Geoengineering: We should not play dice with the planet

The fate of the Biden administration’s agenda on climate remains uncertain, captive to today’s toxic atmosphere in Washington, DC. But the headlines of 2021 leave little in the way of ambiguity — the era of dangerous climate change is already upon us, in the form of wildfires, hurricanes, droughts and flooding that have upended lives across America. A recent UN report on climate is clear these impacts will worsen in the coming two decades if we fail to halt the continued accumulation of greenhouse gases in the atmosphere.

To avert disaster, we must chart a different climate course, beginning this year, to achieve steep emissions reductions this decade. Meeting this moment demands an all hands-on-deck approach. And no stone should be left unturned in our quest for meaningful options for decarbonizing our economy.

But while it is tempting to pin our hopes on future technology that might reduce the scope of future climate damages, we must pursue such strategies based on sound science, with a keen eye for potential false leads and dead ends. And we must not allow ourselves to be distracted from the task at hand — reducing fossil fuel emissions — by technofixes that at best, may not pan out, and at worst, may open the door to potentially disastrous unintended consequences. 

So-called “geoengineering,” the intentional manipulation of our planetary environment in a dubious effort to offset the warming from carbon pollution, is the poster child for such potentially dangerous gambits. As the threat of climate change becomes more apparent, an increasingly desperate public — and the policymakers that represent them — seem to be willing to entertain geoengineering schemes. And some prominent individuals, such as former Microsoft CEO Bill Gates, have been willing to use them to advocate for this risky path forward.     

The New York Times recently injected momentum into the push for geoengineering strategies with a recent op-ed by Harvard scientist and geoengineering advocate David Keith. Keith argues that even in a world where emissions cuts are quick enough and large enough to limit warming to 1.5 degrees Celsius by 2050, we would face centuries of elevated atmospheric CO2 concentrations and global temperatures combined with rising sea levels.

The solution proposed by geoengineering proponents? A combination of slow but steady CO2 removal factories (including Keith’s own for-profit company) and a quick-acting temperature fix — likened to a “band-aid” — delivered by a fleet of airplanes dumping vast quantities of chemicals into the upper atmosphere.

This latter scheme is sometimes called “solar geoengineering” or “solar radiation management,” but that’s really a euphemism for efforts to inject potentially harmful chemicals into the stratosphere with potentially disastrous side effects, including more widespread drought, reduced agricultural productivity, and unpredictable shifts in regional climate patterns. Solar geoengineering does nothing to slow the pace of ocean acidification, which will increase with emissions.

On top of that is the risk of “termination shock” (a scenario in which we suffer the cumulative warming from decades of increasing emissions in a matter of several years, should we abruptly end solar geoengineering efforts). Herein lies the moral hazard of this scheme: It could well be used to justify delays in reducing carbon emissions, addicting human civilization writ large to these dangerous regular chemical injections into the atmosphere. 

While this is the time to apply bold, creative thinking to accelerate progress toward climate stability, this is not the time to play fast and loose with the planet, in service of any agenda, be it political or scientific in nature. As the recent UN climate report makes clear, any emissions trajectory consistent with peak warming of 1.5 degrees Celsius by mid-century will pave the way for substantial drawdown of atmospheric CO2 thereafter. Such drawdown prevents further increases in surface temperatures once net emissions decline to zero, followed by global-scale cooling shortly after emissions go negative.

Natural carbon sinks — over land as well as the ocean — play a critical role in this scenario. They have sequestered half of our historic CO2 emissions, and are projected to continue to do so in coming decades. Their buffering capacity may be reduced with further warming, however, which is yet another reason to limit warming to 1.5 degrees Celsius this century. But if we are to achieve negative emissions this century — manifest as steady reductions of atmospheric CO2 concentrations — it will be because we reduce emissions below the level of uptake by natural carbon sinks. So, carbon removal technology trumpeted as a scalable solution to our emissions challenge is unlikely to make a meaningful dent in atmospheric CO2 concentrations.

As to the issue of climate reversibility, it’s naïve to think that we could reverse nearly two centuries of cumulative emissions and associated warming in a matter of decades. Nonetheless, the latest science tells us that surface warming responds immediately to reductions in carbon emissions. Land responds the fastest, so we can expect a rapid halt to the worsening of heatwaves, droughts, wildfires and floods once we reach net-zero emissions. Climate impacts tied to the ocean, such as marine heat waves and hurricanes, would respond somewhat more slowly. And the polar ice sheets may continue to lose mass and contribute to sea-level rise for centuries, but coastal communities can more easily adapt to sea-level rise if warming is limited to 1.5 degrees Celsius. 

While it’s appealing to think that a climate “band-aid” could protect us from the worst climate impacts, solar geoengineering is more like risky elective surgery than a preventative medicine. This supposed “climate fix” might very well be worse than the disease, drying the continents and reducing crop yields, and having potentially other unforeseen negative consequences. The notion that such an intervention might somehow aid the plight of the global poor seems misguided at best.

When considering how to advance climate justice in the world, it is critical to ask, “Who wins — and who loses?” in a geoengineered future. If the winners are petrostates and large corporations who, if history is any guide, will likely be granted preferred access to the planetary thermostat, and the losers are the global poor — who already suffer disproportionately from dirty fossil fuels and climate impacts — then we might simply be adding insult to injury.

To be clear, the world should continue to invest in research and development of science and technology that might hasten societal decarbonization and climate stabilization, and eventually the return to a cooler climate. But those technologies must be measured, in both efficacy and safety, against the least risky and most surefire path to a net-zero world: the path from a fossil fuel-driven to a clean energy-driven society.

Kim Cobb is the director of the Global Change Program at the Georgia Institute of Technology and professor in the School of Earth and Atmospheric Sciences. She was a lead author on the recent UN Intergovernmental Panel on Climate Change (IPCC) Sixth Assessment Report. Follow her on Twitter: @coralsncaves

Michael E. Mann is distinguished professor of atmospheric science and director of the Earth System Science Center at Penn State University. He is author of the recently released book, “The New Climate War: The Fight to Take Back our Planet.” Follow him on Twitter: @MichaelEMann