Vegetation change has shaped global temperatures over the past 10,000 years – Is it up because of that?
WASHINGTON UNIVERSITY IN ST. LOUIS
Follow the pollen. According to research from a climate scientist at Washington University in St.
Warmer temperatures bring to the trees – and then even warmer temperatures, according to new modeling simulations published April 15 in Scientific advance.
Alexander Thompsona postdoctoral associate in earth and planetary sciences in the Arts & Sciences, updated simulations from a key climate model to reflect the role of vegetation changes such as a major driver of global temperature over the past 10,000 years.
Thompson has long had trouble with models of Earth’s atmospheric temperature since the last ice age. Too many of these simulations show temperatures warming continuously over time.
But climate proxy records tell a different story. Many of these sources show a marked peak in global temperatures occurring between 6,000 and 9,000 years ago.
Thompson has a hunch that the models might consider the role of changes in vegetation in favor of effects from atmospheric carbon dioxide concentrations or the ice cover.
“The pollen records show a large expansion of vegetation during that time,” Thompson said.
“But previous models showed only a limited amount of vegetation growth,” he said. “So, although some other simulations have included animal vegetation, the change in vegetation is not nearly enough to explain what the pollen record shows.”
In fact, the changes to the vegetation cover are substantial.
In the early Holocene, the current geological era, the Sahara desert in Africa was greener than it is today – it was more like a grassland. Other vegetation in the Northern Hemisphere including arctic and mid-latitude coniferous and deciduous forests also thrives.
Thompson took evidence from the pollen record and designed a set of climate modeling experiments called Community Earth System Model (CESM), one of the models that is rated as the best in such a series. He ran simulations to account for a range of changes in vegetation that had not been considered before.
“The vegetation that expanded during the Holocene warmed the earth by up to 1.5 degrees Fahrenheit,” Thompson said. “Our new simulations tie closely to paleontological proxies. So it’s exciting that we can point to vegetation in the Northern Hemisphere as one of the potential factors that will allow us to resolve this controversial issue. Holocene temperature conundrum. ”
Understanding the scale and timing of temperature changes throughout the Holocene is important because it is a period of recent history, geologically speaking. The development of agriculture and human civilization took place during this time, so many scientists and historians from different disciplines are interested in understanding other early and middle Holocene climates. How does it compare to today?
Thompson conducted this research while a graduate student at the University of Michigan. He is continuing his research in the climate scientist’s laboratory Bronwen Konecky at the University of Washington.
“Overall, our study emphasizes that it is important to account for vegetation change,” Thompson said. “Future climate change projections are more likely to provide reliable predictions if they include changes in vegetation.”
JOURNEYS
Scientific advance
DOI
RESEARCH METHODS
Simulation / computational modeling
RESEARCH SUBJECTS
Do not apply
ARTICLE TITLE
Vegetation change in Northern Hemisphere leads to Holocene heat maximum
ARTICLE PUBLICATION DATE
April 15, 2022
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