least net-zero carbon dioxide emissions and substantially cutting other greenhouse gas emissions. Every action matters: with every additional increment of warming, impacts for Ireland will increase substantially.

B.1   Deep, rapid, immediate and sustained emission reductions are required to keep global warming in line with the key Paris Agreement temperature goal. To stabilise the global climate requires global carbon dioxide emissions to reach at least net-zero, with emissions of other greenhouse gases substantially reduced on a sustained basis. If we can reach net-zero global carbon dioxide emissions by mid-century, then components such as temperature and precipitation, which react within years to decades to changes in radiative forcing, would stabilise within the lifetime of many of today’s younger citizens. However, sea-level will continue to rise and will take thousands of years to stabilise, even once net zero emissions are reached.

B.2 Early and rapid global action on emission reductions would likely leave an Irish climate that is still broadly recognisable

in comparison to today, whereas delayed action would very likely leave an Irish climate that is increasingly unrecognisable as the century progresses. Under Early action scenarios, the temperature increase averaged across the island of Ireland relative to the recent past (1976–2005) would reach 0.91°C [0.44–1.10°C] by mid-century before falling back to 0.80°C [0.34–1.07°C] at the end of the century. Whereas under Late action scenarios, by the end of the century it is projected that the temperature increases could be 2.77°C [2.02–3.49°C]. Intense precipitation extremes become more frequent and extreme with further warming in most regions of Ireland across a range of extreme precipitation indices. Storm surges and extreme waves will pose an ever-increasing threat to Ireland as sea levels continue to rise.

B.3   Future changes in climate will have impacts greater than those already experienced for all aspects of Irish society, the environment and economy. Significant potential sectoral impacts and challenges arising from further climate change include:

• Significant impacts on biodiversity on land and in the ocean are projected with additional warming. Changesin temperature and precipitation are likely to increase the occurrence and spread of invasive species and the competitive pressures faced by Ireland’s native species.
• Climate change will impact all aspects of Irish agriculture. While increases in productivity can be expected for some crops, decreases can be expected for others.
• With all major cities and many regional towns located close to the coast, Ireland is highly exposed to sea level rise,storm surges and coastal erosion, especially in softer sediment coastal zones.
• Projected changes in future river flows show a wide range; however, increases in extremes of both floods and droughts are expected, based on findings from the majority of available studies. Impacts on water resources, water quality and floods are likely to cascade across other sectors.
• Ireland’s built environment is exposed to flood risks from rivers, the sea and rainfall extremes. Increases in extremespresent challenges for the integrity of built environments and heritage sites.
• Ireland depends on critical infrastructure for delivering public services, economic development and a sustainableenvironment. These are exposed to a range of climate extremes. Failures in critical infrastructure can cascade across other sectors and present a multi-sector risk.
• Climate change impacts will directly and indirectly affect health and wellbeing, while vulnerability is likely toincrease as Ireland’s population ages over the coming decades. Critical health infrastructure, including hospitals and care homes, faces increased risks from heat and flood extremes.
• Tourism is highly exposed and vulnerable to climate change. Warmer summers are often perceived as an opportunity for Irish tourism through increasing visitor numbers. However, without careful management, this could create damaging and unsustainable pressures on sensitive heritage sites and environments.

C.  Delivering a climate neutral Ireland

Having peaked in 2001, Ireland’s greenhouse gas emissions have reduced in all sectors except agriculture. However, Ireland currently emits more greenhouse gases per person than the EU average. A legal basis for deep, rapid and sustained national emissions cuts now exists, although current policy and action remain insufficient to meet these aims. The pathway forwards is clearer for energy, transport and the built environment than for agriculture and land use. For all sectors there are many challenges to overcome.

C.1   Ireland has made limited progress in reducing greenhouse gas emissions to date and there is a very long way to go.  Ireland is currently ranked second highest across the EU when all greenhouse gas emissions are considered on a per person basis.

C.2   In 2021, Ireland legislated for 5-yearly carbon budgets and sectoral emissions ceilings which set a limit on the amount of greenhouse gas emissions that can be released over defined periods. These budgets were consistent with a target for a 51% reduction in total greenhouse gas emissions (including in land use, land use change and forestry (LULUCF)) by 2030, compared with 2018, and a long-term national climate objective of climate neutrality by 2050 at the latest. Currently deployed policies and actions are insufficient and Ireland is not presently on track to meet these statutory greenhouse gas emission reduction targets. Greenhouse gas emission estimates for 2021 and 2022 indicate that 47% of Ireland’s first carbon budget has been emitted within 40% of the budget’s time frame (2 years of the 5-year budget period).

C.3   There is a significant gap in the literature available for climate-neutral pathways in Ireland. These knowledge gaps, especially in the LULUCF sector, make understanding and achieving Irish climate neutrality highly challenging and need to be urgently addressed.

