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|CLIMATE CHANGE IN CONTEXT
Climatic Factors and Projections for Temperature, Precipitation, and Evapotranspiration. Snow and lake levels are also explored.
Climate factors or forcings that push the climate to change include both natural factors and human influences. Two key natural events and processes are the intensity of the sun reaching the earth and the concentration of volcanic dust which reflects light back into space. Human influences forcing climate change include changes in greenhouse gas, stratospheric ozone depletion, local air pollution, and alterations of land use. All of these affect both how much energy gets through to earth and how much energy is reflected back into space.
At the regional scale – espcially in industrialized areas – local air pollution gases and particles, alterations of land use and sooty aerosols have a warming effect. Sulphate aerosols have a cooling effect due to their atmospheric chemistry.
These model projections show greater certainty that the greatest changes in temperature and precipitation will be in the Arctic. Analysis of recent trends and observations in 2004 fit these scenarios. The projections for climate change show that the greatest warming will be in the Arctic.
Quick Time Global Temperature Changes until to 2100
Global scenarios modeling climate changes on a larger scale are used to project global trends over longer periods of time based on data collected earlier. The climate change scenarios project an increase in global temperature of up to 6 degrees during the twenty-first century but not in all areas of the globe.
The polar areas of the globe are projected to experience much greater warming. This will have large-scale impacts in Ontario such as ecosystems moving north, less ice cover, and an increase in total precipitation with less snow and more extreme events in the higher latitudes.
The number of hot days is projected to increase in the future. Using CGCM1 (GHG+A) data, the probability of days over 32oC is projected to increase by a factor of 4 from today’s average of around 5 days per year to 20 days per year in 2050.
Source: Hengeveld, H.G. 2000. Projections for Canada’s Climate Future: A Discussion of Recent Simulations with the Canadian Global Climate Model. Meteorological Service of Canada, Environment Canada. 27pp.
1. Why is this temperature chosen as significant?
2. How does this relate to human health?
3. How is this affected by the “heat island” effect in Toronto?
The graph below uses several climate change models to project the percentage change in precipitation vs. mean temperature change in oC. A number of GCMs use a range of scenarios. The base line for this 2050 scenario is the climate data for 1961-1990.
St. Lawrence Basin annual temperature change (oC) vs annual precipitation change (%) for 2050 KEY TO MODELS
1. Which range of mean temperatures (oC) includes most of the data?
2. Which range of percentages of precipitation change includes most of the data?
3. Predict the climate for 2050 on the basis of your findings.
ACTIVITY 3 Research
Check out the graphs for 1961-1990. What is was the trend over the 30-year period?
When data from the Great Lakes Watershed from 1961-1990 is used to run climate change scenarios for 2050, the trend is towards less snow and more rain.
The two figures below compare the number of days of rain and days of snow for two weather stations.
Data from 1961-1990 from the stations is used for modeling the years 2040-2069 to show the shift in seasonal forms of precipitation impacted by climate change for Kenora and Windsor below.
Graph of comparison of days with rain and days with snow for Windsor weather station for the current climate (1961-1990) and 2050 scenario climate from climate model CGCM1.
Source: Environment Canada
1. Locate these two cities on a map of Ontario. State the longitude and latitude for each.
2. Describe the overall shape of the two parts of the graphs and list the key differences.
3. What is the number of days of difference between the past and predicted for rain and for snow?
ACTIVITY 5 Research
1. What is the overall trend expressed in weeks per year?
2. List some ways that this change would affect each of these two cities.
1. In what months is more rain expected in the future for Windsor in this scenario?
2. What 3 months will experience almost no snow when compared to the past?
3. Change the above answers to days and calculate the percentage change for each.
Even if there were greater precipitation each year, precipitation may not be as available in key seasons. Precipitation falling more as rain than as snow in extreme events may be more harmful than helpful both to natural and built ecosystems. Seasonal changes in precipitation may mean increase in winter runoff and earlier spring melts or freshets, leaving lower water levels in the summer and fall.
Snow depth modeling
The predicted change in precipitation as reduced snow cover due to temperature increases can also be modelled using the effects of changes on carbon dioxide concentration. The first figure below shows the current carbon dioxide with current snow cover depth in centimeters modeled with real data as a base line. The second figure below shows the current data of snow cover depth (cm) modeled to show the impact of the predicted doubled concentration of carbon dioxide.
Current snow cover depth (cm) using real data from 1983 to 1987 to model snow Current depth (cm) for actual depths and predicted depths. The same data is used to model for a climate with 2x C02 concentration in the second graph.
Source: Environment Canada
1. What is the average change in depth in centimeters of snow cover between current concentrations of the green house gas CO2 and doubled concentrations using this climate change model?
