Climate explained: did atomic bomb tests damage our upper atmosphere?



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Brett Carter, RMIT University and Rezy Pradipta, Boston College


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I recently read an article stating the atomic bomb testing in the Pacific destroyed so much of the upper atmosphere that the US could no longer bounce communications off the atmosphere and had to deploy artificial satellites for communication. Is this true? And just how much damage did they do?

The article the question refers to doesn’t mention satellites, so let’s focus on the atmospheric damage part of the question. Indeed, surface and atmospheric (high-altitude) detonations of nuclear weapons can have short-term and long-term effects.

One short-term effect was a temporary blackout of long-distance high-frequency (HF) radio communication over the surrounding area. But this radio communication blackout was not a result of the nuclear explosions destroying the ionosphere.




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On the contrary, the nuclear detonations temporarily increased the natural level of ionisation in the upper atmosphere.

The ionosphere and radio communication

The Earth’s ionosphere is a natural layer of charged particles at approximately 80-1,000km altitude. This ionised portion of the Earth’s upper atmosphere largely owes its existence to solar radiation, which strips electrons from neutral atoms and molecules.

The ionosphere consists of three major layers, known as D, E and F layers. The lower D and E layers typically exist only during daylight hours, while the highest F layer always exists.

A graphic showing the various layers of the ionosphere.
The ionosphere showing the approximate levels of the D, E and F layers. The D and E layers are much weaker at night time. The two yellow arrows show example ray paths of high-frequency radio waves from transmitters at ground level. Encounters with the D layer will result in some absorption.
The Conversation, CC BY-ND

These layers have distinct characteristics. The E and F layers are very reflective to HF radio waves. The D layer, on the other hand, is more like a sponge and absorbs HF waves.

In long-distance HF radio communications, the radio waves are bounced back and forth between the ionosphere and the Earth’s surface. This means you don’t need to establish a line of sight for HF radio communication.

Many applications, such as emergency services and aircraft/maritime surveillance, rely on this mode of HF radio propagation.

But this radio communication scheme only works well when there is a reflective E or F layer, and when the absorbing D layer is not dominant.

During regular daytime hours, the D layer often becomes a nuisance because it weakens radio wave intensity in the lower HF spectrum. However, by changing to higher frequencies you can regain broken communication links.

The D layer may become even more dominant when intense X-ray emissions from solar flares or energetic particles are impacting the atmosphere. The absorbing D layer then breaks any HF communication links that traverse it.

Bomb blasts and the ionosphere

Nuclear detonations also produce X-ray radiation, which leads to additional ionisation in all layers of the ionosphere. This makes the F layer more reflective to HF radio waves, but, alas, the D layer also becomes more absorptive.

This makes it difficult to bounce radio waves off the ionosphere for long-distance communication soon after a nuclear explosion, even though the ionosphere stays intact.

Beyond additional ionisation, shock waves from nuclear detonations produce waves and ripples in the upper atmosphere called “atmospheric gravity waves” (AGWs).

These waves travel in all directions, even reaching the ionosphere where they cause what are known as “travelling ionospheric disturbances” (TIDs), which can be observed for thousands of kilometres.

Other atmospheric disturbances

Bomb blasts are not the only things that cause disturbances in the atmosphere.

In September 1979, there were reports of bright flashes of light off the South African coast, igniting theories South Africa had nuclear weapon capabilities.

Analysis of ionospheric data from the Arecibo Observatory, in Puerto Rico, confirmed the presence of waves in the ionosphere that corroborated the theory of an atmospheric detonation. But whether the detonation was artificial or natural could not be determined.

The reason for the ambiguity is that meteor explosions and nuclear detonations in the atmosphere both generate AGWs with similar characteristics.

Atmospheric Gravity Waves (AGW) and Travelling Ionospheric Disturbances (TID)
Common sources of atmospheric gravity waves (AGW) that could cause travelling ionospheric disturbances (TID).
Rezy Pradipta, Author provided

The 2013 Chelyabinsk meteor explosion in Russia generated waves in the ionosphere that were detected all across Europe, and as far away as the United Kingdom.

Volcanic eruptions, such at the 1980 Mount St Helens eruption in the US, and large earthquakes, such as the 2011 Tohoku earthquake in Japan, are other examples of energetic processes at the ground impacting the upper atmosphere.

Waves observed in the ionosphere above Japan during the 2011 Tohoku earthquake.

Another well-known source of ionospheric disturbances is the geomagnetic storm, typically caused by coronal mass ejections from the Sun or solar wind disturbances impacting Earth’s magnetosphere.

Satellites as backup

In summary, nuclear detonations can impact the upper atmosphere in many ways, as do many other non-nuclear terrestrial and solar events that carry enormous energy. But the damage (so to speak) isn’t permanent.




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Did the impact of these nuclear tests on the ionosphere specifically lead to the immediate launch of communications satellites? Not directly, because the impacts were temporary.

