Climate
Change and the Wildfire Explosion
by Staff Writers
Athens GA (SPX) May 24, 2013
Wildfires impact atmospheric conditions through emissions of
gases, particles, water, and heat. Some of the article focuses on
radiative forcing from fire emissions. Radiative forcing refers to
the change in net (down minus up) irradiance (solar plus longwave)
at the tropopause, the top of the troposphere where most weather
takes place.
Concerns continue to grow about the effects of climate change on
fire. Wildfires are expected to increase 50 percent across the
United States under a changing climate, over 100 percent in areas
of the West by 2050 as projected by some studies. Of equal concern
to scientists and policymakers alike are the atmospheric effects
of wildfire emissions on climate.
A new article published in the journal Forest Ecology and
Management by U.S. Forest Service scientists synthesizes recent
findings on the interactions between fire and climate and outlines
future research needs.
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 article
homes in on the effect 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," says Liu, lead author and 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 article focuses on
radiative forcing from fire emissions. Radiative forcing refers to
the change in net (down minus up) irradiance (solar plus longwave)
at the tropopause, the top of the troposphere where most weather
takes place.
Smoke particles can generate radiative forcing mainly through
scattering and absorbing solar radiation (direct radiative
forcing), and modifying the cloud droplet concentrations and
lifetime, and hence the cloud radiative properties (indirect
radiative forcing). The change in radiation can cause further
changes in global temperatures and precipitation.
"Wildfire emissions can have remarkable impacts on radiative
forcing," says 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."
Other major findings covered in the synthesis include:
+ The radiative forcing of smoke particles can generate
significant regional climate effects, leading to lower
temperatures at the ground surface.
+ Smoke particles mostly suppress cloud formation and
precipitation. Fire events could lead to more droughts.
+ Black carbon, essentially the fine particles of carbon that
color smoke, plays different roles in affecting climate. In the
middle and lower atmosphere, its presence could lead to a more
stable atmosphere. Black carbon plays a special role in the
snow-climate feedback loop, accelerating snow melting.
Land surface changes may be triggered that also play into future
effects. "Wildfire is a disturbance of ecosystems," says Liu.
"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 article concludes by outlining issues that lead to
uncertainties in understanding fire-climate interactions and the
future research needed to address them.