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Hacking planet Earth will not save us from ourselves

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By Kevin Trenberth

· 5 min read

Last year was by far the warmest on record for global mean surface temperatures and global sea surface temperatures , and February 2024 was the hottest month for global sea surface temperatures. Moreover, the monthly mean carbon dioxide measured at Mauna Loa Observatory, Hawaii, showed the rate of increase of carbon dioxide in the atmosphere over the past year was the highest ever. 

There is no sign human-induced climate change is under control. On the contrary, it marches on at greater rates, posing a threat to all.

As I have described previously, the exceptional warmth of the past year is because of a strong El Niño that kicked in about May 2023, making surface and sea surface temperatures not only the highest in every month since then, but also highest by a very large increment.

However, global heating from increasing carbon dioxide from human activities is the primary driver of the warming climate. We will continue to experience natural variability from El Niño and weather, but the impacts are greatly modulated by the warming, especially through rain bombs (such as in Auckland on January 27, 2023), more intense storms and risk of flooding, stronger drying where it’s not raining, enhancing drought, risk of wildfire and heatwaves, and generally greater extremes. 

The attempts to rein in increasing carbon dioxide by limiting fossil fuel use have so far failed, and failed dismally. A raft of regional conflicts around the world has added to the problem. 

It has led in some quarters to increasing thoughts about employing geoengineering to hack the planet, as featured in a New York Times article this month: “As the disastrous effects of climate change mount, Congress has asked federal scientists for a research plan, private money is flowing and rogue start-ups are attempting experiments – all signs that momentum around solar geoengineering is building fast.”

A number of methods have been proposed as a way to cool our warming planet including injecting tiny particles into the stratosphere to reflect sunlight. Other proposals include injecting sea salt into clouds to increase their brightness and using giant space parasols to block the sun. All of these cut down on the solar radiation absorbed, but sunshine is not the problem. The problem is the increasing carbon dioxide and other greenhouse gases in the atmosphere consequent to the burning of fossil fuels, as detailed below.

My colleagues and I first explored the hazards of this approach over a decade ago, in which we compared the effects of the Mount Pinatubo volcanic eruption in 1991 on the hydrological cycle as an analog of geoengineering. We raised the very real ethical issues. 

 I used the following fable to illustrate the point:

Once upon a time in an idyllic country, near a small town and a farming community, a rope hung out of the sky. One pull on the rope changed the weather from fine and sunny to cloudy and rainy, and the next pull changed it back. For many years the people cooperated; the farmers used the rains to help grow crops, and the townspeople enjoyed the sunny periods. But there came a time when the townspeople protested the rain and wanted more sunshine. The farmers were concerned about their crops. And so arguments broke out, with a person from the town pulling on the rope, followed quickly by a farmer pulling it again, and they pulled and pulled and . . . broke the rope.

There are major scientific concerns as to whether geoengineering can actually work effectively and if it is viable economically, and who would pay for the considerable ongoing costs, but I’d argue the most important consideration, and obstacle, is “who controls the rope”. For instance, the strongest proposals for cooling the planet through geoengineering are those that advocate for blocking the sunlight in some fashion, perhaps to emulate a volcanic eruption, as happened for Mount Pinatubo. This event produced a global cooling, but it also greatly affected monsoon systems and weakened much of the hydrological cycle for a year or so.

After all, the global warming problem is one of increased trapping of outgoing infrared radiation to space. Spreading a veil of dust to block the sun (as has been proposed) cuts down on the incoming solar radiation but in between the incoming solar radiation and the outgoing infrared radiation is the entire weather and climate system and the hydrological cycle. There is a major risk this could change the water cycle and weather patterns. The science is complex and evolving but the question remains: who gets to pull the rope? And if someone pulled the rope, and the result was a major drought on the other side of the world in a powerful nation, would it lead to major wars?

It is one thing to have the climate changing because of inadvertent consequences of human activities, but it is quite another to attempt to deliberately change climate to counteract the warming, which will inevitably benefit any particular group, at the expense of others.

So what should we do about climate change? We could, for a start, give up on the notion that geoengineering will save us from ourselves. Globally, the pressure must increase to cut emissions and use of fossil fuels. In New Zealand we must recognise that global warming continues apace, and that more complete assessments of vulnerability of all infrastructure and activities is essential, along with much greater attention to building resilience and planning for the consequences. 

This article is also published on Newsroom. illuminem Voices is a democratic space presenting the thoughts and opinions of leading Sustainability & Energy writers, their opinions do not necessarily represent those of illuminem.

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About the author

Kevin Trenberth is a Distinguished Scholar at the National Center for Atmospheric Research (NCAR) and an honorary affiliate faculty at the University of Auckland in New Zealand. He was previously employed as a research scientist in the New Zealand Meteorological Service and as a Professor at the University of Illinois for nearly 7 years. He has been prominent in most of the Intergovernmental Panel on Climate Change (IPCC) scientific assessments of Climate Change and has also extensively served the World Climate Research Programme (WCRP).

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