Rising levels of atmospheric carbon dioxide in the atmosphere has meant that large parts of the Earth have shown significant greening over the last 35 years.
Researchers studying NASA satellite data on the Earth's vegetation coverage have discovered that plants have significantly increased their leaf cover over the last 35 years to the point that new growth across the planet is equivalent to an area twice as large as the continental United States. According to the study, the largest contributor to this greening is the growing level of carbon dioxide (CO2) in the atmosphere.
Using data collected from instruments such as NASA's Moderate Resolution Imaging Spectrometer mounted on the AquaProbe satellite and the National Oceanic and Atmospheric Administration's Advanced Very High Resolution Radiometer (such as that deployed on NOAA's DSCOVR satellite), an international team of researchers has determined that CO2 fertilization explains fully 70 percent of the greening effect observed.
Of the approximately 10 billion tons of carbon spewed into the atmosphere from human-created sources every year, about 50 percent is stored for the short-term in the oceans and in plants. Generally, this has been shared relatively evenly between vegetation and the seas acting as carbon sinks. Now, with an increased level of uptake in plants, as demonstrated by their increased leaf growth, there may be a slight shift in that storage towards the vegetation on land.
However, CO2 fertilization isn't the only factor involved; it may be a large proportion, but another greenhouse gas produced as a by-product of human activities, nitrogen, is responsible for almost a further 10 percent of the observed greening, according to the researchers.
"The second most important driver is nitrogen, at 9 percent," said professor Ranga Myneni, from Boston University. "So we see what an outsized role CO2 plays in this process."
As a result, whilst the increasing CO2 concentrations in the atmosphere may be beneficial to plants in the short term, it still remains the major contributor to rapid climate change. Keeping heat in the Earth's atmosphere by reducing longwave heat radiation into space, CO2 has been on the rise since the dawn of the industrial era, and continues to increase as we burn more fossil fuels for energy production.
Concentrations haven't been as high as they are today for at least the past 500,000 years, and climate change is increasing the temperature of the planet, forcing sea levels to rise, glaciers and sea ice to melt, and adversely increasing severe weather patterns and increasing storm strength.