Frequently Asked Questions about the Actuaries Climate Index

1. WHAT IS THE ACTUARIES CLIMATE INDEX? The Actuaries Climate Index (ACI) is an objective measure of changes in extreme weather and changes in sea level relative to the base period of 1961 through 1990. The Index is an educational tool designed to help inform actuaries, public policymakers, and the general public on changes in these measures over recent decades. We intend to update the index quarterly, as data for each meteorological season is available. We also intend to publish a second index, the Actuaries Climate Risk Index (ACRI), based on the historical correlations of economic losses, deaths and injuries to the ACI data.

2. WHY ARE ACTUARIES WEIGHING IN ON CLIMATE CHANGE DISCUSSIONS? Actuaries are experienced in the assessment and mitigation of financial consequences of risks and in the summarization and presentation of complex data. Climate change is having a financial impact on insurance consumers and the insurance industry, and actuaries are well positioned to conduct deep analysis to map out what has been happening since 1961.

3. WHO IS SPONSORING THE ACI? The ACI is the result of a research project jointly funded by actuarial organizations of the United States and Canada. The organizations are the American Academy of Actuaries, the Casualty Actuarial Society, the Canadian Institute of Actuaries, and the Society of Actuaries.

4. WHO DEVELOPED THE INDICES? The four actuarial organizations formed two committees that were responsible for managing the research and developing the indices: the Climate Change Committee and the Climate Index Working Group. In addition, Solterra Solutions, a consulting firm in Victoria, B.C., was contracted by the actuarial organizations to provide climate science expertise and research into the appropriate data and methodology for constructing the indices.

5. WHAT ARE THE COMPONENTS OF THE ACTUARIES CLIMATE INDEX? The Index examines changes in the frequency and duration of extreme temperatures (highs and lows separately), heavy precipitation, drought, and strong wind, as well as changes in sea level. The Index is available for 12 regions in the United States and Canada and examines how the six components, and the composite thereof, are changing over time by region and across the two countries.

6. WHY DID YOU CHOOSE THESE SIX COMPONENTS? The committees selected these six components for the Actuaries Climate Index because they are representative of the key impacts of climate on people and the economy.

7. WHAT IS THE WEIGHT GIVEN TO EACH COMPONENT IN CALCULATING THE VALUE OF THE ACI? The Actuaries Climate Index is based on the average of the six components, with changes in the frequency of extreme low temperatures subtracted from the sum of the other five components before taking the average. Low temperature frequencies tend to move in the opposite direction of high temperature frequencies, and it is the difference between the two that best reflects the impact of changes in climate. Users can access the values of each component to analyze the data for their own purposes.

8. WILL THERE BE GLOBAL CLIMATE INFORMATION AVAILABLE EVENTUALLY? The Actuaries Climate Index focuses on Canada and the United States at this time, reflecting the constituencies of the sponsors of the project. Efforts are underway by other actuarial organizations to consider replicating the ACI methodology in other regions of the World. The methodology can easily be applied in other countries where good data is available.

9. WHO PROVIDES THE DATA BEHIND THE INDEX? The data is gathered from the following public data sources:

Drought, Temperature, & Precipitation

  • Global Historical Climatology Network (GHCN) Daily, from the NOAA Satellite and Information Service, is an integrated database of daily climate summaries from land surface stations across the globe. The grids each cover a surface area of 2.5 degrees longitude by 2.5 degrees latitude.
  • GHCNDEX is a dataset based on GHCN Daily. It provides gridded, station-based indices of temperature- and precipitation-related climate extremes and was developed by the Climate Change Research Centre and the Australian Research Council’s Centre of Excellence for Climate System Science.
  • CLIMDEX (Datasets for Indices of Extreme Weather) is developed and maintained by researchers at the Climate Change Research Centre (CCRC), The University of New South Wales (UNSW) and funded by the Australian Research Council and the Australian Department of Climate Change and Energy Efficiency through Linkage project LP100200690 and in collaboration with the University of Melbourne, Climate Research Division (Environment Canada) and NOAA’s National Climatic Data Center (USA). See also: Expert Team on Climate Change Detection and Indices at the World Meteorological Organization.

Sea Level


  • The National Centers for Environmental Prediction (NCEP) reanalysis data, done in conjunction with the National Center for Atmospheric Research (NCAR), is provided by the National Oceanic and Atmospheric Administration’s Oceanic and Atmospheric Research/Earth System Research Laboratory Physical Sciences Division in Boulder, Colorado, USA.


10. ARE YOU PROVIDING THIS CLIMATE INFORMATION TO REGULATORS? The committees and partnering organizations have informed regulators about the creation of this climate Index and directed them to the Actuaries Climate Index website. The Index was developed to provide more information on extreme weather events for actuaries, public policymakers, and the public. Two of the sponsoring organizations, the American Academy of Actuaries in the United States and the Canadian Institute of Actuaries in Canada, will work with interested policymakers who wish to utilize the Index.


11. HAVE THERE BEEN ANY SIGNIFICANT CHANGES IN THE ACI METHODOLOGY SINCE THE FIRST RELEASE? In April of 2019, a change was made to the ACI calculation methodology. The methodology used to produce releases prior to April 2019 is referred to as “ACI 1.0”, while the methodology currently in use is referred to as “ACI 1.1”. A description of the change of methodology, and the rationale for the change, can be found in the data disclosure.