ConserveOnline - California Climate Stress Reports

California Climate Stress Reports - Overview

By Kirk Klausmeyer on 4/28/2009 | Keyword(s): Climate Stress Report

The Nature Conservancy’s (TNC’s) Climate Stress Reports are designed to help our staff better understand the projected future stresses from climate change over the next century. Each report has the same format but focuses on a specific landscape where we work, called a “Last Great Place”.

What is in the Climate Stress Report?

The Climate Stress Reports relate observed climate data from the 20th century to potential future climate change by 2100 so TNC staff can begin to understand how different climate will be at site relative to what they have experienced.

The first section in the report summarizes the Drought Stress Index and Heat Stress Index for each site. These indices compare past climate with potential future climate in a single metric for each landscape, helping TNC staff estimate how much climate at their site will change so they can begin to assess species vulnerability.
The second section summarizes the future potential changes in precipitation and temperature at each project site.
The last section summarizes past precipitation and temperature at each site between 1900 and 2000.

How can TNC staff use these reports?

With these reports, we hope TNC staff will be able to:

Begin to identify which species are going to be most at risk from projected changes in temperature or precipitation
Better understand observed climate variation at each site over time
Have concrete examples of projected climate change at each site for use in documents and proposals.

Where can I download these reports?

You can follow this link to see the list of 27 Last Great Places that have completed Climate Stress Reports.

You can also download a poster-size map of the Drought Stress Index and the Heat Stress Index for California

What data sources were used?

The observed climate summaries were generated from the PRISM climate layers, which we have from 1895-2007 for every month for precipitation, minimum, maximum and average daily temperatures for the continental United States at 800m resolution. To learn more about this dataset and the methods used to generate it, please visit http://www.prism.oregonstate.edu.

The future climate projection summaries were generated from 15 Global Climate Models (GCMs) run to support the International Panel on Climate Change (IPCC) Forth Assessment Report. To learn more about these data, please visit http://www-pcmdi.llnl.gov/ipcc/about_ipcc.php. We converted and downscaled these data using a change factor approach and a spline interpolation to match the 800m resolution of the PRISM data.

How were the Drought and Heat Stress Indices created?

The drought stress index is calculated by comparing the future (2070-2099) 30-year mean projection of total annual precipitation for every 800m pixel to the observed annual values between 1900 and 1999. The index is calculated based on the number of observed years that are greater than the future projection. Thus a value of 70 means that the future projection is drier than 70 of the 100 years between 1900 and 1999. We classified this value into the following categories: 0-50 is low, 50-66 is medium, 66-99 is high, and 100 is unprecedented. The heat stress index is calculated and classified the same way except we use July maximum temperatures and count up the number of observed years that are less than (cooler) than the future projection. We calculated these values for all 15 of the GCMs, and generated a standard deviation between these values. We consider a standard deviation of 20 or greater as “high” uncertainty and a value of 0-20 as “low” uncertainty.

Who created these reports?

These reports were generated by the Climate Change Adaptation Team based in the TNC’s San Francisco Office. If you would like to cite these reports, please use the following format:

The Nature Conservancy California. “Climate Stress Report, Version 1.1”. April 28, 2009. Available online at http://conserveonline.org/workspaces/CA.climate.change