Is it too late to reverse climate change?

Is it too late to undo climate damage? I'll check what the latest science says about reversing warming.

No, it is not too late to limit climate change, but it is too late to fully reverse it back to pre-industrial conditions on a human timescale - action now determines how much worse it gets.

Some change is already locked in and irreversible

•NASA says: "Humans have caused major climate changes to happen already, and we have set in motion more changes still."

•However, if we stopped emitting greenhouse gases today, "the rise in global temperatures would begin to flatten within a few years. Temperatures would then plateau but remain well-elevated for many, many centuries."

•"While the effects of human activities on Earth's climate to date are irreversible on the timescale of humans alive today, every little bit of avoided future temperature increases results in less warming that would otherwise persist for essentially forever."

The Intergovernmental Panel on Climate Change (IPCC) makes the same distinction:

> “A large fraction of climate change is largely irreversible on human time scales,” the most recent assessment report from the Intergovernmental Panel on Climate Change (IPCC) warned. Only if human emissions were “strongly negative over a sustained period”—for example, if tree planting and other activities were to sequester far more carbon than humans release—would climate change begin to be reversed.

Other studies note the same inertia:

> even if human emissions of CO2 were cut to zero today, there is an inertia in the climate system that would continue for hundreds to thousands of years as the system attempts to re-equilibrate.

For that reason the short answer from NASA experts is:

> The short answer is that 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.

Why "not too late" still matters

NASA says: "But it may not be too late to avoid or limit some of the worst effects of climate change."

Responding will involve a two-tier approach:

•“Mitigation” – reducing the flow of greenhouse gases into the atmosphere

•“Adaptation” – learning to live with, and adapt to, the climate change that has already been set in motion.

A tipping point is defined as the point at which "small changes become significant enough to cause a larger, more critical change that can be abrupt, irreversible, and lead to cascading effects." Recent IPCC assessments suggest tipping points could be reached at much lower warming than previously thought - around 1.5°C rather than 5°C.

Can we come back down if we overshoot 1.5°C?

Scientists now talk about "overshoot" - temporarily exceeding 1.5°C and then bringing temperatures back down with net-negative emissions.

•"Studies indicate that if we limit peak warming to well below two degrees C, there will still be some hope of bringing the temperature down in the future by removing far more carbon from the atmosphere than we emit, an approach called net-negative emissions. Simply achieving net-zero emissions—a major goal of many industrial countries—is no longer sufficient to limit warming to 1.5 degrees C."

•Even with a return to 1.5°C: "even if we reduce warming to 1.5 degrees C sometime before century’s end, some losses will be irreversible. Ecosystems will be transformed, species will vanish and vulnerable communities will bear lasting scars."

In general:

> Some climate-related damage to humans and ecosystems will be irreversible, and some could be partially reversed with significant delay.

Examples often given as irreversible on human timescales: sea-level rise from melted ice sheets, loss of polar ice, species extinction and ocean acidification. Reversible on shorter timescales with cooling: heat waves, mortality from heat, storms, droughts and flooding.

What would reversal require?

The IPCC and other assessments say limiting warming to 1.5°C without overshoot would require "unprecedented transitions in all aspects of society" and rapid, deep and immediate emissions cuts - not delay. To actually reverse warming after an overshoot would require not just reaching net-zero, but sustaining net-negative CO2 for decades: removing more CO2 than we emit through massive deployment of carbon dioxide removal, forest restoration, and technological capture, while also cutting other greenhouse gases like methane.

Without major action, NASA notes, global temperature is on track to rise by 2.5°C to 4.5°C by 2100, a level that greatly increases the risk of crossing tipping points where the cost and difficulty of reversal rises sharply.

In summary:

•Too late to prevent any climate change: No - warming already observed cannot be undone quickly.

•Too late to prevent catastrophic, runaway climate change: No - every 0.1°C avoided reduces risks, and every year of earlier action makes adaptation more effective and less costly.

•Reversal is possible only in the sense of slowly drawing temperatures back down after peak warming, at great cost and time, and with some damages never recovered.

Citations (3)

1nasa.govGovernment
Is it too late to prevent climate change? - NASA Science
Backs: “No, it is not too late to limit climate change, but it is too late to fully reverse it back to pre-industrial conditions on a human timescale - action now determines how much worse it gets. Some change is already locked in and irreversible. NASA says: "Humans have caused major climate changes to happen already, and we…”
2nasa.govGovernment
NASA Jet Propulsion Laboratory Blog | Ask the Expert - Is It too Late to Reduce Climate Change?
Backs: “Only if human emissions were “strongly negative over a sustained period”—for example, if tree planting and other activities were to sequester far more carbon than humans release—would climate change begin to be reversed. Other studies note the same inertia: even if human emissions of CO2 were cut to zero today, there…”
3scientificamerican.comNews and mediaquality 0.86
Why the Climate Warming Goal of 1.5 Degrees C Isn’t a Lost Cause—Even If We Overshoot It | Scientific American
Backs: “"Studies indicate that if we limit peak warming to well below two degrees C, there will still be some hope of bringing the temperature down in the future by removing far more carbon from the atmosphere than we emit, an approach called net-negative emissions. Simply achieving net-zero emissions—a major goal of many…”