When people are asked what the biggest challenge of our time is, many people answer it’s climate change. I too, acknowledge that it’s one of the biggest challenges of our time. However, I don’t know if it’s the biggest one though. I don’t know, because I see climate change within in the context of the planetary boundaries. Climate change is just one of those boundaries, one out of nine. It’s important to see the context of the planetary boundaries. Today I’ll tell you about planetary boundary climate change.
The 9 Planetary Boundaries
If you want to know something about climate change, you first have to know what the plantary boundaries are. The planetary boundaries is a framework to show the safe operating space of humans on planet earth. It literally shows how far we as humans can go without disrupting the earth, on all fronts. The framework was created by Rockstöm et al. There are 9 planetary boundaries defined. So, on 9 different fronts we humans have a boundary as to what we can do or use. If we stay within the 9 planetary boundaries, we have a sustainable future for all humans and other living beings.
One of those boundaries is climate change. I included a picture below and as you can see, climate change is in the middle on the top, next to novel entities. It’s important to remember that this is one out of nine boundaries. Fixing climate change is a huge challenge taking decades because we need to transform our entire economy, don’t get me wrong. But if we fix climate change, meaning we bring it back to within the boundary (the dotted circle), we’re not entirely done yet. We still have 8 other boundaries to keep an eye on.

The Planetary Boundary Climate Change
The plantary boundary for climate change consists of two elements. The first one is set in parts per million. This means that the threshold says how many parts of CO2 can be in one million parts in the atmosphere. The boundary is set at 350 parts of CO2 per million parts in the atmosphere. Sounds difficult, but the number of 350 is all you need to know. We can measure what the actual ppm concentration is. In 2023, the concentration was 419 parts per millon. That’s why this boundary is crossed already.
The second part of the boundaries says that there can be no more than 1 watt per m2 of radiative forcing (caused by humans) at the top of the atmosphere. In 2023, we were are 2.9 watt per m2. I can’t explain this threshold in a simple language. The point is again that the threshold is 1, we can measure this and we’re very far over the safe boundary. Further than the ppm threshold.
Global planetary boundary
Why I think climate change gets the most attention from all boundaties, is because of the global thresholds and their scale. Rockström et al. distuingish the boundaries. For three, climate change, ocean acidification and stratospheric ozone, they say that they’re systemic processes on a global scale. Two of those boundaries, climate change and ocean acidification are also the only two boundaries that have only global scale thresholds. There cannot be any regional difference (like with freshwater use). We, as a global collective, have to face these boundaries together. That is why I think climate change is such a difficuly boundary.
Relationship with ocean acidification
The climate change boundary has a strong relationship with the ocean acidification boundary. That’s because they’re both affected by CO2. Both the atmosphere and the ocean take up CO2. The ocean takes up about 25%. The boundary of climate change is mostly about parts per million of CO2 in the atmosphere. Ocean acidification is a bit more indirect. The CO2 makes the pH-value of the sea go down. This then kills off sea life (mostly coral). This sea life normally secretes aragonite, but this number is declining (as the sea life is dying). That’s why the ocean acidification boundary is about aragonite saturation levels. If we manage to lower CO2-levels, we can do something about both the climate change boundary and the ocean acidification boundary. In my opinion, that’s good news.
Solution
This article will become way too long if I want to disect what we need to do bring the climate change ppm levels back to within the boundary, in practical terms. Books have been written about that. But theoretically, the mission is simple. We need to stop emitting CO2. CO2 is primarily released from burning fossil fuels (and biomass) and from forrest fires. Want to know how to do this on a personal level? You can read all about it on this blog.
Even if we stop emitting CO2 today, we’re not entirely there. Because we have already emitted too much, the boundary is already crossed. We also need to take out the overshoot op CO2 out of the atmosphere. Right now, there’s just one way to do this: by planting trees. So that’s the second part of the solution.
I hope you now understand what the planetary boundary climate change entails and how it relations to all environmental problems we face today. Want to know more about the other plantary boundaries? I have listed the ones I already wrote an article about in the category the 9 planetary boundaries on this blog.
Yours sincerely,
Romee
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