Climate change is occurring at
especially rapid rates in some areas of the U.S. In national parks, climate
change challenges the ability of park managers to preserve natural and cultural
resources. To understand the “climate change exposure” of national parks—that
is, the magnitude and direction of ongoing changes in climate—we investigated
how recent climates compare to historical conditions. This recently published
research (Monahan & Fisichelli 2014) updates the basic climate inventories
for 289 national park units. Here, we summarize results for Cedar Breaks
National Monument, including areas within 30-km (18.6-mi) of the park’s
boundary. We evaluated climate-change exposure by asking which of 25
biologically relevant climate variables recently (past 10–30 years) experienced
“extreme” values relative to the 1901–2012 historical range of variability. We
define “extreme” conditions (e.g., extreme warm, extreme wet) as exceeding 95%
of the historical range of conditions.
Methods
To evaluate recent climate values
within the context of historical conditions, we used the following methods
(also illustrated in Figure 1): • For each temperature and precipitation
variable, we analyzed data within three progressive time intervals, or “moving
windows,” of 10, 20, and 30 years to calculate a series of averages over the
entire period of analysis (1901–2012). For example, in progressive 10-year intervals,
we calculated averages of temperature and precipitation for 103 blocks of time
(1901–1910, 1902–1911 . . . 2003–2012), and repeated this approach for the 20
and 30-year “windows.” This type of analysis helps to smooth year-to-year
fluctuations to identify longer-term trends that characterize the park’s
historical range of variability (HRV). The three windows encompass both near-
and long-term management and planning horizons, as well as important climatic
periods and cycles.
We compared the average temperature and
precipitation values for each of the most recent 10, 20, and 30 year intervals
(2003– 2012; 1993–2012; and 1983–2012) to those of all corresponding intervals
across the entire period of 1901–2012. These results (expressed as percentiles)
describe “recent” conditions relative to historical conditions. For example, a
90th percentile for annual average temperature over the most recent 10-year
interval (2003–2012) means that the annual average temperature during this time
exceeded 90% of annual average temperatures for all 10-year periods from 1901
to 2012. • We then averaged the percentiles of the most recent 10, 20, and
30-year time periods and computed the maximum difference in recent percentile.
For each park and climate variable, this resulted in both an overall measure of
recent climate change exposure with respect to HRV (dots in Figure 2), and an
estimate of sensitivity to moving window size (length of bars in Figure 2).
 |
Figure 1. Time series used to characterize the historical range of variability and most recent percentile for annual mean temperature at Cedar
Breaks National Monument (including areas within 30-km [18.6-mi] of the park’s boundary). The blue line shows temperature for each year, the
gray line shows temperature averaged over progressive 10-year intervals (10-year moving windows), and the red asterisk shows the average
temperature of the most recent 10-year moving window (2003–2012). The most recent percentile is calculated as the percentage of values on the
gray line that fall below the red asterisk (see results of most recent percentiles for all temperature and precipitation variables in Figure 2).
|
Results
Recent percentiles for 14
temperature and precipitation variables at Cedar Breaks National Monument
appear in Figure 2. Results for “extreme” variables at the park were as
follows:
·
Five temperature variables were “extreme
warm” (annual mean temperature, maximum temperature of the warmest month,
minimum temperature of the coldest month, mean temperature of the warmest
quarter, mean temperature of the coldest quarter).
·
No temperature variables were
“extreme cold.” • No precipitation variables were “extreme dry.”
·
No precipitation variables were
“extreme wet.”
Key points for interpreting these results in the context of
park resources include:
·
Recent climatic conditions are
already shifting beyond the historical range of variability.
·
Ongoing and future climate change
will likely affect all aspects of park management, including natural and
cultural resource protection as well as park operations and visitor experience.
·
Effective planning and management
must be grounded in our comprehension of past dynamics, present conditions, and
projected future change.
·
Climate change will manifest itself
not only as changes in average conditions, as summarized here, but also as
changes climate events (e.g., more intense storms, floods, or drought). Extreme
climate events can cause widespread and fundamental shifts in conditions of
park resources.
 |
| Figure 2. Recent temperature and precipitation percentiles at Cedar Breaks National Monument (including areas within 30-km [18.6-mi] of the park’s boundary). Black dots indicate average recent percentiles across the 10, 20, and 30-year intervals (moving windows). Variables are considered “extreme” if the mean percentiles are <5th percentile or >95th percentile (i.e., the gray zones, where recent climate is pushing the limits of all observed climates since the year 1901). Black bars indicate the range of recent percentiles across 10, 20, and 30-year moving windows (larger bars indicate higher sensitivity to moving window size). |
Climate Change Adaptation
These findings can inform climate
change adaptation at Cedar Breaks National Monument by helping park managers,
planners, and interpreters to understand how recent climates compare to past
conditions. For example, these findings may be used to:
·
Characterize park exposure to recent
climate change in a vulnerability assessment.
·
Develop plausible and divergent
futures for use in a climate-change scenario planning workshop.
·
Synthesize desired future conditions
(i.e., reference conditions) for use in a Resource Stewardship Strategy or
other National Park Service management plan.
·
Create interpretive materials for
communicating with local communities and park visitors.