Ancient civilizations emitted greenhouse gasses, too; the red and orange dots above
mark indirect measures of methane in the atmosphere over the past two millennia.
Scientists have thought that humans only started emitting significant quantities of greenhouse gasses in the 19th century, after the Industrial Revolution—and the fossil fuels that powered it—took hold. But a study in Nature today suggests that our history as heavy emitters stretches back much farther, to the charcoal fires of the Roman Empire and the intensive agriculture of Han China.
To examine carbon emissions past, the research team analyzed more than 50 ice cores from Greenland, gauging levels of the greenhouse gas methane in Earth’s atmosphere going back to 100 B.C. They looked at specific carbon signatures in the methane to determine whether it came from burning coal and other materials—meaning humans might have been involved—or a natural biological process, then used mathematical models to further narrow down manmade emissions from naturally occurring ones. Human emissions, they found, were noticeable, though minuscule compared to post-industrial levels; only perhaps 10% human methane emissions over the past 2,000 years were produced before 1800. For a time when there were far fewer people around, however, that’s still a lot of methane to be sending off into the atmosphere.
Starting this week, NASA will have a new eye in the sky to better sort out the way that greenhouse gases, air pollution, and solar activity interact to affect the climate of our planet. The Glory satellite, currently set to launch on Friday, will spy on changes both in our atmosphere and in the sun.
Its main job will be to study fine airborne particles known as aerosols. Smaller than the diameter of a human hair, these specks can move great distances across the globe and are largely responsible for hazy skies. [The New York Times]
Greenhouse gases and their contribution to climate change have been the subject of much research, of course, but aerosols remain murkier. Climate scientist James Hansen, a member of the Glory team, says researchers must use an uncertainty range for modeling aerosols that’s three to four times greater than what they use with greenhouse gases, simply because the contribution of aerosols is much less understood.
The Glory mission will, if all goes according to plan, collect data on the micro-physical, chemical and optical properties of aerosols using two instruments—an Aerosol Polarimetry Sensor (ARS) and a Total Irradiance Monitor (TIM)—that will monitor the climate system and provide new data for scientists working on the issue of climate change. The APS will collect visible and near-infrared data scattered from aerosols and clouds and the TIM, mounted on a special track that allows it move independent of the satellite, should record total electromagnetic radiation given off by the sun that hits the top of Earth’s atmosphere. [The Atlantic]
For several years now, the Environmental Protection Agency has been lurching toward enacting rules to regulate greenhouse gases under the Clean Air Act. Yesterday, the first steps of the EPA’s new rules went into effect.
The new regulations come in two parts, the first of which limits the emissions allowed by new cars and light trucks.
The rules apply to 2012 model vehicles, which can be sold starting Sunday. They must now follow toughened CAFE fuel efficiency standards laid out in May. With industry on board—though there’s some grumbling—these steps are relatively uncontroversial. [ScienceNOW]
The second and more contentious part of EPA’s action are new rules for power plants, factories, and refineries. Beginning yesterday (January 2), any new plant that will emit more than 100,000 tons of carbon dioxide (or the equivalent) annually will need an EPA permit, as will existing plants that install new capacity that emits 75,000 tons or more. The regulations for all existing plants will follow this July, when those that emit the equivalent of 100,000 annual tons will need permits to do so.
Cooking all your meals on an old-fashioned stove indoors is bad for you and bad for the Earth: The smoke from those fires causes heart and lung problems for millions of people, the soot contributes to global warming and glacier melt, and the need for so much wood drives deforestation. Yet, out of necessity, nearly half the people in the world cook this way.
This week, a United States and United Nations-backed effort took the first tiny steps to try to turn that around. Secretary of State Hillary Clinton says that the U.S. will give $50 million in seed money to the new Global Alliance for Clean Cookstoves, an organization with the intention of providing cleaning-burning cooking stoves to families around the world. Other partners will each provide $10 million.
Intense fertilizer use. Gas-guzzling farm equipment. Plowing up land. At first glance, industrial-scale agriculture doesn’t necessarily seem like an environmental positive. But, Stanford scientists say, looks can be deceiving.
Jennifer Burney and colleagues calculated the net effect of agriculture on greenhouse gas emissions from 1961 to 2005, a period when crop yields shot up dramatically. And while agriculture does produce plenty of emissions, those totals were overwhelmed by the emissions savings achieved by greater agricultural productivity. In short, higher yields mean plowing up less land, and plowing up less land means more carbon sequestered in undisturbed forests and soils. The study appears in the Proceedings of the National Academy of Sciences.
All other things being equal, the researchers found that agricultural advances between 1961 and 2005 spared a portion of land larger than Russia from development and reduced emissions by the equivalent of 590 gigatonnes of carbon dioxide — roughly a third of the total emitted since the start of the Industrial Revolution [Nature].
Behind the ongoing back-and-forth fights over climate change that usually focus on carbon, there has lingered the threat of the powerful greenhouse gas methane being released into the atmosphere and causing even worse trouble. In August we reported on a study that noted methane bubbling up from the seafloor near islands north of Norway, giving scientists a scare. This week in Science, another team reports seeing the same thing during thousands of observations of the East Siberian Arctic Shelf on Russia’s north coast, which is even more worrisome because it’s a huge methane deposit.
The shelf, which covers about 800,000 square miles, was exposed during the last ice age. When the region was above sea level, tundra vegetation pulled carbon dioxide from the air as plants grew. That organic material, much of which didn’t decompose in the frigid Arctic, accumulated in the soil and is the source of modern methane [Science News]. Now underwater, it’s covered by a layer of permafrost. But that permafrost seems to be becoming unstable, thanks to the fact that the water on top of it is warmer than the air it was exposed to back when it was on dry land.