for context and a little (more) compare and contrast, an earlier one of hers:
Global Climate Forcing by Criteria Air Pollutants Annual Review of Environment and Resources Vol. 37: 1-24 (Volume publication date November 2012) DOI: 10.1146/annurev-environ-082310-100824 Nadine Unger School of Forestry and Environmental Studies, Yale University, New Haven, Connecticut 06511; email: nadine.unger@yale.edu ABSTRACT Ambient air pollution has significant impacts on global climate change in complex ways, involving both warming and cooling, and causes an estimated one million deaths every year. Modeling studies and observations from a suite of platforms, including those that are space based, have revealed that air pollution is a widespread global phenomenon. The net effect of air pollution is a global cooling that is masking 50% of the committed greenhouse gas (GHG) warming from the Industrial Revolution. Aggressive air pollution abatement and climate stabilization strategies that reduce cooling pollutants may lead to a short-term warming surge that is unsafe for ecosystems and the human population, imposing complex trade-offs in policy making. Conversely, selective reduction of warming air pollutants to mitigate near-term climate change may offer opportunities for synergistic policy development. Reducing and preventing the accumulation of fossil-fuel carbon dioxide (CO2) in the atmosphere is the only sustainable way to protect climate safety in the long term. Here, the current understanding of air pollution effects on global climate change is reviewed, including assessment by individual pollutant, precursor emission, economic sector, and policy-relevant scenarios. (emphasis added) http://www.annualreviews.org/doi/abs/10.1146/annurev-environ-082310-100824
there will of course be further responses -- but here are two so far:
NY Times forests oped is out on a limb: protecting trees still key to solving climate change
By Steve Schwartzman | Bio | Published: September 20, 2014
In an oped in Saturday's New York Times (To Save the Planet, Don't Plant Trees .. http://www.nytimes.com/2014/09/20/opinion/to-save-the-planet-dont-plant-trees.html), Nadine Unger argues that reducing deforestation and planting trees won't help fix climate change but will rather make it worse. One might ask how the 2,000-plus scientists and experts on Intergovernmental Panel on Climate Change (IPPC) got this one wrong – they found tropical deforestation the second largest source of carbon pollution, after burning fossil fuels for energy– but in fact it's Unger who's way out on a limb here.
Steve Schwartzman, Director of Tropical Forest Policy
When trees grow, they absorb carbon dioxide (CO2) from the atmosphere and store it as carbon in their trunks, branches, leaves and roots. When people cut the trees down and burn them to clear forest for cattle pasture or crops, as they have at a rate of 13 million hectares of forest per year in the tropics over the last decade, this releases CO2 back into the atmosphere.
Unger argues that forests absorb more sunlight than crops or grassland, which reflect more sunlight back into space and cool the earth. But that's not true in the tropics. In tropical forests like the Amazon, where deforestation is happening and thus where the Climate Summit's attention is focused, trees take up water from rainfall and evaporate it through their leaves, and create cloud cover. These clouds reflect even more sunlight than grasslands or bare earth, thus cooling the earth more. This is why large-scale deforestation disrupts rainfall regimes – and why deforestation in the Amazon, if unchecked, may reduce rainfall in California .. https://connect2.edf.org/f5-w-687474703a2f2f626c6f67732e6564662e6f7267$$/climatetalks/2014/02/24/californias-carbon-market-could-help-stop-amazon-deforestation/.
Emissions from tropical deforestation are, from the perspective of the atmosphere, just the same as emissions from burning fossil fuels – carbon that was wood, coal, oil or gas is turned into CO2 and released to the atmosphere. In a living forest, trees do die and, over time release CO2 to the atmosphere. But then new trees grow, and absorb that CO2 again – not the case when forests that have stored carbon for centuries are replaced by grass to feed cattle or oil palm plantations.
Contrary to Unger’s claims, the "high risk" is to ignore the 200 billion tons of at-risk carbon stocks in the world’s tropical forests. In fact, as the IPCC has concluded, stopping tropical deforestation is a critical priority for controlling climate change.
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