How mainstream climate science supported the global warming time machine fantasy

When the Paris Agreement on climate change was launched in December 2015, it briefly looked like the rarest of things: a political victory for climate activists and delegates from the world’s poorest regions, who had been threatened by colonization by today’s wealthy nations They have contributed little to the climate crisis – but they will feel its worst consequences.

The world had finally agreed on an upper limit for global warming. And in a move that stunned most experts, it had embraced the expanded 1.5C target, the limit that small island states acutely threatened by sea level rise had tirelessly pushed for years.

At least it seemed that way. It soon became clear that the Paris Agreement’s ambitious limit was no longer much of a limit at all. When the Intergovernmental Panel on Climate Change (or IPCC, the world’s leading body of climate experts) gave its authority to the 1.5°C temperature target with its 2018 special report, something strange happened.

Almost all modeled pathways to limiting global warming to 1.5°C above pre-industrial levels involved temporarily exceeding this target. Both still reached a temperature of 1.5°C at some point (the cut-off date was the coincidental endpoint of 2100), but not before overshooting for the first time.

Scientists responsible for modeling the Earth’s climate response to greenhouse gas emissions caused primarily by the burning of fossil fuels called these “exceedance scenarios.” They became the dominant way in which climate change mitigation was imagined almost as soon as talk of temperature limits arose.

In effect, it said: Staying below a temperature limit is the same as first exceeding it and then, a few decades later, using methods to remove carbon from the atmosphere in order to lower temperatures again.

Some parts of the scientific literature claimed that this was nothing more than fantasy. A new study published in Nature has now confirmed this criticism. It found that humanity’s ability to warm the Earth’s temperature back below 1.5°C after it has been exceeded cannot be guaranteed. Many effects of climate change are fundamentally irreversible. It could take decades to reverse them, well beyond the horizon relevant to climate policy. For the political decision-makers of the future, it will not matter much that temperatures will fall again at some point; The impacts they need to plan for are those of the exceedance period itself.

The rise of overshoot ideology

Even if average global surface temperatures eventually reverse, regional-scale climate conditions may not necessarily follow the global trend and could end up evolving differently than before. For example, delayed changes in ocean currents could cause the North Atlantic or Southern Ocean to continue to warm while the rest of the planet does not.

Any losses and damages that accumulate during the exceedance period itself would, of course, be permanent. For a farmer in Sudan whose livestock is perishing in a heatwave that could have been avoided at 1.5C, it is little comfort to know that temperatures will return to that level when her children grow up.

Added to this is the questionable feasibility of carbon removal on a global scale. Planting enough trees or energy crops to reduce global temperatures would require entire continents of land. Direct air capture of gigatons of carbon would consume enormous amounts of renewable energy, thus competing with decarbonization. Whose land will we use for this? Who bears the burden of this excessive energy consumption?

If a reversal cannot be guaranteed, it is clearly irresponsible to sanction a supposedly temporary exceedance of the Paris targets. And yet that’s exactly what scientists have done. What motivated her to take this dangerous path?

Our own book on the subject (Overshoot: How the World Surrendered to Climate Breakdown, published last week by Verso) provides a history and critique of the idea.

When overshoot scenarios were launched in the early 2000s, economic reasons were the most important reason. Rapid, short-term emissions cuts were considered prohibitively expensive and therefore unpalatable. Cost optimization required that they be postponed as far into the future as possible.

The models used to predict possible mitigation paths had these principles written into their code and therefore were largely unable to calculate “low” temperature targets such as 1.5 or 2°C. And because the modelers could not imagine transcending the deeply conservative constraints with which they were working, something else had to be transcended.

One team came up with the idea that it might be possible in the future to remove carbon on a large scale, helping to reverse climate change. The EU and then the IPCC picked up on this, and overshoot scenarios soon became widespread in the specialist literature. Consideration for mainstream economics led to the defense of the political status quo. This in turn led to reckless experiments with the climate system. The conservatism or fatalism regarding society’s ability to change turned into extreme adventurism towards nature.

Time to bury the time machine

Just as the climate movement won an important political victory and forced the world to commit to ambitious temperature limits, an influential group of scientists, reinforced by the world’s most authoritative scientific body on the issue, effectively helped blunt the climate movement. When everything is said and written about the post-Paris period, this will surely be one of its greatest tragedies.

By invoking the overshoot-and-return fantasy, scientists invented a mechanism to delay climate action, inadvertently giving credibility to those (and there are many) who have no real interest in curbing emissions here and now; Who will use any excuse to keep the flow of oil, gas and coal flowing a little longer?

The results of this new work make it clear: There is no time machine waiting in the starting blocks. As soon as the 1.5°C limit is behind us, we must assume that this threshold has finally been exceeded.

Then only one path remains to ambitiously curb climate change, and no amount of carbon dioxide removal can free us from the inconvenient political implications.

To prevent climate collapse, we must bury the overshoot-and-return fantasy and with it another illusion: that the Paris goals can be achieved without destroying the status quo. One barrier after another will be broken if we fail to block fossil fuel assets and limit the ability to continue profiting from oil, gas and coal.

We will not be able to curb climate change without confronting and defeating fossil fuel interests. We should expect climate scientists to be open about this.

This article is republished from The Conversation under a Creative Commons license. Read the original article.