Few days ago, I was talking to a friend about how harsh this winter season has been. How we weren't able to get any work done because it was so hard to get out of the bed from under the layers of blankets and quilts. We welcomed our new year with warnings from meteorological department about severe cold waves. Entire north India was gripped in freezing temperatures for weeks. Naively, my friend said, but now with global warming, winter should've been less harsh, right! They say our temperature has increased by 1°-2° C, why are we still having so much cold!
I tried explaining her whatever little I knew about global warming and climate change. Yes, average temperatures are going up but climate change is much more than global warming. But even I didn't know how exactly planet's weather systems work, what is extreme weather and how is it connected with climate change. So here I am, on yet another quest to know as much as I can about the complications of extreme weather events. I'm going to explore the connections between rising temperatures, harsher winters, floods, fires, droughts and cyclones.
Water cycle and wind currents -
In a previous post I wrote about the carbon cycle and how carbon emissions are disturbing it. Today I will explore another, even more crucial cycle, the water cycle and how global warming is affecting it.
As the name suggests, water cycle is the circulation of water across the planet, among the ocean, land and the air. It evaporates from ocean into the air, condenses to form clouds, get carried away with wind and then precipitates onto the land in the form of rain or snow. Pretty simple right ! Now let's go into the details.
Most of the water evaporates from tropical oceans. Tropics because they receive direct sunlight at 90 angle and oceans because they have more water than land, plus oceans occupy a large surface area too. As the water evaporates, it rises above the surface of the ocean and leads to the formation of clouds.
Since tropics receive more energy from sun than the rest of the planet, the air here is warmer than the temperate and polar regions. Warmer air is lighter than the cooler air, which creates a pressure difference, causing wind currents. These wind currents are also influenced by earth's eastward rotation. Wind currents are also created because of the temperature difference between ocean and land. (Imagine a breezy beach !)
These wind currents carry the clouds with them, from the ocean to the land, where they precipitate in the form of rain or snow. Stable wind pattern means stable weathers across the planets. Every region will continue to receive their share of rain, the wet places will remain wet and the dry will stay dry.
What's changing -
Unfortunately, nothing is stable in this delicate and intricate climate cycle if we mess up even a single element. Disturbed carbon cycle increases the temperature of atmosphere which disturbs both water cycle and wind currents. But how !
Every 1°F rise allows the atmosphere to hold 4% more water vapor. Increased temperature means more water will vaporize from the ocean and denser clouds will form, which will result into intense rainfall. This accelerates the rate at which water circulates in and out of the atmosphere, also known as an intensification of the water cycle. But this doesn't mean more rainfall at everywhere.
The places where wind was previously accumulating clouds, will now have to deal with more and even denser clouds, resulting in heavy downpour and possibly floods. The regions where the wind never brought clouds, will still have no clouds and will suffer from drought due to global warming.
It never rains but it pours -
Intensification of water cycle causes wet places to get wetter. They'll receive more amount of rain than before. It is also important to consider how this rain falls. Earlier rain used to come lightly, spread over a few weeks. Due to the intensification brought by global warming, it now rains heavily over a short span of time. For example in India, during monsoon season, rainfall occurs as short intense bursts instead of steady showers across months. The total rainfall is compressed into just 100 hours of torrential rain.
"If you have more than 100 millimeters of rainfall within 24 hours, it is called an extreme rainfall event, but the problem is that we are getting 100 millimeters of rainfall within an hour now. Even the definition of extreme rainfall events will have to change considering the quantity of rain, the intensity of rainfall we are experiencing now." Chandra Bhushan, International Forum for Environment, Sustainability and Technology
In 2019, 11 states of India faced extreme rainfall and associated floods, resulting in over 1200 deaths and huge loss to infrastructure and agriculture. The rapid warming of the Indian Ocean due to climate change is leading to more cyclones, drowning South Asia, as storms gather more quickly and become more intense.
