“But previous models only show a limited amount of vegetation growth,” he said. “So even though some of these other simulations included dynamic vegetation, that wasn’t enough vegetation change to explain what the pollen records suggest.”
In reality, the changes in the vegetation cover have been significant.
During the early Holocene – the current geological epoch – the Sahara desert in Africa became greener than today, it was more grassland.
Other northern hemisphere vegetation, including mid-latitude and arctic coniferous and broadleaf forests, also flourished.
Thompson took evidence from the pollen records and designed a set of experiments with a climate model known as the Community Earth System Model (CESM). He ran simulations to account for a range of changes in vegetation that had not previously been accounted for.
“The expansion of vegetation during the Holocene warmed the globe by up to 1.5 degrees Fahrenheit,” Thompson said.
Understanding the scale and timing of temperature change throughout the Holocene is important because the rise of human agriculture and civilization occurred during this time.
“Overall, our study underscores that accounting for vegetation change is critical,” Thompson said.
“Projections of future climate change are more likely to produce more reliable predictions if they include changes in vegetation.”