C.4   Achieving net zero carbon dioxide emissions by 2050 requires significant and unprecedented changes to Ireland’s energy system. Policies tailored to suit different stages of technology development are critical for achieving a net zero energy system. Established technologies, such as wind energy, solar photovoltaics and bioenergy, will be key in meeting short-term emission reduction targets (i.e. 2030), whereas offshore wind infrastructure is expected to be the backbone of future energy systems. This can only be achieved with appropriate support schemes, regulation and investments for synergistic growth of offshore wind and other renewable technologies. Future energy choices post 2030 need greater exploration to plan for the required transition. In sectors such as transport and the built environment, reaching net-zero principally, although not exclusively, is going to be achieved through electrification.

C.5   Deep emission reductions within the agriculture and land use sectors are a critical aspect of Ireland’s efforts to mitigate climate change and to transition to a low-carbon economy. Optimal use of no-regret livestock management measures, including increasing the dairy Economic Breeding Index, improving herd genetics, improving animal health and promoting efficient feeding strategies, will help in reducing greenhouse gas emissions. Despite the recognition of the importance of agricultural emissions and land use removals, there is a critical research gap in determining the specific levels of emissions that can feasibly be balanced with land use practice. The research on land use, land use change and forestry suggests that the primary means to get to net zero for this sector is through unprecedented rates of afforestation and the rewetting of organic soil along with a significant reduction in herd numbers. The majority of the mitigation options available in Ireland are still in the early implementation stages, and there is an urgent need for Ireland to explore various diversification strategies to enable deep mitigation.

D.  Adapting to climate change and ensuring a climate resilient Ireland

Ireland needs to be resilient to ongoing and future climate change impacts. This requires increased focus upon and investment in adaptation that can protect us from future climatic impacts. Current implementation of adaptation is too slow and fragmented. Doing better requires financing, working with people and nature, monitoring and evaluating outcomes, and increasing public and private sector involvement.

D.1   Ireland has set the national objective to transition to a climate resilient, biodiversity-rich, environmentally sustainable and climate-neutral economy by 2050 at the latest. Resilience refers to the ability to absorb and respond to climate change by implementing effective adaptation actions and sustainable development to reduce negative climate impacts, while also taking advantage of any opportunities. Looking to the future, aside from climate change, social, environmental and economic challenges in energy, health, housing, and an ageing population, together with biodiversity loss, all increase vulnerability to climate change impacts.

D.2   Climate change is happening now, and therefore adaptation needs to be given increased attention. Actions taken today to reduce vulnerabilities and exposure and increase resilience will have benefits now, while shaping the future, and should be seen as an investment rather than a short-term cost. We are not starting from an ideal position for adaptation due to ageing infrastructures and significant and ongoing deterioration in environmental quality, including declines in water quality, biodiversity, and ecosystem quality.

D.3   Mitigation and adaptation are inherently linked. The more warming experienced, the greater the challenge of adaptation. At the same time, even if the world is successful in meeting the temperature goal of the Paris Agreement, adaptation to a changed climate will still be required. Adaptation actions can entail ‘response risks’, which may result in maladaptation. These include the risk of adaptation actions being ineffective and / or unjust or having unintended adverse effects. Opportunities need to be created to evaluate and learn from experience to avoid maladaptation.

D.4  Adaptation is mandated in national legislation and integrated with EU policy. Governance structures and oversight mechanisms have been developed. Many sectors nationally and local authorities have developed their first iteration of adaptation plans, while investment in climate action regional offices (CAROs) is supporting capacity development. Research is advancing, and the National Framework for Climate Services is delivering more tailored and user-friendly climate services. Community engagement and widening of adaptation actions to include nature-based approaches and non-structural measures is being increasingly recognised.

D.5   While many sectors have developed adaptation plans, many have shown limited progress on implementation of these.  Other sectoral plans are missing, including critical areas such as the built environment, tourism and sport, and financial services, while cross-cutting issues such as coastal environments also need to be addressed. Critically, developing a climate-resilient Ireland will require sufficient public and private investment and financial support in ways that recognize the value of ecosystem services and the importance of societal wellbeing. Knowledge gaps for adaptation and resilience also remain to be addressed. Assessments of impacts are uneven across sectors and need to be regularly updated. As a small, open economy in an increasingly interconnected world, Ireland is also exposed and vulnerable to climate change impacts and policy responses in other parts of the world.

D.6   Key actions necessary to build momentum and develop a pathway to a climate-resilient Ireland across scales include: defining objectives; ensuring just adaptation / resilience; increasing finance and moving beyond the limits of traditional cost–benefit analysis; placing a greater focus on monitoring and evaluation; understanding the social dimensions of adaptation; working with people and nature; minimising response risks; integrating climate uncertainty into decision making; and avoiding lock-in and maintaining flexibility.