New research improves global climate models

December 15, 2015 by Leah Burrows, Harvard University
New research improves global climate models
Clouds move over the Amazon rainforest

When it comes to understanding climate change, there is the easy part and the hard part. The easy part is understanding how greenhouses gasses such as carbon dioxide and methane trap solar radiation and warm the planet. The hard part is figuring out how atmospheric particles impact cloud formation, which scatters solar radiation and cools the planet.

Clouds, as you probably learned in grade school, are created as evaporated water forms droplets around airborne . Prior to the industrial revolution, these particles came from organic sources, like plants, or naturally occurring wildfires, dust storms, and sea spray. But beginning around 1750, humans have poured carbon, sulfate and other aerosols into the atmosphere, increasing atmospheric particulates up to 100-fold in many locations.

How this increase is affecting is unclear, in part because little is known about the behavior of these particles.

Now, research led by the John A. Paulson School of Engineering and Applied Sciences (SEAS) provides a new twist to a recently proposed theory about atmospheric particulates and paints a clearer picture of how these particles behave. The research, published in Nature Geoscience, found that atmospheric particles tied to plant life can be either solid or liquid depending on the environment in which they form. The findings expand on a previous study that posited such particles favor a solid state.

"These findings swing the scientific pendulum," said Scot Martin, the Gordon McKay Professor of Environmental Chemistry, who led the research. "Clouds behave differently depending on whether they form on populations of solid or liquid particles. The state of the particles will determine which processes to include in models predicting climate change, enhancing the accuracy of these models."

The research was conducted in collaboration with Amazonas State University, University of São Paulo, and the National Institute of Amazonian Research as part of the GoAmazon2014/5 project supported by the Department of Energy.

The previous research, which found that over forests are in a solid or semisolid state, was conducted in a boreal (pine) forest in Finland. There, pine trees release alpha-pinene, an organic building block that reacts with other substances such as ozone to produce atmospheric organic particulate matter. (Alpha-pinene is also what we smell when we smell pine.)

Martin and his team decided to test that theory in the Amazon rainforest, which has about 80 percent humidity, compared to the pine forest's 30 percent. In the Amazon, the reaction products of the compound isoprene provides the basic building block for atmospheric organic particulate matter.

The team found that 80 percent of the time, the atmospheric organic particles that formed in the Amazon were in a liquid state. Liquid particles absorb molecules from the gas phase and grow. Semi-solid particles, on the other hand, grow layer by layer and remain smaller, which affects the types of clouds that form and their propensity to rain.

"Our study found that regionality plays an important role in the state of liquid and dry particles," said Adam Bateman, a postdoctoral fellow at SEAS and first author of the study. "The state of the particles depends on where you are, the kind of biome you have, and what the trees are emitting. Pine trees emit different compounds and do so in drier conditions, with the net result of particles that are semi-solid, and climate modeling will be different as a result."

The research in the Amazon also provides a window back in time, to a pre-industrial world. Because the Amazon is so remote, it is protected from an influx of particles caused by industrial pollution.

"The Amazon represents a natural laboratory to explore what the world was like in 1750," Martin said. "Here, we can ask questions about how these particles occur naturally, how big they get and what kind of clouds they form—and then compare that to the modern world. This research touches on all the topics of that we need to think about, whether particulates are organic or not."

Explore further: Jelly-like atmospheric particles resist chemical aging

More information: Adam P. Bateman et al. Sub-micrometre particulate matter is primarily in liquid form over Amazon rainforest, Nature Geoscience (2015). DOI: 10.1038/ngeo2599

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4 comments

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cantdrive85
1.5 / 5 (8) Dec 15, 2015
New research improves global climate models

Well this claim is complete and utter bollocks, the science has already been "settled". By definition, there can be no improvement on something after its been settled.
runrig
4.3 / 5 (6) Dec 15, 2015
New research improves global climate models

Well this claim is complete and utter bollocks, the science has already been "settled". By definition, there can be no improvement on something after its been settled.

For the nth time ...
What is settled is that the planet is warming due to the emission of anthro CO2, which has a GHE known of for ~150 yrs - empirical science and NOT up for argument.
A GH forcing 140% greater that pre-industrial.
What is NOT settled is the distribution of energy within the climate system - hence improvements in GCM's will continue to be made for a long time into the future.
Models show us we are correct but are not definitive.
Oh, and you're back on ignore.
leetennant
4.3 / 5 (6) Dec 15, 2015
New research improves global climate models

Well this claim is complete and utter bollocks, the science has already been "settled". By definition, there can be no improvement on something after its been settled.

For the nth time ...
What is settled is that the planet is warming due to the emission of anthro CO2, which has a GHE known of for ~150 yrs - empirical science and NOT up for argument.
What is NOT settled is the distribution of energy within the climate system - hence improvements in GCM's will continue .


Which is why they're called "deniers" because they're denying basic physics. This argument is akin to smoking 10 packs a day because "science is never settled" and they don't have a complete and accurate model of every single human body on the planet to map how each will individually respond to the carcinogens. Just because our models aren't complete doesn't change the fact we know that smoking causes cancer.
ForFreeMinds
1.7 / 5 (6) Dec 15, 2015
"New research improves global climate models"

They obviously need a lot of improvement considering the models' predictions all overestimate the future temperature.

I'd suggest that the climate models should be tested for 25 years to validate their accuracy. Especially before changing any government policy based on them.

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