|SCIENCE & TECHNOLOGY|
Pacific takes in heat to put global warming on hold
India to help build largest telescope on ground Prof Yash
Prof Yash Pal
Pacific takes in heat to put global warming on hold
CHANGES in the flow of heat between the atmosphere and the Pacific Ocean could help to explain the recent “pause” in global warming that has seen a fall in the rate at which global surface temperatures have risen over the past 15 years or so, a new study has suggested.
The current global warming hiatus, where the increase in global temperatures has levelled off, can be explained at least in part by natural changes to a cold Pacific Ocean current called La Nina which may have helped to absorb excess heat from the atmosphere, scientists said.
It is further evidence that the deep ocean may be playing a major role in helping to dampen down temperature rises at the surface. A previous study, for instance, found that the heat being absorbed by the deep ocean is equivalent to the power generated by 150 billion electric kettles.
Although global average temperatures are now higher than they have ever been since modern records began, they have not increased as fast over the past 10 or 15 years as some climate models have predicted, leading climate “sceptics” to claim that global warming has stopped.
Climate scientists have countered by saying that the last decades was still warmer than any previous decade, with 12 of the 14 hottest years on record occurring since 2000, and that periods of natural variability, with temperatures falling temporarily, are always to be expected.
Calculations suggest that the overall heat balance of the Earth is showing a positive trend, with more solar heat coming in than thermal energy that is lost into space. Climate researchers have argued that deep parts of the ocean are likely to be absorbing this extra heat, rather than it accumulating at the Earth’s surface.
The latest study by Yu Kosaka and Shang-Ping Xie of the Scripps Institution of Oceanography in San Diego supports this idea by a theoretical study of the cold La Nina current in the eastern Pacific, which they found is capable of taking up huge amounts of heat from the atmosphere over a period of decades.
“Our results show that the current hiatus is part of natural climate variability, tied specifically to a La Nina-like decadal cooling,” the researchers said in the journal Nature. “Although similar decadal hiatus events may occur in the future, the multi-decadal warming trend is very likely to continue with greenhouse gas increase,” they said.
In their computer modelling experiment, the two researchers altered the amount of heat flowing between the east Pacific Ocean and the atmosphere so that the sea surface temperatures in the computer model were forced to agree with the actual observations.
“This results in the realistic simulation of the recent surface warming slowdown globally and some unusual weather patterns such as drought experienced in the southern United States,” said Richard Allan, a climate scientist at Reading University, who was not involved with the research.
“This new study adds further evidence that the recent slowdown in the rate of global warming at the Earth’s surface is explained by natural fluctuations in the ocean and is therefore likely to be a temporary respite from warming in response to rising concentrations of greenhouse gases,” Dr Allan said.
“This is important since it adds to a great body of evidence in continuing to confirm the realism of projected dangerous warming in the future due to human activities such as burning fossil fuels,” he said. — The Independent
India to help build largest telescope on ground
THE signing of the agreement on master partnership for the construction of Thirty-Meter Telescope (TMT) — considered world’s largest ground-based optical and infrared telescope ever built — by five partner countries, Canada, China, India, Japan and the US, has cleared the decks for the participation of Indian industries in this prestigious project which is expected to become operational by 2022.
As per the agreement, India will be a 10 per cent partner in this $1.5-billion project. The “new technology” TMT is essentially a segmented mirror telescope, with its primary 30-m mirror made up of 492 hexagonal segments of 1.44 m each. According to researchers, the sheer size of the telescope will allow it to peer deeper into the cosmos and help unravel many of the hitherto-unknown aspects of the universe.
“TMT with its adaptive optics gives us much finer quality of detail than the Hubble Space Telescope,” says Richard Ellis, Professor of Astronomy at California Institute of Technology, USA.
A Pondicherry-based specialist firm, General Optics Asia Limited (GOAL), which makes strategic components for India’s space and defence sector, will be involved in making a part of the mirror segments going into TMT as well as the edge sensors designed to provide data about the height and tilt of the mirrors.
“Only a few countries can make mirrors. This project can make India big in optics,” says Eswar Reddy, Associate Professor at the Bangalore-based Indian Institute of Astrophysics (IIA), one of the Indian research institutes participating in the project. It is for the first time that GOAL will be developing a sophisticated mirror system for a high-profile telescope project. Reddy also revealed that India is into designing a mirror-coating system and exploring the possibilities of setting up a unit to polish 100 segments of the telescope mirror. Incidentally, such a technology could also be used in satellites, future fusion reactors and medical imaging.
