You may have seen the news headlines of recent extreme events like droughts, floods and intense forest fires. Well, believe it or not, all these events are deeply connected.
“As the US west bakes in a prolonged drought, parts of the eastern half of the country have faced the opposite problem as extreme rainfall and fierce winds took their toll on communities".
- The Guardian
Extreme weather events are a direct consequence of a phenomenon called “intensification of the water cycle” which is caused by global warming.
In this article, we will learn the importance of the water cycle and the expected consequences on our planet.
What Is The Water Cycle?
In the water cycle, four main processes take place:
1 Evaporation (from oceans, rivers and transpiration from trees or plants).
2 Condensation (when water evaporated to the atmosphere condensate in clouds).
3 Precipitation (e.g. snow and rain).
4 Collection (when water goes back to oceans or soils).
This cycle is a fundamental key to understand weather patterns on Earth.
What has been going on for the last decades is a complete alteration of this cycle.
The leading cause for this alteration is the observed temperature increase caused by anthropogenic greenhouse gas emissions.
Global Warming & The Water Cycle Intensification
The water cycle’s intensification can be defined as an enhancement in water’s evaporation and precipitation fluxes.
Higher temperatures (caused by global warming) increase the water-holding capacity of the atmosphere. This means that more water can be absorbed in the air for a more extended period.
An increased amount of water vapour retained in the atmosphere leads to an increased convergence of moisture and thus to more intense precipitations (e.g. floods).
However, this increase in mean precipitation levels also reduces the number of wet days and an expansion in the dry season. This happens because, under these warmer conditions in the atmosphere, a longer “recharge time” (and thus longer dry periods) is needed for moisture to replenish the atmosphere and achieve the saturation levels necessary for precipitation.
This leads to another phenomenon called “rich get richer”, which is already taking place and explains why wet regions are getting wetter and dry areas are getting drier.
Water Vapour Can Enhance Global Warming Increasing Temperatures
In addition to intensifying the water cycle, water vapour in the atmosphere negatively affects our planet.
Water vapour is a greenhouse gas. However, most of the time, when we talk about greenhouse gases, we hear carbon dioxide (CO2), methane (CH4) or even nitrous oxide (N2O). This is because all of these greenhouse gases stay for more extended periods in the atmosphere.
Unlike other greenhouse gases, water vapour remains in the atmosphere for shorter periods, of around 10 days. After this time, it precipitates in rain or snow as a part of the water cycle. In the meantime, it acts as a greenhouse gas. Water vapour accounts for approximately 60% of Earth’s heat-trapping, meaning it significantly affects global warming.
The more water vapour in the atmosphere, the hotter the Earth’s surface will get in a shorter amount of time; higher temperatures make the atmosphere retain more water vapour. So yes, it’s almost like a domino effect.
More temperature leads to more vapour, which leads to more temperature, and so on.
Consequences Of The Water Cycle’s Intensification
So we mentioned that the water cycle’s intensification leads to more rain in shorter periods and extends the dry season.
This extent of the dry season causes soil moisture to decrease, which leads to plant-water stress and, therefore, a decrease in crops productivity.
In addition to this, the higher humidity in the air (because more water vapour is trapped) could increase plant’s susceptibility to diseases, fungal infections and insect damage.
Floods & Droughts
Water cycle intensification leads to an increase in extreme weather events, especially significant storms, floods, and droughts. Sadly, human-induced climate change is likely the main driver of the current extreme rainfall events around the world. This includes an increase in frequency and the intensity/duration of these extreme events.
An article published on August 28th 2021 on Hurricane Ida in The Guardian stated:
“Last year there were 30 named Atlantic storms, including seven major hurricanes, a record high. Experts have linked the climate crisis and global heating to the increased frequency of more powerful and destructive weather systems.”
We drastically need to reduce planet-heating emissions in order to reduce the severity of these weather events. All moisture coming from the atmosphere will be deposited on the surface of the earth, these events will soon be made worse as a direct consequence of climate change.
Some of the implications of an increase in these extreme events are:
· Increased risk of flood-related mortality
· Severe damages to infrastructure
· More frequent and severe crop losses
· Increases in soil degradation and erosion
· Loss of forest productivity
· Lack of sustainability of water resources, especially in arid and semiarid areas
· Increased risk of forest fires
Forest fires are expected to be more frequent and more intense if the climate situation is not reversed.
What causes this is the extent of the dry season, which means soil and tree structures will get drier.
When wood lacks moisture, it burns more efficiently. Like when we make a fire, and we pick the drier branches. Imagine a forest full of very dry branches and drier year after year. This leads to a higher combustion rate and thus to uncontrollable fires.
The thing is that fires also release CO2 as a product of combustion.
CO2 contributes to global warming.
This leads to hotter and, therefore, drier seasons.
So like water vapour, forest fires are both a cause and a consequence of global warming.
The climate conditions that we are experiencing today are anomalous on Earth. However, events that were once considered to be extremely rare may become more and more common. Many of these are both causes and consequences of global warming and, therefore, climate change.
If you are still unsure about the importance of Global Warming and Climate Change I encourage you to have a read of our summary of the IPCC report on the Travel For Change blog.
About The Writer
Belén Silva is a Chemical engineer from Argentina. She started her freelance writing and environmental consulting career after working for many years in the automotive industry as an environmental engineer. In addition, she has a personal project of environmental communications that includes a blog, an Instagram account and a Youtube channel. You can read more from her on her website Idonella.
Huntington, H., “Chapter One - Climate warming-induced Intensification of the Hydrologic Cycle: An Assessment of the Published Record and Potential Impacts on Agriculture” (2010), Advances in Agronomy (109).
Vinogradova, N.T., Ponte, R.M., “In Search of Fingerprints of the Recent Intensification of the Ocean Water Cycle” (2017), Journal of Climate (30-14).
Giorgi, F. et al., “Higher Hydroclimatic Intensity with Global Warming” (2011), Journal of Climate (24-20).