The latest issue of Nature magazine has a fascinating article that goes some of the way in vindicating Ronald Reagan’s infamous “gaffe” about how trees cause air pollution (because they do), but offers much much more about the problems of politicized and supposedly “settled” climate science. The article is called “How Much Can Forests Fight Climate Change?“, and it walks through just how unsettled this question is. The subhed to the story offers a good summary: “Trees are supposed to slow global warming, but growing evidence suggests they might not always be climate saviours.”
Toward the end of the article is this stunning statement from Christopher Williams, an ecologist at Clark University in Worcester, Massachusetts, who is studying the issue:
“I have heard scientists say that if we found forest loss cooled the planet, we wouldn’t publish it.”
Why not? I thought science was the search for truth, no matter what. You will not be surprised to learn that dissenters from climate orthodoxy in this subfield have received death threats.
The whole article is worth reading if you have the time, but here are a few highlights:
Although trees cool the globe by taking up carbon through photosynthesis, they also emit a complex potpourri of chemicals, some of which warm the planet. The dark leaves of trees can also raise temperatures by absorbing sunlight. Several analyses in the past few years suggest that these warming effects from forests could partially or fully offset their cooling ability. . .
Some researchers worry about publishing results challenging the idea that forests cool the planet. One scientist even received death threats after writing a commentary that argued against planting trees to prevent climate change. . .
Atmospheric chemist Nadine Unger, then at Yale University in New Haven, Connecticut, conducted one of the first global studies examining one part of this exchange: the influence of volatile organic compounds, or VOCs, emitted by trees. These include isoprene, a small hydrocarbon that can warm the globe in several ways. It can react with nitrogen oxides in the air to form ozone — a potent climate-warming gas when it resides in the lower atmosphere. Isoprene can also lengthen the lifetime of atmospheric methane — another greenhouse gas. Yet isoprene can have a cooling influence, too, by helping to produce aerosol particles that block incoming sunlight. . .
In other words, Reagan was right after all. But let’s keep going:
Unger ran an Earth-system model that estimated the effects of chemical emissions from forests. Her results suggest that the conversion of forests to farmland throughout the industrial era might have had little overall impact on climate3. Clearing forests liberated carbon stored in trees, but increased Earth’s albedo (leading to cooling) and decreased emissions of VOCs that can both cool and warm. . .
Ecologist Sunitha Pangala at Lancaster University, UK, spent much of 2013 and 2014 in the Amazon rainforest, where she placed gas-measuring chambers around the trunks of more than 2,300 trees. “What we were really surprised about was the magnitude at which these trees are emitting methane,” says Pangala. She and Vincent Gauci at the Open University in Milton Keynes, UK, and their colleagues reported in 2017 that trees account for around half of the Amazon’s total methane emissions. . .
Researchers are now turning to sophisticated computer models and using larger and more-comprehensive data sets to nail down exactly what forests in different places do to the climate. In some cases, the results have been sobering. Last October, a team led by ecologist Sebastiaan Luyssaert at the Free University of Amsterdam modelled a variety of European forest-management scenarios. The researchers concluded that none of the scenarios would yield a significant global climate impact, because the effects of surface darkening and cloud-cover changes from any added forests would roughly eliminate their carbon-storage benefits.
By this point, however, there are lots of interests selling “carbon credits” for planting trees, and this practice is being included in the emissions accounting systems of the UN climate circus and the Paris Climate Accord. Just watch what happens if anyone proposes to hit the “pause” button on this until scientists get a clearer picture.
P.S. Periodic reminder from Prof. Kerry Emanuel of MIT, a mainstream climate scientist:
Scientists are most effective when they provide sound, impartial advice, but their reputation for impartiality is severely compromised by the shocking lack of political diversity among American academics, who suffer from the kind of group-think that develops in cloistered cultures. Until this profound and well-documented intellectual homogeneity changes, scientists will be suspected of constituting a leftist think tank.