New study warns of dangers of ‘overachieving’ climate targets

Last month, an important study was published in the journal. Naturecalled “Overconfidence in climate overshoot” As scientists continue to issue increasingly dire warnings about the catastrophic consequences of global climate change, the findings of this new paper serve as another stark reminder of the urgent need to limit global warming by immediately reducing greenhouse gas (GHG) emissions.

In particular, the document emphasizes the need to prevent climate targets from being “overachieved.” Overshoot refers to a scenario in which a proposed warming target (typically 1.5°C above pre-industrial levels) is initially exceeded, but efforts to remove carbon dioxide later cool the Earth to the same temperature.

Commenting on the significance of the new study, Lund University professors Wim Carton and Andreas Malm explained At the heart of the exceedance proposals is the following sentence: “Staying below the temperature limit is the same as first crossing it and then, after a few decades, using methods to remove carbon from the atmosphere to lower the temperature again.”

However, this assumption can only be considered accurate if it is assumed that 1) it is scientifically feasible that global temperatures can be “reset back” to target levels, and 2) there are no significant climate impacts associated with the exceedance scenario.

A new study casts serious doubt on both of these assumptions. A climate scenario that initially exceeds the 1.5°C target could theoretically reverse this additional warming and achieve the target over the long term. But compared to a trajectory that never reached 1.5°C, the exceedance itself could lead to a host of climate impacts.

This is true even if the final average temperature in both scenarios is the same. According to the authors of the new study: “We show that global and regional climate change and its risks once exceeded are different from a world that avoids it.”

The research team was led by Karl-Friedrich Schleisner, head of the climate science department at the Berlin research institute Climate Analytics. A study of climate models found that exceedance scenarios outlined in previous reports were overconfident about the viability of climate change mitigation.

There are essentially two components to these latest discoveries. First, returning to average global warming of 1.5°C after exceeding it is far from guaranteed and, at the very least, is likely to be much more challenging than once expected.