Just like Indian monsoon, Atlantic hurricanes and Pacific atmospheric rivers have also grown to be more progressive in last couple of years. In 2017, hurricane Harvey in Texas set a record by dumping an astounding 26 inches of water in just one day. On the other hand in west coast of US, the 2019 water year experienced 41 atmospheric rivers, 11 of them strong. These ARs contributes to 90% of the region's major flood events, incurring an average cost of $1 billion every year.
(Atmospheric river is a really cool phenomena which I didn't know about before starting this article. Read more about them here.)
Fun winters, not so fun now
For two consecutive years, India Meteorological Department has been issuing a strange warning, urging people to not drink alcohol during New year's celebration. Why ? Because in winters of both 2019 and 2020, north India was gripped under an unusually strong spell of cold wave, and alcohol increases the chances of cold stroke. Cold wave occurs in plains if temperature goes below 10°C and/or is 4.5 notches less than season's normal for two consecutive days.
These long and powerful cold waves are brought to north Indian plains by western disturbances. These Western disturbances originates from the Mediterranean sea, Caspian sea and black sea, travel eastward until they are slowed down by the Himalayan range. At that point these disturbances precipitates in the form rain or snow all over North India. Due to global warming, stronger western disturbances form, which results into harsher winters in Indian subcontinent.
"The climate change affecting the intensity and frequency of Western Disturbances can bring mercury down in northern region in years to come. The Himalayan Region and the Indo-Gangetic plains covering almost entire north India could be more vulnerable to extreme weather" - Dr Bhupinder B. Singh, Centre for Climate Change Research, India
Another similar and interesting phenomenon is "Warm arctic-cold continents pattern". Arctic ocean on the north pole is the most fragile ecosystem on the planet and is worst hit by the global warming. This warming Arctic is now responsible for some of the worst cold snaps North America and Eurasia have experienced in last few years. Let's find out how!
Due to Earth's tilt, polar regions receive less solar energy and there's a large temperature difference between equator and poles. Because of this temperature difference, there's a continuous and low pressure zone that rotates like a cyclone at each of the pole, called polar vortex. When the arctic ocean was colder, the vortex was stable and the cold air remain confined to the north pole only.
But now, since the arctic is warming due to global warming, this vortex becomes unstable, gets fragmented and begins interacting with air outside the polar zone, particularly of the North America and Eurasia. This is called "warm arctic-cold continents pattern". Studies shows that during mid-winter to late-winter of recent decades, when the Arctic warming trend is greatest, severe winter weather—including both cold spells and heavy snows—became more frequent in the eastern United States. Some of these cold snaps are famously nicknamed as Snowpocalypse, Snowmaggedon, and Snowzilla.
Perfect summers, not anymore -
This one is pretty obvious and most popular of all extreme weather events. More greenhouse gases in our atmosphere, more energy retention and hence increase in temperatures. Simple!
Year 2020 was the hottest year on record, tying with year 2016. In fact, the warmest 10 years on record have all occurred after 2005. Hottest were 2020 & 2016, followed by 2019, 2015, 2017, 2018, 2014, 2010, 2013 and 2005. And scientists predict that most of the years of next decade are very likely going to be top ten hottest.
With such record setting heat, heat waves are becoming an increasingly common phenomenon in all the continents. A heatwave occurs when a region's temperature exceed by 5 degrees for three consecutive days. In 2019 Europe saw its most intense heatwave ever when hot air from Sahara migrated towards Europe. This set all time high records in many European countries like Germany, United Kingdom, Belgium, Netherlands.
Not only the intensity of heatwave is increasing, there frequency and length is also soaring. For example, number of heatwaves in United states increased to 6 per year in 2010s from 2 per year in 1960s. The length of heatwave season also increased by 47 days in 2010s compared to 1960s.
In 2018, much of Northeast Asia suffered from record breaking heatwave which baked Japan, Korea and China for 48 days. India too faced a deadly heatwave in 2019, which gripped entire north India for 32 days. The highest temperatures occurred in Churu, Rajasthan (also happens to be my hometown), reaching up to 50.8 °C.
