GR: There’s lots of loose talk going around about “geoengineering” our way out of the climate-change disaster. I say it’s loose talk because there’s been no serious testing of efficacy and long-term consequences. Actually, scientists have analyzed most of the ideas such as blasting sunlight-blocking particles into the atmosphere, converting CO2 to useful materials, and so forth and found that such techniques fall short of what’s needed. The article below describes another debunking, this time the idea that we could clear the air by planting CO2-absorbing forests.
Climatologists have determined that we have already released enough carbon, methane, and other greenhouse gases to cause disastrous climate changes. And so far, the way we might save a fair portion of our civilization is to stop burning coal, oil, gas, and even wood now.
“If the world’s nations really do intend to contain global warming to within 2°C, there is no alternative to drastic cuts in greenhouse gas emissions, according to a new study.
“The tree could be regarded as low-technology carbon removal machinery and, in theory, carefully managed plantations could soak up the carbon released from fossil fuel combustion. But the sheer scale of such plantations would have devastating environmental costs, scientists say.
“If we continue burning coal and oil the way we do today and regret our inaction later, the amounts of greenhouse gas we would need to take out of the atmosphere in order to stabilise the climate would be too huge to manage,” says Lena Boysen from the Potsdam Institute for Climate Impact Research, who led the study, published in Earth’s Future journal.
Trees are not the answer
“If the forests were planted on productive land, then humans would lose the soils urgently needed to nourish a population of 9bn. If the trees were planted on less productive terrain, the necessary costs in water and nitrogen-based fertiliser would be devastating. Either way, natural ecosystems would be irreparably damaged.
“And then the trees grown to absorb carbon would have to be stored deep underground, to prevent the carbon returning to the atmosphere to accelerate global warming rather than limit it.
“Even if we were able to use productive plants such as poplar trees or switchgrass, and store 50% of the carbon contained in their biomass, in the business-as-usual scenario of continued, unconstrained fossil fuel use, the sheer size of the plantations for staying at or below 2°C of warming would cause devastating environmental consequences,” Boysen says.
“The world’s great forests are part of the climate machinery, and more than 195 nations agreed in Paris in 2015 to take steps to contain climate change, both by managing the way they used land and by switching from fossil fuels to renewable sources of energy.
“So carbon storage in the form of woodland is one component of a complex problem. Boysen and colleagues report that they looked at a number of scenarios to see whether, even in theory, massive investment in tree planting could remove sufficient quantities of carbon from the atmosphere.
“In the climate drama currently unfolding on that big stage we call Earth, CO2 removal is not the hero who finally saves the day after everything else has failed”
“One scenario required 6.9 billion hectares of plantation, fed by 570 million tons of nitrogen each year, and even the smallest theoretical plantation would have extended over a billion hectares and consumed 96 million tons of nitrogen fertiliser every year. One billion hectares is 10 million square kilometres: an area bigger than the whole of Canada.” –Tim Radford (Continue: Planting trees will not slow global warming – Climate News Network.)