Monthly Archives: June 2017

Tipping points are real: Gradual changes in CO2 levels can induce abrupt climate changes

During the last glacial period, within only a few decades the influence of atmospheric CO2 on the North Atlantic circulation resulted in temperature increases of up to 10 degrees Celsius in Greenland – as indicated by new climate calculations from researchers at the Alfred Wegener Institute and the University of Cardiff. Their study is the first to confirm that there have been situations in our planet’s history in which gradually rising CO2 concentrations have set off abrupt changes in ocean circulation and climate at “tipping points.” These sudden changes, referred to as Dansgaard-Oeschger events, have been observed in ice cores collected in Greenland. The results of the study have just been released in the journal Nature Geoscience.

Ice core sample taken from drill. Photo by Lonnie Thompson, Byrd Polar Research Center, Ohio State University. [Public domain], via Wikimedia Commons
Previous glacial periods were characterised by several abrupt climate changes in the high latitudes of the Northern Hemisphere. However, the cause of these past phenomena remains unclear. In an attempt to better grasp the role of CO2 in this context, scientists from the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI) recently conducted a series of experiments using a coupled atmosphere-ocean-sea ice model.

First author Xu Zhang explains: “With this study, we’ve managed to show for the first time how gradual increases of CO2 triggered rapid warming.” This temperature rise is the result of interactions between ocean currents and the atmosphere, which the scientists used the climate model to explore. According to their findings, the increased CO2 intensifies the trade winds over Central America, as the eastern Pacific is warmed more than the western Atlantic. This is turn produces increased moisture transport from the Atlantic, and with it, an increase in the salinity and density of the surface water. Finally, these changes lead to an abrupt amplification of the large-scale overturning circulation in the Atlantic. “Our simulations indicate that even small changes in the CO2 concentration suffice to change the circulation pattern, which can end in sudden temperature increases,” says Zhang.

Further, the study’s authors reveal that rising CO2 levels are the dominant cause of changed ocean currents during the transitions between glacial and interglacial periods. As climate researcher Gerrit Lohmann explains, “We can’t say for certain whether rising CO2 levels will produce similar effects in the future, because the framework conditions today differ from those in a glacial period. That being said, we’ve now confirmed that there have definitely been abrupt climate changes in the Earth’s past that were the result of continually rising CO2 concentrations.”

For more information visit:-

via Blogger http://ift.tt/2tcQuAO

Advertisements

Solar paint offers endless energy from water vapor

Researchers have developed a
solar paint that can absorb water vapour and split it to generate hydrogen –
the cleanest source of energy.

The paint contains a newly
developed compound that acts like silica gel, which is used in sachets to
absorb moisture and keep food, medicines and electronics fresh and dry.

Sun with sunspots and limb darkening as seen in visible light with solar filter. By Geoff Elston [CC BY 4.0 (http://ift.tt/1eRPUFd)%5D, via Wikimedia Commons
But unlike silica gel, the new
material, synthetic molybdenum-sulphide, also acts as a semi-conductor and
catalyses the splitting of water molecules into hydrogen and oxygen.

Lead researcher Dr Torben
Daeneke, from RMIT University in Melbourne, Australia, said: “We found
that mixing the compound with titanium oxide particles leads to a
sunlight-absorbing paint that produces hydrogen fuel from solar energy and
moist air.

“Titanium oxide is the
white pigment that is already commonly used in wall paint, meaning that the
simple addition of the new material can convert a brick wall into energy
harvesting and fuel production real estate.

“Our new development has
a big range of advantages,” he said. “There’s no need for clean or
filtered water to feed the system. Any place that has water vapour in the air,
even remote areas far from water, can produce fuel.”

His colleague, Distinguished
Professor Kourosh Kalantar-zadeh, said hydrogen was the cleanest source of
energy and could be used in fuel cells as well as conventional combustion
engines as an alternative to fossil fuels.

“This system can also be
used in very dry but hot climates near oceans. The sea water is evaporated by
the hot sunlight and the vapour can then be absorbed to produce fuel.

“This is an extraordinary
concept – making fuel from the sun and water vapour in the air.”

For more information visit:-

via Blogger http://ift.tt/2rHFSto

Which Earth-Size Planets are Habitable?

A University of Oklahoma
post-doctoral astrophysics researcher, Billy Quarles, has identified the possible
compositions of the seven planets in the TRAPPIST-1 system. Using thousands of
numerical simulations to identify the planets stable for millions of years,
Quarles concluded that six of the seven planets are consistent with an
Earth-like composition. The exception is TRAPPIST-1f, which has a mass of 25
percent water, suggesting that TRAPPIST-1e may be the best candidate for future
habitability studies.

“The goal of exoplanetary
astronomy is to find planets that are similar to Earth in composition and potentially
habitable,” said Quarles. “For thousands of years, astronomers have
sought other worlds capable of sustaining life.”

The Earth seen from space, by NASA/Apollo 17 crew; taken by either Harrison Schmitt or Ron Evans [Public domain or Public domain], via Wikimedia Commons
Quarles, a researcher in the
Homer L. Dodge Department of Physics and Astronomy, OU College of Arts and
Sciences, collaborated with scientists, E.V. Quintana, E. Lopez, J.E. Schlieder
and T. Barclay at NASA Goddard Space Flight Center on the project. Numerical
simulations for this project were performed using the Pleiades Supercomputer
provided by the NASA High-End Computing Program through the Ames Research
Center and at the OU Supercomputing Center for Education and Research.

TRAPPIST-1 planets are more
tightly spaced than in Kepler systems, which allow for transit timing
variations with the photometric observations. These variations tell the
researchers about the mass of the planets and the radii are measured through
the eclipses. Mass and radius measurements can then infer the density. By
comparing Earth’s density (mostly rock) to the TRAPPIST-1 planets, Quarles can
determine what the planets are likely composed of and provide insight into
whether they are potentially habitable.

TRAPPIST-1f has the tightest
constraints with 25 percent of its mass in water, which is rare given its
radius. The concern of this planet is that the mass is 70 percent the mass of
Earth, but it is the same size as Earth. Because the radius is so large, the
pressure turns the water to steam, and it is likely too hot for life as we know
it. The search for planets with a composition as close to Earth’s as possible
is key for finding places that we could identify as being habitable. Quarles
said he is continually learning about the planets and will investigate them
further in his studies.

TRAPPIST-1 is a nearby ultra-cool
dwarf about 40 light-years away from Earth and host to a remarkable planetary
system consisting of seven transiting planets. The seven planets are known as
TRAPPIST 1b, c, d, e, f, g and h.

For more information visit:-


via Blogger http://ift.tt/2sk0iIR