Pyrocumulonimbus clouds and fire tornadoes, caused by the intense bushfires that have been ravaging Australia, are “creating their own weather” and causing fires to intensify and spread far and wide.
In this diary, we take a deeper look at the science behind pyrocumulonimbus clouds, how they are formed, what effect they have on the fires themselves and how they affect global climate. Earlier, we wrote a diary covering the science behind bushfires and the climate in Australia. Also take a look at other diaries at this site which cover the news and the politics behind Australia’s bushfires.
What is a pyrocumulonimbus cloud?
The cumulonimbus flammagenitus cloud (CbFg), also known as the pyrocumulonimbus cloud (pyroCb), is a high anvil-like intense cloud system rapidly formed by wildfires or volcanic eruptions. Pyrocumulonimbus clouds in turn can cause wildfires to intensify and spread and can have long-term effects on global climate.
NASA describes it as the “fire-breathing dragon of clouds.”
How are pyrocumulonimbus clouds formed?
We will focus here on wildfire-caused pyrocumulonimbus clouds. Take a look at this excellent diagram from BOM Australia when reading the description below -
- The intense heat of a the fire causes hot air and smoke to rise rapidly creating a smoke plume. Air rushing in from nearby areas sometimes create fast spinning vortexes seen as fire tornadoes or firenadoes.
- The rising hot air draws in cooler air from surrounding areas, which helps cool the plume as it rises. At higher elevations, reduced atmospheric pressure causes the plume to expand and cool even further.
- Eventually, moisture in the plume condenses and forms thunder-storm-like cumulus clouds.
- Condensation causes latent heat to be released, which makes the cloud warmer and more buoyant and causes the cloud air to further accelerate upwards, reaching heights of 5 miles.
- Falling rain evaporates and cools when it comes in contact with dry air, producing an intense rush of downward wind called a downburst.
- Collisions of ice particles in the very cold upper parts of these clouds cause a build-up of electrical charge, which is released as lightning.
There is a feedback loop in this process causing the plumes and clouds to intensify and grow in size. Positive feedback loops play a key role in many weather phenomenon.
The pyrocumulonimbus clouds can, in turn, intensify and further spread bushfires -
- The intense updrafts generate strong winds of air drawn in from surrounding areas. These cause the fire to burn hotter and spread faster.
- The strong and high plumes can carry large burning embers and fling them far and wide, igniting new fires (called spot fires).
- Lightning from the pyrocumulonimbus clouds can ignite new fires far from the origin of the plume.
- The intense downbursts can hit the ground and burst outwards, spreading the fire in unpredictable directions.
- On rare occasions, rain can reach the ground and douse out portions of a bushfire.
Here is a video showing the formation of pyrocumulonimbus clouds at a fire in 2016.
Examples of pyrocumulonimbus clouds and firenados
A small but intense firenado caught on camera -
A larger firenado and plume, the precursor to pyroCb clouds -
A fire thunderstorm warning on Jan 4 -
Pyrocumulonimbus cloud formation on Jan 4 —
Another pyrocumulonimbus cloud formation on Jan 4 -
Another pyrocumulonimbus cloud formation on Jan 4 -
Pyrocumulonimbus cloud seen by passengers on an airplane flight —
Satellite imagery of pyrocumulonimbus cloud and lightning over Mallacoota on Dec 29 -
The ultimate man-made pyrocumulonimbus cloud.
Pyrocumulonimbus cloud over Hiroshima
For decades this "Hiroshima strike" photo was misidentified as the mushroom cloud of the atomic bomb that fell on 6th August 1945. However, due to its much greater height, the scene was identified in March 2016 as the pyrocumulonimbus cloud that engulfed the city, a fire that reached its peak intensity some three hours after the bomb. en.wikipedia.org/...
Effects on Climate
Pyrocumulonimbus clouds can cause long-term change in global climate.
- Bushfires and pyrocumulonimbus clouds inject large amounts of CO2 into the upper atmosphere, thereby increasing global warming.
