In order to provide the context which informs decisions around action on climate change, a brief summary is provided here on the science of climate change from the leading subject matter resources.
What is climate change?
"Climate change refers to any significant change in the measures of climate lasting for an extended period of time" (Environmental Protection Agency, 2016). Climate change may include major shifts in temperature, precipitation, winds, or extreme weather that occur over the long-term. While weather refers to a condition (e.g. snowfall) that occurs over a period of hours or days, climate refers to average weather conditions that we experience over decades or longer.
While the term global warming has often been used in place of climate change, this term is misleading as changes in climate, including temperature, will be experienced differently across various regions of the world.
What are greenhouse gases?
Greenhouse gases (GHGs) trap heat in the atmosphere by absorbing thermal infrared radiation (i.e. heat). This process, referred to as the greenhouse effect, causes the atmosphere to heat up, and subsequently the earth to warm as well. Primary greenhouse gases include: carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), water vapor (H2O), ozone (O3), and fluorinated gases.
The effect of a greenhouse gas on climate change depends on the concentration in atmosphere, how long they stay in the atmosphere, and how powerful they are at trapping heat. Each greenhouse gas has a unique global warming potential (GWP), which is a measure of how much heat they absorb in the atmosphere over a period of time relative to carbon dioxide. While carbon dioxide has a GWP of 1, other gases, such as methane and nitrous oxide, are more powerful at absorbing heat.
What causes climate change?
Both humans and natural factors contribute to climate change. Humans contribute to climate change through the combustion of fossil fuels and other processes that release of greenhouse gases into the atmosphere (e.g. driving cars, heating buildings, agriculture, chemical processes). To a lesser degree, humans also contribute to climate change by removing carbon sinks, such as clearing forests that would otherwise absorb carbon dioxide.
Natural factors, such as the sun, the earth's orbit, and volcanic activity also impact the climate. However, scientists have concluded that the degree and rate of warming we are experiencing today is primarily the result of human activity.
How is climate change measured?
For decades humans have been taking thousands of measurements of the Earth's air, water, and land every day. Scientists gather these measurements from a multitude of technological sources all around the world. Specifically when investigating climate change, scientists use these sources to measure the amount of greenhouse gases in the atmosphere all around the world.
Not only are scientists able to measure the current climate condition of the earth, they are also able to decipher the levels of greenhouse gases that existed in the past. For example, ancient air bubbles trapped deep in the ice of Greenland and Antarctica reveal how much carbon dioxide was present thousands of years ago. Scientists have discovered that there is more carbon dioxide in the atmosphere now than at any other time in at least 650,000 years, and the amount of carbon dioxide and other greenhouse gases is continuing to increase at an unprecedented rate.
To learn more about current and future changes in the Earth's climate, scientists use climate models. A climate model is a computer program that uses mathematical equations to describe how the land, the atmosphere, oceans, life forms, and energy from the sun affect each other and the Earth's climate. Using these equations, models can predict how a change in one part of the climate system, such as increasing greenhouse gases or decreasing Arctic sea ice, will affect other parts of the Earth in the future.
Scientists test their models by comparing the results with real measurements. They only use models that have proven to be useful in understanding past and present changes in the Earth's climate, such as the global temperature changes recorded over the last century.
What signs of climate change already exist?
Using observations, measurements, and models, scientists have been able to demonstrate a number of signs of climate change happening worldwide already.
- Higher temperatures
- Changing rain and snow patterns
- More droughts
- Warmer oceans
- Rising sea level
- Wilder weather
- Increased ocean acidity
- Shrinking sea ice
- Melting glaciers
- Less snowpack
- Thawing permafrost
What are the consequences of climate change?
Climate change will affect people and environments around the world in a number of ways with varying severity. There are a number of impacts from climate change that are already occurring.
