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Posted by: Global Warming in CAUSES June 6, 2013 1 Comment 1 Views

Lithosphere

Lithosphere besides compositional classification, the Earth is separated into layers based on mechanical properties. The topmost layer is called the lithosphere, composed of tectonic plates that float on top of another layer known as the asthenosphere. The term lithosphere is derived from the Greek words lithos, meaning rock, and sfaira, or sphere. The rigid, brittle lithosphere extends about 70 kilometers and is made up of Earth’s crust and the upper part of the mantle underneath. It is broken into a mosaic of rigid plates that move parallel across the Earth’s surface relative to each other lithosphere.

The lithosphere rests on a relatively ductile, partially molten layer known as the asthenosphere, which derives its name from the Greek word asthenes, meaning “without strength.” The asthenosphere extends to a depth of about 400 kilometers in the mantle, over which the lithospheric plates slide along. Slow convection currents within the mantle, generated by radioactive decay of minerals, are the fundamental heat energy source that causes the lateral movements of the plates on top of the asthenosphere. According to the plate tectonic theory, there are approximately twenty lithospheric plates, each composed of a layer of continental crust or oceanic crust.

These plates are separated by three types of plate boundaries. At divergent boundaries, tensional forces dominate the interaction between the lithospheric plates, and they move apart and new crust is created. At convergent boundaries, compression of lithospheric plate material dominates, and the plates move toward each other where crust is either destroyed by subduction or uplifted to form mountain chains. Lateral movements due to shearing forces between two lithospheric plates create transform fault boundaries. The lithosphere earthquakes and volcanic activities are mostly the result of lithosphere plate movement and are concentrated at the plate boundaries.

The lithosphere´s plates move at a rate of about 3 centimeters per year. The distribution and relative movement of the oceanic and continental plates across the latitude also have profoundly affected the global climate. The major contributing factors are differences in surface albedo, land area at high latitudes, the transfer of latent heat, restrictions on ocean currents, and the thermal inertia of continents and oceans. Lithosphere according to the present configuration of oceans and continents, the lithosphere low latitudes have a greater influence on surface albedo because the lower latitudes receive a greater amount of solar radiation than the higher latitudes.

U.N researchers: Global warming clock is at ‘five minutes to midnight’

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Humanity has pushed the world’s climate system to the brink, leaving itself only scant time to act, the head of the UN’s group of climate scientists said on Monday.

“We have five minutes before midnight,” warned Rajendra Pachauri, whose organisation will this month release the first volume of a new assessment of global warming and its impacts.

“We may utilise the gifts of nature just as we choose, but in our books the debits are always equal to the credits,” Pachauri told a conference marking the 20th anniversary of the environmental organisation Green Cross International, quoting fellow Indian Mahatma Gandhi.

“May I submit that humanity has completely ignored, disregarded and been totally indifferent to the debits?

“Today we have the knowledge to be able to map out the debits and to understand what we have done to the condition of this planet,” Pachauri said.

The IPCC is made up of several hundred scientists worldwide.

It is due to release the first volume of its long-awaited Fifth Assessment Report on September 27.

The first tome will look at the scientific evidence for climate change; two more follow next year, focussing on the impacts and the options for tackling the problem.

A leaked draft two weeks ago said that human activity is almost certainly the cause of climate change.

The draft also forecast that sea levels could rise by 90 centimetres (three feet) by the end of the century, and all but dismissed recent claims of a slowdown in the pace of warming which climate-change sceptics have seized upon.

In its previous reports, the IPCC has warned that unbraked warming will drive many species to extinction and hike the frequency or intensity of droughts, heatwaves and floods, affecting food security and water supplies for many millions.

“We cannot isolate ourselves from anything that happens in any part of this planet. It will affect all of us in some way or the other,” Pachauri said.

Reining in greenhouse-gas emissions was still possible if countries, including in the developing world, rethought their approach to economic growth, he said.

That would boost energy security, cut pollution and improve health, and also offer new job opportunities, he added.

