How have scientists come to the conclusion that global climate is rapidly changing? It’s based on the scientific method and repeated hypothesis testing. Specifically, by observing global temperature and precipitation records over the long term and looking for significant change. While atmospheric conditions have been subtly changing for decades, we’ve only been consistently and directly measuring key climate indicators like atmospheric carbon dioxide levels since the 1960’s. However, the widespread existence of weather stations around the world, with regular, reliable weather observations, allows us to go further back in time to see the pattern of changing climate over the last century and beyond.
In this lab, we will analyze actual temperature records from some of the longest running weather stations in Canada, to determine if they demonstrate a trend in changing climate over time. Then, to make sure we are not cherry-picking data from a few select stations, we will compare these results to a statistically larger selection of weather stations to look at the broad trends. At the end of this lab, you will have a good sense of one line of evidence for contemporary climate change.
After completion of this lab, you will be able to:
- Read and graph monthly average temperatures by decade from historical data sources;
- Analyze trend lines in graphed data for change over time;
- Interpret histograms; and
- Understand the basis in data for modern climate change
What Causes Climate to Change Over Time?
Atmospheric gases play a significant role in maintaining a global energy balance. Through transmission, reflection, absorption, and refraction they affect radiation from the sun on its way to the Earth’s surface. Energy from the Sun comes as shortwave energy at the UV and visible end of the electromagnetic spectrum. Energy re-emitted from the Earth is much lower in temperature and longer wavelength. This is the basis for the greenhouse effect. Some of the re-emitted longwave radiation from the Earth is temporarily trapped within the atmosphere before it escapes back into space, resulting in heat retention.
The differing wavelengths between incoming solar radiation and outgoing radiation re-emitted by the Earth allow atmospheric gases to play specific roles in controlling the transmission of these wavelengths. For example, water vapour (H2O), absorbs mostly in the longwave end of the spectrum, blocking energy re-emitted from the Earth (Figure 6.2). In contrast, oxygen (O2) and ozone (O3), absorb mostly in the shortwave end of the spectrum (high-energy incoming solar radiation). This difference—where high-energy radiation is passed through the atmosphere, but lower energy radiation is prevented from escaping—permits the greenhouse effect,
Read this summary of the major factors involved in forcing climate to change over time.
One of the first scientific stations to measure carbon dioxide (CO2) concentrations over long periods is still operational at Mauna Loa in Hawai’i. The data recorded here have allowed us to track detailed changes in carbon dioxide concentrations over time. These concentrations are usually measured in ppm (parts per million) where 1 ppm CO2 represents 1 CO2 particle per million atmospheric particles.
Since initial measurements at Mauna Loa began, we have augmented our understanding of global CO2 concentrations with more measuring stations and satellite measurements. This has allowed us to see a spatial distribution in CO2 emissions across the globe, and also better understand global energy budget.
For an interesting way to visualize the pathway of escaping longwave (infrared) radiation, check out this website. See how the difficulty of this game changes between atmospheric concentrations of CO2 in the 1900s to expected concentrations in 2025:
Measuring Spatial Variation in the Earth’s Energy Budget
If Earth’s energy budget is out of balance, global temperatures will start to rise or fall. When this happens, ecosystems need to adjust and, depending on the rate of change, this can be difficult to accomplish.
One way to analyze change in countries around the world is by using temperature records that extend into the historic past. Canada has several sites for which daily temperature records cover at least a 100-year period. These data are archived at Environment Canada and can be accessed here. Others have organized this data into virtual globes like this one to make it easier to explore.
The data collected from these locations is incredibly valuable for reconstructing changes in temperature over time, and analyzing how changes might be different at separate locations around the globe. This reinforces the importance of keeping consistent long term scientific datasets for the good of society in general, so we can better understand the systems we inhabit.
Since the 1970’s space-based measurements have been possible from satellites that are measuring atmospheric and surface conditions on the Earth. ERBS (Earth Radiation Budget Satellite) launched in 1984 and collected data on Earth’s radiation budget. One of the modern satellite systems to take over this role is CERES (Clouds and the Earth’s Radiant Energy System).
In these exercises you will do the following:
- Review the greenhouse effect and the basis for contemporary climate change
- Analyze the pattern of carbon dioxide concentration in the atmosphere over recent decades using this website.
- Observe and graph temperature trends from several Canadian weather stations over at least a century of time using this virtual globe.
- Determine how the long term pattern of your analyzed weather stations fit in the broader pattern of Canadian weather station observations.
Figure 6.4 shows a detailed view of the atmospheric window. The top graphic shows spectral intensity of the radiation, the middle graphic shows the complete picture of absorption/scattering (gray) and transmission (white), and the bottom graphic breaks down the absorption/scattering and transmission into individual atmospheric components.
- There are spaces for two labels, Label X and Label Y under the first graph. Which of these labels should be “shortwave” and which should be “longwave”?
- What is the range of transmitted wavelengths for downgoing radiation coming from the Sun? (Give your answer in micrometers (μm).)
- What is the range of transmitted wavelengths for upgoing radiation released from the Earth’s surface? (Give your answer in micrometers (μm).)
- Does a greenhouse gas like carbon dioxide (CO2) absorb mostly longwave or mostly shortwave radiation?
- Water vapor also acts as a greenhouse gas, yet it is not often talked about in the media with respect to climate change. Why are scientists more concerned about the impact of CO2 in the atmosphere than water vapor?
- Look at the monthly averages for atmospheric CO2 measured at Mauna Loa, Hawai’i.
a. What was the maximum CO2 concentration measured in 1960?
b. What was the maximum CO2 concentration measured in 2017?
- Based on the information in the previous questions, how much has CO2 concentration increased on average per year?
