Posts tagged change
Fourmile canyon blaze yields new insight into climate change, CU scientists say
Aug 27th
CU-NOAA study provides first direct evidence of
heat-trapping effects of wildfire smoke particles
heat-trapping effects of wildfire smoke particles
When the Fourmile Canyon Fire erupted west of Boulder in 2010, smoke from the wildfire poured into parts of the city including a site housing scientists from the University of Colorado Boulder’s Cooperative Institute for Research in Environmental Sciences and the National Oceanic and Atmospheric Administration.
Within 24 hours, a few researchers at the David Skaggs Research Center had opened up a particle sampling port on the roof of the building and started pulling in smoky air for analysis by two custom instruments inside. They became the first scientists to directly measure and quantify some unique heat-trapping effects of wildfire smoke particles.
“For the first time we were able to measure these warming effects minute-by-minute as the fire progressed,” said CIRES scientist Dan Lack, lead author of the study published today in the Proceedings of the National Academy of Sciences.
The researchers also were able to record a phenomenon called the “lensing effect,” in which oils from the fire coat the soot particles and create a lens that focuses more light onto the particles. This can change the “radiative balance” in an area, sometimes leading to greater warming of the air and cooling of the surface.
While scientists had previously predicted such an effect and demonstrated it in laboratory experiments, the Boulder researchers were one of the first to directly measure the effect during an actual wildfire. Lack and his colleagues found that lensing increased the warming effect of soot by 50 to 70 percent.
“When the fire erupted on Labor Day, so many researchers came in to work to turn on instruments and start sampling that we practically had traffic jams on the road into the lab,” Lack said. “I think we all realized that although this was an unfortunate event, it might be the best opportunity to collect some unique data. It turned out to be the best dataset, perfectly suited to the new instrument we had developed.”
The instrument called a spectrophotometer can capture exquisite detail about all particles in the air, including characteristics that might affect the smoke particles’ tendency to absorb sunlight and warm their surroundings. While researchers know that overall, wildfire smoke can cause this lensing effect, the details have been difficult to quantify, in part because of sparse observations of particles from real-world fires.
Once the researchers began studying the data they collected during the fire, it became obvious that the soot from the wildfire was different in several key ways from soot produced by other sources — diesel engines, for example.
“When vegetation burns, it is not as efficient as a diesel engine, and that means some of the burning vegetation ends up as oils,” Lack said. In the smoke plume, the oils coated the soot particles and that microscopic sheen acted like a magnifying glass, focusing more light onto the soot particles and magnifying the warming of the surrounding air.
The researchers also discovered that the oils coating the soot were brown, and that dark coloration allowed further absorption of light, and therefore further warming the atmosphere around the smoke plume.
The additional warming effects mean greater heating of the atmosphere enveloped in dark smoke from a wildfire, and understanding that heating effect is important for understanding climate change, Lack said. The extra heating also can affect cloud formation, air turbulence, winds and even rainfall.
The discovery was made possible by state-of-the-art instruments developed by CIRES, NOAA and other scientists, Lack said. The instruments can capture fine-scale details about particles sent airborne by the fire, including their composition, shape, size, color and ability to absorb and reflect sunlight of various wavelengths.
“With such well-directed measurements, we can look at the warming effects of soot, the magnifying coating and the brown oils and see a much clearer, yet still smoky picture of the effect of forest fires on climate,” Lack said.
CU scientists discover a new threat from air pollution
Aug 8th
CU-led team discovers new atmospheric compound
tied to climate change and human health issues
An international research team led by the University of Colorado Boulder and the University of Helsinki has discovered a surprising new chemical compound in Earth’s atmosphere that reacts with sulfur dioxide to form sulfuric acid, which is known to have significant impacts on climate and health.
The new compound, a type of carbonyl oxide, is formed from the reaction of ozone with alkenes, which are a family of hydrocarbons with both natural and man-made sources, said Roy “Lee” Mauldin III, a research associate in CU-Boulder’s atmospheric and oceanic sciences department and lead study author. The study charts a previously unknown chemical pathway for the formation of sulfuric acid, which can result both in increased acid rain and cloud formation as well as negative respiratory effects on humans.
“We have discovered a new and important, atmospherically relevant oxidant,” said Mauldin. “Sulfuric acid plays an essential role in Earth’s atmosphere, from the ecological impacts of acid precipitation to the formation of new aerosol particles, which have significant climatic and health effects. Our findings demonstrate a newly observed connection between the biosphere and atmospheric chemistry.”
A paper on the subject is being published in the Aug. 9 issue of Nature.
Typically the formation of sulfuric acid in the atmosphere occurs via the reaction between the hydroxyl radical OH — which consists of a hydrogen atom and an oxygen atom with unpaired electrons that make it highly reactive — and sulfur dioxide, Mauldin said. The trigger for the reactions to produce sulfuric acid is sunlight, which acts as a “match” to ignite the chemical process, he said.
But Mauldin and his colleagues had suspicions that there were other processes at work when they began detecting sulfuric acid at night, particularly in forests in Finland — where much of the research took place — when the sun wasn’t present to catalyze the reaction. “There were a number of instances when we detected sulfuric acid and wondered where it was coming from,” he said.
