Heavy Rain Events Have Always Occurred, But Are They Changing?

Heavy Rain Events Have Always Occurred, But Are They Changing?
A woman wades into flood waters in Calgary, Alta., on June 14, 2020, after a major hail storm damaged homes and flooded streets.
THE CANADIAN PRESS/Jeff McIntosh

Extreme weather and climate events causing extensive damage are a fact of the climate, and this year is no exception.

On June 13, a mammoth hailstorm pounded Calgary with damage in excess of $1 billion dollars, the most expensive hailstorm in Canadian history. In early July, eastern Canada was subjected to both persistent extreme heat coupled with high humidity and major flooding.

As we cope with these events, questions invariably arise about what role climate change may have played. Has a particular extreme been made worse because of our changing climate? How will these extremes change in the future?

Water cycle accelerating

Many of these questions are linked with the hydrologic cycle — the evaporation of water from the Earth’s surface and its vegetation, the transport of water vapour in the atmosphere from one place to another and the ultimate return of the water to the surface as precipitation.

The water cycle speeds up when the climate warms. A warmer atmosphere holds more water vapour, creating the potential for more intense precipitation events. The evidence that human activity has warmed the global climate over the past century is incontrovertible. Satellite data available since 1988 indicate that the atmosphere has moistened, and that this is primarily due to the human-induced warming of the climate.

Individual extreme events are, however, influenced by many other factors. A storm can leave behind moisture at the surface that can re-evaporate and strengthen subsequent events.

The collision between a cold front and a lake breeze can lead to heavy precipitation. A delayed lake freeze-up during a warm winter can enhance lake-effect snowfall. Or a drought could limit local evapo-transpiration — evaporation from the land surface and transpiration from plants — eliminating the rainfall that comes from local moisture recycling and further intensifying hot, dry conditions.

Heavy rainfall

Many studies have examined precipitation-related change, usually focusing on average conditions rather than extremes. This is understandable because individual events, like a tornado or hail storm, are complex, and sparse ground observations and evolving techniques mean there aren’t yet long-term records that allow scientists to reliably estimate trends.

In contrast, numerous rainfall records beginning in the 1950s or earlier exist across the globe. Statistical analyses of data from these rain gauges confirm that rainfall extremes have grown more intense at the global and continental levels, in agreement with climate models.

Basement apartment after a severe thunderstorm  (heavy rain events have always occurred but are they changing)
A man surveys the damage to his basement apartment after a severe thunderstorm caused localized flooding in Toronto on July 8, 2020.
THE CANADIAN PRESS/Carlos Osorio

There are broad indications that these changes in rainfall extremes are due to human influence on the climate at global and continental scales. Extreme one-day rainfall events that occurred about once every 20 years in the past are now occurring about once every 15 years.

Even so, scientists still struggle to confidently say that a particular extreme rainfall event is the result of climate change. This is because there is naturally a large amount of variation in precipitation in one place, and the signal from climate change can get hidden within the natural noise.

Future extremes

Not all places have seen one-day rainfall extremes grow more intense over the past several decades, but that doesn’t mean it won’t happen in the future. The science indicates, with considerable confidence, that as the climate continues to warm, precipitation extremes will become substantially more intense in the mid-latitudes and northern land areas, including Canada.

Although details are uncertain, heavy snowfall, freezing rain and hail will all change with continued warming. For example, a recent study suggests that large hail could become more likely in Alberta by mid-century, but less likely in some other parts of Canada.

There is no doubt that human-induced greenhouse gas emissions have changed the climate. Nevertheless, the human imprint is often difficult to see in local meteorological observations. Despite that lack of direct “in your backyard” evidence, we should prepare for a future in which many precipitation-related extremes will become more intense.The Conversation

About the Authors

Francis Zwiers, Director, Pacific Climate Impacts Consortium, University of Victoria and Ronald Stewart, Professor, Environment and Geography, University of Manitoba

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

Related Books

Life After Carbon: The Next Global Transformation of Cities

by Peter Plastrik , John Cleveland
1610918495The future of our cities is not what it used to be. The modern-city model that took hold globally in the twentieth century has outlived its usefulness. It cannot solve the problems it helped to create—especially global warming. Fortunately, a new model for urban development is emerging in cities to aggressively tackle the realities of climate change. It transforms the way cities design and use physical space, generate economic wealth, consume and dispose of resources, exploit and sustain the natural ecosystems, and prepare for the future. Available On Amazon

The Sixth Extinction: An Unnatural History

by Elizabeth Kolbert
1250062187Over the last half-billion years, there have been Five mass extinctions, when the diversity of life on earth suddenly and dramatically contracted. Scientists around the world are currently monitoring the sixth extinction, predicted to be the most devastating extinction event since the asteroid impact that wiped out the dinosaurs. This time around, the cataclysm is us. In prose that is at once frank, entertaining, and deeply informed, New Yorker writer Elizabeth Kolbert tells us why and how human beings have altered life on the planet in a way no species has before. Interweaving research in half a dozen disciplines, descriptions of the fascinating species that have already been lost, and the history of extinction as a concept, Kolbert provides a moving and comprehensive account of the disappearances occurring before our very eyes. She shows that the sixth extinction is likely to be mankind's most lasting legacy, compelling us to rethink the fundamental question of what it means to be human. Available On Amazon

Climate Wars: The Fight for Survival as the World Overheats

by Gwynne Dyer
1851687181Waves of climate refugees. Dozens of failed states. All-out war. From one of the world’s great geopolitical analysts comes a terrifying glimpse of the strategic realities of the near future, when climate change drives the world’s powers towards the cut-throat politics of survival. Prescient and unflinching, Climate Wars will be one of the most important books of the coming years. Read it and find out what we’re heading for. Available On Amazon

From The Publisher:
Purchases on Amazon go to defray the cost of bringing you InnerSelf.comelf.com, MightyNatural.com, and ClimateImpactNews.com at no cost and without advertisers that track your browsing habits. Even if you click on a link but don't buy these selected products, anything else you buy in that same visit on Amazon pays us a small commission. There is no additional cost to you, so please contribute to the effort. You can also use this link to use to Amazon at any time so you can help support our efforts.

