Climate scientists who specialize in predicting the earth’s future have developed a new computer modeling tool that factors in the role forests play in mitigating greenhouse gases.
The product, developed by scientists for use by scientists worldwide, could bring results that inform policymakers who make decisions that affect how everyone lives.
The model is called the RCP 4.5., or “Representative Concentration Pathway,” with 4.5 short for “4.5 Watts per square meter of radiative forcing,” or the amount of heat trapped in the atmosphere. (It is for scientists, so check out the links.)
“RCP 4.5 is a new scenario of how human interactions with the atmosphere might change over the next 100 years,” says Allison Thomson, a Pacific Northwest National Laboratory scientist who worked on the program.
The Representative Concentration Pathway 4.5 (RCP 4.5, for short)is the work of the Pacific Northwest National Laboratory and Joint Global Change Research Institute at the University of Maryland.
RCP 4.5 is one of four climate change modeling programs developed by the international Integrated Assessment Modeling Consortium.
The ultimate goal: link the four models so that scientists may communicate with each other across continents about climate change.
The model projects carbon emissions, injects economics and puts a price tag on carbon. It includes options for reducing carbon, such as using wind, nuclear and solar power; using alternative fuels for vehicles; conserving energy; and adding more forests and preserving the ones we have. And it sets a limit on radiative forcing.
“It’s a strong mitigation case, which means you have to use a list of every possible option for reducing emissions,” Thomson says.
Putting a value on carbon also is key.
Earlier models didn’t have the economics, says Mark Harmon, a forestry professor at Oregon State University.
“They’ve done a good job trying to deal with a very complicated issue,” says Harmon, who finds the message of the modeling crystal clear:
“To try to do just one thing isn’t feasible. There are a number of things that can be done and in combination make a substantial difference.”
Managing forests, one of his specialties, is made more difficult by competing demands for trees and dealing with the politics that surround environmental issues.
Currently, forests’ policymakers rely mainly on three climate-management strategies, Harmon says.
Simply allow forests to grow.
Harvest and use trees as biofuels.
Log forests and turn them into wood products that will replace products formerly created by using fossil fuels.
Harmon sees problems. “If you have a big forest and cut it down, you have a carbon debt to be repaid that could take hundreds of years,” he says in his critique of the third strategy.
Harmon says all forests are not created equally. Each tree species has its own capacity for storing carbon.
Thomson agrees, explaining that typically, forests accumulate carbon faster right after they’ve been planted for the first few decades’ growth. They grow rather rapidly and they continue to accumulate carbon in their older years, but it’s at a slower rate.
“So in the model in particular we do account for some differences in forest growth rates overtime in different regions of the world,” she says.
And in the atmosphere, carbon is carbon.
“The atmosphere doesn’t care where the carbon molecule came from. It’s going to trap the same amount of heat, whether it came from deforestation or a coal-fired power plant,” she says. “And so what we say is, ‘Okay, then they should all cost the same amount of money to emit.’ If there’s a cost on your emissions, then that should also apply to deforestation or activities that result in deforestation.”
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