Now, for the first time, a study comprehensively calculates the relative contributions of the components responsible for that heating, known as the greenhouse effect.
These contributions ¡°are among the most misquoted statistics in public discussions of climate change,¡± the authors write. Their study has been accepted for publication in the Journal of Geophysical Research -- Atmospheres, a journal of the American Geophysical Union.
"The existing literature is quite confused," Schmidt says. "If you ask a lot of climate scientists, straight up, 'how much of the current greenhouse effect is due to carbon dioxide?', you get all sorts of numbers."
With the new study, Schmidt says, the team is aiming to provide a single estimate for the contribution of each of the major factors, which can help cut through the confusion and serve as a reference for public discussions of climate change.
The study found that water vapor was the biggest contributor to the greenhouse effect, responsible for about 50 percent of the effect. The next biggest contributor is clouds, contributing about 25 percent of the greenhouse effect. Clouds come in various types, with high thin clouds more effective at trapping heat and lower, thicker clouds more effective at reflecting sunlight, cooling the Earth. The study focused on the heat-trapping ability of clouds.
After that comes carbon dioxide, contributing about 20 percent of the greenhouse effect. Other trace gases and aerosols contribute only about 5 percent, the study found. That includes a variety of greenhouse gases such as methane, which comes from burping livestock, irrigation, landfills and mining activities, and nitrous oxide, also known as laughing gas, which comes mainly from the decomposition of chemical fertilizers on croplands. Soot in the air also has a warming effect, making up part of this 5 percent.
Schmidt and colleagues arrived at these numbers by tweaking computer simulations of the planet, known as climate models. They did one set of tests where they subtracted each of these contributors ¡ª such as carbon dioxide ¡ª one at a time, to see how much less heat would be trapped. They also did another set of tests in which they removed all the greenhouse contributors, and then added them back individually. The numbers above are, in essence, averages of the results from these two tests.
Overall, the greenhouse effect warms the planet by about 33 degrees Celsius (60 degrees Fahrenheit), turning it from a frigid ice-covered ball with a global average temperature of about -17 degrees C (1 degree F), to the climate we have today. Heat-absorbing components contribute directly to that warmth by intercepting and absorbing energy passing through the atmosphere as electromagnetic waves. But that direct heating effect can also have secondary effects ¡ª for instance, when additional carbon dioxide raises the planet's temperature, then the air can become more humid, carrying more heat-trapping water vapor. This in turn heats the planet further, amplifying the effect of a dose of additional carbon dioxide. This is a main reason why scientists are concerned that people are rapidly raising the levels of carbon dioxide in the atmosphere.
To test increasing carbon dioxide¡¯s effect, the researchers simulated the consequences of doubling its concentration in their model. The experiment resulted in some additional greenhouse heating attributable directly to the added gas soaking up more energy, but 5 times as much of a boost in greenhouse heating overall. The researchers report that ¡°the extra net absorption by carbon dioxide has been amplified by the response of water vapor and clouds¡.¡±
Even though methane, nitrous oxide, ozone, soot, and a variety of other factors only contribute about 5 percent of today's greenhouse effect, "you can't ignore them," Schmidt says. "Even though their contribution is small, they're changing very fast," he adds. Preventing them from adding further to the blanket of heat-trapping substances is another lever, besides cutting carbon dioxide emissions, that could fight global warming.
Schmidt collaborated on the study with Goddard Institute colleagues Reto Ruedy, Ron Miller and Andrew Lacis.Title:
Peter Weiss | American Geophysical Union
The importance of biodiversity in forests could increase due to climate change
17.11.2017 | Deutsches Zentrum für integrative Biodiversitätsforschung (iDiv) Halle-Jena-Leipzig
Win-win strategies for climate and food security
02.10.2017 | International Institute for Applied Systems Analysis (IIASA)
Heat from the friction of rocks caused by tidal forces could be the “engine” for the hydrothermal activity on Saturn's moon Enceladus. This presupposes that...
The WHO reports an estimated 429,000 malaria deaths each year. The disease mostly affects tropical and subtropical regions and in particular the African continent. The Fraunhofer Institute for Silicate Research ISC teamed up with the Fraunhofer Institute for Molecular Biology and Applied Ecology IME and the Institute of Tropical Medicine at the University of Tübingen for a new test method to detect malaria parasites in blood. The idea of the research project “NanoFRET” is to develop a highly sensitive and reliable rapid diagnostic test so that patient treatment can begin as early as possible.
Malaria is caused by parasites transmitted by mosquito bite. The most dangerous form of malaria is malaria tropica. Left untreated, it is fatal in most cases....
The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.
Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...
Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.
That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...
Computer Tomography (CT) is a standard procedure in hospitals, but so far, the technology has not been suitable for imaging extremely small objects. In PNAS, a team from the Technical University of Munich (TUM) describes a Nano-CT device that creates three-dimensional x-ray images at resolutions up to 100 nanometers. The first test application: Together with colleagues from the University of Kassel and Helmholtz-Zentrum Geesthacht the researchers analyzed the locomotory system of a velvet worm.
During a CT analysis, the object under investigation is x-rayed and a detector measures the respective amount of radiation absorbed from various angles....
15.11.2017 | Event News
15.11.2017 | Event News
30.10.2017 | Event News
23.11.2017 | Information Technology
23.11.2017 | Physics and Astronomy
23.11.2017 | Life Sciences