Is it too late to reverse climate change?

Is it too late to reverse climate change? I'll gather the latest science on what's still reversible and what isn't.

No, it is not too late - but we cannot fully "reverse" climate change to a pre-industrial climate in our lifetimes. Scientists distinguish between what is already irreversible and what can still be avoided.

1. What is already irreversible on human timescales

Human activities have already caused significant and irreversible changes for people alive today.

> The effects of climate change are already being felt, and some are irreversible on the timescale of humans alive today

According to NASA, if we stopped emitting greenhouse gases today, the rise in global temperatures would begin to flatten within a few years, but temperatures would remain elevated for centuries. This means that effects such as the loss of sea ice, melting glaciers and ice sheets, sea-level rise, and more intense heat waves, will continue to be felt by those alive today and future generations.

Even with zero emissions 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.

Sea level is a clear example:

Other irreversible changes include so-called tipping points in the climate system. Climate scientists agree that an important property of Earth's climate is the existence of tipping points in which climate subsystems switch from one state to another, often in ways that cannot easily be reversed. Real-world examples include coral reef collapse, Amazon dieback, and Greenland and West Antarctic ice sheet collapse.

The reports emphasize: some damaging Earth system tipping points are already being crossed... It's important to note that negative climate tipping points cannot be reversed.

2. What can still be changed - Why it is NOT too late

The short answer from NASA experts 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.

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

The key principle is: Every tenth of a degree matters.

> Every tenth of a degree of warming matters, but the report highlights that if we act now, it is not too late to keep temperatures close to 1.5°C (on the condition that we get to net-zero by 2050)

And:

> "There is no such thing as too late when it comes to climate change. ... Every tenth of a degree matters,"

This is because with every additional increment of global warming, changes in extremes continue to become larger. More emissions will lead to more climate extremes and widespread damaging effects. Every avoided increase in temperature results in less warming, which is a benefit that will persist for a long time.

3. Can we actually REVERSE warming?

To truly reverse warming and bring temperatures back down, not just stabilize them, would require:

Scientific models show that if warming overshoots 1.5°C and is then swiftly reversed, tipping risks can be minimized, but higher temperatures even if eventually reversed will still lead to higher sea level rises in the following decades and centuries. The worst-case overshoot could trigger tipping points such as the collapse of the West Antarctic ice sheet which will be impossible to reverse for many millennia.

Bottom line

You cannot turn the clock back to the climate of 1950 in a few years. Some damage, especially sea-level rise and ice sheet loss, is locked in for centuries.

But you can stop making it worse, and you can eventually bring temperatures back down if the world reaches net-zero and then removes carbon. That is why scientists say it is now or never to limit warming, and that rapid, deep cuts that halve emissions by 2030 are needed- not because it's too late after that, but because every year of delay locks in more irreversible impacts and makes the remaining path much harder and more expensive.