Is it too late to reverse climate change?

Is reversal still possible? I'll pull the latest climate science on what's reversible and what's not.

No — it is not too late to limit the worst of climate change — but it is too late to completely and quickly reverse it to pre-industrial conditions.

Scientists describe it as two different problems:

1. Some warming and impacts are already locked in and effectively irreversible on human timescales

> 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

That irreversibility is confirmed by multiple assessments:

•According to the Intergovernmental Panel on Climate Change — modern humans have never before seen the observed changes in our global climate, and some of these changes are irreversible over the next hundreds to thousands of years

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

•Somewhere between 15–40% of the carbon dioxide that humanity emits will remain in the atmosphere for up to a thousand years, with roughly 10– 25% of it persisting for tens of thousands of years

•Even if by some miracle the nations of the world could bring carbon dioxide levels back to those of the pre-industrial era, it would still take 1,000 years or longer for the climate changes already triggered to be reversed

•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

NASA summarizes the current trajectory:

> Without major action to reduce emissions, global temperature is on track to rise by 2.5°C to 4.5°C (4.5°F to 8°F) by 2100, according to the latest estimates

Key systems risk abrupt, irreversible changes if thresholds are crossed. Scientists have identified tipping points including:

•the melting of the ice sheets in West Antarctica and Greenland; the rapid thawing of large swaths of Arctic permafrost; the slowing of the North Atlantic subpolar gyre; and tropical coral reef die-off

•In the context of climate science, a tipping point refers to a critical threshold... which, if exceeded, can cause sudden, dramatic, and often irreversible changes to the earth’s systems

Once crossed, these changes can severely affect ecosystems and are difficult to reverse or are even irreversible due to an intensifying feedback loop

2. It is NOT too late to avoid the worst and partially reverse warming

The scientific consensus 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

> Science cannot erase the warming that has already happened, but evidence shows it can still slow future climate change and reduce many of the worst projected impacts through rapid, sustained cuts in greenhouse gas emissions

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

Why action still matters enormously:

•The IPCC confirms that there is no “tipping point” for the planet as a whole. ... every bit of warming we avoid will reduce the extremes of climate fluctuation. ... It will never be too late to take action for the climate

•While it is too late to reverse some of the negative impacts, the report also found that “strong and sustained” reductions of greenhouse gases could lead to temperature stabilization in 20-30 years

This is why scientists emphasize mitigation and adaptation together:

> But it may not be too late to avoid or limit some of the worst effects of climate change. Responding to climate change 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

Can we actively reverse climate change with technology?

Partial reversal is theoretically possible through aggressive emission reductions combined with massive carbon dioxide removal efforts, such as Direct Air Capture, restoring forests, and ocean alkalinity enhancement.

But there are limits:

> Our results suggest that while negative emissions, at the scale of deployment considered here, allow to restore global mean surface air temperature to a lower level, they are ineffective at reversing responses in climate system components with long response timescales such as thermosteric sea level rise

In other words, we could eventually bring global average temperature down again if we go net-negative (remove more CO2 than we emit), but sea-level rise, ocean heating, and ice-sheet loss would continue for centuries even after that.

Bottom line

•Too late to prevent any climate change? Yes. We are already living with it.

•Too late to reverse it completely in our lifetimes without immense effort? Yes — full reversal would take centuries to millennia.

•Too late to make a difference? No. Every fraction of a degree matters. Every ton of CO2 we don't emit prevents warming that would otherwise last essentially forever, and rapid cuts now can stabilize temperatures within decades and avoid triggering the most dangerous, irreversible tipping points.

Citations (3)

1nasa.govGovernment
Is it too late to prevent climate change? - NASA Science
Backs: “However, if we stopped emitting greenhouse gases today, the rise in global temperatures would begin to flatten within a few years.”
2nasa.govGovernment
Effects - NASA Science
Backs: “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. That irreversibility is confirmed by multiple assessments:…”
3nasa.govGovernment
NASA Jet Propulsion Laboratory Blog | Ask the Expert - Is It too Late to Reduce Climate Change?
Backs: “Even if by some miracle the nations of the world could bring carbon dioxide levels back to those of the pre-industrial era, it would still take 1,000 years or longer for the climate changes already triggered to be reversed. Even if human emissions of CO2 were cut to zero today, there is an inertia in the climate…”