Wednesday, September 24, 2014

Save the Planet - Kill a Tree?

Tree's cause global warming?  At least according to the New York Times (which means I'm already skeptical): The Science Was Settled, Except... Reforestation Raises Global Warming?
The NY Times continues to disorient their readers with a newUnsettled Science piece and a bit of a plug for Ronald Reagan; this time we hear from the Tree Deniers:
To Save the Planet, Don’t Plant Trees
Apparently it is all about the albedo and the air pollution caused by, yes, trees.
NEW HAVEN — AS international leaders gather in New York next week for a United Nations climate summit, they will be preoccupied with how to tackle the rising rate of carbon emissions. To mitigate the crisis, one measure they are likely to promote is reducing deforestation and planting trees.
Deforestation accounts for about 20 percent of global emissions of carbon dioxide. The assumption is that planting trees and avoiding further deforestation provides a convenient carbon capture and storage facility on the land.
That is the conventional wisdom. But the conventional wisdom is wrong.
In reality, the cycling of carbon, energy and water between the land and the atmosphere is much more complex. Considering all the interactions, large-scale increases in forest cover can actually make global warming worse.
This is counterintuitive...
I'll say. As trees grow they act as a carbon sink but:
Besides the amount of greenhouse gases in the air, another important switch on the planetary thermostat is how much of the sun’s energy is taken up by the earth’s surface, compared to how much is reflected back to space. The dark color of trees means that they absorb more of the sun’s energy and raise the planet’s surface temperature.
Climate scientists have calculated the effect of increasing forest cover on surface temperature. Their conclusion is that planting trees in the tropics would lead to cooling, but in colder regions, it would cause warming.
In order to grow food, humans have changed about 50 percent of the earth’s surface area from native forests and grasslands to crops, pasture and wood harvest. Unfortunately, there is no scientific consensus on whether this land use has caused overall global warming or cooling. Since we don’t know that, we can’t reliably predict whether large-scale forestation would help to control the earth’s rising temperatures.
So, did the deforestation of most of the world with the growth of mankind's population contribute to the Little Ice Age? An interesting thought.

It also sort of depends on how you take the temperature.  Under a tree canopy, the temperature can be several degrees cooler than outside on bare ground, or on top of the canopy during the day, but warmer at night. Trees also provide a cooling influence by transporting water to the canopy and evaporating it through their leaves; a primitive "swamp cooler" refrigerator.

So shit was more complicated than scientists originally thought? How could that ever happen?  Maybe they should look at the numbers again. It's almost always way more complicated than your first or second thought about it.
Worse, trees emit reactive volatile gases that contribute to air pollution and are hazardous to human health. These emissions are crucial to trees — to protect themselves from environmental stresses like sweltering heat and bug infestations. In summer, the eastern United States is the world’s major hot spot for volatile organic compounds (V.O.C.s) from trees.
Trees cause air pollution? Wait for it...
As these compounds mix with fossil-fuel pollution from cars and industry, an even more harmful cocktail of airborne toxic chemicals is created. President Ronald Reagan was widely ridiculed in 1981 when he said, “Trees cause more pollution than automobiles do.” He was wrong on the science — but less wrong than many assumed.
OK, I had, and have a hard time believing trees can outdo cars, but still - two plugs for Reagan in one Saturday? OK, polluting trees shouldn't be news (2003, 2004) but I try to learn something new every day . . .
Since 1981, forests, at least in the US, have expanded, while air pollution, particularly nitrogen oxides have been declining due to catalytic converters etc.  So maybe trees are a more important source than cars. (But the data don't show it).

I'd still rather have the haze from the Blue Ridge Mountains than the smog from Los Angeles.
. .

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