Climate-neutral is no longer enough - this is what the LMU chief climatologist says about the current climate situation

Created: 03/30/2022, 08:59

By: Matthew Schneider

A flooded federal highway near Erftstadt last summer.

Climate change is one reason for the floods.

© Marius Becker/dpa

The chief climatologist at the LMU coordinates the largest German research project on carbon capture.

This is how she sees the current climate situation.

Munich - The reports of the Intergovernmental Panel on Climate Change are becoming more threatening from year to year.

Storms, droughts, floods: Julia Pongratz is certain that global warming will have catastrophic effects.

She is the senior climatologist at the Ludwig-Maximilians-University in Munich and coordinates the largest German research project on carbon capture.

She says: "If we don't quickly remove CO2 from the atmosphere, we will miss our climate targets."

Climate change: "It also has to do with eating habits"

Ms. Pongratz, you coordinate the work of more than 100 scientists on carbon capture, CDR for short.

What does it mean?

CDR stands for "Carbon Dioxide Removal", i.e. a series of methods for removing CO2 from the atmosphere by absorbing the CO2 and storing it for as long as possible.

In Europe in particular we are putting a lot of work into the energy transition.

What do we need this for?

The shift towards CO2-free energy production is also the most important factor.

With the political measures planned so far, however, we will miss the Paris 1.5° target globally and end up closer to 2°.

If you take the measures that are already being implemented, we are currently getting around 3°.

The consequence would be that droughts or flood disasters like the one in the Ahr Valley in 2021 would become more frequent.

For the 1.5° target, however, we have to get to net zero, which means, on balance, not emitting any climate-active gases at all.

The problem is not only the slow pace of energy transformation, but also the hard-to-avoid emissions, such as those caused by agriculture or long-distance flights.

To compensate for them, we urgently need to start removing the CO2 from the atmosphere.

How can CO2 be bound?

The easiest way is via photosynthesis: Plants use the sun's energy to build solid biomass with the gaseous CO2 from the atmosphere.

So the carbon stays in the plant and oxygen goes back into the air.

The carbon remains stored until the plant is decomposed or burned.

So the cheapest way is to grow a forest.

In Central Europe, around 70 tons of carbon per hectare are bound in the biomass, and sometimes even more in the soil.

At the same time, however, it is important to protect existing storage.

And which ones are they?

This includes the Amazon rainforest, which not only binds around 150 tons of carbon per hectare in its biomass, but is also home to enormous biodiversity and controls the global weather.

Or take mangrove forests that live in the salt water close to the coast: They not only store a lot of CO2 – per square meter even more than rainforests, but also mitigate storm surges.

And if the wood is felled from the forest and used for a long time - for example in houses or furniture - and at the same time also replaces materials such as cement or steel, the production of which emits a lot of CO2, you achieve a double effect.

In general, we are always on the lookout for multiple uses: a forest is important for biodiversity or for local recreation.

From this point of view, many cost issues are put into perspective.

Because of the growing world population, we need more and more arable land - that's a conflict.

Yes, but that also has to do with eating habits.

If people eat a lot of meat, we need more space because we would have to use a lot more feed for one kilo of meat.

Food waste could also be significantly reduced.

Nevertheless, we have shown that forest cover could be expanded globally by about eight million square kilometers without interfering with agriculture.

That would lower the global mean temperature by about 0.3°.

“You would have to crush the Matterhorn about twice a year”

What are the possibilities?

It is researched how to accelerate the natural weathering of rock.

During this process, which naturally takes place on a time scale of hundreds of thousands of years, the atmospheric carbon reacts with young rock and is bound there over the long term.

The process can be shortened to decades by rasping the rock very finely.

Of course, you need the appropriate infrastructure and logistics.

In order to fully compensate for global emissions, the Matterhorn would have to be crushed about twice a year.

Some researchers want to sink the CO2 into the sea.

If the CO2 were introduced into the deep ocean by ship or pipeline, it would be shielded from the atmosphere for decades or even centuries.

But there are two problems: On the one hand, dead zones would arise around the injection site and we cannot currently predict how such CO2 input will affect marine life.

Also, nowhere is the ocean completely calm, meaning the CO2 would eventually come back up.

However, research is also being carried out into whether the ocean chemistry can be changed in such a way that the ocean absorbs more CO2, or whether the growth of algae can be stimulated using iron as a fertiliser.

The hope for the latter is that the algae will store CO2 as they grow and sink to the depths after they die, where they will no longer be decomposed.

So far, however, the algae are often decomposed,

before they can be deposited in the ocean sediment.

In certain places in the sea, however, it could work.

Are there also technical possibilities?

The most immediate form is probably direct air capture.

The CO2 should be caught directly from chimneys or the atmosphere.

It reacts chemically with certain substances and is bound.

If you heat the mixture, it will be released again.

You can then pump the CO2 into gas cylinders, pipelines or geological reservoirs, for example.

Oil exploration companies do this in part because the higher pressure makes the oil rise better.

However, capture has so far been very expensive: it is currently assumed that it is typically several hundred euros per tonne of CO2.

“We need a mix of CDR measures”

Critics doubt the safety of these cave storages.

Of course, it can always happen that a geological reservoir is not completely sealed or opens up due to some influence.

Then the CO2 is released back into the atmosphere.

Therefore, the carbon in solid form - such as timber or in weathered rock - is stored with less risk.

In the form of building materials, it can also be used economically, which increases acceptance.

But trees grow relatively slowly, you said hurry up.

The decisive factor is the growth per year, and young forests in particular are very productive.

What worries me more is the question of how well forests will thrive in the future in the face of increasing droughts and extreme heat.

It should not be forgotten, however, that forests are relevant to the climate far beyond the issue of carbon storage and can cool local temperatures by several degrees, mitigate heat waves or contribute to the formation of precipitation.

However, we should not rely solely on one measure.

We need a mix of CDR measures, because some methods are now available on a large scale, others only later, because we have to spread the risk that individual methods will not bring the hoped-for potential, because the natural conditions and social acceptance are very are different.

What else is there?

In land use, in addition to forests and their use, biomass plantations are also used as CDR measures. These are fast-growing grasses such as elephant grass or short-rotation plantations whose biomass can then be used to generate heat and energy, with the CO2 being separated.

However, biomass can also be converted into long-lived biochar, for example by carbonizing the material.

We know from the slash-and-burn economy in the Amazon rainforest that the charcoal can remain in the ground for at least 500 years without decomposing.

It is also obviously useful for agriculture because it improves water and nutrient levels in the soil.

So here again we see an example that CDR measures should be evaluated beyond their ability to store CO2,

Interview: Matthew Schneider