The albedo effect refers to the amount of radiation reflected by the surface of the planet. Light-colored snowy surfaces, for instance, reflect more light and heat back into space than darker forests.
Climate scientists have suggested that the Pliocene epoch might provide a glimpse of the planet's future if humankind is unable to curb carbon dioxide emissions. During the Pliocene, the two main factors believed to influence the climate atmospheric CO2 concentrations and the geographic position of the continents were nearly identical to modern times. But scientists have long wondered why the Pliocene's global surface air temperatures were so much warmer than Earth's pre-industrial climate.
The answer might be found in highly reactive compounds that existed long before humans lived on the planet, Unger says. Terrestrial vegetation naturally emits vast quantities of volatile organic compounds, for instance. These are critical precursors for organic aerosols and ozone, a potent greenhouse gas. Wildfires, meanwhile, are a major source of black carbon and primary organic carbon.
Forest cover was vastly greater during the Pliocene, a period marked not just by warmer temperatures but also by greater precipitation. At the time, most of the arid and semi-arid regions of Africa, Australia, and the Arabian peninsula were covered with savanna and grassland. Even the Arctic had extensive forests. Notably, Unger says, there were no humans to cut the forests down.
Using the NASA Goddard Institute for Space Studies Model-E2 global Earth system model, the researchers were able to simulate the terrestrial ecosystem emissions and atmospheric chemical composition of the Pliocene and the pre-industrial era.
According to their findings, the increase in global vegetation was the dominant driver of emissions during the Pliocene and the subsequent effects on climate.
Previous studies have dismissed such feedbacks, sugg
|Contact: Kevin Dennehy|
Yale School of Forestry & Environmental Studies