Unravelling the Enigma of Aerosol Masking: The Climate Effect We Need to Talk About

Amid a tumultuous summer marked by devastating floods in Libya and Greece, and the tragic loss of tens of thousands of lives, it’s chilling to observe that major news outlets have largely overlooked the profound climate implications tied to these disasters.

Journalists reporting on them often merely include a benign mention of climate change at the end of the article, as in this recent example from the BBC: ‘Climate change has increased the intensity and frequency of tropical storms, leading to an increase in flash flooding and greater damage.’

A single sentence after a record-breaking rainstorm hit Hong Kong and after weeks of similar climate-related disasters striking countries all around the world. No mention of the failure of our leaders to agree on phasing out fossil fuels at G20. No mention of the hundreds of thousands of lives lost to increased temperatures. The BBC offers a passing, copy and paste comment on the front and centre crisis facing humanity.

Let’s dive deeper than this banality and shed light on a complex subject that potentially lies behind the increase in ocean temperatures and subsequent storms: the reduction of cooling aerosols found in greenhouse gases.

Around the globe, we’ve witnessed a barrage of extreme weather events, with one particularly underreported yet pivotal occurrence being the recent marine heatwave. The North Atlantic waters have surged to record-breaking temperatures, surpassing previous records by more than a degree. To put it into perspective, in July the waters around Florida reached temperatures akin to a warm bath. This scorching heat is taking a toll on our coastlines, suffocating thousands of fish as oxygen levels plummet in warmer waters. 

As our planet warms, the oceans are absorbing an escalating amount of atmospheric heat. This has, in part, contributed to maintaining the Earth’s overall temperature equilibrium despite soaring greenhouse gas levels. However, the oceans are now warming at an alarming rate.

Source: Leon Simons

One significant factor behind this is the recent reduction of atmospheric particles known as aerosols. Aerosols are small particles in the air that can either cool or warm the climate, depending on the type and colour of the particle. Examples of aerosols can be natural like dust and volcanic ash or created through air pollution like sulphates. Sulphates actually cool the planet at high altitudes by reflecting sunlight like a layer of dirty insulation. This phenomenon is known as the “masking effect“.

So, and hold on to something for this, emissions are both warming the atmosphere through greenhouse gases and cooling it through air pollution at the same time. This complex interplay has been a known challenge for some time, yet scientists and the media have been reticent to broach the topic. Nevertheless, it’s imperative to address it, as it has important implications for our efforts to decarbonize society.

So, just how significant is this? According to the latest IPCC report, aerosols have cooled the planet by an estimated range of 0 to 0.8 degrees Celsius, with 0.4C being the most likely. While this range may seem broad and uncertain, it’s a critical concern. Adding 0.8 degrees Celsius to our existing 1.2-degree world would already propel us beyond the 2-degree limit, ushering in an era of intensified extreme weather, mass casualties, and millions of displaced individuals seeking refuge from uninhabitable lands.

Consider the map below, illustrating the impact of global heating on the likelihood of deadly combinations of temperature and humidity conditions. It’s a gut-wrenching prospect, with millions potentially at risk of death in just a matter of hours. Such temperatures would need mass migrations to cooler climates that could also pose a huge threat to societal stability.

Source: IPCC 2023 Report

While aerosols from greenhouse gases cooling the planet at high altitudes is understandably confusing, their terrible health impacts at low altitudes are obvious. They pollute our air and so surround us with health hazards. An estimated 8 million annual deaths are attributed to air pollution. This staggering toll is larger than the scale of the Holocaust. It’s happening every year and it’s largely due to the combustion of fossil fuels. 

Never could we see the effects of aerosols more clearly than in the COVID-19 pandemic. As we suddenly reduced aerosol pollution from fossil-fueled activity, the cleaner, clearer air warmed the atmosphere by around 0.2° C. But at the same time, this reduction in air pollution was estimated to have saved 77,000 lives in China alone. What’s more, people could enjoy clear horizons and views for the first time in years.

Aerosols also contribute to the formation of acid rain as water particles coalesce around these airborne pollutants. This is a phenomenon often associated with sulphur aerosols prevalent in shipping fuel. In 2020, the International Maritime Organization enacted stricter limits on sulphur emissions, resulting in a significant reduction of these polluting aerosols from shipping.

This is a necessary move away from polluting fossil fuels and acid rain. It is also revealing what many scientists were worried about – that sulphate aerosol reduction has contributed to this summer’s record high ocean temperatures. We’ve removed the thick sulphate clouds to reveal just how fragile our world is to global warming’s effects.

Addressing the conundrum of aerosol masking presents a formidable challenge. We must sound the alarm to the potential warming already locked into our planet’s atmosphere and break out of false security silos. We have been inadvertently shielded from increased warming by an unlikely source. Now, we must act according to the risk they pose by rapidly reducing fossil fuels, selectively reducing the worst black carbon emissions and drawing down existing carbon with nature-based solutions.

While there is no easy solution, the first crucial step is to acknowledge and expand discussions surrounding this issue beyond the confines of niche climate science circles. Chat about it in the pub and with your family. Push your newspaper to write about it. It’s a huge risk and it deserves some airtime.

Only with a deepened, visceral knowledge of the threats we face, can we be better equipped to confront the complex dilemmas of our age.