 

enafarzh-CNzh-TWdanltlfifrdeiwhihuiditjakomsnofaplptruesswsvthtrukurvi

follow InnerSelf on

facebook-icontwitter-iconrss-icon

 Get The Latest By Email

{emailcloak=off}

LATEST VIDEOS

Five Climate Disbeliefs: A Crash Course In Climate Misinformation
The Five Climate Disbeliefs: A Crash Course In Climate Misinformation
by John Cook
This video is a crash course in climate misinformation, summarizing the key arguments used to cast doubt on the reality…
The Arctic Hasn't Been This Warm For 3 Million Years and That Means Big Changes For The Planet
The Arctic Hasn't Been This Warm For 3 Million Years and That Means Big Changes For The Planet
by Julie Brigham-Grette and Steve Petsch
Every year, sea ice cover in the Arctic Ocean shrinks to a low point in mid-September. This year it measures just 1.44…
What Is A Hurricane Storm Surge and Why Is It So Dangerous?
What Is A Hurricane Storm Surge and Why Is It So Dangerous?
by Anthony C. Didlake Jr
As Hurricane Sally headed for the northern Gulf Coast on Tuesday, September 15, 2020, forecasters warned of a…
Ocean Warming Threatens Coral Reefs and Soon Could Make It Harder To Restore Them
Ocean Warming Threatens Coral Reefs and Soon Could Make It Harder To Restore Them
by Shawna Foo
Anyone who’s tending a garden right now knows what extreme heat can do to plants. Heat is also a concern for an…
Sunspots Do Affect Our Weather But Not As Much As Other Things
Sunspots Do Affect Our Weather But Not As Much As Other Things
by Robert McLachlan
Are we headed for a period with lower Solar activity, i.e. sunspots? How long will it last? What happens to our world…
Dirty Tricks Climate Scientists Faced In Three Decades Since First IPCC Report
Dirty Tricks Climate Scientists Faced In Three Decades Since First IPCC Report
by Marc Hudson
Thirty years ago, in a small Swedish city called Sundsvall, the Intergovernmental Panel on Climate Change (IPCC)…
Methane Emissions Hit Record Breaking Levels
Methane Emissions Hit Record Breaking Levels
by Josie Garthwaite
Global emissions of methane have reached the highest levels on record, research shows.
kelp forrest 7 12
How The Forests Of The World’s Oceans Contribute To Alleviating The Climate Crisis
by Emma Bryce
Researchers are looking to kelp for help storing carbon dioxide far beneath the surface of the sea.

LATEST ARTICLES

Creative Destruction: The Covid-19 Economic Crisis Is Accelerating the Demise of Fossil Fuels
Creative Destruction: The Covid-19 Economic Crisis Is Accelerating the Demise of Fossil Fuels
by Peter Newman
Creative destruction “is the essential fact about capitalism”, wrote the great Austrian economist Joseph Schumpeter in…
Global Emissions Are Down By An Unprecedented 7% — But Don’t Start Celebrating Just Yet
Global Emissions Are Down By An Unprecedented 7% — But Don’t Start Celebrating Just Yet
by Pep Canadell et al
Global emissions are expected to decline by about 7% in 2020 (or 2.4 billion tonnes of carbon dioxide) compared to 2019…
Decades of Unsustainable Water Use Has Dried Up Lakes and Caused Environmental Destruction
Decades of Unsustainable Water Use Has Dried Up Lakes and Caused Environmental Destruction in Iran
by Zahra Kalantari et al
Salt storms are an emerging threat for millions of people in north-western Iran, thanks to the catastrophe of Lake…
Climate Sceptic or Climate Denier? It's Not That Simple and Here's Why
Climate Sceptic or Climate Denier? It's Not That Simple and Here's Why
by Peter Ellerton
Climate change is now climate crisis and a climate sceptic now a climate denier, according to the recently updated…
The 2020 Atlantic Hurricane Season Was A Record-Breaker, and It's Raising More Concerns About Climate Change
The 2020 Atlantic Hurricane Season Was A Record-Breaker, and It's Raising More Concerns About Climate Change
by James H. Ruppert Jr. and Allison Wing
We’re looking back at a trail of broken records, and the storms may still not be over even though the season officially…
Why Climate Change Is Making Autumn Leaves Change Colour Earlier
Why Climate Change Is Making Autumn Leaves Change Colour Earlier
by Philip James
Temperature and day length were traditionally accepted as the main determinants of when leaves changed colour and fell,…
Take Caution: Winter Drownings May Increase As Ice Thins With Climate Change
Take Caution: Winter Drownings May Increase As Ice Thins With Climate Change
by Sapna Sharma
Every winter, the ice that forms on lakes, rivers and oceans, supports communities and culture. It provides…
There Are No Time-Travelling Climatologists: Why We Use Climate Models
There Are No Time-Travelling Climatologists: Why We Use Climate Models
by Sophie Lewis and Sarah Perkins-Kirkpatrick
The first climate models were built on fundamental laws of physics and chemistry and designed to study the climate…