Is it too late to reverse climate change?

It's not too late to make a difference — but time is tight. I'll pull the latest science on what can still be reversed and what can't.

No, it is not too late to act on climate change - but it is too late to prevent all effects, and reversing it completely will take centuries.

Scientists describe it as a dangerous myth that it is too late to save the climate, and that the idea it is too late to halt the climate crisis is not true.

The more accurate short answer from science is:

> it's not too late to act, but our past actions may have already locked in certain outcomes and action is needed to avoid more substantial impacts in the future

Here is what that means:

1. Some climate change is already irreversible

The Intergovernmental Panel on Climate Change (IPCC) finds many changes from past and future emissions are not going to be reversed for centuries to millennia, especially when it comes to changes in the ocean, ice sheets and global sea level.

Specifically:
> If global net negative CO2 emissions were to be achieved and be sustained, the global CO2-induced surface temperature increase would be gradually reversed "but other climate changes would continue in their current direction for decades to millennia (high confidence)". According to IPCC, "it would take several centuries to millennia for global mean sea level to reverse course even under large net negative CO2 emissions (high confidence)".

This is because of climate tipping points - thresholds where a small change triggers self-reinforcing feedback loops that lock in irreversible shifts.

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 that keeps much of Europe warm.

In practical terms, humans have already caused major climate changes to happen, and we have set in motion more changes still, and global average temperatures have risen and weather extremes have already increased.

2. We can still slow, limit, and eventually reverse warming

> Yes. 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").

If all human emissions stopped today:
> Earth's temperature would continue to rise for a few decades as ocean currents bring excess heat stored in the deep ocean back to the surface. Once this excess heat radiated out to space, Earth's temperature would stabilize. With no further human influence, natural processes would begin to slowly remove the excess carbon dioxide from the atmosphere, and global temperatures would gradually begin to decline.

Experts think the additional warming from this "hidden" heat is unlikely to exceed 0.9°F (0.5°C).

> It's true that without dramatic action in the next couple of decades, we are unlikely to keep global warming in this century below 2.7° Fahrenheit (1.5° Celsius) compared to pre-industrial temperatures - a threshold that experts say offers a lower risk of serious negative impacts. But the more we overshoot that threshold, the more serious and widespread the negative impacts will be, which means that it is never "too late" to take action.

3. What "reversing" would actually require

A temporary overshoot of 1.5°C might be reversible by the end of the century, but it's a monumental challenge. It requires not just reaching net-zero emissions globally, but actively removing vast quantities of carbon dioxide already in the atmosphere.

To have a chance of limiting warming to 1.5°C, the IPCC says we must:

Transitioning to energy sources that do not emit greenhouse gases, such as solar, wind, biofuels, and nuclear, can slow the pace of climate change, though a major departure from business as usual in how the world uses and produces energy will be required.

Bottom line

In short: We cannot undo what has already happened overnight, but we can still determine how bad it gets.