Scientists have done a new experiment and found that the rate of climate change over the next century could be higher than previously anticipated.
The results of the experiment at the Department of Energy's Oak Ridge National Laboratory (ORNL) and at the National Center for Atmospheric Research are published in the current issue of Biogeosciences.
They illustrate the complexity of climate modeling by demonstrating how natural processes still have a strong effect on the carbon cycle and climate simulations.
According to ORNL's Peter Thornton, lead author of the research paper, the inclusion of these processes is a necessary step to improve the accuracy of climate change assessments.
"We've shown that if all of the global modeling groups were to include some kind of nutrient dynamics, the range of model predictions would shrink because of the constraining effects of the carbon nutrient limitations, even though it's a more complex model," he said.
To date, climate models ignored the nutrient requirements for new vegetation growth, assuming that all plants on earth had access to as much "plant food" as they needed.
But, by taking the natural demand for nutrients into account, the researchers have shown that the stimulation of plant growth over the coming century may be two to three times smaller than previously predicted.
Since less growth implies less CO2 absorbed by vegetation, the CO2 concentrations in the atmosphere are expected to increase.
However, this reduction in growth is partially offset by another effect on the nitrogen cycle: an increase in the availability of nutrients resulting from an accelerated rate of decomposition - the rotting of dead plants and other organic matter - that occurs with a rise in temperature.
Combining these two effects, the authors discovered that the increased availability of nutrients from more rapid decomposition did not counterbalance the reduced level of plant growth calculated by natural nutrient limitations; therefore less new growth and higher atmospheric CO2 concentrations are expected.
This breakthrough is one more step toward a more realistic prediction for the future of the earth's climate.