Is it too late to reverse climate change?

Is it too late to turn climate change around? I'll check the latest science on what's reversible and what's still within our power to change.

No — it is not too late to limit the worst impacts, but climate change cannot be fully "reversed" quickly to the way it was before industrialization. Scientists describe the situation as irreversible but not unstoppable.

What is already locked in

> 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.

NASA experts summarize it as:

> 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.

Reasons for the lag:

The Intergovernmental Panel on Climate Change (IPCC) warns:

> A large fraction of climate change is largely irreversible on human time scales

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.

What is still possible to prevent or reduce

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

NASA describes 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.

Yes — we can slow the rate and limit the amount of warming by reducing emissions of heat-trapping gases

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

It is true that without dramatic action in the next couple of decades, we are unlikely to keep warming below 1.5°C compared to pre-industrial — a threshold that offers 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.

Can we overshoot and come back down?

It is technically possible to surpass a climate target and bring global temperatures back down later, and the IPCC message is often summarized as:

> It’s not too late if we take climate action now

However:

> Every little bit of warming exposes the planet to worse climate impacts—and some of these effects can’t be undone by lowering temperatures after the fact. Some climate effects are irreversible.

Studies indicate:

> The warning is stark: 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. Nevertheless, ensuring that the overshoot of 1.5 degrees C is only temporary would curtail the damage and offer some chance of recovery.

> Simply achieving net-zero emissions—a major goal of many industrial countries—is no longer sufficient to limit warming to 1.5 degrees C.

We would need net-negative emissions — removing far more carbon than we emit — to bring temperatures down.

Irreversible risks that grow with delay

> The likelihood of crossing irreversible tipping points increases with the magnitude and duration of higher temperatures. These include the destabilisation of major ice sheets, degradation of the Amazon rainforest, and disruption of the Atlantic Meridional Overturning Circulation

Research has shown we are already approaching tipping points at 1.5 degrees warming, including coral reef die-offs, permafrost thawing, and ice sheet collapses that could lead to irreversible changes. Some changes — sea-level rise, loss of polar ice, species extinction — are considered irreversible, while others like heat waves and storms may be reduced if warming is reversed, but with significant delay.

Bottom line:

In the words of NASA: the benefits of reduced emissions occur on the same timescale as the political decisions that lead to those reductions — meaning action now still matters immediately.