Reducing emissions is not enough: we need to sequester carbon
In this blog post, we aim to inspire a healthy dose of climate-related dread. We want you, dear reader, to understand the frightening reality of the climate crisis, introduce one way we can frame the scope of the challenge, and, in doing so, underscore the vital importance of carbon sequestration in managing this crisis.
Let’s start with the easy part: explaining what’s wrong. The Intergovernmental Panel on Climate Change (IPCC) is a collection of the world’s leading climate scientists responsible for clearly explaining to policymakers the state of climate science. The IPCC has, since 2018, suggested that we ought to shoot for a warming event less than 1.5ºC, since things get bad really fast after that. Their most recent report, sleekly named “The Working Group I contribution to the Sixth Assessment Report,” paints a rather bleak picture of the future.
Under emissions in line with current pledges under the Paris Agreement (known as Nationally Determined Contributions, or NDCs), global warming is expected to surpass 1.5°C above pre-industrial levels, even if these pledges are supplemented with very challenging increases in the scale and ambition of mitigation after 2030.
In other words,
To provide a bit of context about what this means for you, the following is a deceptively cheerful breakdown of a 1.5ºC vs. a 2ºC warming scenario, brought to you by the World Wildlife Fund.
The big fear with crossing this threshold has to do with these things called feedback loops, which, in the climate arena, are basically vicious self-perpetuating cycles of warming. Let’s consider the ice caps. Ice reflects a lot of light back into the atmosphere, a process known as the albedo effect. When the ice melts, albedo declines, which warms the oceans, which melts more ice, which further reduces albedo. There are unfortunately a great number of feedback loops just like this. It is quite possible and, depending on who you ask, probable that the Earth will enter a cycle of exponential warming. We may follow in the footsteps of infernal Venus and succumb to a runaway greenhouse effect.
Ok, so now that we are all good and frightened, let’s begin the next stage of grief: bargaining. Fossil fuels drive the modern economy, so shifting away from them overnight is obviously not possible. Carbon budgets are a helpful way of visualizing how much CO2 we can emit without going beyond a planetary boundary of warming. Each possible warming scenario carries with it a corresponding “emission ceiling.” The 2018 report indicated that the emission ceiling for a 1.5 degree warming event was somewhere in the ballpark of 580 billion metric tons. This number is a useful way of determining which mitigation scenarios are good faith efforts, and which are the product of political misrepresentation.
It’s pretty clear that humanity isn’t going to suddenly stop emitting greenhouse gases. In fact, we still have a lot of work to do to simply level out. 2020 was the first year global CO2 emissions actually fell, and that was due to a global pandemic. Reducing emissions is the long-term goal, but we can’t stay within our budget without pulling carbon out of the air in the meantime.
A 2019 study published in the journal Science found that the global effort to plant a trillion trees (roughly 900 million hectares) could indefinitely sequester 205 gigatons of carbon dioxide. Given our hard cap of 580 billion metric tons, that means reforestation can contribute roughly 35% of our emission reduction goals. This math was supported by the United Nations during the drafting of the Paris Climate Agreement, which outlines a plan of planting trees to sequester a third of global emission targets.
Reforestation is the most promising approach among many much more expensive and sometimes frightening alternatives. There are many companies at work creating massive synthetic trees called direct air capture machines that suck carbon out of the air. These initiatives face many challenges: they are extremely expensive, the manufacturing process carries with it a great deal of its own carbon emissions, and the technology isn’t scalable enough to address the problem it hopes to solve. Trees, on the other hand, take care of long-term sequestration automatically. Some scientists suggest that a failure to reduce emissions requires planetary scale experimentation called geoengineering. One such idea suggests we spray aerosols into the atmosphere that deflect sunlight, ensuring that the globe doesn’t overheat. There are myriad issues associated with geoengineering projects, namely the ethical problems associated with treating the entire biosphere as an experimental guinea pig.
When the various options are taken into account, it’s clear that the most immediate and reliable solution is also the most intuitive. Reforestation is a timeless, tested carbon sequestration technique with numerous external benefits beyond saving the world from climate change. On top of supporting wildlife, providing local communities with renewable resources, and generally making us feel happy, forests also happen to be the most available, scalable, and affordable carbon draw-down solution.