May 23rd, 2013 by James Ayre
Changes in the climate are intimately connected with wildfires, both causing them and being being caused by them. Recent research has estimated that wildfires will increase by around 50% across most of the US, and by as much as 100% in the West, by 2050, as a result of climate change. And with this increase in the frequency/extent of wildfires, greenhouse gas emissions will rise too.
And now, new research, recently published in the journal Forest Ecology and Management, has synthesized “recent findings on the interactions between fire and climate and outlines future research needs.” Written 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 report focuses on the effects that emissions from wildfires will have 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.”
Atmospheric conditions are affected by fires through the effects of the gases, particles, water, and heat, that is emitted during wildfires. “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.”
Some of the other important findings covered by the report, 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.”
– Changes in land surface use may also factor 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.”
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