2. What is the effect of the change in snow cover depth when shown by a straighter vertical line?
3. What is the maximum change in centimeters of snow depth seen in the same time period due to a doubling of the concentration of green house gas CO2 that causes warmer air temperatures?
Present research shows that the Great Lakes levels respond to climate variability and that the levels will be hitting record lows more often as water levels decline. Great Lakes water levels may be lower by one to two meters causing loss of wetlands. Loss of this habitat will affect fish and migrating waterfowl populations. Shallower rivers and streams, especially if unshaded, will warm more quickly.
Water levels in the Great Lakes have also varied considerably over the past century. Low levels of lake water follow the driest terrestrial years.
The graph below shows data for Lake Erie. For 70 years of Lake Huron data check Section 5.2.2a Hydrology.
Source: Data from Environment Canada, Burlington
1. When was the first driest period? the second dry period?
2. While water levels have dropped dramatically during the past few years, levels are still well above the historical extremes shown.
3. Complete the graph for 2020. What other factors may have to be considered?
ACTIVITY 9 Research
What effect does this change in levels have on Ontario habitats, economy?
1. Examine the graph to understand why the dark line can represent the mean.
2. What is the overall trend from 1900 to 2000? What factors influence this change?
Water demand may outrun supply in many areas of the province. Available water supply will be reduced due to more surface evaporation and less groundwater recharge. At the same time, an increasing Ontario population will demand more water. There may be a reduction in the water supply even if there is an increase in precipitation.
Research in one area showed a 16% reduction in stream flow even though the precipitation had increased by 33%! The Moira /Trent River watershed is projected to have the same amount of precipitation but 18% reduction in annual flow of water. Any annual reduction in precipitation will have a greater effect. For example, 27% loss of precipitation caused 83% in annual flow in one area!
The Bay of Quinte data from 1971-1992 is used below as the base line to model the climate change scenario for 2030, 2050, 2090. The figure below shows the Relative Change in monthly potential evapotranspiration for the climate change scenarios (CGM1). Evapotranspiration will increase with warmer temperatures. The bigger the surface area, the more water will evaporate.
Relative Change in monthly potential evapotranspiration for climate change scenarios (CGM1) modeled on 1971-1992 baseline data from the Bay of Quinte.
A report to Environment Canada, Environmental Adaptation Research Group, Burlington.
ACTIVITY 11 Locate the Bay of Quinte on a map of Ontario.
1. Describe the general pattern predicted in all scenarios for the 4 seasons during one year.
2. How does this pattern relate to the average?
3. What does the y axis tell you?
Lowering of water levels in lakes impacts the natural aquatic world. bringing about shoreline and wetland changes, species changes, and changes in pollution concentration. These changes in turn may cause an increase in the degree of tainting of the odor and flavor of water, and remaining species of fish and wildlife.
Effects of increased air temperature changes on factors that control water quality
A summary based on Murdoch et al., 2002.
On hydrological factors
1. Increased water temperatures – decreased oxygen carrying capacity, increased concentration of chemicals, nutrients and pollutants, decreased ice cover period, ice jam flooding and depth of ice
2. Increased rates of production, decomposition and chemical reactions
3. Decreased water volume affects dilution of chemical inputs – increased chemical concentration
4. Invasion of temperature-sensitive exotic species – more algal blooms
On terrestrial factors affecting vegetation
1. Changes in species distribution of native species as leaching rates of nutrients change.
2. Invasion of temperature sensitive exotic plants and pests changing carbon cycle and storage.
3. Increased rates of soil bacterial processes increasing rates of nitrate released in waters.
Effects of increased air temperature changes and decreased moisture on factors that control water quality. Based on Murdoch et al. 2002.
On hydrological factors
1. Increased water temperatures due to decreased flow providing less dissolved oxygen and supporting more chemical reactions due to increased concentrations of chemical’s
2. Lower ground water levels and decreased stream discharge – increased concentrations/decreased export
3. Increased lake stratification – greater sediment biomass accumulation/ larger layer without oxygen
On terrestrial factors affecting vegetation
1. Changes in erosion due to decreased rate infiltration followed by an overall increase in flash runoffs and more concentrated episodes of non-point source pollution and sediments
2. Changes in chemical export from watersheds due to decreased weathering, soil flushing,(for example, of acid rain) and the effect an earlier, smaller snow-melt on ion exchanges.
3. Increased frequency of fire followed by increased sedimentation due to reduced vegetative cover.
Locate the closest body of water near you. Using the information in this section, predict the conditions for the next 10 years. Hint: check with local planners and developers.