Laws that favor the use of diesel, rather than gasoline, engines in cars may actually encourage global warming, according to a new study. Although diesel cars obtain 25 to 35 percent better mileage and emit less carbon dioxide than similar gasoline cars, they can emit 25 to 400 times more mass of particulate black carbon and associated organic matter ("soot") per kilometer [mile]. The warming due to soot may more than offset the cooling due to reduced carbon dioxide emissions over several decades, according to Mark Z. Jacobson, Associate Professor of Civil and Environmental Engineering at Stanford University.
Writing in the Journal of Geophysical Research-Atmospheres, Jacobson describes computer simulations leading to the conclusion that control of fossil-fuel black carbon and organic matter may be the most effective method of slowing global warming, in terms of the speed and magnitude of its effect on climate. Not only does soot warm the air to a much greater extent than does carbon dioxide per unit mass, but the lifetime of soot in the air (weeks to months) is much less than is that of carbon dioxide (50 to 200 years). As such, removing soot emissions may have a faster effect on slowing global warming than removing carbon dioxide emissions.
The model Jacobson used tested 12 identifiable effects of airborne particles, known as aerosols, on climate, eight of which had not previously been described in scientific literature. Jacobson notes that it is not currently possible to quantify each of these effects individually, only the net effect of all of them operating simultaneously.
"Since 1896, when Svante Arrhenius first postulated the theory of global warming due to carbon dioxide, control of carbon dioxide has been considered the most effective method of slowing warming," Jacobson says in an interview. "Whereas carbon dioxide clearly causes most global warming, control of shorter-lived warming constituents, such as black carbon, should have a faster effect on slowing warming, which is the conclusion I have drawn from this study. The Kyoto Protocol of 1997 does not even consider black carbon as a pollutant to control with respect to global warming."
The reason the issue of diesel versus gasoline is important, says Jacobson, is that, in Europe, one of the major strategies for satisfying the Kyoto Protocol is to promote further the use of diesel vehicles and specifically to provide a greater tax advantage for diesel. Tax laws in all European Union countries, except the United Kingdom, currently favor diesel, thereby inadvertently promoting global warming, Jacobson says. Further, some countries, including Sweden, Finland, Norway, and the Netherlands, also tax fuels based on their carbon content. These taxes also favor diesel, he notes, since diesel releases less carbon per kilometer [mile] than does gasoline. Nevertheless, the small amount of black carbon and organic matter emitted by diesel may warm the atmosphere more over 100 years than the additional carbon dioxide emitted by gasoline.
In Europe and the U.S., particulate emissions from vehicles are expected to decline over the next decade. For example, by 2005, the European Union will introduce more stringent standards for particulate emissions from light duty vehicles of 0.025 grams per kilometer [0.04 grams per mile]. Even under these standards, diesel powered cars may still warm the climate more over the next 100 years than may gasoline powered cars, according to the study.
The state of California is implementing an even more restrictive standard in 2004, allowing only 0.006 grams per kilometer [0.01 grams per mile] of particulate emissions. Even if the California standard were introduced worldwide, says Jacobson, diesel cars may still warm the climate more than gasoline cars over 13 to 54 years.
In an interview, Jacobson said that new particle traps being introduced by some European automobile manufacturers in their diesel cars appear to reduce black carbon emissions to 0.003 grams per kilometer [0.005 grams per mile], even below the California standard. "I think this is great, and it is an indication that tough environmental laws encourage industry to change. But," he said, "diesel vehicles emitting at this level may still warm the climate more than gasoline over a 10 to 50 year period, not only because of black carbon emissions, but also because the traps themselves require addition fuel use. Gasoline/battery hybrid vehicles now available not only get better mileage than the newest diesels but also emit less black carbon."
