Thursday, February 24, 2011



Sometime in the next 20 years, Arctic soil that has been frozen since the last ice age will begin thawing in response to rapidly warming polar temperatures and start releasing a vast reservoir of carbon into the atmosphere. A new study puts the first numbers and dates on these "irreversible" permafrost emissions, and it looks like enough to kick the global warming trend into another gear.
The carbon is released by the decay of roots and other organic material exposed to the atmosphere after thousands of years of being locked away in the deep freeze of permanently frozen Arctic dirt.
Research scientist Kevin Schaefer at the National Snow and Ice Data Center in Boulder, CO, and colleagues, writing in the journal Tellus, estimate that by 2200, the melting of up to 60 percent of the Northern Hemisphere's permafrost could add some 190 billion tons of carbon to the atmosphere.
Schaefer says 190 gigatons is "equivalent to roughly half the total fossil fuel emissions since the dawn of the industrial age." Looked at another way, he says, it represents about 20 percent of the total amount of carbon in the atmosphere today.
The researchers identify a positive permafrost carbon feedback effect on the climate, although they are not yet able to provide estimates of the impact of this feedback on global warming.
"Carbon emissions from thawing permafrost will accelerate or amplify the warming due to the burning of fossil fuels, Shaefer said in an email to Discovery News. "However, we cannot state at this time the exact increase in temperature. We plan to make such estimates in our next round of simulations."
Those estimates could be crucial to achieving whatever emissions targets may be sought in the years ahead.
"The thaw and decay of permafrost carbon is irreversible and accounting for the PCF (permafrost carbon feedback) will require larger reductions in fossil fuel emissions to reach a target atmospheric CO2 concentration," the scientists write.
Image: Location of Permafrost in the Northern Hemisphere. Glaciers and the Greenland Ice Sheet are violet, and Arctic Sea Ice is light blue. From NSIDC/Wikimedia Commons.



Identifying the source of a particle floating in the atmosphere makes finding a needle in a haystack sound easy. But the robotic probe attached to NASA's new satellite, named Glory, will do just that from over 400 miles above the Earth's surface.
The satellite will carry a particle identifying instrument, called the Aerosol Polarimetry Sensor (APS), along with another probe called the Total Irradiance Monitor (TIM). The two instruments will work together to help scientists understand the dynamics of global warming and identify its causes.
In late February, Glory will join a group of satellites, known as the Afternoon Train, already orbiting the Earth. Everyday, the Afternoon Train, or A-Train, flies over the equator at roughly 1:30 p.m. local time. The Afternoon Train allows scientists to observe multiple atmospheric conditions in essentially the same place and time every day.
The four satellites already in orbit, Aqua, CloudSat, CALIPSO, and Aura, are already monitoring clouds and water vapor, weather patterns, greenhouse gas concentrations, and other influences on the Earth's climate. The new probes on Glory will add two new abilities to the Afternoon Train's repertoire, measuring the sun's energy and analyzing the composition of aerosols.
When scientists talk about aerosols, they mean tiny particulates floating in the air, not including clouds. When you spray a can of paint, what comes out is an aerosol. Some aerosols are natural, such as dust and volcanic ash, others are put there by human activities, like carbon black (soot) from burning coal.
The Aerosol Polarimetry Sensor will observe light waves bouncing off particles in Earth's atmosphere. Different types of particles reflect light differently. By knowing what types of particles are floating around and in what quantities, the scientists hope to nail down their sources.
Glory's other passenger, the Total Irradiance Monitor will help researchers understand the seemingly simple equation of climate change:
(Sun's energy striking the Earth) – (Sun's energy bouncing off or otherwise released into space) =(Amount of warming or cooling of the Earth.)
If more energy is coming in than is being released back out, the Earth is getting hotter. But trying to quantify energy-in versus energy-out requires measurements of day-to-day changes in solar energy reaching Earth. The Total Irradiance Monitor will monitor the entire spectrum of energy coming from the sun toward Earth's equator.
By knowing how the whole spectrum of electromagnetic energy, from X-ray to infrared, fluctuates scientists will better understand how the sun itself effects the Earth's temperature. That way, changes in the sun's energy can be sorted out from natural and human-caused influences on the climate.

No comments:

Post a Comment