"We are used to facing 47-48 degree temperature in summers and below freezing point in winters. But the intense heat that we are facing this time is unprecedented." - A resident of India's hottest City, Churu
Droughts and Fires
Warmer temperatures, combined with lower precipitation give birth to another problem, droughts. The likelihood and severity is made worse by climate change. As discussed earlier, the intensification of water cycle means the wet places like tropics will get wetter while the dry places like subtropics will get drier. That's because the wind patterns that didn't bring in moisture earlier to the dry regions, will now bring even less of it due to intensification of water cycle. Plus higher temperature causes the soil moisture to evaporate, which can cause crop failure and groundwater reservoirs to deplete. Some of notable droughts in last decade were observed in central Europe, Southern Africa, Eastern Australia, and Southeast US.
Increasing temperature also cause plants to dry up, forming a fuel source which leads to larger wildfires. Climate change is set to increase the number of wildfires and the area covered by them. We have saw some of the major wildfires in last two years, Siberian wildfire in 2019, Amazon rain forest wildfires in 2019 and Australian bush fire in 2019. In 2020, California saw its largest wildfire season in recorded history. Models have predicted that climate change could increase the frequency of fires globally by 19% in 2050 relative to 2015, if temperatures reach 1.8°C above pre-industrial levels.
Shifting seasons
Climate change is also messing with the traditional concept of four seasons. In general we have four seasons, winter (Dec-Jan-Feb), spring(Mar-Apr-May), summer(Jun-Jul-Aug) and autumn(Sep-Oct-Nov). Because of global warming, a change in the timing and duration of these seasons is observed. This phenomenon is called season creep. This causes changes in all four traditional seasons, spring is coming earlier, summer is longer, autumn is delayed and then winter is shorter. A notable impact of this shift has been seen on the blooming time of cherry blossom, in Japan and Washington DC, where the flowers are blooming one week early now.
In US, spring is arriving 10 to 14 days earlier than it used to 20 years ago. On the other hand, autumn is delayed by 14 days compared to 1990s. As a result, summers are now 13 days longer and winters are 20 days shorter than they used to be. But why should it matter ? Disruptions in the timing of these seasons can have a variety of impacts on ecosystems and human society. It doesn't affect all the species and systems uniformly, some are hit worse than the others.
Different species respond to different environmental cues, these cues tell plants when to bloom and when to shed leaves, tell birds when to migrate, where to migrate, when to lay eggs etc. Season creep has put these cues out of balance. Some species adapt to these changes while some can't and this creates ecological misalignment, which can be fatal. For example, in Southeast US, A group of pregnant horses accidentally consumed a caterpillar, which caused them to miscarry. This particular caterpillar lives on trees and usually eaten by migratory birds. But that season the birds arrived late, and the caterpillar fell from trees to the grass that horses used to eat. Many such ecological imbalances are occurring around the world.
Season creep also results into habitat loss and habitat shrinking. Due to warming, hardwood trees in north america have been migrating north towards cooler temperatures, since the warmed habitat is no longer suitable for them. A lot of animal species are also migrating towards north in search for favorable conditions, resulting into shrinking habitat.
For humans, season creep affects agriculture the most among all the industries. Growing seasons are increasing but so is the invasive pest population. Earlier, longer chilly winter used to keep the populations of pests in check, but now with shorter and milder winters, pests population is increasing rapidly in some parts of the world. Early spring means the snow will melt earlier, and then there'll be less water available for spring sowing season.
That's it for this one. I know its a lot to process but what I've written here is just scratching the surface. There's a lot more to each of these topics, and all of them need their separate articles to understand them fully. I hope it's clear that why climate change isn't just about increasing temperatures, it's about messing up with the delicate ecosystem our planet is. For the next article, I'm gonna focus on how to deal with this overwhelming problem that is climate change. I've only heard of some strategies and solutions to climate change, can't wait to delve deeper and bring you another satisfactory read. Stay curious!