Large areas of southern Australia at higher risk of bushfires this summer

Posted 6 minutes ago

Photo: Southern Australia Seasonal Bushfire Outlook 2013 – 14. (Bushfire CRC)

Bushfire researchers say vast swathes of Australia face above average chances of grass fires and bushfires this summer, after months of above average temperatures.

The Bushfire Cooperative Research Centre has released its seasonal bushfire outlook for the south of the country.

It found recent warm weather, coupled with generous rainfalls has led to a build up of dry fuel in grasslands and forests.

The last 12 months have been the warmest on record, according to the weather bureau, and most states recorded their warmest winter since records began.

Large parts of southern Australia, especially along the east and west coasts extending inland, face above normal fire potential this fire season.

However, fire authorities said the at-risk area is not as extensive as last season, when the danger zone extended right across the south of the country.

Victoria

The risk of fire is above average throughout Victoria’s heartland and in the east, including east Gippsland.

“Forests are expected to be more flammable than normal due to the lingering effect of last summer’s extreme dryness and heat,” Bushfire CRC’s outlook said.

“Strong drying of soils and fuels has also commenced in east Gippsland, which may result in early bushfire activity if this trend continues.”

Fire authorities say spring rainfall patterns will dictate the severity of the fire risk and grass growth is being closely monitored.

“Certainly western, central and north-east Victoria would appear at this stage to be the highest risk areas,” said Victoria’s Fire Services Commissioner Craig Lapsley.

“We have got areas that are forested and grassland environments that will be significantly impacted by the spring rains which will see growth and which brings additional grass in the grasslands that will dry out.

“The summer months are the critical periods for Victorians to be focused on fire.”

A normal fire season is expected in the Mallee, west and south Gippsland and coastal parts of south-west Victoria.

New South Wales

With the exception of north-eastern coastal areas and the far west, NSW is expecting above average bushfire conditions this season.

Above average rainfall over the past three years has led to a build up of grass fuel across parts of the state.

The Rural Fire Service says it has already had to deal with a significant number of bushfires after one of the state’s warmest winters on record.

The areas of most concern include the Tablelands, the Upper Hunter and west of the Great Dividing Range.

Forested areas on the central and southern NSW coast and ranges have been drying out due to below average rainfall since July.

“The areas around Tamworth and Taree and the Upper Hunter, as well as some parts of the southern part of the state around Shoalhaven, have brought forward the bushfire danger commencement to the beginning of September so obviously they’re seeing an increase in fire activity already,” said RFS Deputy Commissioner Rob Rogers.

“If you have a prolonged period of warming it tends to dry out the fuels more and it makes the fuels more readily burn.

“Fires take hold quicker and obviously it’s more difficult then for brigades to suppress.

“Particularly if there’s some of those extreme temperature days like we saw in the last summer, where we saw some records broken in temperature, that’s obviously of concern to us too, particularly if it’s very dry.”

The far north coast and north coast are also at a higher risk of fire. But the risk could be eased if there is above average rainfall.

Normal fire conditions are likely in the far west of the state.

South Australia

Photo: Researchers say there is a build up of fuel due to rainfall and warm weather. (ABC TV)

Above normal fire potential is predicted in the North West Pastoral and Flinders districts due to abundant rain and the growth of grass fuels.

The rest of the state, including the agricultural areas, can expect normal levels of fire activity.

The Bushfire CRC outlook raises concerns about adequate fire-fighting resources in SA.

“The North West Pastoral and Flinders districts may pose resourcing issues this fire season, as was experienced in the North West Pastoral district last season, where firefighters and aircraft were committed for lengthy periods,” it said.

Tasmania

Normal fire activity is expected across Tasmania this season, but small areas in the Derwent Valley and the mid-east coast are currently drier than usual.

Most of the state has experienced average or above average soil moisture, reducing fire activity for the moment.

But it also provides ideal conditions for growth, which may be a trigger for large fires in the new year if it dries out.

