Projected Impact of Mid-21st Century Climate Change on Wildfire Hazard in a Major Urban Watershed outside Portland, Oregon USA (original) (raw)
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Climatic Change, 2014
Seasonal changes in the climatic potential for very large wildfires (VLWF≥ 50,000 ac~20,234 ha) across the western contiguous United States are projected over the 21st century using generalized linear models and downscaled climate projections for two representative concentration pathways (RCPs). Significant (p≤0.05) increases in VLWF probability for climate of the mid-21st century (2031-2060) relative to contemporary climate are found, for both RCP 4.5 and 8.5. The largest differences are in the Eastern Great Basin, Northern Rockies, Pacific Northwest, Rocky Mountains, and Southwest. Changes in seasonality and frequency of VLWFs d7epend on changes in the future climate space. For example, flammability-limited areas such as the Pacific Northwest show that (with high model agreement) the frequency of weeks with VLWFs in a given year is 2-2.7 more likely. However, frequency of weeks with at least one VLWF in fuel-limited systems like the Western Great Basin is 1.3 times more likely (with low model agreement). Thus, areas where fire is directly associated with hot and dry climate, as opposed to experiencing lagged effects from previous years, experience more change in the likelihood of VLWF in future projections. The results provide a quantitative foundation for management to mitigate the effects of VLWFs.
High-temporal resolution meteorological output from the Parallel Climate Model (PCM) is used to assess changes in wildland fire danger across the western United States due to climatic changes projected in the 21st century. A business-as-usual scenario incorporating changing greenhouse gas and aerosol concentrations until the year 2089 is compared to a 1975-1996 base period. Changes in relative humidity, especially drying over much of the West, are projected to increase the number of days of high fire danger (based on the energy release component (ERC) index) at least through the year 2089 in comparison to the base period. The regions most affected are the northern Rockies, Great Basin and the Southwest -regions that have already experienced significant fire activity early this century. In these regions starting around the year 2070, when the model climate CO 2 has doubled from present-day, the increase in the number of days that ERC (fuel model G) exceeds a value of 60 is as much as two to three weeks. The Front Range of the Rockies and the High Plains regions do not show a similar change. For regions where change is predicted, new fire and fuels management strategies and policies may be needed to address added climatic risks while also accommodating complex and changing ecosystems subject to human stresses on the region. These results, and their potential impact on fire and land management policy development, demonstrate the value of climate models for important management applications, as encouraged under the Department of Energy Accelerated Climate Prediction Initiative (ACPI), under whose auspices this work was performed.
Future southcentral US wildfire probability due to climate change
Climatic Change
Globally, changing fire regimes due to climate is one of the greatest threats to ecosystems and society. In this paper, we present projections of future fire probability for the southcentral USA using downscaled climate projections and the Physical Chemistry Fire Frequency Model (PC2FM). Future fire probability is projected to both increase and decrease across the study region of Oklahoma, New Mexico, and Texas. Among all end-of-century projections, change in fire probabilities (CFPs) range from − 51 to + 240%. Greatest absolute increases in fire probability are shown for areas within the range of approximately 75 to 160 cm mean annual precipitation (MAP), regardless of climate model. Although fire is likely to become more frequent across the southcentral USA, spatial patterns may remain similar unless significant increases in precipitation occur, whereby more extensive areas with increased fire probability are predicted. Perhaps one of the most important results is illumination of climate changes where fire probability response (+, −) may deviate (i.e., tipping points). Fire regimes of southcentral US ecosystems occur in a geographic transition zone from reactant-to reaction-limited conditions, potentially making them uniquely responsive to different scenarios of temperature and precipitation changes. Identification and description of these conditions may help anticipate fire regime changes that will affect human health, agriculture, species conservation, and nutrient and water cycling.
Regional analysis of large wildfire potential given climate change scenarios is crucial to understanding areas most at risk in the future, yet wildfire models are not often developed and tested at this spatial scale. We fit three historical climate suitability models for large wildfires (i.e. ≥ 400 ha) in Colorado andWyoming using topography and decadal climate averages corresponding to wildfire occurrence at the same temporal scale. The historical models classified points of known large wildfire occurrence with high accuracies. Using a novel approach in wildfire modeling, we applied the historical models to independent climate and wildfire datasets, and the resulting sensitivities were 0.75, 0.81, and 0.83 for Maxent, Generalized Linear, and Multivariate Adaptive Regression Splines, respectively. We projected the historic models into future climate space using data from 15 global circulation models and two representative concentration pathway scenarios. Maps from these geospatial analyses can be used to evaluate the changing spatial distribution of climate suitability of large wildfires in these states. April relative humidity was the most important covariate in all models, providing insight to the climate space of large wildfires in this region. These methods incorporate monthly and seasonal climate averages at a spatial resolution relevant to land management (i.e. 1 km2) and provide a tool that can be modified for other regions of North America, or adapted for other parts of the world.
