Is climate change good

How bad is climate change?

It's a bulky concept, but one that couldn't be of greater importance to humanity: climate sensitivity. How much does the earth heat up when the amount of CO2 in the atmosphere rises from 280 parts per million (ppm), which was the amount before the industrial age, to 560? We are currently at 414 particles per million. A research team has now succeeded in determining more precisely how warm it will really be. The climate researcher Zeke Hausfather, Climate director of the think tank The Breakthrough Institute, was there and classifies the findings.

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DEFAULT: What did you learn?

Housefather: Two things. It is less likely than expected that climate change will be very mild. There's a very, very small chance the earth will warm less than two degrees if the CO2 in the atmosphere doubles. At the same time, our study shows that very high temperatures of over five degrees are less likely than expected. For over 40 years, the best scientific guess was: If we double the amount of CO2, there is probably an increase of 1.5 to 4.5 degrees. We narrowed it down to 2.3 to 3.9 degrees. But that's still rough, with a probability of 66 percent. There is still a ten percent chance that the sensitivity is above five degrees. But that is not the realistic scenario.

DEFAULT: That's enough risk for me. That would be an absolute disaster.

Housefather: That we can't rule that out is cause for concern, yes. But you don't necessarily need a high level of climate sensitivity for climate change to become a major problem. Because we can more than double the CO2 in the atmosphere - or less. What emissions we cause is much more important.

DEFAULT: 560 ppm would be a doubling. Where are we?

Housefather: We're about halfway, at 414 ppm. If emissions stay constant, we will be around 560 ppm by 2080. But in the end they rose again, then it goes faster.

DEFAULT: What amount do the Paris goals of 1.5 degrees expect?

Housefather: In order to keep the warming below two degrees, it is calculated at 430 ppm by 2100. But there they are higher in 2050, at 460 ppm. If the emissions go to zero between 2050 and 2070, the CO2 concentration will slowly decrease again because the oceans and surfaces absorb CO2. For the 1.5 degree target, the value by 2100 is 380 ppm. Right where it was in 2005. It's very, very difficult to achieve.

DEFAULT: Even the two degrees are very, very difficult to achieve, right?

Housefather: The two-degree scenario is simpler. There are two options for 1.5 degrees. Either all global emissions will go to zero in two decades, which is extremely difficult, especially when you think of developing countries. Or it will take three to four times the area of ‚Äč‚ÄčIndia by 2080 or 2090 for technologies that remove CO2 from the atmosphere. Which is not very likely either. For two degrees we have 40 years to get to net zero. From today's point of view, this is easier. We are currently on the way to three degrees. But getting the curve from three to two is easier than getting it to 1.5. Two degrees is difficult, but possible.

DEFAULT: After 40 years of research, why is it still not possible to narrow down how strongly the climate reacts to CO2?

Housefather: The earth is very complex, and unfortunately there are nowhere a few extraplanets on which we could conduct experiments. So we have to model the earth, and we don't understand everything yet. Simple physics tells us that if we keep everything else constant, twice as much CO2 will result in just over a degree of warming. But not everything else remains constant.

DEFAULT: What changes?

Housefather: The warmer it gets, the more water vapor there is in the atmosphere. It's a powerful greenhouse gas, but it doesn't stay in the atmosphere that long. Ice and snow melt, which previously reflected sunlight and thus cooled. The hardest part is understanding what happens to clouds and aerosols. Lower clouds reflect more radiation back into space. Higher clouds trap the rays in the atmosphere. We don't know exactly how the mix will change. That creates uncertainty. Small particles, such as sulfur, also play an important role in the formation of clouds. If we pollute the earth less, there will be fewer of these particles - and we still don't know exactly what kind of effect that will have.

DEFAULT: Some say climate change is an existential threat to humanity. You seem more and more optimistic. Why?

Housefather: If emissions keep rising, especially if we burn more coal, we will create risks for extremely catastrophic consequences that put human civilization as we know it at risk. But I believe that such a world is much less likely than it was a decade ago.


Housefather: Because some large countries have taken at least some measures. The use of coal, the most climate-damaging form of energy, has been falling since 2013. Clean energies have become very cheap. There is still a lot of work to be done to decarbonise the economy, but I expect emissions to remain pretty constant or only increase slightly. It's possible that this will change again if Trump is re-elected and he gives people money to burn coal, or if a cold war breaks out with China that slows technological progress. But I don't think we're on that path. I personally assume, regardless of our study, that we will have two to 4.5 degrees more by 2100. That is potentially catastrophic, especially around 4.5 degrees.


Housefather: But how catastrophic it becomes depends on the resilience of societies. In an unequal world where many do not have access to technology to adapt to the climate, there are more existential threats. In a world that is more prosperous and more equal, less. In 1970, 50,000 people died from the effects of cyclones in Bangladesh. A few hundred today. There are still too many, but much less. That's because there are early warning systems, alarms, evacuation plans - and so on. I see climate change more as a multiplier of existing existential risks than an existential risk in itself. Countries with weak institutions and high inequality could be pushed over the edge and lead to catastrophic conflicts.

DEFAULT: And the environment?

Housefather: The situation is very different for nature. They can adapt much less than humans in the short time. Even a three-degree world would be catastrophic for many ecosystems, for the Amazon rainforest, the Arctic, boreal forests, etc. We muddle into a world that is very dangerous for humans and nature, but probably not the end of the world. Still, there is the risk of total disaster if the world stops doing more to reduce emissions.

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