Poking the angry beast: Purple rain
by Jess Spear
Article originally published in Issue 4 of Rupture, Ireland’s eco-socialist quarterly, buy the print issue:
‘Poking the Angry Beast’ is a regular column on the science of climate change.
The birds are out again. As I write, they’re darting in and out of the hedgerows collecting bits of moss and grass for their nests. Spring has arrived, and in Ireland, that means daffodils are dotting the landscape followed by the dandelions and daisies, the bees and the butterflies. The days are getting longer and (a tad) warmer. We’re all breathing a collective sigh of relief, as we exhale the cold winter (four months of locked down) air and inhale the pollen-filled spring breeze (with the hope of a warm and less restrictive summer).
Spring is also happening earlier - weeks earlier in some cases. And, while we might rejoice in the earlier respite from winter, warmer than average temperatures are causing all kinds of havoc for ecosystems. The web of life is thinning out as the rhythm of plant and animal reproduction - evolved over millions of years to occur just when food and pollinators are at their peak - is increasingly out of sync. Orchids that lure male bees to spread their pollen are now thwarted by the earlier arrival of female bees; birds migrating north to feed on caterpillars are arriving too late, and the eggs of ground-nesting birds are destroyed by farmers who are sowing their fields earlier.[1] Yet, earlier spring temperatures don’t just frustrate orchids and starve birds, they also disrupt major weather systems affecting more than a billion people.
““Earlier spring temperatures don’t just frustrate orchids and starve birds, they also disrupt major weather systems affecting more than a billion people.“”
For the people of India, the latter part of spring marks the beginning of the monsoon season and the commencement of much-needed rains. Eighty per cent of the annual rainfall in India occurs during the monsoon season. The whole region experiences one of the most dramatic seasonal shifts on the planet, with arid, brown terrain transformed into lush and vividly green landscapes. Rainwater nourishes crops and also helps bring relief from the unbearably hot temperatures in April and May. With 70 per cent of the population employed in agriculture which heavily depends on rain, the monsoon today and historically has imprinted itself on Indian life and culture. As the writer and scholar GRK Murty explains, “[the] Indian economy and its arts—literature, music, painting, indeed its very romance with life—are draped in monsoons, particularly their timeliness, evenness, and sufficiency.”[2]
The Indian monsoon has always been variable. It’s “shaped by a symphony orchestra of phenomena as varied as the heating of the Tibetan plateau, trade winds of the southern hemisphere, and the spinning of the earth.”[3] But with climate change, sea-level rise, and industrial agricultural practices added to the mix, that variability is likely to increase hardship, deaths and possibly lead to the forced displacement of hundreds of millions of people.[4]
Images by: Arne Hückelheim
Here comes the wind
The monsoon season begins as the Northern Hemisphere emerges from winter and the wind begins to shift. In South Asia, the enormous Tibetan plateau and Himalayan Mountains absorb the increasing solar radiation while the Indian Ocean just offshore stays relatively cool. The air above the fast-heating land rises, and, in turn, creates an area of low pressure beneath it, drawing in the relatively cooler air from out at sea where the pressure is relatively higher.
The physics behind this is pretty simple. You’ve probably heard the weather reporter on the telly talking about high and low-pressure zones above this or that area, bringing rain or some other change in the weather, right? The air temperature difference between the land and sea, or between any two places on earth really, is what causes the wind to blow. This is also how your hoover works - the motor powers a fan that draws in air, creating a low-pressure zone between the hoover relative to the air outside of it. This pressure difference “sucks” in the surrounding air and with it, the dust, pet hair, and whatever else is light enough to get swept up in it.[5] The Himalayas act like a gigantic hoover drawing in air from offshore.
As the wind shifts, from blowing offshore (from land to sea) to blowing onshore (from sea to land), it picks up moisture along the way. This is why the monsoon - which technically is a shift in the wind - is associated with lots of rain. The moisture-laden wind reaches the Himalayas, which not only draw the wind in but also act to block its passage northwards. It rises and cools, releasing the rain onto the Indian subcontinent.
How steep is your hill?
The temperature gradient, between land and sea, is what drives the monsoon and the rains it brings. You can imagine the temperature gradient kind of like a hill (see Figure 1), with ocean temperature at the top and land temperature at the bottom. The wind is like a ball that falls from top to bottom. Normally the hill is very steep, the difference between land and ocean temperature is high, so the ball of wind moves swiftly from the ocean to the land, carrying water vapour along with it.
