The amount of carbon dioxide released into the atmosphere by burning of fossil fuels is at a staggering all time high of 34 billion tonnes, having risen every decade since the 1960s. Not surprisingly, our carbon dioxide emissions from fossil fuels, and land-use changes, including deforestation, have raised the atmospheric concentration of this major greenhouse gas to a level unprecedented in human history.
What’s more, the concentration of atmospheric carbon dioxide has risen so rapidly over the past few decades that Earth’s temperature has yet to fully adjust to the new warmer climate it dictates. This means that even if we could magically stop our carbon dioxide emissions from fossil fuels overnight, we have already committed Earth to transition to a warmer climate. Global temperatures have risen by more than 1°C since the 1970s. How much more warming are we likely to experience? Another 0.5°C, 1.5°C, 2.5°C or worse? Scientists are working urgently to try and better constrain this number. Meantime, over 190 nations worldwide signed up to the 2015 Paris Agreement with the goal of limiting warming to less than 2°C and ideally less than 1.5°C. Given the current situation, even a lenient 2°C target now looks wildly optimistic, especially given 34+ billion tonnes of carbon dioxide are added every year we delay mitigation measures.
This is why, along with the United Nations and the National Academy of Sciences in the United States, the UK’s Royal Society acknowledges drastic phase-down of our carbon dioxide emissions from burning fossil fuels for energy will be insufficient to avoid seeding catastrophic human-caused climate change. We actually have to start removing carbon dioxide from the atmosphere, safely, affordably, and within the next 20 years.
Enter, the kingdom of plants.
Hundreds of millions of years ago, during the Devonian Period (393-383 millions of years ago), plants bioengineered a cooler climate as the spread of forests lowered atmospheric carbon dioxide levels. As their root systems evolved to become larger and more complex, trees generated soils and accelerated the breakdown of rocks and minerals into minute grains, forming dissolved bicarbonate in the process. Eventually, this bicarbonate washed into the oceans, where the carbon it carries was stored for hundreds of thousands of years or locked up on the sea floor.
We now think it may be possible to mimic those processes to remove carbon dioxide from the atmosphere. The method would be to dress the soils of agricultural landscapes with crushed rapidly weathering rocks, such as basalt. This biogeochemical soil improvement could also boost yields by adding plant-essential nutrients, helping reverse soil acidification, and helping restore degraded agricultural top soils that provide food security for billions of people. Although there are possible drawbacks and unintended consequences, the approach may be practicable. Humans have put over ten million square kilometres of land to the plough, and application of crushed rock to this farmland could be feasible by exploiting existing infrastructure.
However, at the very best, this approach might remove only about 1/10th of our current emissions.
We could also undertake reforestation of forested lands once cleared for agriculture and afforestation of new areas, again mimicking the ancient spread of forests across the continents. Planting millions of trees could help by storing carbon dioxide in forest biomass and soils. Undertaken across a sufficiently large area of the globe, these actions might sequester another few billion tonnes of carbon dioxide.
Even these sorts of radical measures will not represent a sufficient climate restoration plan, however. A wider portfolio of carbon removal techniques will be required to scrub sufficient amounts of carbon from the atmosphere each year. But the technologies need multibillion dollar investment to move them from the lab to pilot schemes and then to determine which can scale massively. At the same time, we will need to fundamentally transform our global energy systems to halt carbon emissions.
As Erik Solheim, until recently the executive director of the United Nations Environment Programme, has remarked, “if we invest in the right technologies, ensuring that the private sector is involved, we can still meet the promise we made to our children to protect their future. But we have to get on the case now.”
Right now, carbon dioxide removal looks like a prohibitively expensive option for helping slow the pace of climate change. Taking action places an enormous burden on young people and future generations. But taking no action asks them to face dire consequences including intensifying droughts, heat-waves, storms, ice-sheet melt and sea-level rise flooding coastal regions. This is the intergenerational injustice of our time.
Our current crisis is urgent and unfolding at a time when global food demand will need to more than double before the end of the century. Can we sustainably feed a crowded planet, preserve the wonderful diversity of life on Earth, and stabilize the climate? These are the daunting challenges facing humanity. Faced with the collective moral failure of world leaders to act, it is hardly surprising that young people worldwide are bravely striking for action on climate change supported by thousands of scientists. At stake is nothing less than the future of humanity.
Feature Image credit: “Green and white leaf plant” by Jackie DiLorenzo. Public Domain via Unsplash.