Actuaries Climate Index At a Glance

The Actuaries Climate Index (ACI) is intended to provide a useful monitoring tool—an objective indicator of the frequency of extreme weather and the extent of sea level change. This section provides graphics of the ACI by region and component.

The Actuaries Climate Index has six components, each of which is a monthly or seasonal time series beginning in 1961 based on measurements from an extensive network of meteorological stations and coastal tide stations within the United States and Canada. Where possible, the components measure extremes rather than averages, because extremes have the largest impact on people and property. All data is standardized to measurements over the 30-year reference period of 1961 to 1990, and the key metric is a five-year moving average, which reduces the noise of the time series data and allows users to see a clear climate signal. The index will be updated each quarter by reporting on the most recent available meteorological season (three months ending February, May, August, and November). In addition to the overall ACI for Canada and the United States combined, it is available by individual component, for Canada and the contiguous United States (i.e., excluding Alaska) separately, as well as for 12 sub-regions.

The six climate index components are:

  1. Frequency of temperatures above the 90th percentile;
  2. Frequency of temperatures below the 10th percentile;
  3. Maximum 5-day rainfall in the month;
  4. Consecutive dry days;
  5. Winds above the 90th percentile; and
  6. Sea level.

More information is available in the Executive Summary. For a detailed description of the methodology behind the index, please read the Development & Design document.