4 recent studies tell us that forest thinning for the production of wood pellets and clear cutting for wind parks are really dumb ideas.
Reforestation and afforestation (R&A) are among the most prominent ideas for the sequestration of CO2 and thus viewed by alarmists as a climate solution. But others doubt forests play much of a role.
Wood pellets mean double barrel warming
Another solution proposed for climate protection is to burn wood pellets instead of oil and natural gas for heating buildings. Wood pellets are viewed as renewable and thus are supposed to be brakes on climate change. But now recent studies suggest that burning wood pellets coming from harvested trees in forest thinning operations may instead be accelerating warming.
HAT-TIP: Die kalte Sonne here.
Cloud–albedo effects due to land–atmosphere interactions
In their study, “Cloud cooling effects of afforestation and reforestation at midlatitudes” the team of authors led by Sara Cerasoli carefully analyzed R&A at midlatitudes. Using both satellite data and atmospheric boundary-layer models, they show that by including cloud–albedo effects due to land–atmosphere interactions, the R&A cooling at midlatitudes becomes prevalent.
This means that scientists earlier had not adequately taken the clouds that formed due to forests into account. These high albedo clouds play a major role in terms of having a cooling effect. Clouds tend to form more over intact forests than they do over forest-free areas.
Forests along with the clouds they help create, act to cool surface temperatures. Thus efforts to keep forests intact at midlatitudes would help cool the earth’s surface.
To the contrary, efforts that lead to the thinning or even the destruction of forests — e.g. wood pellet production — will serve to lessen the cooling effect, or even cause warming. The paper states:
While an increased water vapor in the atmosphere due to forests may result in greater radiation absorption (16), the impact is minor compared to the radiative effect caused the change in albedo, so that evaporative cooling is essentially a nonradiative effect.”
Forests mean more cooling cloud formation
A similar result was reached in another paper published last year in Nature Communications: “Revealing the widespread potential of forests to increase low level cloud cover” authored by Duveiller et al.
Using global satellite data, they found “that for 67% of sampled areas across the world, afforestation would increase low level cloud cover, which should have a cooling effect on the planet.”
Changes in cloud fractional cover (CFrC) following potential afforestation as derived from satellite data, expressed in relative terms with respect to the average cloudiness over every grid cell. Source. Figure 1 here.
The authors also found that forest type plays a role, “notably in Europe where needleleaf forests generate more clouds than broadleaf forests.”
10% forest canopy opening led to 0.46°C warming!
Also a recent study in the journal Ecological Solutions and Evidence by Jeannette S. Blumröder et al (2021) found a profound surface temperature impact by forests. The authors found:
Logging 100 trees per hectare increased maximum temperature by 0.21–0.34 K at ground level and by 0.09–0.17 K in 1.3 m above ground. Opening the forest canopy by 10% significantly increased Tmax, measured 1.3 m above ground by 0.46 K (including pine and beech stands) and 0.35 K (only pine stands).”
Thinned out forests lose their cooling capacity. Source: Jeannette S. Blumröder et al, Figure 2.
The study found that poor forestry practices in Northern Germany led to a decreased temperature cooling capacity by the forest that had increasing wood harvest activities. “The maximum temperature was higher in forests with relative low stand volume. Therefore, high stock and dense canopy would provided an insurance against heat and drought events.”
“From all the variables, researchers identified the degree of canopy openness and the quantity of logged trees, both directly controlled by forest management, as the main factors for the reduction of maximum temperatures in the forest interior. They found the maximum temperature to be higher in forests with more cut trees and more open canopy.”
Big difference between forest and free air temperature
Yet another paper published last year, ForestTemp – Sub-canopy microclimate temperatures of European forests by Haesen et al, found that “the tree canopy functions as a thermal insulator” and that “sub-canopy air temperatures differ substantially from free-air temperatures, being on average 2.1°C (standard deviation ± 1.6°C) lower in summer and 2.0°C higher (±0.7°C) in winter across Europe.”
There’s no doubt that intact forests play an important role on temperature. In the spring and summer, thinned out forests heat up markedly more than those with a completely closed canopy.
Forest thinning and clearing operations, e.g. for harvesting trees for wood pellet production or wind park construction, not only lead to higher surface temperatures, but also to a rapid injection of CO2 into the atmosphere when the wood pellets are burned.
In the end, it means wood pellets are backfiring. They lead to forest degradation, and even more rapid CO2 emissions and pollution from their burning. The practice just couldn’t possibly be dumber.
7 responses to “Green Fuel Folly: Forest Thinning (For Wood Pellet Production) Has A Profound Surface Warming Impact”
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But we have to cut down the forests to save the planet.
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I like to spend time in the woods. I’ve noticed that under pine trees less snow reaches the ground, and it melts faster. Also, on top of a ski mountain I saw that a pine tree had melted 6 ft of snow under it down to bare ground. I put this down to the tree thermalizing sunlight and reradiating it downward.
M. Gosselin has made a simple mistake, and should revise or retract this piece in the light of it .
He has confused landscape albedo with solar flux on the thinned forest floor.
Since on global average trees absorb more sunlight than bare ground, removing shade by thinning trees means more solar energy is reflected back into space than if it were absorbed by foliage.
The subtracted 10% of the solar flux( corrected for sun angle thrugh the day ) would have heated the darker foliage more than the forest floor, so the increase in near surface temperature is not a proxy for tropospheric heating as a whole.
Don’t forget that trees transpire moisture which is a cooling effect. So-called Global Warming is absent over the US Great Plains, possibly due to the extensive irrigation providing moisture for plant transpiration.
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