But in the Cold War setting, the potential for adversaries to even briefly interrupt over-the-horizon communications would certainly have been a motivating factor in developing communications satellites as backup.The Conversation

Brett Carter, Senior lecturer, RMIT University and Rezy Pradipta, Research scientist, Boston College

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Super-charged: how Australia’s biggest renewables project will change the energy game



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John Mathews, Macquarie University; Elizabeth Thurbon, UNSW; Hao Tan, University of Newcastle, and Sung-Young Kim, Macquarie University

Australia doesn’t yet export renewable energy. But the writing is on the wall: demand for Australia’s fossil fuel exports is likely to dwindle soon, and we must replace it at massive scale.

The proposed Asian Renewable Energy Hub (AREH) will be a huge step forward. It would eventually comprise 26,000 megawatts (MW) of wind and solar energy, generated in Western Australia’s Pilbara region. Once complete, it would be Australia’s biggest renewable energy development, and potentially the largest of its type in the world.

Late last week, the federal government granted AREH “major project” status, meaning it will be fast-tracked through the approvals process. And in another significant step, the WA government this month gave environmental approval for the project’s first stage.

The mega-venture still faces sizeable challenges. But it promises to be a game-changer for Australia’s lucrative energy export business and will reshape the local renewables sector.

Map showing proposed location of the Asian Renewable Energy Hub.
Map showing proposed location of the Asian Renewable Energy Hub.
AREH

Writing on the wall

Australia’s coal and gas exports have been growing for decades, and in 2019-20 reached almost A$110 billion. Much of this energy has fuelled Asia’s rapid growth. However, in recent weeks, two of Australia’s largest Asian energy markets announced big moves away from fossil fuels.

China adopted a target of net-zero greenhouse emissions by 2060. Japan will retire its fleet of old coal-fired generation by 2030, and will introduce legally binding targets to reach net-zero emissions by 2050.

There are signs other Asian nations are also moving. Singapore has weak climate targets, but on Monday inked a deal with Australia to cooperate on low-emissions technologies.

Night scene in Japan
Japan wants to decarbonise its economy by using hydrogen.
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Export evolution

The Asian Renewable Energy Hub (AREH) would be built across 6,500 square kilometres in the East Pilbara. The first stage involves a 10,000MW wind farm plus 5,000MW of solar generation – which the federal government says would make it the world’s largest wind and solar electricity plant.

The first stage would be capable of generating 100 terawatt-hours of renewable electricity each year. That equates to about 40% of Australia’s total electricity generation in 2019. AREH recently expanded its longer term plans to 26,000MW.

The project is backed by a consortium of global renewables developers. Most energy from AREH will be used to produce green hydrogen and ammonia to be used both domestically, and for shipping to export markets. Some energy from AREH will also be exported as electricity, carried by an undersea electrical cable.

Another Australian project is also seeking to export renewable power to Asia. The 10-gigawatt Sun Cable project, backed by tech entrepreneur Mike Cannon-Brookes, involves a solar farm across 15,000 hectares near Tennant Creek, in the Northern Territory. Power generated will supply Darwin and be exported to Singapore via a 3,800km electrical cable along the sea floor.




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The export markets for both AREH and Sun Cable are there. For example, both South Korea and Japan have indicated strong interest in Australia’s green hydrogen to decarbonise their economies and secure energy supplies.

But we should not underestimate the obstacles standing in the way of the projects. Both will require massive investment. Sun Cable, for example, will cost an estimated A$20 billion to build. The Asian Renewable Energy Hub will reportedly require as much as A$50 billion.

The projects are also at the cutting edge of technology, in terms of the assembly of the solar array, the wind turbines and batteries. Transport of hydrogen by ship is still at the pilot stage, and commercially unproven. And the projects must navigate complex approvals and regulatory processes, in both Australia and Asia.

But the projects have good strategic leadership, and a clear mission to put Australian green energy exports on the map.

Red sand and tussocks of grass
Australia’s Pilbara region would be home to Australia’s biggest renewables development.
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Shifting winds

Together, the AREH and Sun Cable projects do not yet make a trend. But they clearly indicate a shift in mindset on the part of investors.

The projects promise enormous clean development opportunities for Australia’s north, and will create thousands of jobs in Australia – especially in high-tech manufacturing. As we look to rebuild the economy after the COVID-19 pandemic, such stimulus will be key. All up, AREH is expected to support more than 20,000 jobs during a decade of construction, and 3,000 jobs when fully operating.

To make smart policies and investments, the federal government must have a clear view of the future global economy. Patterns of energy consumption in Asia are shifting away from fossil fuels, and Australia’s exports must move with them.




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The Conversation


John Mathews, Professor Emeritus, Macquarie Business School, Macquarie University; Elizabeth Thurbon, Scientia Associate Professor in International Relations / International Political Economy, UNSW; Hao Tan, Associate professor, University of Newcastle, and Sung-Young Kim, Senior Lecturer in International Relations, Discipline of Politics & International Relations, Macquarie School of Social Sciences, Macquarie University

This article is republished from The Conversation under a Creative Commons license. Read the original article.