Since the primary mirror of the telescope would be made of an array of 492 identical mirrors segments, the main challenge in its working would be to ensure that the segments remained aligned properly all the time and all the segments work as a single unit. The edge sensors and actuators would help in this task.
“India’s contribution is to a lot of the key parts of the primary mirror system and the main mirror is 30-m in diameter. That is the most important parameter in any telescope,” says Garry Sanders, Project Manager, TMT.”
The mirror is made out of 492 hexagonal segments and all of them act like one mirror. All of the supports, very delicate ones, will be made in India. Besides mirror segments, India will supply 1,500 actuators and 3,000 edge sensors. Incidentally, the edge sensors are designed to sense the real-time displacement of segments due to gravity and temperature while tracking objects in the sky. This information is conveyed to actuators which move the segments, so that all the 492 segments act as a single monolithic mirror to make available the best possible image of objects in the sky.
TMT, like most other ground-based observatories, will have its spatial resolution limited by the prevailing atmospheric turbulence. However, it happens to be the first ground-based telescope to incorporate the technology of Adaptive Optics (AO) as an integral component of the observation system. AO makes for the correction of the blurring caused by atmospheric distortion that limits observational capacity of ground-based telescopes.
Bangalore-based Avasarala Technologies Ltd (ATL) and Mumbai-based Godrej and Boyce are the two other Indian companies, along with GOAL, which are gearing up to provide vital components for use in TMT.
Incidentally, both ATL and Godrej and Boyce have been associated with the Indian space programme as a supplier of components and systems for satellites and launch vehicles. These two companies will be responsible for building the Structure Support Assembly (SSA) to support the mirrors. SSA demands precision engineering and the ability to utilise critical steel and aluminium alloys. Reddy describes SSA as a very complicated system. India has also the responsibility of building the entire actuator system. ATL will also be responsible for producing actuators required for TMT.
India’s Department of Science and Technology will be the main agency coordinating the Indian participation in the project. Besides IIA, the other Indian institutes participating in the project are Inter-University Centre for Astronomy and Astrophysics, Pune, and Aryabhata Research Institute of Observational Sciences, Nainital. As envisaged now, Indian astronomers will get observational time in proportion to India’s total share in the project.
We were taught that waves are just a disturbance, and they travel in a particular direction such that the particles of the medium vibrate about their mean position. My question is, in space, i.e., vacuum, there are no such particles, then what causes this disturbance and if at all it’s caused, how does it travel in vacuum?
You seem to understand that light, microwaves and radio waves are all electromagnetic waves. They do not need a material medium to travel. After all Sun’s energy reaches in the form of light; heat and radio waves travel to us through great vacuum. If you are a stududent of physics, you would know the electromagnetic theory which was, and will remain, one of the greatest intellectual achievements of humankind. An essential element of the electromagnetic theory is that radiation consists of oscillating electric and magnetic fields that propagate in a direction normal to the planes of oscillation of the electric and magnetic fields. There is no point in my going on and on. You should consider yourself lucky that you might have a chance to understand and ultimately enjoy and wonder about the cleverness with which this universe has been constructed. The intellectual sophistication of the design is accompanied by great spiritual delectation. Apply yourself a little and partake of a lifelong and lasting joy. No, we do not need a material medium for propagation of light and other radiation.
Readers can e-mail questions to Prof Yash Pal at firstname.lastname@example.org
LONDON: Scientists have grown the first 'mini human brains' in a laboratory and say their success could lead to new levels of understanding about the way brains develop and what goes wrong in disorders like schizophrenia and autism.
Researchers based in Austria started with human stem cells and created a culture in the lab that allowed them to grow into so-called “cerebral organoids” — or mini brains — that consisted of several distinct brain regions.
BEIJING: China will land its first probe on the moon at the end of this year, state media reported yesterday, the next step in an ambitious space programme whichincludes eventually building a space station. In 2007, China launched its first moon orbiter, the Chang’e One orbiter, named after a lunar goddess, which took images of the surface and analysed the distribution of elements.
NEW YORK: Penguin populations in Antarctica surged during the Little Ice Age — a cold period between 1500 and 1800 AD, a new study suggests. Past studies have suggested penguins actually thrive when the climate is relatively warm, since cold climates increase sea-ice extent, which makes it difficult for the birds to access their beach colonies and food-rich waters. Researchers Liguang Sun and Zhouqing Xie, from the University of Science and Technology of China, analysed how the populations of Adelie penguins changed over the past 700 years in the Ross Sea, a region in Antarctica that is at a higher latitude than previous study sites. — Agencies