Step 5: Understanding trends in climate

A first step in assessing these potential impacts is to highlight or estimate the major current and expected trends (direction, magnitude, and extent) of climate-related hazards. The purpose of addressing the following questions is to assess the range of future conditions. This step provides a link between the current vulnerability (hazards experienced so far), trends in hazards and the need for urgent action. If the trends observed above are consistent with the range of scenarios for future climate change, then the rationale for urgent action is much stronger.

Guiding questions:

• What are the documented historical trends in these hazards?
• Is the nature and location of these hazards changing, and if so, how?
• What kinds of predictions have been made on these hazards for the area in question?

A useful starting point for evaluating climatic trends is to categorize these trends as those conforming either to: deviations from normal values, or geographic/temporal shifts in occurrences, as in the table below.

Typology of climate-related variability and change: guiding questions, methods of measurement and potential data sources

The following provides a typology of the kind information to be cited in such a summary. Note that the trends are characterized in terms of several variables. An example, drawn from a preliminary analysis of the ACCCA project, is available in the table below.

• Current Likelihood => How often these events occur?

• Trend in Likelihood => Coupled with predicted patterns, are the occurrences of these events likely to increase/decrease or otherwise change?

• Trend in Magnitude => Are these events likely to become more or severe in their impacts?

• Trend in location => Are the events likely to expand into areas currently not impacted, or are they likely to become more localized?

• Other trend descriptions => Could include a variety of conditions exhibited by these events, such as their temporal variation (are they likely to be more severe during specific months? Are they likely to be more severe when coupled with other events, such as famines, etc.?)

Summary Table of Trends in Climate Related Hazards

Data Sources

The choice method and data to be used to offer validation and support for observed and predicted trends in climate-related hazards will among countries and sectors, reflecting data quality and availability, as well as the time constraints of the project. A general guidance resource for climate data is the recent report on Climate information for adaptation and development needs by the World Meteorological Organisation, 2007.

Data Sources to Define Trends

Related Pages

Step 1: Identify Climate Vulnerability Exposure

Step 2: Assessing Conditions and Trends

Step 3: Identifying Hazards

Step 4: Analysing the Impacts of Climate Change