But the temperature gradient, or, to stay with our analogy, hill, has been disturbed. Ninety per cent of the heat trapped by burning fossil fuels has been absorbed by the oceans.[6] That means the top of the hill has been lowered, reducing the temperature gradient. At the other end, a cooling effect has occurred from air pollution and land-use change (that is, deforestation in favour of farming crops). Forests are darker than farmed land, so less heat is absorbed today than in the past. Air pollution can reflect solar radiation and reduce the amount reaching the land.[7] Cooler land equals cooler air above it, effectively raising the bottom of our hill and further reducing the temperature gradient. Combined, the two effects - warmer oceans and cooler land - probably reduced overall wind power and are thought to explain the weaker than normal monsoon rainfall from 1950 to 2002.[8]
Now that it’s raining more than ever
However, a warmer world will mean warmer air, and warmer air holds more moisture. So even if the wind speed is reduced, when it does reach the land, it’s packed with water vapour. This doesn’t mean that all will be fine, though. While droughts have increased and overall some areas of India have experienced less rainfall than average, since the start of the 21st-century, extreme rainfall events - events that cause massive flooding - have dramatically increased in India. So sensitive is Indian agriculture and life to monsoon variability that a rise or fall in rainfall volume by 10 per cent or more leads to disaster. Scientists estimate that rainfall will increase by nearly 20 per cent (relative to 1961-1999) by end of this century.[9]
Floods are common during the monsoon season. But it’s not flooding per se that is the problem - it’s the severity of the floods. It’s the areas impacted that weren’t impacted before. It’s the unpredictability, the waters rising faster than you expected, and the ways of living, the decisions made that previously kept your family safe no longer being sufficient.[10] It’s the cyclones, supercharged from the warmer than normal Indian Ocean, hitting on top of the torrential rains.[11]
The Indian poet Jayanta Mahapatra wrote that “[t]here are two things which connect human beings: what is above and what is below. The sky is above you and the earth beneath you and anything that connects earth and sky is rain. It is a bond you cannot miss. It has a process itself. It is a link. Therefore, rain is a linking process, and so, the very act of your living”.[12] Climate change rips apart this connection. All the ways that we and the orchids and the birds and the bees have evolved and learned to survive and thrive are no longer adequate in our increasingly disordered world.
The end & the beginning
When asked about the meaning of the song ‘Purple Rain’, the artist formerly known as Prince explained that it “pertains to the end of the world and being with the one you love and letting your faith/god guide you through the purple rain”.[13] The song’s co-writer Lisa Coleman reportedly had a different take. She said the song represented “a new beginning. Purple, the sky at dawn; rain, the cleansing factor.”[14] So, the purple rain represents both the end and (possibly) the beginning.
These communities on the ‘frontlines’ of climate disaster, the 25 million people displaced from monsoon floods in 2019 in India and nearby Bangladesh, Nepal and Myanmar[15], and all those affected by the tragedy of last years floods, are a glimpse into the future capitalism is speedily racing Earth and all of its inhabitants towards.
We can either choose to look away at people drowning and suffering, thinking “it’s not me or my family, we won’t experience that”, or we can recognise that our shared world, our lives and our future, are all at risk. It could be the end, but it doesn’t have to be. If we take action to end the capitalist-fueled climate disaster, here and now, where we are, there’s the opportunity to make a new beginning.
Jess Spear was research scientist for the U.S. Geological Survey at the St. Petersburg Coastal and Marine Science Center, and then micopaleontologist at the Burke Museum of Natural History at the University of Washington. You can follow her at @jdubspear
Notes
1. nytimes.com/2018/04/04/climate/animals-seasons-mismatch.html
2.Murty, GRK, ‘India’s Romance with Monsoon Rains: A Peep into Poetic Expressions and Personal Experiences’ (December 11, 2014). The IUP Journal of English Studies, Vol. IX, No. 3, September 2014, pp. 54-73.
3. thehindu.com/society/every-silver-lining-has-a-cloud/article19554527.ece
4. See Camilla Royle, 2021. ‘Migration in an era of climate catastrophe’, International Socialism Journal, v. 169. Royle makes important arguments about how socialists should consider the issue of climate refugees, recognising “the agency of refugees themselves, rather than taking a liberal view that treats them as either passive victims or objects of charity.”
5. This is similar to the Bernoulli effect which is how aeroplanes can fly. Aeroplane wings are designed such that air moves faster above the wing than below, creating a low-pressure zone above the wing relative to the air below. The air below the wing moves up, creating lift. You can see this at home by holding a roll of toilet paper (with the paper coming over the top - ie, the right way!) and blowing across the top. The paper should rise as the air below it moves up.
6. climate.gov/news-features/understanding-climate/climate-change-ocean-heat-content
7. theatlantic.com/science/archive/2019/01/indias-monsoon-powerful-agent-climate-change/579940/
8. Katzenberger, A., et. al., 2021. Robust increase of Indian monsoon rainfall and its variability under future warming in CMIP6 models, Earth Syst. Dynam., 12, 367–386.
9. Ibid.
10. nytimes.com/2020/07/15/world/asia/monsoon-asia-bangladesh-india.html
11. thethirdpole.net/en/climate/cyclones-south-asia/
12. Murty, GRK, India’s Romance with Monsoon Rains: A Peep into Poetic Expressions and Personal Experiences (December 11, 2014). The IUP Journal of English Studies, Vol. IX, No. 3, September 2014, pp. 54-73.
13. nme.com/blogs/nme-blogs/20-things-you-didnt-know-about-purple-rain-766800
14. cheatsheet.com/entertainment/what-prince-said-about-the-meaning-of-purple-rain.html/
15. indiatoday.in/india/story/600-people-killed-over-25-million-affected-flooding-india-bangladesh-nepal-myanmar-un-1574258-2019-07-27