May 22, 2013
Wildfires May Strengthen Long-Term Climate Change, Warns US Forest Service
redOrbit Staff & Wire Reports - Your Universe Online
The US Forest Service voiced its concern on Tuesday over the atmospheric effects of wildfire emissions on climate change, saying the issue is of great importance to scientists and policymakers alike.
The warnings are particularly important given recent projections of an average 50-percent increase in wildfires across the US — and over 100 percent in some areas of the West — by 2050, the Service said.
The agency pointed to a recent study by Forest Service scientists published in the journal Forest Ecology and Management, which synthesized the latest findings on the interactions between fire and climate. Authored by research meteorologists Yongqiang Liu and Scott Goodrick from the Forest Service Southern Research Station (SRS), and Warren Heilman from the Northern Research Station, the analysis focused on the effects of emissions from wildfires on long-term atmospheric conditions.
“While research has historically focused on fire-weather interactions, there is increasing attention paid to fire-climate interactions,” said Liu, a team leader with the SRS Center for Forest Disturbance Science.
“Weather, the day-to-day state of the atmosphere in a region, influences individual fires within a fire season. In contrast, when we talk about fire climate, we´re looking at the statistics of weather over a certain period. Fire climate sets atmospheric conditions for fire activity in longer time frames and larger geographic scales.”
Wildfires impact atmospheric conditions through emissions of gases, particles, water and heat.“¯Some of the Forest Service study focuses on ℠radiative forcing´ from fire emissions, which refers to the change in net irradiance at the tropopause, the top of the troposphere where most weather takes place. Irradiance refers to the power of electromagnetic radiation per a specified unit of area.
Smoke particles can generate radiative forcing mainly by scattering and absorbing solar radiation (known as direct radiative forcing), and by modifying the lifetime and concentration of cloud droplets. The change in radiation can cause further changes in global temperatures and precipitation.
“Wildfire emissions can have remarkable impacts on radiative forcing,” said Liu.
“During fire events or burning seasons, smoke particles reduce overall solar radiation absorbed by the atmosphere at local and regional levels. At the global scale, fire emissions of carbon dioxide contribute substantially to the global greenhouse effect.”
Liu said wildfires could also trigger land surface changes that could play into future effects.
“Wildfire is a disturbance of ecosystems,” he explained.
“Besides the atmospheric impacts, wildfires also modify terrestrial ecosystem services such as carbon sequestration, soil fertility, grazing value, biodiversity, and tourism. The effects can in turn trigger land use changes that in turn affect the atmosphere.”
The authors of the study outlined several factors that lead to uncertainties in understanding fire-climate interactions, and suggest areas where future research is need to address these issues.