Countries, cities, companies, and individuals are addressing climate change by pledging to become carbon neutral or even carbon negative. But what does this mean and how can it be meaningfully accomplished?
Carbon’s an element, right? What does it have to do with climate change?
Yep, carbon (C) is a chemical element with an atomic number of 6. It’s abundant (4th most common element in the universe, 15th most common element on Earth, and 2nd most common element in the human body) and essential to life. It’s also versatile. It can be found in the oceans, the air we breathe, rocks like limestone, the soil and in all living things. Importantly, carbon is dynamic and can easily move between these different places. A carbon atom can be part of a plant one day, an animal the next, and then travel downstream into the ocean or up into the air the next. The continuous movement of carbon is aptly called the carbon cycle.
When carbon is in the air it is part of the atmosphere – a layer of gases that surround Earth. In the atmosphere, carbon is attached to oxygen as carbon dioxide (CO2) or to hydrogen as methane (CH4). These two molecules – along with a handful of other gases – have unique structures that enables them to trap heat that would otherwise escape into space. This heat-trapping process is called the greenhouse effect. Just like the glass panes in a greenhouse, these gases allow energy from the sun to enter Earth’s atmosphere but block heat from escaping.
Greenhouse gases are important. Without them, Earth’s average temperature would be freezing (around 0°F or -18°C)! However, today the greenhouse effect is becoming too strong. A rapid increase in greenhouse gases is leading to global climate change. Of all the greenhouse gases carbon dioxide receives the most attention, not because it is the most potent or abundant greenhouse gas, but because it is the one most responsible for current changes in global temperatures.
Today’s atmospheric carbon dioxide levels are higher than at any point in the past 800,000 years. One driver of this increase is major land use changes. Humans use around two-thirds of Earth’s ice-free land to work, live, play, raise livestock, and grow crops. Compared to the original forest, wetlands, grasslands, etc. these new landscapes have a lower capacity to absorb carbon. The other key driver is the burning of fossil fuels like petroleum, coal, natural gas, and Orimulsion.
Fossil fuels are the buried remains of plants and animals that lived thousands of years ago. These remains have been compressed underground for millions of years and so have a high carbon content and, consequently, a large amount of energy locked within them. Around 200 years ago we began digging up fossil fuels and using them to power our factories, cars, and power plants. Our society is partially a result of having access to these powerful energy sources. However, using them also moves carbon that was previously stored for millions of years underground into the atmosphere.
Tracking Carbon Emissions
Even though carbon dioxide is constantly being released into the atmosphere, it’s hard to see. One reason for this is that the gas is invisible, odorless, and tasteless. Another reason is that these gases do not stay near to where they were emitted. Instead they quickly disperse into the global atmosphere.
Carbon footprints are a tool used by individuals, groups, companies, and even nations to examine and better understand their emissions. In this context, “footprint” is a metaphor for the total impact that something or someone has, and “carbon” is shorthand for all greenhouse gas emissions that are causing climate change. Carbon footprints are typically expressed as tons of carbon dioxide equivalent (CO2e). This is a metric measure that converts all greenhouse gas emissions to the CO2 amount that would have the same global warming impact.
However, carbon footprints only tell half the story. Every day, people, companies, and governments are also addressing climate change and finding ways to reduce their CO2e emissions. These positive actions can be tallied into a carbon handprint. For example, an individual can grow their carbon handprint by reducing their energy consumption, talking with others about the causes and consequences of climate change, and inventing and sharing new energy solutions.
Balancing the Sheets
Companies, governments, individuals, and other groups become carbon neutral by balancing carbon footprints with carbon handprints. The most important part of this by far is directly reducing emissions e.g. shrinking the company’s/country’s/individual’s carbon footprint. This step is essential because reaching a safe level of carbon dioxide in the atmosphere and will require everyone to make large emission cuts.
A useful stop gap method is buying carbon offsets. You can think of offsets as a carbon accounting mechanism. An emitter of carbon dioxide can pay to compensate for these emissions by helping someone else reduce their carbon footprint or by funding projects that remove greenhouse gases from the atmosphere (and then safely storing/converting these gases). This is a much faster way to achieve net carbon neutrality.
Today carbon offsets are a multi-billion dollar global market. This market helps fund amazing projects that replant costal mangrove forests, build wind turbines, install methane capturing digester in dairy farms, and provide households with solar stoves, etc. At the same time many are skeptical of this market. Rapid expansion combined with a lack of standardization and regulation means that it can be difficult to purchase offsets that truly create new and permanent emissions reductions and that the reductions are not double counted.
Next, read this Nature article on the European Unions proposed law to reduce emission to net zero by 2050.
Finally have your students calculate their own carbon footprint and then challenge them to take neutralizing carbon handprint actions by going here and downloading the “Questions” and “Actions” word documents under the RESOURCES tab.