In practice, less than 0.1 percent of light vehicles in the United States run on diesel fuel, whereas more than 25 percent do in Europe. (Almost a third of new European cars in 2000 were diesel powered.) In both the United States and Europe, virtually all heavy trucks and buses are diesel powered, and American diesel consumption rates for all modes of ground transportation combined are about 75 to 80 percent of those in Europe.
Control of fossil fuel black carbon and organic matter will not by itself eliminate long term global warming, says Jacobson. This would require reductions in emissions of carbon dioxide and other greenhouse gases, in addition to reduction of particles. Other strategies to be considered for reducing black carbon and organic matter from the atmosphere could include the phasing out of indoor biomass and coal burning and improved particle collection from jet fuel and coal burning, he says. This reduction would provide the additional benefit of reducing the 2.7 million people who die annually from air pollution, as estimated by the World Health Organization. The health costs of particulate pollution range, in industrial countries, from $200,000 to $2.75 million per ton, Jacobson notes.
The research was supported by NASA, the Environmental Protection Agency, the National Science Foundation, the David and Lucile Packard Foundation, and the Hewlett-Packard Company.
Harvey Leifert | Stanford University
Conservationists are sounding the alarm: parrots much more threatened than assumed
15.09.2017 | Justus-Liebig-Universität Gießen
A new indicator for marine ecosystem changes: the diatom/dinoflagellate index
21.08.2017 | Leibniz-Institut für Ostseeforschung Warnemünde
Plants and algae use the enzyme Rubisco to fix carbon dioxide, removing it from the atmosphere and converting it into biomass. Algae have figured out a way to increase the efficiency of carbon fixation. They gather most of their Rubisco into a ball-shaped microcompartment called the pyrenoid, which they flood with a high local concentration of carbon dioxide. A team of scientists at Princeton University, the Carnegie Institution for Science, Stanford University and the Max Plank Institute of Biochemistry have unravelled the mysteries of how the pyrenoid is assembled. These insights can help to engineer crops that remove more carbon dioxide from the atmosphere while producing more food.
A warming planet
Our brains house extremely complex neuronal circuits, whose detailed structures are still largely unknown. This is especially true for the so-called cerebral cortex of mammals, where among other things vision, thoughts or spatial orientation are being computed. Here the rules by which nerve cells are connected to each other are only partly understood. A team of scientists around Moritz Helmstaedter at the Frankfiurt Max Planck Institute for Brain Research and Helene Schmidt (Humboldt University in Berlin) have now discovered a surprisingly precise nerve cell connectivity pattern in the part of the cerebral cortex that is responsible for orienting the individual animal or human in space.
The researchers report online in Nature (Schmidt et al., 2017. Axonal synapse sorting in medial entorhinal cortex, DOI: 10.1038/nature24005) that synapses in...
Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...
Using ultrafast flashes of laser and x-ray radiation, scientists at the Max Planck Institute of Quantum Optics (Garching, Germany) took snapshots of the briefest electron motion inside a solid material to date. The electron motion lasted only 750 billionths of the billionth of a second before it fainted, setting a new record of human capability to capture ultrafast processes inside solids!
When x-rays shine onto solid materials or large molecules, an electron is pushed away from its original place near the nucleus of the atom, leaving a hole...
For the first time, physicists have successfully imaged spiral magnetic ordering in a multiferroic material. These materials are considered highly promising candidates for future data storage media. The researchers were able to prove their findings using unique quantum sensors that were developed at Basel University and that can analyze electromagnetic fields on the nanometer scale. The results – obtained by scientists from the University of Basel’s Department of Physics, the Swiss Nanoscience Institute, the University of Montpellier and several laboratories from University Paris-Saclay – were recently published in the journal Nature.
Multiferroics are materials that simultaneously react to electric and magnetic fields. These two properties are rarely found together, and their combined...
19.09.2017 | Event News
12.09.2017 | Event News
06.09.2017 | Event News
22.09.2017 | Medical Engineering
22.09.2017 | Physics and Astronomy
22.09.2017 | Physics and Astronomy