A new study has found methane emissions from natural wetlands this century have outpaced the grimmest worst-case scenarios possible. The RCP 8.5 scenario ( Representative Concentration Pathway ) will deliver a 4.3-celsius increase in the world's average temperature rise by 2100. The system is based on carbon concentration in the atmosphere that will provide 8.5 watts of energy to global warming per square meter across the planet.
The study in Nature Climate Change used a wetland model that found intensified methane release from 2000 to 2021. With 2020 and 2021 exponential growth with the powerful short-lived (10-20 years) greenhouse gas CH4 has a global warming potential 80 times more potent than carbon dioxide, which lasts in the atmosphere for centuries.
Wetlands have always been a carbon sink, but no more. Our natural ally has become a carbon source and portends disastrous consequences in the fight against global warming.
Ayesha Tandon writes in Carbon Brief:
However, 40% of methane emissions are from natural sources. Waterlogged soils called wetlands, which are inundated with water for at least part of the year, are the world’s largest natural source of methane emissions.
Wetlands take many different forms, ranging from Arctic permafrost peatlands to tropical mangrove plantations to salt marshes. Around 40% of all species live or breed in wetlands. They also provide key ecosystem services, such as water filtration and are important carbon sinks. As such, wetland restoration is often discussed as an important climate mitigation option.
However, wetlands also release greenhouse gases into the atmosphere. The new study explores how climate change is affecting methane emissions in two key types of wetlands – permafrost wetlands and tropical wetlands.
Found in cold temperatures at high latitudes, permafrost wetlands consist of partially frozen and waterlogged soils. As the climate warms and the permafrost thaws, long-dormant microbes are starting to “wake up” and release methane into the atmosphere.
Meanwhile, tropical wetlands which are typically found in hot and humid climates. As the changing climate causes shifts in rainfall patterns, new soils are becoming waterlogged and these wetlands are expanding, the paper says.
Overall, this means that global warming is driving greater wetland methane emissions. This process is called the “wetland methane feedback”.
In 2020 the UN's International Maritime Organization required international shipping industries to significantly reduce the sulfur dioxide gas they release into the atmosphere. The gas has masked some of the greenhouse gases in the atmosphere. Without sulfur dioxide over the centuries, warming temperatures would be higher than they are today.
From MIT Technology Review:
Studies have found that ships have a net cooling effect on the planet, despite belching out nearly a billion tons of carbon dioxide each year. That’s almost entirely because they also emit sulfur, which can scatter sunlight in the atmosphere and form or thicken clouds that reflect it away.
In effect, the shipping industry has been carrying out an unintentional experiment in climate engineering for more than a century. Global mean temperatures could be as much as 0.25 ˚C lower than they would otherwise have been, based on the mean “forcing effect” calculated by a 2009 study that pulled together other findings (see “The Growing Case for Geoengineering”). For a world struggling to keep temperatures from rising more than 2 ˚C, that’s a big helping hand.
There are very good reasons to cut sulfur: it contributes to both ozone depletion and acid rain, and it can cause or exacerbate respiratory problems.
But as a 2009 paper in Environmental Science & Technology noted, limiting sulfur emissions is a double-edged sword. “Given these reductions, shipping will, relative to present-day impacts, impart a ‘double warming’ effect: one from [carbon dioxide], and one from the reduction of [sulfur dioxide],” wrote the authors. “Therefore, after some decades the net climate effect of shipping will shift from cooling to warming.”
Sulfur pollution from coal burning has a similar effect. Some studies suggest that China’s surge in coal consumption over the last decade partly offset the recent global warming trend (though coal does have a strong net warming effect).
Sea surface temperatures are now the highest recorded since 1981. Added to warming from the imminent El Nino, even more, heat will negatively impact the climate system.
Meteor Blades and boatsie both wrote diaries on the release of the IPCC AR6. Neither received many eyes. Considering the gravity of the crisis, the lack of curiosity is beyond disappointing.
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What a beautiful world we live in, populated with fascinating life forms. What a heartbreaking shame that we are taking them down with us.