- Increased spread of disease
- Increased air pollution
- Temperature related illnesses
- Crop losses
- Increased power shortages, blackouts, and demand
- Public water and reservoir shortages
- Increased species extinctions
- Disappearing habitats and ecosystems
Beyond these impacts that are already occurring, a vast number of even more severe consequences are likely to arise if emissions continue to increase. The Intergovernmental Panel on Climate Change (IPCC) Climate Change 2014 Impacts, Adaptation, and Vulnerability document identifies several high probability risks associated with dangerous levels of anthropogenic interference with climate change.
Risk of death, injury, ill-health, or disrupted livelihoods in low-lying coastal zones and small island developing states and other small islands, due to storm surges, coastal flooding, and sea level rise.
Risk of severe ill-health and disrupted livelihoods for large urban populations due to inland flooding in some regions.
Systemic risks due to extreme weather events leading to breakdown of infrastructure networks and critical services such as electricity, water supply, and health and emergency services.
Risk of mortality and morbidity during periods of extreme heat, particularly for vulnerable urban populations and those working outdoors in urban or rural areas.
Risk of food insecurity and the breakdown of food systems linked to warming, drought, flooding, and precipitation variability and extremes, particularly for poorer populations in urban and rural settings.
Risk of loss of rural livelihoods and income due to insufficient access to drinking and irrigation water and reduced agricultural productivity, particularly for farmers and pastoralists with minimal capital in semi-arid regions.
Risk of loss of marine and coastal ecosystems, biodiversity, and the ecosystem goods, functions, and services they provide for coastal livelihoods, especially for fishing communities in the tropics and the Arctic.
Risk of loss of terrestrial and inland water ecosystems, biodiversity, and the ecosystem goods, functions, and services they provide for livelihoods.
Why not just adapt?
When discussing climate change, adaptation refers to taking action that seeks to reduce a population's vulnerability to relatively sudden changes in climate and thus offset the negative consequences that have been outlined above. Adaptation differs from mitigation, which describes action taken to reduce greenhouse gas emissions and minimize the severity of climate change impacts.
The question is often raised as to whether efforts should be focused adaptation measures rather than mitigation. Scientists agree that if people keep adding greenhouse gases into the atmosphere at the current rate, the average temperature around the world could increase by about 2 to 7°C by the year 2100. If large scale changes are made, such as quickly transitioning to renewable resources instead of fossil fuels, the temperature increase will be less—about 1 to 3°C. Regardless of action taken now global temperatures will still increase, though by how much remains to be seen.
Adaptation efforts are now just as necessary as mitigation efforts. However, the longer we fail to mitigate climate change and allow global temperatures to increase, the more expensive adaptation efforts will be. A study on the Economics of Adaptation to Climate Change by the World Bank (World Bank, 2011) has found that the cost between 2010 and 2050 of adapting to an approximately 2 degree Celsius warmer world (best case scenario) by 2050 is in the range of $70 billion to $100 billion a year for a developing country. In its report Paying the Price: the Economic Impacts of Climate Change for Canada, the National Roundtable on the Environment and the Economy suggested that the economic impact on Canada could reach $5 billion per year by 2020 and between $21 and $43 billion per year by 2050.
What can be done?
Addressing climate change and taking action to mitigate greenhouse gas emissions is an enormously important undertaking that everyone must play a part in. There are countless ways in which to do so, and the MCCAC is a great starting point for municipalities looking to get started.
The MCCAC has compiled a list of simple Energy Saving Actions that can be undertaken by any municipality and their residents to save energy, reduce greenhouse gas emissions, while also saving money. Accompanying this, the MCCAC also offers Energy Efficiency Toolboxes which contain a number of tools to experiment with. Each tool can provide a range of information on different areas of energy consumption and allow you to understand how to become more efficient.
The MCCAC also provides financial rebate programs to help make taking action on climate change more affordable for municipalities.
Please explore the remainder of the MCCAC website and do not hesitate to email firstname.lastname@example.org with any questions.