Climate Overshoot: The Important Conversation We’re Not Having

A newly released paper, Planning for Change: Conservation-Related Impacts of Climate Overshoot, published in Oxford University Press journal, BioScience, examines the potentially substantial impacts climate overshoot could have on our ecosystems and species around the globe, and how we must account for peak warming temperatures as we navigate the ongoing climate crisis.

Climate overshoot, a period where global mean temperatures rise above warming targets before settling back down, is a likely occurrence in roughly 90 percent of climate change scenarios that target 1.5° Celsius of warming. Scenarios that hold global mean temperature to 1.5°C could include an overshoot period that ranges from 1.56°C to 1.85°C for a 15 to 70 year duration, before falling back to 1.5°C. A climate overshoot period is also possible for 2.0°C scenarios, given the current lack of scope and ambition in existing mitigation commitments.

“Overshoot has been invisible in the world’s climate discussions for far too long,” says Rebecca Shaw, chief scientist of World Wildlife Fund. “Unless we start addressing overshoot’s potential impacts, what we must do to avoid them and how we also must plan for them, we risk missing the full narrative of climate change’s impacts.”

Climate overshoot involves both a warming and a cooling period. During the warming phase, species and humans may migrate to more suitable habitats. Humans may convert new land for agriculture and struggle with disease and food security. When the temperatures begin to cool back down to the end-of-century target, species and humans may need to migrate again. But these migration pathways and original habitats may have been permanently transformed or destroyed during the warming period.

While it is possible to take the steps needed to avoid damaging impacts, we need to act now. As world leaders gather this week in Madrid for the United Nations Climate Change Conference COP 25 to address national commitments to the climate crisis, we must think beyond just end-of-the-century stabilized outcomes and place additional focus on addressing climate overshoot and the role peak warming would play for our ecosystems, communities and the planet.

“There are many ongoing efforts that make us feel hopeful about climate solutions,” says Shaw. “We can remain motivated to ramp up these efforts and use the available science on climate overshoot as we plan towards a sustainable future.”