In the laboratory, Mauldin and his colleagues combined ozone — which is ubiquitous in the atmosphere — with sulfur dioxide and various alkenes in a gas-analyzing instrument known as a mass spectrometer hooked up with a “flow tube” used to add gases. “Suddenly we saw huge amounts of sulfuric acid being formed,” he said.
Because the researchers wanted to be sure the hydroxyl radical OH was not reacting with the sulfur dioxide to make sulfuric acid, they added in an OH “scavenger” compound to remove any traces of it. Later, one of the research team members held up freshly broken tree branches to the flow tube, exposing hydrocarbons known as isoprene and alpha-pinene — types of alkenes commonly found in trees and which are responsible for the fresh pine tree scent.
“It was such a simple little test,” said Mauldin. “But the sulfuric acid levels went through the roof. It was something we knew that nobody had ever seen before.”
Mauldin said the new chemical pathway for sulfuric acid formation is of interest to climate change researchers because the vast majority of sulfur dioxide is produced by fossil fuel combustion at power plants. “With emissions of sulfur dioxide, the precursor of sulfuric acid, expected to rise globally in the future, this new pathway will affect the atmospheric sulfur cycle,” he said.
According to the U.S. Environmental Protection Agency, more than 90 percent of sulfur dioxide emissions are from fossil fuel combustion at power plants and other industrial facilities. Other sulfur sources include volcanoes and even ocean phytoplankton. It has long been known that when sulfur dioxide reacts with OH, it produces sulfuric acid that can form acid rain, shown to be harmful to terrestrial and aquatic life on Earth.
Airborne sulfuric acid particles — which form in a wide variety of sizes — play the main role in the formation of clouds, which can have a cooling effect on the atmosphere, he said. Smaller particles near the planet’s surface have been shown to cause respiratory problems in humans.
Mauldin said the newly discovered oxidant might help explain recent studies that have shown large parts of the southeastern United States might have cooled slightly over the past century. Particulates from sulfuric acid over the forests there may be forming more clouds than normal, cooling the region by reflecting sunlight back to space.
Most of the laboratory experiments for the study were conducted at the Leibniz-Institute for Tropospheric Research in Leipzig, Germany.
Co-authors on the study include Torsten Berndt and Frank Stratmann from the Leibniz-Institute for Tropospheric Research; Mikko Sipilä, Pauli Paasonen, Tuukka Petäjä, Theo Kurtén, Veli-Matti Kerminen and Markku Kulmula from the University of Helsinki in Finland; and Saewung Kim from the National Center for Atmospheric Research in Boulder. Mauldin also is affiliated with NCAR and the University of Helsinki.
The study was funded by the European Commission Sixth Framework program, the Academy of Finland, The Finnish Center of Excellence, the European Research Council, the Kone Foundation, the Väisälä Foundation, the Maj and Tor Nessling Foundation, the Otto Malm Foundation and the U.S. National Science Foundation.
Population growth unsustainable, says CU prof, and the end will not be pretty
Jul 31st
“You cannot sustain population growth. It’s not debatable,” says University of Colorado Boulder Professor Emeritus Al Bartlett. “It’s based on arithmetic. It’s not debatable unless you want to debate arithmetic.”
In an educational video entitled “Population, Consumption, and Climate: A Conversation with Al Bartlett,” the professor reprises themes from his notorious talk on population. Bartlett came to CU-Boulder in 1950 to join the Department of Physics. In the 1950s and today, he notes society and governments view steady growth as the centerpiece of the global economy.
“I got to thinking about the fact that people didn’t really understand the arithmetic of steady growth,” he said. “So I put together a talk. I first gave it in September of 1969 on the arithmetic of growth.”
Bartlett has since delivered that well-known lecture more than 1,700 times to audiences worldwide. He often cites an analogy of human population growth and multiplying bacteria. Using an animation that shows bacteria doubling over a fixed period of time, the video illustrates the arithmetic of steady growth and how quickly resources are depleted as growth continues.
“There will be limits,” cautions Bartlett.
The world population topped 7 billion in March 2012, according to the United States Census Bureau. Bartlett explains that despite the fact that population growth rates in developing countries may be 3-4 times higher than the U.S. rates, a significant problem with population resides in the United States because of high per capita demand for energy and resources.
“The average child born in the United States will have, over its lifetime, 10-20 times the impact on world resources as a child born in an underdeveloped nation,” he says. “So we’ve got to address the problem at home.”
In addition to the strain on the earth’s natural resources, excessive consumption contributes to climate change because resource extraction, manufacturing, and transportation produce a great deal of carbon dioxide. And, according to Bartlett, “if any fraction of global warming can be attributed to the actions of humans, that’s all the proof you need to say the human population today is greater than the carrying capacity of the earth.”
Population, Consumption, and Climate: A Conversation with Al Bartlett is part of a video series viewable at Learn More About Climate, produced by CU-Boulder’s Office for University Outreach and Landlocked Films.
The Learn More About Climate initiative brings climate change-related information to communities across the state.The website is an online outreach tool that localizes climate change through interviews with leading scientists and everyday Coloradans to explain how climate change is affecting our state. The site also offers resources for teachers, students, policy makers, and community members who want to learn more about this critical issue.