International Journal of Wildland Fire, 2021
Numerous devastating air pollution events from wildfire smoke occurred in this century in the western USA, leading to severe environmental consequences. This study projects future fire emissions in this region under climate change with a focus on comparing the relative contributions from future changes in burned area, fuel loading and fuel moisture. The three properties were projected using an empirical fire model, a dynamical global vegetation model and meteorological conditions respectively. The regional climate change scenarios for the western USA were obtained by dynamical downscaling of global climate projections. The results show overall increasing wildfires and fuel loading and decreasing fuel moisture. As a result, fire emissions are projected to increase by ~50% from 2001–2010 to 2050–2059. The changes in wildfires and fuel loading contribute nearly 75% and 25% of the total fire emission increase, respectively, but the contribution from fuel moisture change is minimal. The ...
Over 21,000 future California residential wildfire risk scenarios were developed on a monthly 1/8° grid, using statistical wildfire models. We explore interactions between two global emissions scenarios, three climate models, six spatially explicit population growth scenarios derived from two growth models, and a range of parameters defining properties' vulnerability to loss. Scenarios are evaluated over two future time periods relative to historic baselines. We also explore effects of spatial resolutions for calculating household exposure to wildfire on changes in estimated future property losses. Our goal was not to produce one authoritative set of future risk scenarios but rather to understand what parameters are important for robustly characterizing effects of climate and growth on future residential property risks. By end of century, variation across development scenarios accounts for far more variability in statewide residential wildfire risks than does variation across climate scenarios. However, the most extreme increases in residential fire risks result from combining high-growth/high-sprawl scenarios with the most extreme climates considered here. Case studies for the Bay Area and the Sierra foothills demonstrate that, while land use decisions profoundly influence future residential wildfire risks, effects of diverse growth and land use strategies vary greatly around the state.
Projecting wildfire emissions over the south-eastern United States to mid-century
International Journal of Wildland Fire, 2018
Wildfires can impair human health because of the toxicity of emitted pollutants, and threaten communities, structures and the integrity of ecosystems sensitive to disturbance. Climate and socioeconomic factors (e.g. population and income growth) are known regional drivers of wildfires. Reflecting changes in these factors in wildfire emissions estimates is thus a critical need in air quality and health risk assessments in the south-eastern United States. We developed such a methodology leveraging published statistical models of annual area burned (AAB) over the US Southeast for 2011–2060, based on county-level socioeconomic and climate projections, to estimate daily wildfire emissions in selected historical and future years. Projected AABs were 7 to 150% lower on average than the historical mean AABs for 1992–2010; projected wildfire fine-particulate emissions were 13 to 62% lower than those based on historical AABs, with a temporal variability driven by the climate system. The great...
The costly interactions between humans and wildfires throughout California demonstrate the need to understand the relationships between them, especially in the face of a changing climate and expanding human communities. Although a number of statistical and process-based wildfire models exist for California, there is enormous uncertainty about the location and number of future fires, with previously published estimates of increases ranging from nine to fifty-three percent by the end of the century. Our goal is to assess the role of climate and anthropogenic influences on the state's fire regimes from 1975 to 2050. We develop an empirical model that integrates estimates of biophysical indicators relevant to plant communities and anthropogenic influences at each forecast time step. Historically, we find that anthropogenic influences account for up to fifty percent of explanatory power in the model. We also find that the total area burned is likely to increase, with burned area expected to increase by 2.2 and 5.0 percent by 2050 under climatic bookends (PCM and GFDL climate models, respectively). Our two climate models show considerable agreement, but due to potential shifts in rainfall patterns, substantial uncertainty remains for the semiarid inland deserts and coastal areas of the south. Given the strength of human-related variables in some regions, however, it is clear that comprehensive projections of future fire activity should include both anthropogenic and biophysical influences. Previous findings of substantially increased numbers of fires and burned area for California may be tied to omitted variable bias from the exclusion of human influences. The omission of anthropogenic variables in our model would overstate the importance of climatic ones by at least 24%. As such, the failure to include anthropogenic effects in many models likely overstates the response of wildfire to climatic change.
Climate and demographic impacts on wildfire air pollution hazards during the 21<sup>st</sup> century
Atmospheric Chemistry and Physics Discussions, 2016
Wildfires pose a significant risk to human livelihoods and are a substantial health hazard due to emissions of toxic smoke. It is widely believed that climate change, through increasing the frequency of hot weather conditions, will also lead to an increase in wildfire activity. More recently, however, new research has shown that trends in population growth and urbanisation can be as important for fire prediction as changes in climate and atmospheric CO 2 , and that under certain scenarios, fire activity may continue to decline through most of the 21 st century. The present study reexamines these results from the perspective of air pollution risk, focussing on emissions of airborne particulate matter (PM2.5). We combine an existing ensemble of simulations using a coupled fire-dynamic vegetation model with current observation-based estimates of wildfire emissions to predict future trends. Currently,