A new climate change study seems to suggest that a rise in carbon dioxide (CO2) emissions has helped plants propagate around the planet. The findings see contrarians (aka climate change skeptics) reasserting their claim that additional CO2 is beneficial for the planet, since foliage harness these emissions for growth. But the researchers behind the study, Greening of the Earth and its Drivers, insist the extra emissions and subsequent “fertilization effect” are more likely signs of a troubled system struggling to adjust.
A tremendous amount of vegetated land has experienced greening, according to satellite data collected and analyzed by 32 authors from 24 institutions in eight countries. The new greenery is equivalent to more than four billion giant sequoias. If all the extra leaves were laid flat, they’d cover the continental United States – twice! Added CO2 accounts for 70 percent of that growth, with climate change, increased nitrogen, and changes in land management accounting for fractions each. Despite global temperatures reaching a record high last year, only four percent of the world’s vegetated land has experienced depletion.
It’s easy to understand how contrarians would consider these findings evidence of the benefits of CO2 emissions. If plant greening were the sole concern, additional CO2 emissions would indeed be advantageous. But CO2 emissions have negative consequences that can ripple through the environment, disrupting the Earth’s feedback mechanisms that keep the system regulated.
Dr. Philippe Ciais of the Laboratory of Climate and Environmental Sciences rejects the contrarians’ position as single-minded. “The fallacy of the contrarian argument is two fold,” he told BBC News. “First, the many negative aspects of climate change are not acknowledged. Second, studies have shown that plants acclimatize to rising CO2 concentration and the fertilization effect diminishes over time.” The study’s lead author, Professor Ranga Myneni of Boston University, added that extra greenery would not make up for the other effects of climate change, such as rising sea levels, ocean acidification, and the loss of Arctic sea ice.
Still, Professor Judith Curry, former chair of Earth and atmospheric sciences at the Georgia Institute of Technology, insists that scientists engage with the arguments of climate change skeptics. Speaking to BBC News, Curry said, against scientific consensus, the contrarians’ position “reflects conflicts of values and a preference for the empirical (i.e. what has been observed) versus the hypothetical (i.e. what is projected from climate models).” This conflict may likewise exist in the general public.