Climate represents the statistical properties of the weather. Climate change is about how these distributions change over time. Understanding how climate change signals emerge above natural variability in the future is the purpose of the Emergence/Whakahura programme. Among the aspects of shifting climate distributions that matter most for social, economic and environmental systems are changes in the extremes. Extreme weather, in the form of floods, droughts, and storms has changed in recent decades, and will continue to have a disproportionately large impact on our environment, society and the economy. We aim to improve understanding of how and why extreme weather has affected New Zealand in the 20^th century, and to develop new tools to improve the forecasting of extreme weather events.

The changing frequency and severity of extreme events will have significant impacts on New Zealand. Understanding extreme weather phenomena is consistently noted as critical for effective and efficient adaptation decisions. Examples are found in all sectors, including: drought for agriculture, urban pluvial flooding for planning, fluvial flooding for farmland, storms for transport networks, cyclones and storm surges for coastal communities, fire hazards for forestry, rural, and semi-rural communities, and any sudden-onset weather event that can affect economic activity.

These events have flow-on effects for insurance and financial institutions, economic development, long term community resilience, and spatial planning. Understanding the changing nature of extreme events under climate change is the area in which we aim to make a global contribution that is highly relevant to New Zealand. With our world-leading team (including collaborators from the University of Oxford, Lawrence Berkeley National Laboratory, UK MetOffice, Wharton Business School, and the London School of Economics), we will be addressing this major gap in understanding extreme weather events.

Our team will be:

• identifying how extremes have previously damaged New Zealand’s environmental, social and economic systems, and compiling a comprehensive database of these losses,
• detecting how climate change signals have emerged above natural variability in extreme events from the recent past (i.e., the problem of attribution),
• elaborating on how climate change signals will emerge above variability in the future,
• estimating damages and losses, for New Zealand, from future extreme events, and
• creating better tools for near real-time modelling of extreme events, and incorporating these into national weather forecasting

What results are expected and what will be their impacts?

The main benefit of our research programme will be improved well-being through informed decision-making in the face of fast-changing distributions of weather extremes. This will be delivered through the knowledge, predictions, and tools we will design around the needs of government, industry, iwi and individuals. In addition, the focus on the aggregate and systemic impacts of extreme weather events under climate change will be of interest to individual investors, financial institutions, and regulators (the Treasury, the Reserve Bank, and major iwi asset holders).

Specific benefits include:

• Key decision-makers and investors becoming better-informed regarding the most likely damaging weather events in the next 40 years, and the likely systemic effects of these on the economy.
• Stakeholders and researchers having access to a rich database of past losses (environmental, economic and cultural) from extreme weather events in New Zealand.
• Individuals having access to improved forecasts of near-term extreme events.
• Iwi/hapū improving protection and management of their assets in the face of climate change induced extreme weather.
• Cultivating and enhancing climate science fluency among researchers, stakeholders and the general public.