- Smoke in the lower stratosphere can block sunlight, causing small amounts of global cooling. OTOH, black carbon particles can act as heat absorbers.
- Carbon fallout can coat glaciers and ice sheets across the world, increase heat absorption, and accelerate melting.
- Smoke and water vapor can disrupt the ozone layer.
Fire debris has been detected on glaciers in New Zealand over 2000 km away. It will accelerate melting that is already taking place due to global warming.
Note that so far, the contribution of wildfires to global warming is small compared the main culprit — the burning of fossil fuels. But feedback loops can change that.
Long term solutions
I don’t want to end the diary with just descriptions of the problems. So, let’s take a look at some of the solutions for mitigating and arresting climate change. This is by no means a comprehensive list, but is gives us a flavor of what is possible and what is being partially practiced.
Here is a proposal from Rene Castro Salazar, an assistant director general at the UN Food and Agriculture Organization. He and others like him think that modest investments in improved land practices to restore degraded land to pasture, food crops and trees can convert enough carbon into biomass to stabilize CO2 emissions and buy us time to deploy more comprehensive solutions.
Here is a similar proposal for Australia focusing on transitioning to green energy -
This study looks at a multi-pronged comprehensive global solution to prevent the 1.5C scenario -
The study looks at transitioning to green energy, improvements in energy efficiency, and better land and soil management.
- WWS (Wind, Water and Solar) reduces energy needs by 57%.
- The upfront capital needed for this transition worldwide (which is spread over 30 years) is about $73 trillion. However, this cost pays for itself in about 7 years due to the $11 trillion in annual energy cost savings due to WWS over fossil fuels. In the United States, the capital cost of the Green New Deal is $7.8 trillion. In Europe, it is $6.2 trillion. In China, it is above $16 trillion.
- WWS creates 28.6 million more long-term, full-time jobs than lost worldwide, including 3.1 million in the United States, 2.9 million in Europe, and over 8.5 million in China. It needs only 0.65% of the world’s land, of which two-thirds is space between wind turbines that can be used for multiple purposes.
- To avoid 1.5°C global warming, at least 80% of the transition needs to occur by 2030 and 100% by no later than 2050.
Here is a 15-part sobering thread by David Roberts, who writes for Vox.com about energy politics, where he argues that the only way to get past current symbolic victories is political change. We have to wrest power away from right-wing parties to save earth.
Click on the tweet to see the full thread.
Here is a poetic and inspirational message by Climate justice writer Mary Annaïse Heglar -
Epilogue
The loss of life and livelihoods, of flora and fauna, the effect on health and the economy and the effect on climate caused by these bushfires will be felt for months and years to come. And there will be more such episodes in the future.
But large scale positive change will only occur if we throw the climate-science-denying bums out. That’s where you and I come in; we need to keep educating our electorate about climate science, about the urgency of of the situation, about the science behind it and about various mitigation techniques that are at hand that will help avoid disaster and create jobs and wealth for everyone, not just the fossil fuel industry or right-wing parties.
P.S.
Hopefully, this and the other diary will help improve your understanding of climate science and help smack down nonsensical arguments from your conservative friends who claim that climate change is a hoax or that bushfires are caused by sun spot activity, exploding horse manure or by leftist arsonists.
Further Reading
- Climate Science, Global Warming and Australian Bushfires — www.dailykos.com/...
- Cumulonimbus flammagenitus — en.wikipedia.org/…
- When bushfires make their own weather — media.bom.gov.au/…
- Fire tornadoes and dry lightning are just the start of the nightmare when a bushfire creates its own storm — www.abc.net.au/...
- The worst wildfires can send smoke high enough to affect the ozone layer — www.sciencenews.org/…
- Fire-Induced Storms: A New Danger from the Rise in Wildfires — e360.yale.edu/…
- How Wildfires Can Affect Climate Change (and Vice Versa) — insideclimatenews.org/...