- Look at the graph demonstrating the growth rate of CO2 in our atmosphere as measured at Mauna Loa, Hawai’i. 10-year averages are indicated by the black lines on the graph:
a. What was the average yearly increase in carbon dioxide at Mauna Loa over the decade of the 1960s?
b. What was the average yearly increase in carbon dioxide at Mauna Loa over the decade of the 2000s?
c. According to this graph have humans been successful in reducing the rate of carbon dioxide accumulation in the atmosphere?
We know that there are many natural sources of CO2 emissions that contribute to the atmospheric CO2 reservoir. To better visualize the human contribution, we need to separate the human-generated component from the natural sources.
Imagine a world where the only contributions to carbon dioxide in the atmosphere are from people (non-human sources of CO2 do not exist). How much carbon dioxide would build up in the atmosphere every year, simply from human activities like burning fossil fuels?
Watch the animation CO2 from Fossil Fuel Combustion. The animation shows how much carbon dioxide was added to the atmosphere in the years 2011 and 2012 by human activity. Pay special attention to the geography of the emissions. In particular, notice where the main sources of fossil fuel emissions are located, and how that relates to population distribution. (Click here to see a map of population density.)
- Which hemisphere has a higher buildup of carbon dioxide? Why do you think this is the case?
- List three significant source regions for carbon dioxide release.
- Describe one impact that global circulation patterns have on distributing atmospheric carbon dioxide around the globe.
Your instructor will assign you one of four weather stations for analysis.
|Number||Weather Station ID||Weather Station Name|
|2||403718690000||Prince Albert, Saskatchewan|
|3||403716000000||Sable Island, Nova Scotia|
Open the virtual globe. Explore the data available and how to use the time slider at the bottom of the globe. Some brief instructions are below:
- Runs best with Google Chrome.
- 60mb of temperature data is used so the initial download may be slow.
- Click and drag to rotate the globe.
- Scroll to zoom in and out.
- The timeline is animated with the spacebar or play button.
- Clicking the timeline changes time as well.
- Shift-click-drag on the globe to select a region on the map and generate temperatures for the histogram.
- Use the Search tool to find individual weather stations.
Enter your station name into the search bar and confirm the station ID once you zoom to the station.
- Record the January and July temperatures for your station every 10 years, starting in January 1880. If there is no data, write “No Data”.
- Graph the results of your table. Place the year on the x-axis. Use the left y-axis for the January temperature range and right y-axis for the July temperature range. Draw a separate line with different symbology for the January and July temperatures. You can use this website to print free graph paper.
a. Connect the lines on your graph with straight line segments. Then draw a best fit trend line through the data points.
b. Calculate the slope of the two best fit trend lines for January and July.
c. Is the temperature at your station undergoing a warming or cooling trend, or does it appear neutral?
|Daily Average Temperature||Jan||Feb||Mar||Apr||May||Jun||Jul||Aug||Sep||Oct||Nov||Dec|
|Prince Albert, Saskatchewan||-17.3||-13.8||-6.8||3.3||10.4||15.3||18||16.7||10.5||3.1||-7.2||-14.8|
|Sable Island, Nova Scotia||-4.1||-3.6||-0.2||4.9||10.1||15.2||18.8||19.1||15.5||9.9||4.8||-0.8|
|Monsonee, Ontario (James Bay)||-20||-17.5||-11.1||-1.8||6.8||12.2||15.8||14.9||10.5||3.8||-4.3||-14.5|
- On your graph of temperatures, use the Canadian Climate Normals table to graph a line representing the January and July normals from 1981 to 2010.
- What is the difference between the average temperature from your first three temperature readings, and the 1981-2010 climate normal for:
- Measurements of temperature at weather stations around the globe are some of the best long-term indicators of climate conditions at a specific location.
a. What factors do you think could impact the reliability of the measurements from an individual weather station?
b. How does considering the temperature records across many weather stations over a long period of time help increase confidence that the trends in a climate record reliably reflect actual conditions?
- How do you think the climate trends you observed at your weather station are affecting the biogeography and ecosystem health of that location?
- The recent collapse of a diesel storage tank in northern Russia released ~20 000 litres of diesel fuel into a sensitive Arctic river system. The resource company that owned the storage tank has blamed melting permafrost for destabilizing the foundation of the tank, leading to its failure.
a. Are climate-change related hazards something we should be more aware of (and private corporations should be responsible for monitoring) as we observe accelerating changes in some areas of the globe, like the Arctic?
b. Is it ironic that a company focused on resource extraction is blaming an oil tank failure on melting permafrost and suggesting the company itself is not to blame for the failure? Explain.
IPCC. (2007): Greenhouse Effect. [computer graphic] Retrieved from https://archive.ipcc.ch/publications_and_data/ar4/wg1/en/faq-1-3.html
Lindsey, R. (2009). Atmospheric Window. [computer graphic] Retrieved from https://earthobservatory.nasa.gov/features/EnergyBalance/page7.php
Rohdes, R. (2007). Atmospheric Transmission. [computer graphic] Retrieved from https://commons.wikimedia.org/wiki/File:Atmospheric_Transmission.png
- Figure 6.1 Greenhouse Effect © Andrew Perkins is licensed under a CC BY-NC-SA (Attribution NonCommercial ShareAlike) license
- Figure 6.2 Atmospheric window © NASA is licensed under a Public Domain license
- Figure 6.3 ERBS and CERES © Karla Panchuk is licensed under a CC BY-NC-SA (Attribution NonCommercial ShareAlike) license
- Figure 6_4 Atmospheric Window © Robert Rohdes adapted by Karla Panchuk is licensed under a CC BY-SA (Attribution ShareAlike) license