I get rather weary of perfectly
good scientists running around the country waving thermometers and drawing
conclusions.
Forests are engineered to absorb
energy. We need to get a real handle on
the heat equation itself. This means
measuring the parameters of a cell of woodland and a cell of stripped land and
even a cell of crop land or any other well defined zone.
When you think of the climate in
those terms, a lot of things become easier to address. To start with wind matters. A forest blocks of a huge mass of air and
naturally insulates the soil from wind blown desiccation. Grass land does a much poorer job and desert
does none at all.
Forests absorb energy best and
lose the least. Grasslands absorb energy
but then lets the heat mostly blow away.
However you cut it, deforestation
allows energy to be lost and cooling results.
The worst case of this was the deforestation
of the Sahara and the entire Middle East
during the Bronze Age. This led directly
to a cooler Europe and other significant climatic shifts that included a
cooling of the Gulf Stream . This has continued to the present.
Restoration of those forests and
appropriate agricultural practices will lead to a warmer and more moderate Europe
and a moderation of the climate in the Middle East .
Deforestation causes cooling in Northern US and Canada
by Staff Writers
David CA (SPX) Nov 18, 2011
The researchers calculated that north of Minnesota
The impact of deforestation on global warming varies with latitude,
according to new research from a team of
scientists representing 20 institutions from around the world. The
surprising finding, which researchers say calls for new climate-monitoring
strategies, will be published in the Nov. 17 issue of the journal Nature.
"It depends where the deforestation is," said UC Davis
atmospheric science Professor Kyaw Tha Paw U, a study co-author. "It could
have some cooling effects at the regional scale, at higher latitudes, but
there's no indication deforestation is cooling lower latitudes, and in fact may
actually cause warming."
"Because surface station
observations are made in grassy fields with biophysical properties of cleared
land, they do not accurately represent the state of climate for 30 percent of the
terrestrial surface covered by forests," the study says.
Paw U and his colleagues found that deforestation in the boreal region,
north of 45 degrees latitude, results in a net cooling effect. While cutting
down trees releases carbon into the atmosphere, it also increases an area's
albedo, or reflection of sunlight.
Surface temperatures in open, non-forested, high-latitude areas were
cooler because these surfaces reflected the sun's rays, while nearby forested
areas absorbed the sun's heat. At night, without the albedo effect, open land
continued to cool faster than forests, which force warm turbulent air from
aloft to the ground.
"People are debating whether afforestation is a good idea in high
latitudes," said Xuhui Lee, the study's principal
investigator and professor of meteorology at the Yale School of Forestry and
Environmental Studies.
"If you plant trees you sequester carbon, which is a benefit to
the climate system. At the same time, if you plant trees you warm the landscape
because trees are darker compared to other vegetation types. So they absorb
solar radiation."
Paw U emphasized that the findings should not be viewed as a
"green light" to cut down forests in high latitudes. "The intent
is to clarify where we can see these regional effects using actual temperature
measurements," he said.
"Besides absorbing carbon dioxide,
forest ecosystems have a number of other valuable qualities, even if at certain
latitudes they may be warmer than open areas."
The researchers calculated that north of Minnesota
On the other hand, deforestation south of North Carolina
The researchers collected temperature data from a network of
specialized weather stations
in forests ranging from Florida to Manitoba
"The cooling effect is linear with latitude, so the farther north
you go, the cooler you get with deforestation," said Lee.
David Hollinger, a scientist with the USDA Forest Service and study
co-author, said, "Another way to look at the results is that the climate
cooling benefits of planting forests is compounded as you move toward the
tropics."
The study, "Observed Increase in Local Cooling Effect of
Deforestation at Higher Latitudes," was supported, in part, by grants from
the U.S. Department of Energy and the Yale Climate and Energy Institute.
Forests cooler or warmer than open areas depending on latitude
by Staff Writers
Forests represent one of the most extensive land use types, covering
approximately 30 percent of the terrestrial surface.
A study that will be published in Nature on Thursday concludes that
forests influence temperature, and their influence largely depends on latitude.
David Hollinger, a plant physiologist with the U.S. Forest Service's
Northern Research Station, co-authored the article with principal investigator
Xuhui Lee, a professor of meteorology at the Yale School of Forestry and
Environmental Studies, and a research team
that included 21 scientists from universities and research organizations in the
United States, Canada, and Germany.
The study was supported, in part, by grants from the U.S. Department of
Energy and the Yale Climate and Energy Institute.
"Forests are complicated ecosystems with subtle climate system effects,"
Hollinger said. "This study underscores the need to retune climate models
to reflect that complexity so we can get a better picture of the role forests
play in the landscape."
Results are based on comparisons of air temperature recorded at
meteorological towers located in forested areas in the United States and Canada
and, as a proxy for cleared land, nearby surface weather
stations operated by the National Weather Service and Environment Canada
In a review of data from Florida to Manitoba
North of 45 degrees, approximately the northern border of Vermont,
temperatures recorded in forest interiors were warmer than temperatures
recorded in open areas.
This is largely because year-round night time temperatures in forests
remain higher than open areas due to the mixing down of warm air aloft in
forests. In addition, snow-covered open areas reflect sunlight while dark
forests absorb sunlight and its warmth.
South of 45 degrees, maximum daytime temperatures in forested lands
were lower than over nearby open land, but forest nighttime minimum
temperatures were still higher.
South of 35 degrees, approximately the southern border of Tennessee,
the overall effect was reversed, with forests cooler than open land.
Forests represent one of the most extensive land use types, covering
approximately 30 percent of the terrestrial surface.
"This study makes it clear that at least in southern latitudes,
there are important climatic benefits for maintaining or increasing forest cover,"
Hollinger said
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