The Basics of Climate Science: What is Climate Change, and Why Should we Care about it?
By Daniel T’seleie
What is climate change, and why should we care about it?
This blog is a plain-language attempt at explaining the basics of climate science. But we need to keep in mind that this is not an environmental or scientific issue. Climate change is an issue of basic human rights. Climate change is already responsible for the deaths of more than 100,000 people a year according to the World Health Organization. More than 80 per cent of these people dying are children under five. We need to keep these facts in mind when we talk about climate change and its solutions.
Climate vs. Weather
It’s time to learn a little bit of science, but before we talk about climate science we need to be clear on what we mean by “climate.” The word “climate” refers to long-term patterns of weather, and this is very different from weather as we normally talk about it. The weather can change hour-to-hour, day-to-day and year-to-year, but changes in climate can only be measured over periods of decades.
Climate science is about averages, and weather data spanning at least 30 years is needed to accurately determine changes in climate (this could be data on average or seasonal temperature, average or seasonal rainfall, etc.). Just because this summer is warmer than last summer doesn’t mean the climate has changed, but if the average summer temperature from 1980 to 2010 is warmer than the average summer temperature from 1950 to 1980, this is an indicator of climate change.
Greenhouse gases and the greenhouse effect
Why does the climate change? There are several things that influence the earth’s climate, like the brightness of the sun (which changes over time, just like all stars), the distance from the earth to the sun, the angle at which the earth faces the sun and greenhouse gases.
These factors change over time, and the climate naturally changes over periods of tens of thousands of years or more. But rapid changes in greenhouse gas levels in the last two centuries have caused rapid climatic changes that are unprecedented in earth’s history.
Greenhouse gases are things like carbon dioxide (CO2) and methane. These gases act like a blanket around the earth; they let in sunlight which warms the planet, but then they trap heat radiation and prevent it from going back into space. Greenhouse gases have always been a part of our atmosphere, and a natural greenhouse effect has helped keep the earth at a comfortable temperature since the dawn of human kind.
So what’s the stink with greenhouse gases?
Burning fossil fuels releases carbon dioxide. Since the beginning of the industrial revolution, humans have been burning fossil fuels (like oil, coal, and natural gas) and adding carbon dioxide to the atmosphere. This added carbon is causing the earth’s climate to heat up (global warming), and as the earth warms other aspects of the climate – like precipitation (rain and snow), wind patterns and ocean currents – begin to change. This carbon dioxide will stay in the atmosphere for centuries, if not millennia.
The build-up of additional greenhouse gases in the atmosphere has caused a rapid warming of 0.83 degrees Celsius in the earth’s average temperature over the last 130 years.
This doesn’t sound like a big temperature difference, but remember that this is an average. The actual change on-the-ground varies from region to region. This temperature change also has big impacts on other weather patterns (wind and rainfall) and on ecosystems (plants and animals).
Dangerous climate change?!?!
How can climate change be dangerous, and why can’t we just fix it now or later?
We can stop climate change now, but if we wait until later it will be too late.
By studying the geological data, scientists know that the earth’s climate stays at relatively stable temperatures for long periods of time. Sometimes the temperature shoots up or down (e.g. in and out of ice ages) before stabilizing at another temperature.
Right now, humans are causing the earth’s temperature to rise by adding fossil fuels. But once we raise the temperature enough the earth will take over and heat itself up by a huge amount before stabilizing at a much higher temperature than we are used to.
This happens because of positive feedback. Feedback in the earth’s climate system is like feedback in a microphone. A microphone picks up sound, which is amplified and emitted through a speaker, and then picked up by the microphone, then amplified and emitted through the speaker, etc.
An example of positive feedback in the earth’s climate system is melting ice. Ice and snow are close to white, and this means they reflect a lot of sunlight. As ice and snow in the Arctic melts, less sunlight is reflected and the exposed water and earth absorbs more sunlight and causes more warming to the climate (this is like the difference between wearing a white shirt and a black shirt on a sunny day).
Another example of positive feedback is melting soil. Soil in the Arctic stays frozen all year. It also contains a lot of dead plants that have been frozen there for thousands of years or more. As this soil melts (because of global warming) the dead plant matter begins to decompose, and this releases greenhouse gases. These added greenhouse gases further contribute to global warming and climate change.
So right now humans are causing global warming, but if we don’t get this warming in check then positive feedback loops will take over and continue to warm the earth regardless of what we do. If we enter a period of runaway climate change where feedback loops have taken over, it will be a disaster for humans and ecosystems all over the world, and the loss of human life will be enormous.
This means that we need to stop global warming and climate change before we hit a critical threshold where positive feedback takes over. Many scientists think this threshold is at about 2 degrees Celsius of warming compared to pre-industrial temperatures (remember that we have already hit 0.83 degrees of warming).
How much more can we pollute?
We need to stop burning fossil fuels and polluting with greenhouse gases before the earth’s climate warms to the critical threshold that will send us into dangerous runaway climate change. But how long do we have before this happens?
Scientists are not 100 per cent sure how much greenhouse gases we can put into the atmosphere before we hit runaway climate change, but they have some good ballpark ranges.
The Canadian, Nobel Prize winning climate scientist Andrew Weaver lays out some of this science quite plainly in his book Keeping Our Cool.
According to Weaver, humans have polluted the atmosphere with about 500 billion tonnes of carbon dioxide since the start of the industrial revolution. We can add roughly another 600 to 650 billion tonnes of carbon dioxide to the atmosphere before we raise the earth’s average temperature by 2 degrees Celsius and hit runaway climate change.
Currently humans add about 10 billions tonnes a year of carbon dioxide to the atmosphere every year (Canada adds about 600 million tonnes each year). So if we keep polluting the way we are now, we will hit the critical threshold of atmospheric carbon in about 60 years.
Carbon dioxide stays in the atmosphere for hundreds or even thousands of years, so as long as we keep burning fossil fuels we will eventually add the enough carbon to the atmosphere to enter runaway climate change. We need to make sure we stay well under the atmospheric carbon limit that will send us into runaway climate change, and to do this we need to transition off of fossil fuels.
Who should stop polluting first, and by how much?
Here’s some food for thought from Weaver’s book. Between 1900 and 2002 Canada added 22.6 billion tonnes of carbon to the atmosphere. In that same time period India added 23.1 billion tonnes of carbon, just a slight fraction more than Canada even though India’s population is more than 30 times larger than Canada’s.
When deciding how much each country and each population on the planet must reduce their carbon pollution, we need to take into account our historic responsibility for the current carbon pollution in the atmosphere. Developed countries like Canada have polluted more than developing countries, and are more responsible for causing climate change. Developed countries also have more resources and finances to transition off fossil fuels.
We in Canada should start reducing our carbon pollution immediately and make a serious effort to transition off fossil fuels.
For more information
For more information on climate science, check out these blogs from past Canadian Youth Delegations on the history of climate science, and on disinformation about climate science.