Do you want to offset your carbon footprint? Here’s what you need to know

In the Middle Ages, the Catholic Church offered indulgences, allowing people to exchange donations for slips that promised a reduction in time in purgatory after their death. Less controversial, today someone who indulges too much in the office tea supply may feel compelled to pay for a replacement box. Do carbon offsets resemble the first or the second more closely?

There are many reasons why you might be trying to offset some of your carbon footprint, whether it’s to alleviate general guilt about your lifestyle, to accurately cover a flight’s estimated emissions, or just to do something about it. beneficial for the environment. Regardless of the motivation, all of these efforts are based on the belief that the money you have actually paid will result in the removal of the promised amount of CO₂ from the atmosphere. Otherwise, you’re paying for a lie or at least for a smaller tea box than the one you ordered.

Finding out if they lied to you is really hard. Here’s what you need to know.

Scaling the carbon cycle

Carbon dioxide in the atmosphere is part of a biogeochemical dance called the carbon cycle. Carbon regularly changes shape and area code, cycling between the atmosphere, oceans, ecosystems and even bedrock. Plants take carbon atoms from CO₂ in the air to grow. Herbivores consume plants and exhale carbon as CO₂ yet. Rocks exposed to atmospheric agents attract CO₂ out of the air. Volcanoes release it into the atmosphere. These are just some of the many exchanges in the carbon cycle.

Before the industrial revolution, these flows were in equilibrium, maintaining a stable concentration of CO₂ in the atmosphere. But then we discovered fossil fuels and ways to ignite them for fun and profit. This took more and more carbon that had spent many millions of years locked up deep underground and released it into the atmosphere. Some of that carbon (just over half, actually) has been absorbed by the oceans and terrestrial ecosystems. But the rest accumulated in the atmosphere, pushing greenhouse gas concentrations higher and higher.

To stop the increase of this greenhouse gas, our total net CO emissions₂ it must reach zero. It’s that simple. We can achieve this in part by eliminating the emissions caused by some of our activities. But we will probably also have to offset ongoing emissions to reach net zero.

Some carbon offsetting projects help with this by preventing emissions that would otherwise have occurred. Others promise to preserve something that in terms of the carbon cycle is known as a “sink”: a durable form of carbon such as forests or even mineralized carbonate in the soil. These offsets are not always identical to prevented emissions, as they can have carbon-separated climate effects. Forests, for example, can be darker than their surroundings, so their expansion results in a local warming effect as more sunlight is absorbed. But reforestation also has the potential to provide other ecosystem services such as animal habitats. So there are many factors to consider besides carbon.

Make like a tree and a leaf

Planting trees is a surprisingly simple answer to climate change. (For evidence, see: Instinctive Internet Comments.) But our ability to store carbon in this way is limited. We may undo the emissions caused by past deforestation, but we can never plant enough to cover the rampant use of fossil fuels. But, even if you accept this limitation, a lot can go wrong after your seedlings are pushed into the earth.

Assuming you find a program you can trust to actually plant the promised trees, many things will affect their impact on the carbon cycle over time. The first is the way tree species grow. Some are growing rapidly, accumulating a lot of carbon per acre over the last decade or so, which provides immediate help to our carbon footprint. But fast-growing trees are typically less dense than slower-growing species, so the maximum amount of carbon stored per acre is less.

The faster growing species also tend to have a shorter lifespan. If the trees on this plantation are managed for harvesting, the end of life cycle will come sooner. So where does the carbon go? Some, could be turned into lumber, at which point its value as a carbon sink depends on how long things built with that lumber last, The remaining plant material decays or burns, releasing carbon into the atmosphere, which ends its time as a Sink,

Even if the trees planted are never harvested, their carbon could be released in other ways. Old trees die and rot, of course. Insect infestations can tear through forests, killing trees en masse. Fires can do the same. Some risks like these are increasing due to climate change, which means that carbon storage in forests is becoming less and less safe over time in many regions.