Tag Archives for nuclear weapons

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



Shutterstock/CUTWORLD

Brett Carter, RMIT University and Rezy Pradipta, Boston College


CC BY-ND

Climate Explained is a collaboration between The Conversation, Stuff and the New Zealand Science Media Centre to answer your questions about climate change.

If you have a question you’d like an expert to answer, please send it to climate.change@stuff.co.nz

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.



Read more:
Climate explained: Sunspots do affect our weather, a bit, but not as much as other things

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.



Read more:
Climate explained: how volcanoes influence climate and how their emissions compare to what we produce

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.

Advertisement

There are 10 catastrophic threats facing humans right now, and coronavirus is only one of them


Arnagretta Hunter, Australian National University and John Hewson, Crawford School of Public Policy, Australian National University

Four months in, this year has already been a remarkable showcase for existential and catastrophic risk. A severe drought, devastating bushfires, hazardous smoke, towns running dry – these events all demonstrate the consequences of human-induced climate change.

While the above may seem like isolated threats, they are parts of a larger puzzle of which the pieces are all interconnected. A report titled Surviving and Thriving in the 21st Century, published today by the Commission for the Human Future, has isolated ten potentially catastrophic threats to human survival.

Not prioritised over one another, these risks are:

  1. decline of natural resources, particularly water
  2. collapse of ecosystems and loss of biodiversity
  3. human population growth beyond Earth’s carrying capacity
  4. global warming and human-induced climate change
  5. chemical pollution of the Earth system, including the atmosphere and oceans
  6. rising food insecurity and failing nutritional quality
  7. nuclear weapons and other weapons of mass destruction
  8. pandemics of new and untreatable disease
  9. the advent of powerful, uncontrolled new technology
  10. national and global failure to understand and act preventatively on these risks.

The start of ongoing discussions

The Commission for the Human Future formed last year, following earlier discussions within emeritus faculty at the Australian National University about the major risks faced by humanity, how they should be approached and how they might be solved. We hosted our first round-table discussion last month, bringing together more than 40 academics, thinkers and policy leaders.

The commission’s report states our species’ ability to cause mass harm to itself has been accelerating since the mid-20th century. Global trends in demographics, information, politics, warfare, climate, environmental damage and technology have culminated in an entirely new level of risk.

The risks emerging now are varied, global and complex. Each one poses a “significant” risk to human civilisation, a “catastrophic risk”, or could actually extinguish the human species and is therefore an “existential risk”.

The risks are interconnected. They originate from the same basic causes and must be solved in ways that make no individual threat worse. This means many existing systems we take for granted, including our economic, food, energy, production and waste, community life and governance systems – along with our relationship with the Earth’s natural systems – must undergo searching examination and reform.

COVID-19: a lesson in interconnection

It’s tempting to examine these threats individually, and yet with the coronavirus crisis we see their interconnection.

The response to the coronavirus has had implications for climate change with carbon pollution reduction, increased discussion about artificial intelligence and use of data (including facial recognition), and changes to the landscape of global security particularly in the face of massive economic transition.

It’s not possible to “solve” COVID-19 without affecting other risks in some way.

Shared future, shared approach

The commission’s report does not aim to solve each risk, but rather to outline current thinking and identify unifying themes. Understanding science, evidence and analysis will be key to adequately addressing the threats and finding solutions. An evidence-based approach to policy has been needed for many years. Under-appreciating science and evidence leads to unmitigated risks, as we have seen with climate change.

The human future involves us all. Shaping it requires a collaborative, inclusive and diverse discussion. We should heed advice from political and social scientists on how to engage all people in this conversation.



Read more:
From the bushfires to coronavirus, our old ‘normal’ is gone forever. So what’s next?

Imagination, creativity and new narratives will be needed for challenges that test our civil society and humanity. The bushfire smoke over the summer was unprecedented, and COVID-19 is a new virus.

If our policymakers and government had spent more time using the available climate science to understand and then imagine the potential risks of the 2019-20 summer, we would have recognised the potential for a catastrophic season and would likely have been able to prepare better. Unprecedented events are not always unexpected.

Prepare for the long road

The short-termism of our political process needs to be circumvented. We must consider how our actions today will resonate for generations to come.

The commission’s report highlights the failure of governments to address these threats and particularly notes the short-term thinking that has increasingly dominated Australian and global politics. This has seriously undermined our potential to decrease risks such as climate change.



Read more:
Listen to your people Scott Morrison: the bushfires demand a climate policy reboot

The shift from short to longer term thinking can began at home and in our daily lives. We should make decisions today that acknowledge the future, and practise this not only in our own lives but also demand it of our policy makers.

We’re living in unprecedented times. The catastrophic and existential risks for humanity are serious and multifaceted. And this conversation is the most important one we have today.The Conversation

Arnagretta Hunter, ANU Human Futures Fellow 2020; Cardiologist and Physician., Australian National University and John Hewson, Professor and Chair, Tax and Transfer Policy Institute, Crawford School of Public Policy, Australian National University

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