Is it too late to reverse climate change?

Is reversal still possible? I'll pull the latest science on what can — and can't — be undone.

No, it is not too late to slow, limit and eventually reverse the warming trend - but it is too late to avoid all climate change, and a full reversal would take centuries.

1. Some changes are already locked in

> Humans have caused major climate changes to happen already, and we have set in motion more changes still

NASA and NOAA summarize the science this way:

In other words, stabilizing emissions at today's rates will not stop global warming - emissions must be significantly reduced, not just stabilized. And experts at NASA say that it would take decades — if not centuries — to stop global warming in its tracks.

A NOAA-led study concluded that to a large extent, there's no going back, with climate change largely irreversible For Next 1,000 Years.

The irreversibility is most acute for so-called tipping points. The report warns of "tipping points" with irreversible and cascading effects, including the loss of the West Antarctic and Greenland ice sheets, the loss of the Amazon rain forest and the shutdown of the Atlantic Ocean circulation system.

More specifically, climate tipping points are thresholds where a small change triggers self-reinforcing feedback loops that lock in irreversible shifts. Examples include melting of Arctic sea ice, collapse of ice sheets, disruption of ocean circulation, and loss of permafrost.

2. But it is not too late to avoid the worst impacts

The main scientific consensus from NASA, NOAA and the Intergovernmental Panel on Climate Change (IPCC) is that action now still makes a huge difference:

> While we cannot stop global warming overnight, we can slow the rate and limit the amount of global warming by reducing human emissions of heat-trapping gases and soot (“black carbon”)

> While we cannot stop global warming overnight, or even over the next several decades, we can slow the rate and limit the amount of global warming

> It is never “too late” to take action

Scientists emphasize that the climate is not a binary on/off system and that every fraction of a degree counts:

NASA's framing: But it may not be too late to avoid or limit some of the worst effects of climate change

Completely reversing climate change overnight is not possible. However, we can significantly reduce its impacts by lowering greenhouse gas emissions and restoring natural ecosystems.

3. What "reversing" would actually require

The IPCC and NASA describe a two-tier approach:

> Responding to climate change will involve a two-tier approach: 1) “mitigation” – reducing the flow of greenhouse gases into the atmosphere; and 2) “adaptation” – learning to live with, and adapt to, the climate change that has already been set in motion

Mitigation – reducing climate change – involves reducing the flow of heat-trapping greenhouse gases into the atmosphere, either by reducing sources of these gases or enhancing the “sinks” that accumulate and store these gases (such as the oceans, forests, and soil)

Transitioning to energy sources that do not emit greenhouse gases, such as solar, wind, biofuels, and nuclear, can slow the pace of climate change

The U.S. National Academy of Sciences report Limiting the Magnitude of Future Climate Change explains: "Meeting internationally discussed targets for limiting atmospheric greenhouse gas concentrations and associated increases in global average temperatures will require a major departure from business as usual in how the world uses and produces energy."

Other proposals - collectively known as "climate engineering" or "geoengineering" - such as injecting reflective particles into the upper atmosphere or seeding oceans with iron have been studied, but many climate scientists oppose undertaking geoengineering until we have a much better understanding of possible side effects.

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