Today is World Maritime Day, and the theme for 2020 is Sustainable Shipping, a topic that gets far less attention than it deserves.

Marine shipping is the most carbon dioxide (CO2)-efficient form of transport, responsible for a mere 3% of global climate change. CO2 is the most common greenhouse gas (GHG) and the focus of most climate change mitigation activities. If we reduce emissions in other sectors we shouldn’t need to worry about marine shipping, right? It’s not that simple. For one thing, demand for shipping is growing faster than improvements in fuel efficiency.

More importantly, if we are going to mitigate climate change, we need reductions in GHGs in all sectors in all countries. Evidence of this can be found in the actions of the global community, specifically the signing of the Paris Agreement. The Paris Agreement, which was opened for signatures in April 2016, was a historic moment, as nearly every country in the world committed to reducing climate-altering pollution.

Details regarding the marine shipping industry were absent from the Paris Agreement. Marine shipping was excluded from the Paris Agreement because internationals shipping can’t be covered in countries’ emission quotas. That’s where the International Maritime Organization (IMO) comes in. The IMO is the only organization that can effectively take responsibility for international shipping emissions.

In response to the Paris Agreement, the IMO adopted a strategy to reduce shipping sector emissions by 50% of 2008 levels by 2050 while working toward phasing out the use of greenhouse gases entirely. A worthy goal and a challenge.

In 2017, the IMO reported that emission levels had declined since 2008. The report stated that in 2015, emissions were 8% below 2008 levels even though international shipping had increased by 30%.

A more recent report commissioned by the organization paints a bleaker picture. August 4, 2020, the IMO released its Fourth Greenhouse Gas Study which found a 10% increase in GHG emissions between 2010 and 2018. Most troubling in this report is the 12% increase in short-lived climate pollutants (also called super pollutants).

As the name suggests, short-lived climate pollutants don’t persist in the atmosphere for long, but they do far more damage than CO2. These pollutants, which include black carbon, methane, tropospheric ozone, and hydrofluorocarbons, are responsible for almost 45% of current global warming.

Super pollutants are not only bad for climate change, they’re also environmental toxins that can harm people and ecosystems.

The IMO report found that black carbon emissions have increased by 12% and methane emissions had increased by a whopping 150%. Methane traps 86 times more heat in the atmosphere than CO2. Over a 20-year period, black carbon traps 3200 times more heat than CO2. That’s not a typo. It’s thirty-two hundred times more effective at trapping heat than the greenhouse gas we’re most concerned about.

Here’s where it gets messy. The increases in super pollutants are caused by attempts to meet environmental regulations. In January of this year, stricter rules around sulfur levels in shipping fuels came into effect. Sulphur reductions will decrease air pollution that impacts human health, in particular cardiovascular and respiratory diseases.

To meet the regulations on sulfur levels, shipping companies have started using hybrid fuels. A study conducted by Finland and Germany found that these hybrid fuels are causing a 10% to 85% increase in black carbon emissions.

Black carbon is particularly dangerous in the Arctic because it reduces the reflectiveness of snow and ice, which accelerates warming. And with the Arctic warming, more shipping is going through the region. Next year, the IMO is supposed to agree on regulations for black carbon emissions. This may include banning the use of high black-carbon emitting fuels in the Arctic. I hope it does, and if you care about the Arctic, you should too.

The increase in methane emissions has been attributed to the increased use of liquid natural gas (LNG), which is generally touted as a clean fuel. LNG emits little CO2 or black carbon, but its methane emissions should not be ignored.

It’s like a game of whack-a-mole. As soon as the shipping industry replaces one fuel with another we learn the replacement has dire consequences for the environment.

What’s the solution? I doubt we’ll know until we get there. But one thing is clear: Sustainable shipping is critical to a sustainable future—for the Arctic, for our oceans and for all of us.