Fire ecologist Professor David Bowman, from the University of Tasmania, says people need to stay alert.

“If we had heatwaves like we saw last summer in Tasmania we can have very quickly evolving fire weather conditions which go from fairly benign to quite extreme,” he said.

“I would urge everybody who that’s in bushland settings to be very, very conscious of bushfires.”

He said fuel management is a critical tool, but not the only tool.

“As we’re going into a warmer world we will be looking at other options that will be probably more targetted vegetation management, clearing, creating safer spaces around houses, maybe changing the vegetation types, changing the vegetation types, changing the sorts of houses we have,” he said.

Western Australia

High rainfall across the mid west and desert regions has led to high rate of grass growth and high fuel loads, and consequently, above average fire potential.

Above normal bushfire potential is also forecast in the south west.

A normal fire season is expected for the Wheatbelt, the Nullarbor, east of the Fraser Range.

Queensland

An above normal fire potential has been predicted for areas between Dalby and Warwick, south to the NSW border and west to Goondiwindi.

Also at a heightened risk is the area to the west between Wallumbilla and Dulacca, south to St George and an area extending from the Sunshine Coast hinterland, into the western areas of the Wide Bay Burnett region.

Despite large-scale fires in the northern and western areas of Queensland during the last fire season, there are still vast areas with moderate to abundant grassland fuels and low stock levels that could experience large-scale, fast-running grass fires.

Northern Australia

The seasonal outlook for the north of Australia is released mid-year, ahead of the dry season.

This includes the Northern Territory, as well as northern Western Australia and northern Queensland.

Topics: fires, safety, weather, australia, act, nt, qld, sa, tas, vic, wa, nsw

Increased greenhouse gases and aerosols have similar effects on rainfall

Posted By News On September 1, 2013 – 5:30pm

Although greenhouse gases and aerosols have very distinct properties, their effects on spatial patterns of rainfall change are surprisingly similar, according to new research from the University of Hawaii at Manoa’s International Pacific Research Center (IPRC) and Scripps Institution of Oceanography. The study is published in the September 1 online issue of Nature Geoscience.

Manmade climate change comes mostly from the radiative forcing of greenhouse gases and air pollutants or aerosols. While greenhouse gases are well-mixed in the atmosphere and tend to be evenly distributed around the globe, aerosols vary greatly in local concentration and tend to be found near emission sources such as industrial centers in Asia and North America.

Aerosols affect climate in two ways: one is fast and perturbs the physics and behavior of clouds in minutes to days; the other effect takes years and is mediated by interactions with the ocean and atmosphere. The fast effects of aerosols on clouds have been studied intensely, but their long-term ocean-mediated effect has received little attention.

A team of scientists at the IPRC and Scripps has now provided important new insights based on results from experiments with three state-of-the-art climate models. Even though aerosols and greenhouse gases are concentrated in vastly different regions of the earth, all three models revealed similar regional effects on rainfall over the ocean.

“This came as a big surprise to us,” reflected lead-author Shang-Ping Xie, a professor of climate science and first Roger Revelle Chair in Environmental Science at Scripps. “It took a while for the result to sink in. The result means that it is hard to tell apart the greenhouse and aerosol effects.”

The scientists noted that both aerosol-induced and greenhouse-gas-induced changes in rainfall appear to be mediated by the spatial patterns of sea surface temperature.

“Although much of the aerosol research has focused on microphysical processes, over the ocean the climate response to aerosols appears to be insensitive to details of the micro-processes in clouds,” Xie said. “The climate changes induced by greenhouse gases and by aerosols share a common set of ocean-atmospheric feedback structures, explaining the spatial resemblance between the two types of response.”

“Innovative model experiments are now needed,” says coauthor Baoqiang Xiang, postdoctoral fellow at the IPRC. We want to probe the ocean-atmosphere interaction mechanisms that mediate these rainfall patterns and to determine what forms the foundation. This will allow us to develop more reliable regional climate projections.”

Source: University of Hawaii ‑ SOEST