“SRM” – the dangerous beacon of hope in the fight against the climate crisis

These words come from the Executive Director of the United Nations Environment Program (UNEP), Inge Anders. They appear in the introduction to a report on a speculative, potentially climate-saving technology: Solar Radiation Modification (SRM). The method, in which solar radiation is adjusted, has been a source of hope for years in the fight against global warming.

But it is not that simple, Anders clarifies in the foreword to the report published on Monday. The research is still too immature to be used. At the same time, time is of the essence: climate change has repeatedly shown its destructive power in recent years.

To put a stop to this, a groundbreaking climate agreement was signed in Paris in 2015. This kept global warming “well below” 2 degrees Celsius and ideally below 1.5 degrees compared to pre-industrial levels.

Even though the agreement was considered groundbreaking, there are huge problems in its implementation. The world still seems to slide unhindered into global warming. Some scientists already have doubts about the feasibility of the goal. In an open letter published yesterday, they write:

The 70 scientists who signed the letter therefore, like UNEP, propose to stimulate research into Solar Radiation Modification (SRM).

SRM is what is known as geoengineering. This describes the measures that aim to slow down global warming. To do this, they specifically intervene in certain cycles that affect global climate. In the case of SRM, this is solar radiation.

The world’s climate is determined by how much solar radiation is absorbed by the Earth and how much is reflected back into space. A reduction in solar radiation – and thus the temperature on Earth – can be achieved in various ways. For example, by brightening up clouds, by placing mirrors or umbrellas in space or by releasing aerosols into the stratosphere. In all these methods, the solar radiation would have to be reflected more into space and thus deflected away from the Earth.

Success seems guaranteed, especially when introducing aerosols into the stratosphere. The eruption of the Pinatubo volcano in the Philippines in 1991 proved this. The sulfur particles thrown into the stratosphere by the eruption reflected the sunlight so strongly that the global average temperature dropped by 0.5 degrees. It took three years for the average temperature to return to its previous level.

The researchers behind the open letter cite air pollution as another example of reflective particles. Explain:

That air pollution contributes to climate cooling is doubly bad. Although it is harmful to our health, it only slows down global warming. Because the air will become cleaner in the future with increasingly stricter rules for reducing exhaust gases and emissions. The letter goes on to say that this will quickly reveal a significant but highly uncertain portion of global warming over the coming decades.

If global warming spirals out of control in the future, emergency measures must be in place, UNEP experts and those behind the open letter agree.

This is where the SRM comes into play again. Both groups know that intensive research is already being done into SRM methods. They also know that an SRM implementation can have an impact within a year. According to UNEP, climate modeling results indicated that SRM could reduce various risks of climate change in most regions. This – compared to climate damage – at low cost: for 20 billion euros per year, the world temperature can be reduced by 1 degree Celsius.

UNEP sees a danger in this: for many countries and organizations these costs are within the realm of possibility, which could lead to uncontrolled experiments and implementations. UNEP therefore advocates regulated international cooperation.

At this point, however, the following problem arises, as UNEP writes:

The positive effects of SRM can be calculated to a certain extent, but the uncertainties are not yet. SRM should only be used as a temporary, supportive measure. It is not a solution to climate change. Because they have no influence on the emission of harmful substances. If these emissions are not reduced, it could become dangerous. The UNEP explains:

In this way, effects that cannot be compensated by SRM can be amplified. A sudden stop of a major SRM operation – for example due to a technical error – can have disastrous consequences. In one fell swoop, the Earth would once again be exposed to all the damaging factors that the SRM previously tried to mitigate. For example, the temperature would rise again within a very short time, which would be a shock to the entire environment.

While the possibilities of SRM sound promising, UNEP’s Inger Anders remains cautious:

The scientists behind the open letter share the same view. They advocate research into SRM. However, only under clear conditions:

The researchers are sure: the most sustainable solution in the fight against global warming is still to reduce emissions of harmful substances.