Unit 7 – Weather and Climate Learning Guide
Weather vs Climate
We hear a lot about the dangers of “climate change” these days. How does that differ from “weather?”
Weather is the way the atmosphere is behaving, mainly its effects on life and human activities. The difference between weather and climate is that weather consists of the short-term changes in the atmosphere. Most people think of weather in terms of such as daily heat or cold, humidity, rain or snow, cloudiness or brightness, visibility, and wind.
Here, in Canada weather often changes from minute-to-minute, hour-to-hour, day-to-day, and season-to-season.
Weather can include:
- cloud cover
- freezing rain
- ice storms
- heat waves
Climate, however, is the average of weather over time and space. An easy way to remember the difference is that climate is what you expect to happen in general, like warm days in the summer, and weather is what you actually get, like a cold morning with a sudden rainstorm during a mostly warm summer.
What Climate Means
Climate is how we describe the long-term pattern of weather for a particular area.
It can be seen as the “average weather” for a particular region and time period.
Terms to describe “climate,” are often similar to the terms to describe weather:
- wind velocity
- hail storms
The difference is that when we use these terms to describe “climate” we’re referring to the long-term trends related to each.
For example, after looking at rain gauge data, lake and reservoir levels, and satellite data, scientists can tell if during a summer, an area was wetter than average. If it continues to be wetter than normal over the course of many summers, then this would likely indicate a change in the climate.
Why Study Climate?
Studying climate and a changing climate is VERY important. The resulting predictions impact people all around the world.
Changing climate can:
- alter forests
- change crop growth
- impact water supplies
- affect human health
- challenge animal survival
- cause migration changes
- expand deserts
- shrink existing rangelands
Human activities have altered the chemical composition of the atmosphere through the buildup of greenhouse gases – primarily carbon dioxide, methane, and nitrous oxide.
Many companies make lots of money based on our current harmful practices, which makes them reluctant to change (or even admit that change is needed).
Given that, the heat-trapping property of greenhouse gases is undisputed in the scientific community.
What Is Extreme Weather?
Extreme weather includes unexpected, unusual, unpredictable, severe or unseasonal weather; weather at the extremes of the historical distribution—the range that has been seen in the past. Often, extreme events are based on a location’s recorded weather history and defined as lying in the most unusual ten percent. (Wikipedia)
In recent years some extreme weather events have been attributed to human-induced global warming, with studies indicating an increasing threat from extreme weather in the future.
Hurricanes are the most violent storms on Earth. They form near the equator over warm ocean waters. The scientific term for these storms, wherever they occur, is tropical cyclone. Other names they are given, depending on where in the world they are born, are typhoons or cyclones.
Tornado vs Hurricane
Tropical cyclones are like engines that require warm, moist air as fuel.
- The first ingredient needed for a tropical cyclone is warm ocean water. That is why tropical cyclones form only in tropical regions where the ocean is at least 27 degrees Celsius.
- The second ingredient for a tropical cyclone is wind. In the case of Atlantic hurricanes, the wind blowing westward across from Africa provides the necessary ingredient.
As the wind passes over the ocean’s warm surface, water evaporates and rises.
As it rises, the water vapor cools, and condenses back into large water droplets, forming large cumulonimbus clouds.
information from https://scijinks.gov/hurricane/
A wildfire or a large, destructive fire that spreads quickly over woodland or brush.
Approximately 8,000 wildfires occur each year in Canada. The average area burned is 2.5 million hectares – about half the size of Nova Scotia! Wildfires caused by lightning represent almost half of all these fires, but they represent 80% of the total area burned.
Human-caused fires make up the other half of all wildfires. They occur in more populated areas and so are usually reported and extinguished more quickly.
Wildfires are a seasonal source of danger to people, property and wildlife in British Columbia. They can, however provide a natural benefit in some situations, leading to an argument that perhaps we should allow some wildfires to burn as a long-term plan.
Heavy Rain & Flooding
A result of climate change has been an increase in flooding problems. A warmer climate means more evaporation and more severe rain storms.
While heavy rainfall can be dangerous and result in damage to areas where it happens frequently, sudden huge downpours can be devastating in places not equipped to handle the extra extremes of water. These types of events are happening more and more in recent years.
All cities have drains designed to carry storm water away, but these systems were not usually built for the very heavy, sudden rainfall that is becoming more frequent in the modern era.
Thus, we can expect to see highly damaging flooding and the great loss of property.
Drought is a continuous period of dry weather, when an area gets less than its normal amount of rain, over months or even years.
Crops and other plants need water to grow, and animals need it to live. Droughts can become dangerous to people and other land animals; causing famine and even creating deserts. A drought is a natural event, caused by other weather events like El Niño and high-pressure systems.
How can Climate Change cause both Flooding and Drought??
Remember that higher air temperature means more evaporation? Well, this means that there is less moisture in the soil and bodies of water and more in the air. This means that areas will be drier in general with larger storms happening.
In Canada, we sometimes see “ice storms.” An ice storm is a type of winter storm with an accumuliation of at least 6 mm of freezing rain.
Another name that’s sometimes used for “ice storms” is “a silver thaw” because of the silver appearance of surfaces such as trees and power lines coated with a layer of ice.
Ice storms are generally not violent storms but instead are commonly perceived as gentle winter rains occurring at temperatures just below freezing.
Given that, ice storms can still be very dangerous:
- the accumulated ice can be very heavy
- branches on trees break
- power lines can fall
- roads and sidewalks become very slippery
- emergency vehicles can’t move quickly
“The ice storm of 1998” was one of the largest natural disasters in Canadian history. Between 4 and 10 January 1998, sections of the St. Lawrence Valley from Kingston to Québec’s Eastern Townships received up to 10 cm of ice pellets and freezing rain — more than double the icy precipitation normally received in those areas in a whole year. The storm claimed as many as 35 lives, injured 945, and resulted in the temporary displacement of 600,000 people. Several roads were shut down and massive power outages occurred, cutting off electricity for nearly 1.4 million customers in Québec and over 230,000 in eastern Ontario. The total financial cost of the storm is estimated at $5.4 billion.
Information from https://www.thecanadianencyclopedia.ca/en/article/ice-storm-1998/