For those who have staked their professional reputations on man-induced “climate change” being “settled science,” a new study that confirms rising CO2 levels are driving the “greening” of the planet could be unsettling.
Instead of the western U.S. becoming more arid and brown, as predicted by climate models that assume catastrophic man-made global warming, examination of decades worth of satellite data reveal significant increases in vegetation growth. Indeed, this greening was observed over 25 percent to 50 percent of the vegetated areas of the Earth’s surface, based on analysis of 28-years worth of satellite imagery. The increased biomas serves as a sink, or temporary storage site, for increased CO2.
The study, conducted by an international team of 32 researchers from 24 institutions – representing nine different countries (Australia, China, France, Germany, Japan, Spain, Switzerland, the United States and the United Kingdom) – used satellite data from NASA’s Moderate Resolution Imaging Spectrometer and the National Oceanic and Atmospheric Administration’s Advanced Very High Resolution Radiometer instruments to help determine the leaf-area index, or amount of leaf cover, over the planet’s vegetated regions.
Approximately 32 percent of the Earth’s surface – oceans, lands and permanent ice sheets combined – is covered by leaf growth. Those leaves use energy from sunlight through photosynthesis to chemically combine CO2 taken from the air with water and soil nutrients to produce biomass, making the much-maligned greenhouse gas a plant fertilizer.
Contrary to model predictions, the satellite data showed increases in vegetation growth on up to 50 percent of previously vegetated areas, with a decrease in only 4 percent. The Earth’s increased greening was equivalent to expanding the planet’s vegetation coverage to an area twice the size of the continental U.S.
Carbon dioxide is but one factor accounting for the increased vegetation, but by far the greatest. After isolating all factors, scientists said CO2 fertilization explained 70 percent of the observed greening, nitrogen deposition nine percent, climate change eight percent and land-cover change four percent.
The extent of the last 35 years’ greening was not only missed by climate models but, given the resulting altered environment, could require a rethink of climate-model parameters going forward. The change “has the ability to fundamentally change the cycling of water and carbon in the climate system,” said lead author Zaichun Zhu, a researcher from Peking University, China.
Findings from the study were published this week in the journal Nature Climate Change.
Approximately half the 10 billion tons of carbon emitted each year from human activities is temporarily stored, in equal parts, in the oceans and plants. The latest study shows the potential carbon sink found in vegetation is greater than previously assumed.
However, researchers said the benefits of greening are not without limits.
“Studies have shown that plants acclimatize, or adjust, to rising carbon dioxide concentration and the fertilization effect diminishes over time,” said study co-author Philippe Ciais, associate director of the Laboratory of Climate and Environmental Sciences in France.