The earth’s climate is continually changing – and this is a natural process. Ice sheets have advanced and retreated across earth many times. About 12,000 years ago an ice sheet over 1km thick covered most of BC.
( Reference) Ice Sheet clip (author is Arthur Dyke) http://csdms.colorado.edu/wiki/Movie:Laurentide_Ice_Sheet
What is climate? Climate describes weather conditions over a long period of time. It’s the overall long-term picture of temperature, precipitation, wind and other weather conditions for a region. This graph shows the average the average monthly minimum and maximum temperature and precipitation at Kelowna. This is considered the climate of the region. Climate is influenced by the oceans, mountains, elevation and how far north or south we are from the equator.
Climate is different than weather. Weather is local and temporary. It’s how the atmosphere is behaving at a particular time in a particular place. Temperature, rain, snow, and wind are all elements of weather . Weather is variable, it is constantly changing. When you look out your window, you are looking at weather; when you see or listen to a forecast, they are telling you about the weather.
Probably the most common way we think about climate is air temperature. These graphs show how the yearly surface temperature of the earth has changed over the last 140 years. The 0 line represents the 30-year average of surface temperatures measured between 1961 and 1990.
The top graph shows that from 1860 to about 1980, the measured surface temperature was almost always below the 30-year average, since then the measured surface temperatures have been above the average. This tells us that the average surface temperature trend is rising over this 140-year time frame.
The lower graph shows the earth’s surface temperature over the last 1000 years. The red line shows thermometer measurements and the blue line shows temperature derived from tree rings, corals, ice cores and historical records (insert blue arrow from below to point to it) because we didn’t have thermometers then. The graph highlights the sharp temperature increase between 1900 to 2000 not observed in the previous 900 years.
The warming temperatures and changes to our climate have resulted in other observations as well. According to the BC Government, Historical data from 1900-2013 indicates that: I think inserting these bullets while speaking will make it easier for students to follow
Average annual temperature warmed by 1.4 °C across the province
The night-time minimum average temperature in winter in B.C. increased by 3.1 °C
Annual precipitation increased across the province overall
Average sea level has risen along most of the B.C. coast
Lakes and rivers become free of ice earlier in the spring
Water in the Fraser River is warmer in summer
So if climate is always changing, why are we so concerned about global climate change now? Well, scientists have learned from their studies of the Earth’s climate history, that the planet is warming faster than at any other time in history and this rapid increase in temperature will bring many dramatic changes to our climate, which will also have many negative impacts on ecosystems and people.
What is causing our climate to change so quickly?
One of the primary reasons is that the amount of greenhouse gases like carbon dioxide, methane, and nitrous oxide in the Earth's atmosphere have been rising rapidly since the Industrial Revolution. This graph is called a Keeling curve, named after its founder Charles Keeling. It shows the amount of carbon dioxide in the earth’s atmosphere over time. The graph shows that in the past 800,000 yrs CO2 concentrations have shown cyclical variations over time. However, the rise to over 400 parts per million now being measured is unprecedented. You can learn more about Keeling Curve in the YouTube Video from the SCRIPPS Institution of Oceanography.
Why are carbon dioxide, methane, and nitrous oxide called greenhouse gases? The sun emits radiation, which is trapped by gases in the earth’s atmosphere - this helps keep the earth warm and it is called the Greenhouse effect .
Greenhouse gases in the atmosphere trap heat the same way glass traps heat on greenhouse. As the level of greenhouse gas emissions increase, the amount of heat trapped in the Earth’s atmosphere also increases.
According to the Intergovernmental Panel on Climate Change, the major sources of human caused greenhouse gas emissions are energy production, land use, industry, transportation and the building sector.
According to the British Columbia Government, historical and ongoing greenhouse gas emissions mean climate change impacts are expected to continue for decades. While the challenges are significant, understanding and preparing for potential climate change impacts will help us reduce the risks. The BC Government projects the following impacts for B.C. in the coming century:
Expected temperature increase between 1.3 to 2.7 °C
Increased annual rainfall by up to 12% - however, our summers will be drier. Projected impacts include:
Up to 70% of our glaciers may have disappeared by 2100, meaning
Sea levels are expected to continue to rise along most of B.C.’s coast.
We all do things that increase greenhouse gases in our atmosphere. Driving cars or trucks is a big source so, by making some simple changes like walking, riding the bus, or riding your bike instead of driving a car you can help to reduce emissions
What are some other examples of changes we can make to help reduce the amount of greenhouse gases we emit?
Use BC Tomorrow to see how land use in your watershed could influence climate change and what changes that might bring to your watershed.
British Columbia's future is in your hands! See what you can do!
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