The SO2 Decline and Global Warming
For decades, atmospheric scientists have attributed the rapid increase in global temperatures, particularly since the 1970s, primarily to human-caused increases in greenhouse gases, most notably carbon dioxide (CO2). However, a compelling alternative explanation has emerged: the significant drop in human-produced sulfur dioxide (SO2) emissions, especially since around 1980, might be responsible for much, if not all, of the observed global warming during this period.
Human activities, particularly the burning of fossil fuels like coal, release vast amounts of SO2 into the atmosphere. This gas contributes to what's known as "global dimming" – tiny sulfur particles (aerosols) reflect sunlight back into space, having a cooling effect on the Earth's surface. Since the 1980s, international efforts and regulations, along with shifts in energy production, have led to a substantial decrease in SO2 emissions from power plants and industry.
The reduction in these cooling aerosols means the Earth has been exposed less to this reflective effect. Think of it like removing a temporary "sunscreen" from the planet. If cleaner air (less SO2) means less reflection of sunlight, then it makes intuitive sense that allowing more sunlight to reach the surface could contribute to warming.
Human activities produce sulfur dioxide (SO2), Once in the atmosphere, SO2 transforms into tiny sulfate particles (aerosols).
These aerosols reflect sunlight back into space. This process is called global dimming or aerosol cooling. It has a cooling effect on the Earth's surface temperature, similar to volcanic eruptions.
Humanity is currently emitting 175 million tons of SO2 annually, the facts remain that every year of your life a portion of the energy from the sun is being reflected back into space before it reaches the surface, by our atmospheric emissions.
The image below shows a model of the cooling effect of Land SO2 emissions in degrees Celsius, and Northern Hemisphere sea surface temperatures. It is clear that the world was warming quite rapidly from 1910 up until 1945, which is the beginning of a decade's long increase of Anthropogenic SO2 emissions.
This model is biased by land emissions, so that is why the Northern Hemisphere temperatures are compared, because the North emits the most amount SO2. While land emissions have been reduced by various regulatory bodies and technological improvements since 1980 causing a perceived warming effect, the shipping industry was under no regulations and SO2 emissions over the Oceans increased until 2015.
The Effect of SO2 emissions from Global Shipping
Reducing the sulfur content in shipping fuels, mandated by the ECA in 2015 and the IMO 2020 regulation, had an unexpected and significant impact on climate. Sulfur dioxide (SO2) emissions from ships were a source of tiny sulfate aerosol particles, which acted like reflective sunscreen in the atmosphere. These aerosols, particularly over the reflective Southern Ocean region, scattered incoming sunlight back to space, causing a significant cooling effect. There were no real regulations in place until 2015, in which significant quantities of low Sulphur shipping fuels were being produced and utilized.
By drastically reducing these oceanic SO2 emissions starting in 2015, we inadvertently removed this cooling influence and caused rapid warming in the Southern Ocean and a significant drop in Antarctic Sea Ice.
While Arctic sea ice has experienced significant decline over the past several decades due to warming temperatures, Antarctic sea ice has exhibited a more complex counterintuitive behavior. But the Antarctic behavior rapidly reversed and all gains were lost over the last ten years.
The image below shows a model of the cooling effect of SO2 emissions from shipping activity in degrees Celsius. Southern SST, Antarctic Sea Ice and Lower Stratosphere temperatures are also displayed, and all show the expected behavior from such a change in the radiative properties of the Oceanic Troposphere.
Civil Aviation and Global Warming (Anthropogenic Water Vapor)
Every year, passenger jets silently inject roughly 95 billion gallons of water vapor into the upper atmosphere, creating invisible plumes that are heating the planet. While carbon dioxide from planes gets most of the attention, this hidden climate impact stems from something far less discussed: the transformative effect of aviation on the Earth's water cycle in the stratosphere. As planes climb to cruising altitude, their engines expel water vapor that doesn't fall back as rain but instead spreads across the ozone layer, trapping heat and altering atmospheric dynamics. This 'aerosol of the skies' is now part of the climate crisis—a silent, high-altitude contributor to global warming that demand from freight and passengers are creating faster than we can track its consequences.
Evidence coming soon...
Human activities produce sulfur dioxide (SO2), Once in the atmosphere, SO2 transforms into tiny sulfate particles (aerosols).
These aerosols reflect sunlight back into space. This process is called global dimming or aerosol cooling. It has a cooling effect on the Earth's surface temperature, similar to volcanic eruptions.
Humanity is currently emitting 175 million tons of SO2 annually, the facts remain that every year of your life a portion of the energy from the sun is being reflected back into space before it reaches the surface, by our atmospheric emissions.