Global Dimming: The Climate’s Catch-22?

Climate change should be thought of as an umbrella term that includes a host of different issues and phenomena. One such, somewhat lesser-known, phenomenon is that of ‘Global Dimming’. Never heard of it? Well, allow me to briefly introduce the Catch-22 of the climate crisis.

First observed by scientists in the 1950s and backed up by a continuing trend from then on to the 1990s, Global Dimming is a phenomenon in which a reduced amount of direct solar irradiation reaches the Earth’s surface. Almost contradictory to standard views on climate change, this event leads to a slight cooling effect. The cause of this has been attributed to the rapid increase of aerosol particles in the atmosphere within the same time frame. These particles reflect the sun’s rays, in turn dimming certain regions of the world. Alongside cooling, there are a whole range of different ecological events - decreases in precipitation and disruption to hydrological cycles - that are a result of, or at least worsened by, dimming. A major, and devastating, example was that of the Sahel drought in the 1960s. While the area has long experienced periods of historical drought, the case of the 60s was particularly severe and has been partially attributed to a drastic increase in atmospheric aerosol particles.

The regions that have been most affected appear to have changed over time. Originally, the skies over North America and Europe were recorded as having the highest concentration of particles, and therefore most acute dimming effects, but nowadays, due to changed practices and legislation - the US’ Clean Air Act, for instance - the effect in these regions has lessened. Taking their place are the skies over developing countries such as India and China, where rapid industrialisation has occurred in the last few decades. Moreover, there is a significant and consistent North-South divide, with the global North having a noticeably larger impact on the output of these aerosols than the South. Either way, the problem is still ongoing and doesn’t look set to leave anytime soon.

So, what’s the catch? Well, it is believed that the dimming effects have helped to mitigate the overall impact of global warming. In other words, the reversal of dimming could lead to the acceleration of rising temperatures. In fact, such a reversal has been noted in the regions where the phenomenon was originally observed. As mentioned, various policies aimed at tackling the production and output of aerosol particles across Europe and North America have been successful enough that reversals in the atmosphere above have been noted. With data already pointing to a steadily warming world, the reduction of pollutants in the air (instinctively and exclusively a good thing, one might think) may serve to reaffirm and even propel temperature trends.

Reading this, you may, like I did when I first learned of this nasty little dilemma, feel some existential dread, anguish, and a little bit hopeless. The topic is gloomy. However, it is necessary that awareness of this issue is raised - that is one of the purposes of this blog post: to convey just how damaging, and how big of an impact, global industrial practices can be, and how urgently they need to be changed. Yes, it is depressing, and yes it seems like we may never get ourselves out of this mess. But we can overcome it.

Another purpose of this blog post was to highlight that this supposedly lose-lose situation has a silver lining: scientists, activists, and governments were able to come together and enact policy that had a direct, tangible impact on the climate crisis. Through a combination of ingenuity and collective action, air pollutants were minimised over certain regions. If that same energy were to be applied to the climate crisis as a whole, then we could, as a species, avoid catastrophe.


Fergus Hallwood