In the last few years the world has experienced a "cooler period" since record high temperatures in summer 1998.

This has been used by global warming sceptics as proof that greenhouse gases are not causing a rise in temperatures.

However a new study by Nasa said the warming effect of greenhouse gases has been masked since 1998 because of a downward phase in the cycles of the sun that means there is less incoming sunlight and the El Nino weather pattern causing a cooling period over the Pacific.

But from this year solar activity will begin to pick up again and the El Nino phenomenon will cause storms and heat waves.

The research, to be published in Geophysical Research Letters, was carried out by Nasa's Goddard Institute for Space Studies the US Naval Research Laboratory.

It adds to existing data from the UN's Intergovernmental Panel on Climate Change (IPCC) that predicted temperatures will rise because of an increase in greenhouse gases trapping heat in the atmosphere.

Because greenhouse gases stay in the atmosphere, temperatures are set to increase over the next few years because the world is producing more carbon dioxide.

The new study adds the effect of El Nino, which is entering a new warm phase and of the impact of the solar cycle.

Gareth Jones, a climate research scientist at the Met Office, said the effect of global warming is unlikely to be masked by shorter term weather patterns in the future.

He said that 50 per cent of the 10 years after 2011 will be warmer than 1998. After that any year cooler than 1998 will be considered unusual.

"The amount of warming we expect from human impacts is so huge that any natural phenomenon in the future is unlikely to counteract it in the long term," he said.

from Telegraph …

Njoy …

An optical transistor that uses one laser beam to control another could form the heart of a future generation of ultrafast light-based computers, say Swiss researchers.

Conventional computers are based on transistors, which allow one electrode to control the current moving through the device and are combined to form logic gates and processors. The new component achieves the same thing, but for laser beams, not electric currents.

A green laser beam is used to control the power of an orange laser beam passing through the device.

This offers another possible route to light-based rather than electronic, computing. Such "photonic" computing is desirable because components using optical fibres carrying light could be much faster than those using wires to carry electricity.

However, previous attempts to make optical transistors for such circuits only produced very weak effects. The new device could change that.

Crystal matrix

To make their device, Vahid Sandoghdar and colleagues at the Swiss Federal Institute of Technology in Zurich, suspended tetradecane, a hydrocarbon dye, in an organic liquid. They then froze the suspension to -272 °C using liquid helium – creating a crystalline matrix in which individual dye molecules could be targeted with lasers.

When a finely tuned orange laser beam is trained on a dye molecule, it efficiently soaks up most of it up – leaving a much weaker "output" beam to continue beyond the dye.

But when the molecule is also targeted with a green laser beam, it starts to produce strong orange light of its own and so boosts the power of the orange output beam.

This effect is down to the hydrocarbon molecule absorbing the green light, only to lose the equivalent energy in the form of orange light.

"That light constructively interferes with the incoming orange beam and makes it brighter," says Sandoghar's colleague Jaesuk Hwang.

Chilly problem

Using the green beam to switch the orange output beam from weak to strong is analogous to the way a transistor's control electrode switches a current between "on" and "off" voltages, and hence the 0s and 1s of digital data. And doing it with a single molecule means billions could be packed into future photonic chips.

It's a neat trick, but the Zurich team's work is a long way from commercially viable, says Malcolm Penn, CEO of UK electronics market researcher Future Horizons. The costs of operating at such low, cryogenic temperatures are high, he says.

But Moore's law, which describes how the number of components on a chip roughly doubles every two years, cannot go on forever while computing is based on silicon, he acknowledges, making any novel ideas of value.

"In research labs, silicon chips with features just 15 nanometres wide are already misbehaving as quantum randomness makes devices depart from the way they should work," he explains, "so we need new ideas like this for sure."

from NewScientist …

Njoy …

There are of course neither satellite images nor instrumental records of the climate all the way back to the 13th century, but nature has its own 'archive' of the climate in both ice cores and the annual growth rings of trees and we humans have made records of a great many things over the years - such as observations in the log books of ships and in harbour records. Piece all of the information together and you get a picture of how much sea ice there has been throughout time.

Modern research and historic records

"We have combined information about the climate found in ice cores from an ice cap on Svalbard and from the annual growth rings of trees in Finland and this gave us a curve of the past climate" explains Aslak Grinsted, geophysicist with the Centre for Ice and Climate at the Niels Bohr Institute at the University of Copenhagen.

In order to determine how much sea ice there has been, the researchers needed to turn to data from the logbooks of ships, which whalers and fisherman kept of their expeditions to the boundary of the sea ice. The ship logbooks are very precise and go all the way back to the 16th century. They relate at which geographical position the ice was found. Another source of information about the ice are records from harbours in Iceland, where the severity of the winters have been recorded since the end of the 18th century.

By combining the curve of the climate with the actual historical records of the distribution of the ice, researchers have been able to reconstruct the extent of the sea ice all the way back to the 13th century. Even though the 13th century was a warm period, the calculations show that there has never been so little sea ice as in the 20th century.

In the middle of the 17th century there was also a sharp decline in sea ice, but it lastet only a very brief period. The greatest cover of sea ice was in a period around 1700-1800, which is also called the 'Little Ice Age'.

"There was a sharp change in the ice cover at the start of the 20th century," explains Aslak Grinsted. He explains, that the ice shrank by 300.000 km2 in the space of ten years from 1910-1920. So you can see that there have been sudden changes throughout time, but here during the last few years we have had some record years with very little ice extent.

"We see that the sea ice is shrinking to a level which has not been seen in more than 800 years", concludes Aslak Grinsted.

from sciencedaily …

Njoy …