Side by side images en:User:Ittiz created to show what Mars might look like at various stages while being terraformed in vertical alignment. The horizontal alignment is here: en:Image:MarsTransition.jpg This file is licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license.

Terraforming was a concept I first remember coming across in Star Trek 2: The Wrath of Khan in 1982 when “The Genesis Device”, and its effect on a dead planet, was described as “matter is reorganised with life-generating results”. The astronomer Carl Sagan had previously proposed the planetary engineering of Venus in 1961 and Mars in 1973. Martyn J. Fogg subsequently started publishing articles on terraforming in 1985 before publishing Terraforming: Engineering Planetary Environments in 1995. Fogg defined planetary engineering as using technology to change the global properties of a planet (he called this geoengineering if Earth was the planet in question). Terraforming he defined as planetary engineering which was specifically directed at enhancing the capacity of a planet to support life as we know it.

There are still advocates of terraforming as a project that humans should be actively working towards. Others suggest, that unless Earth is going to be unavoidably uninhabitable, it is likely to be our best bet as a future home for all but a relatively tiny number (Kim Stanley Robinson’s novel Aurora is the most memorable advocate for this position in my view, which takes us on a gruelling exploration of a terraforming expedition over several generations which then allows us to view Earth afresh with alien eyes).

What is clear is that we are not currently terraforming Earth in Fogg’s sense, as most of our planetary engineering (what we call the global economy) appears to be specifically directed at reducing the capacity of Earth to support life as we know it. We are terraforming in reverse.

Terraforming is an example of an idea you might get to as a result of very long-term thinking (there is a nice article about this in Vox, with views from Roman Kznaric, Nick Beckstead, Hilary Greaves and William MacAskill included) – I tend towards the Kznaric view that we cannot predict the knock-on effects of technological shifts in 200 or 300 years, but we know we’ll still need to breathe air and drink water, so working to prevent climate change and pandemics is very likely to be really good for us today, the near future and the long-run future too.

The danger of discussion of the very long-term is that it can create the idea that nothing we do over the next few years matters. However as we have pushed up to and beyond planetary capacity in so many areas now and have developed a global economy with planetary engineering capabilities of unprecedented power, this is no longer true if it ever was. What seems obvious to me is that we mustn’t make decisions now which lock in damage to planetary life-supporting capacity for generations to come, such as the “carbon bombs” described by George Monbiot here.

Terraforming in reverse is not the direction to choose, whichever generation we belong to.

Cartoon of a black ball powering the planet

Imagine all of the fossil fuel energy available to the Earth and its inhabitants before our emissions from using that energy mean that we will have, on average, a climate 1.5oC warmer than pre-industrial levels. Imagine it as a big black ball located, for convenience, in China, as we have exported many of the most carbon-intensive manufacturing processes we all need there, and that we are all sucking the energy we need from this black ball 24/7 until it is exhausted.

We are currently at 1.2oC above pre-industrial levels on average and have seen the consequences this summer in the UK, and in the unprecedented number and size of wildfires still raging across Spain and Portugal in particular, to name a few of the events which have been made much more likely by climate breakdown.

The last estimate of the size of the ball came from the IPCC AR6 Report of 2021, which indicated that the remaining carbon budget to remain with a 50% chance of staying at or below 1.5°C of global warming is 580 billion tonnes CO2 and about 420 billion tonnes CO2 for a two-thirds chance of limiting warming to 1.5°C, all as at 2018. Annual global CO2 emissions in 2019 were 36.7 billion tonnes, in 2020 they were 34.8 billion tonnes and in 2021 they rebounded to 36.4 billion tonnes. So that ball is shrinking very fast.

Why the obsession with 1.5°C? Well, it is what we and most other countries signed up to in Paris in 2015. 2°C was agreed to be a much worse outcome than 1.5°C – we can already see the results of current warming where 20% of the global population lives with 1.5°C warming in at least one season of the year, but a global average of 2°C compared to 1.5°C would increase the proportion of the population exposed to severe heatwaves at least once every 5 years from 14% to 37%. NASA have an article on this here.

Can we make the ball bigger, by removing some of the carbon dioxide? If you look at the pathways that the IPCC discuss, you will see that they are split between those where temperatures are stabilised at or below 1.5°C warming and those which go above but are then brought back down later in the century. In its most recent report published in April, the IPCC said the use of CO2 removal is now “unavoidable”, if the world is to reach net-zero greenhouse gas emissions. Where the UK is in its programme of carbon removal is discussed here. However, to get it into perspective, global carbon removal to date is still in the experimental stage, and there are many problems remaining to be overcome with most of the proposed methods, so such efforts must be additional rather than in anyway an alternative to drastically cutting our emissions.

Back to the ball. If this represented all of the remaining water in the world (the scientific consensus at 3°C warming has Indian monsoon rains failing, the Himalayan glaciers supplying the Indus, Ganges and Brahmaputra, the Mekong, Yangtze and Yellow rivers decreasing by up to 90% and the Amazonian rain forest basin drying out completely), would you think about it differently? Would you continue washing your car every weekend, watering your lawn, and power-washing your drives and patios on the assumption that we would invent a new way of making water? Simon Brodkin has done a good bit in answer to this, which is both very funny and terrifyingly plausible.