Extreme rainfall events have always occurred, but are they changing?

Extreme rainfall events have always occurred, but are they changing?

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Heavy weather and weather events are a fact of the Canadian climate, and this year is no exception.


On June 13 Mammoth hail caused more than $ 1 billion in damage in Calgary, The most expensive hailstorm in Canadian history. Eastern Canada was subjected to both in early July Constant extreme heat with high humidity And Great flood.

In line with these events, questions are constantly being raised as to what climate change has contributed to. Has a particular intensity worsened because of our changing climate? How will this intensity change in the future?

Accelerates the water cycle

Many of these questions are related to the water cycle – evaporation Water Atmospheric water vapor from the Earth’s surface and plants is transported from one place to another and returned to the atmosphere at the water’s surface.

The water cycle speeds up as the weather warms. Warmer climates hold more steam, which creates the possibility of more intense rainfall. Proof of that Human activity The global climate of the last century cannot be warmed. Indicates satellite data available since 1988 The atmosphere was humid, This is it Mainly due to human-induced warming of the climate.

However, individual extreme events are influenced by many other factors. A storm will leave moisture on the surface and it will evaporate again and intensify subsequent events.

A collision between a cold ground and a lake wind can cause heavy rainfall. Freezing the lake during a cold winter will increase the lake’s snowfall. Or drought will limit local vapor-transpiration – surface evaporation and plant transmission. rain By reusing local moisture and intensifying the hot dry conditions.

Heavy rain

Several studies have examined the change associated with rainfall, Usually focuses on average conditions rather than intensity. This is understandable, because individual events, such as a hurricane or hailstorm, are complex, and rare geological observations and evolving technologies mean that there are no long-term records that allow scientists to reliably estimate trends.

In contrast, many rainfall records from around the 1950s or earlier exist around the world. Statistical analysis of the data from these rain gauges confirms that the rainfall intensity has increased even more. Globally And Continental levels, Agrees Climate models.

There are widespread indications that these changes in rainfall intensity were due to Human influence About the weather Globally And Continental scales. These are the biggest one-day rains in the last 20 years Now it happens every 15 years.

However, scientists are still confident that a particular extreme rainfall event is the result of climate change. This is because, naturally there is a big difference in rainfall in one place and the signal from climate change can be hidden within the natural noise.

Future extreme cold

The intensity of one-day rains has not grown more intense in all places in recent decades, but that does not mean it will not happen in the future. Science is confident that as the weather warms, the intensity of rainfall will increase significantly. Central latitudes and northern land areas, Including Canada.

Details are uncertain, but heavy snowfall, freezing temperatures and hail will continue to change with the heat.. For example, a recent study indicates a large hailstorm More likely in Alberta By the middle of the century, but less likely in some other parts of Canada.

There is no doubt that man-made greenhouse gas emissions have changed Weather. However, human footprints are often difficult to spot in local climate monitoring. Despite the lack of direct evidence of “in your backyard,” we must be prepared for a future in which many of the intensities associated with the year will intensify.


A warming California prepares the ground for future flooding


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Source: Extreme rainfall events have always happened, but are they changing? (September 7, 2020) Retrieved September 7, 2020 from https://phys.org/news/2020-09-extreme-precipitation-events.html.

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