Is it too late to reverse climate change?

Leans no

Is it too late to reverse climate change? I'll gather the latest science on what's reversible and what's locked in.

No, it is not too late - but it is also not possible to fully reverse to the pre-industrial climate on human timescales. Scientists distinguish between limiting further warming and truly reversing past warming.

What science says: Not too late to limit worst impacts

> 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

•It will never be too late to take action for the climate - the reverse is also true: every bit of warming we avoid will reduce the extremes of climate fluctuation.

•The IPCC states that urgent and immediate action is needed to avoid the worst impacts. Reducing greenhouse gas emissions can help flatten the rise in global temperatures and prevent further irreversible damage.

•While the window for action is narrowing, it is not too late to mitigate the worst effects.

The scientific community emphasizes that every fraction of a degree of warming avoided matters, and that the benefits of reduced greenhouse gas emissions occur on the same timescale as the political decisions that lead to those reductions.

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

Why full reversal is not possible quickly

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

> 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

Specific irreversible changes include:

•Many of the changes due to past and future greenhouse gas emissions are irreversible for centuries to millennia, especially changes in the ocean, ice sheets, and global sea level

•The impact of climate change will endure for centuries even if emissions were to be stopped now

•The climate change that takes place due to increases in carbon dioxide concentration is largely irreversible for 1,000 years after emissions stop

•Higher temperatures and accompanying changes in climate caused by carbon dioxide emissions will be largely irreversible on human time scales

This includes tipping points and sea-level rise:

•Global sea-level rise is irreversible for centuries, very high confidence

•Potential climate tipping points where rising global temperatures could cause irreversible change include irreversible ice sheet melting

•Greenland ice sheet collapse risks irreversible meltdown at 1.5°C, committing the world to several meters of sea-level rise over centuries

What would happen if we stopped emissions today?

•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. There is a time lag between what we do and when we feel it, but that lag is less than a decade

•Global average temperature is projected to remain approximately constant for many centuries following a complete cessation of emissions. They explain that this is true for all cases except for one in which our net emissions are ‘negative’ for a long period of time. This means we would have to actively remove CO2 from the atmosphere, not just bring emissions to zero.

Without major action, global temperature is on track to rise by 2.5°C to 4.5°C by 2100, according to the latest estimates.

Can we cool the planet back down?

Research suggests that global warming is likely to stop, more or less, once net-zero is achieved globally.

To go beyond stopping warming and actually reverse warming requires net-negative emissions - actively removing CO2:

•In the long term, CDR [carbon dioxide removal] can “help achieve net-negative emissions”, a state where CO2 removal exceeds emissions

•Carbon removal (CDR) could return global average temperatures toward pre-industrial levels after achieving net zero, but would not restore the climate system to pre-industrial conditions

Current IPCC pathways require:

•"Rapid, deep and immediate" cuts to global carbon dioxide emissions, which need to begin declining by 2025 and halve by 2030, must be made immediately... if temperature changes are to remain at or below...1.5 degrees Celsius

•Limiting warming to 2°C requires reaching net-zero carbon dioxide emissions globally by the early 2070s. For 1.5°C, that deadline was the early 2050s

Bottom line

You cannot turn the clock back to 1850 without centuries of sustained carbon removal, and some consequences like ocean heat, acidification, and sea-level rise will continue for centuries to millennia even if we succeed.

But it is absolutely not too late to:

1.Stop making it worse - warming stops when net emissions stop.

2.Avoid every fraction of a degree - which greatly reduces extreme weather, ice loss, and ecosystem damage.

3.Slowly draw down temperatures later this century with carbon removal if we also cut emissions deeply now.

As NASA summarizes: it may not be too late to avoid or limit some of the worst effects of climate change — but that depends on what emissions will be in the years to come.

Citations (2)

1nasa.govGovernment
Ask the Expert - Is It too Late to Reduce Climate Change?
Backs: “Scientists distinguish between limiting further warming and truly reversing past warming. What science says: Not too late to limit worst impacts. 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…”
attribution, article, points to no. Claim: Quoted expert answer that it's not too late to act, though past actions have locked in some outcomes and action is needed to avoid greater future impacts.
2nasa.govGovernment
Is it too late to prevent climate change?
Backs: “While the window for action is narrowing, it is not too late to mitigate the worst effects. The scientific community emphasizes that every fraction of a degree of warming avoided matters, and that the benefits of reduced greenhouse gas emissions occur on the same timescale as the political decisions that lead to those…”
evidence, article, points to no. Claim: Every fraction of a degree avoided matters; it is not too late to mitigate the worst effects of climate change, depending on future emissions.