Lakes and Reservoirs Threatened by Global Warming: Increasing Methane Emissions Could Worsen Climate Scenarios

"Lakes" May Rewrite Climate Scenarios

When it comes to global warming, CO₂ is the main player. However, quietly gaining presence is methane, a more potent greenhouse gas. Over a 100-year scale, methane's warming effect is said to reach about 30 times that of CO₂.ghgprotocol.org

According to the latest research, lakes and reservoirs worldwide may become increasingly important as "major sources" of methane. As warming progresses, lake water temperatures rise, accelerating methane emissions, which in turn further advances warming—a so-called "vicious cycle (feedback)" that may be stronger than previously assumed.phys.org

Why Do Lakes and Reservoirs Emit Methane?

At the bottom of lakes and dam reservoirs, a vast amount of "food" such as fallen leaves, aquatic plants, and soil organic matter accumulates. This is a world low in oxygen, where microorganisms decompose organic matter through processes that do not use oxygen, releasing methane as a byproduct.phys.org

Naturally, the "natural methane" on Earth was considered stable in the long term, balanced by decomposition and atmospheric breakdown and oxidation. However, as human activities warm the entire planet, lake water temperatures rise, and the period of ice cover shortens, this balance begins to crumble. The activity of microorganisms at the lake bottom becomes more vigorous, and methane production accelerates rapidly.phys.org

In high-latitude regions such as the Arctic and Siberia, the number of lakes called "thermokarst lakes" is increasing with the thawing of permafrost, and old organic carbon is being decomposed and escaping into the atmosphere as methane, as shown by multiple studies.ResearchGate

Simulating the Future from Measured Data at 767 Locations

This research was conducted by a team from Linköping University in Sweden and NASA Ames Research Center. The researchers collected measured data from 767 lakes and reservoirs scattered across various climate zones worldwide and constructed a new model incorporating numerous factors such as water temperature changes, ice cover duration, nutrient concentrations, lake size and type, and methane escape routes from the water surface (whether it bubbles up or diffuses in dissolved form).phys.org

By applying this model to multiple warming scenarios (so-called emission pathways) used by the IPCC, they estimate "how methane emissions from lakes and reservoirs could change by the end of this century."phys.org

Worse Than the IPCC's "Worst-Case Scenario"? Methane Emissions Nearly Double

The scenario with the most significant impact is the one where warming progresses the most among those set by the IPCC (high emission scenario). In this case, the current methane emissions from lakes and reservoirs could nearly double by the end of this century.phys.org

Lakes and reservoirs already significantly contribute to global methane emissions, and this increase is estimated to raise global methane emissions by about 10% from current levels.phys.org

At first glance, it might seem like "only 10%." However, methane is a greenhouse gas far more potent than CO₂, and its increase could accelerate the pace of warming beyond expectations. The research team points out that considering such feedback, there is a risk that actual temperature rises could be greater than the "worst-case scenario" assumed by the IPCC.phys.org

Researchers' Warning: "We Must Change This Scenario"

Professor David Bastviken, the lead author of the paper, states, "This study clearly shows that we really need to change the climate scenario as soon as possible." The message is that we need to hit the brakes before entering this "spiral," where the more warming progresses, the more methane lakes and reservoirs emit, accelerating warming.phys.org

Reactions on Social Media: Surprise, Anxiety, and Calls for "Action"

When this news was reported by overseas media, various reactions spread on social media.

• "I never thought lakes were such a big source of emissions. It's not enough to just reduce CO₂."

• "The CO₂ humans emit is even increasing natural methane emissions... the chain of responsibility is too heavy."

• "Shouldn't how we manage dams also be discussed as 'climate policy' from now on?"

Environmental NGO accounts prominently posted that "a 'full set of climate measures' is needed, including not only expanding renewable energy and energy conservation but also conserving and restoring wetlands and lakes."

On the other hand, extreme opinions like "Shouldn't we just cover lakes with concrete?" were also seen, with experts sharing calm remarks such as "Destroying ecosystems is counterproductive" and "Localized measures are not realistic to curb global methane."

On Japanese social media, comments like "After seeing footage of the 'boiling lakes' in the Arctic, I realized the fear of methane" and "Climate change is not a distant future issue; it's already happening" have been posted. The invisible gas rising from lakes seems to make the climate crisis feel more immediate.

Not Just "Bad News": The Effect of Emission Reductions Is Twice as Effective

Reading this far might sound quite bleak. However, the research team also conveys "good news."

Reducing greenhouse gases emitted by human society, especially CO₂, not only curbs warming by that amount but also suppresses the "natural increase in methane emissions from lakes and reservoirs."phys.org

In other words, reducing CO₂ emissions through measures such as reducing fossil fuel use, transitioning to renewable energy, and promoting energy conservation can

1. Directly: Suppress the warming effect of CO₂ itself

2. Indirectly: Suppress the rise in water temperatures of lakes and reservoirs, preventing future methane increases

This could bring about a "double effect."

Science Shows Not Only "Time Limits" but Also "Choices"

The methane rising from northern lakes is not merely a natural phenomenon but a "part of the climate system" linked to human activities. Research on lakes has advanced rapidly over the past 10-20 years, with issues like permafrost thawing, lake ice reduction, and simultaneous release of methane stored under ice making "how to handle lakes and dams" an increasingly important element of climate policy.ResearchGate

At the same time, this research also shows hope that "the scenario can still be changed." While following a high emission scenario might nearly double methane emissions from lakes, conversely, reducing emissions leaves room to avoid that future.phys.org

What We Can Do: Reducing CO₂ Also Suppresses "Invisible Methane"

Finally, let's organize actions that can be taken at the individual level.

• Reduce Energy Use
  Energy conservation at home and in the office, and choosing renewable energy power, directly contribute to reducing CO₂ from fossil fuels.

• Reevaluate Food and Lifestyle
  Reducing food waste and gradually shifting from a meat-centered diet can also help reduce methane from agriculture.Energy

• Express Support for Policies
  Supporting policies that promote renewable energy investment and decarbonization infrastructure can move "large emission sources" that individuals cannot touch.

• Spread Information
  By sharing the theme of "methane from lakes and reservoirs," which has not been well known, understanding of the overall picture of the climate crisis deepens.

Under the calm surface of lakes, the invisible gas methane is gradually increasing—this fact is not a comforting one. However, knowing it is also a starting point for considering "which future we want to choose."

The research presented here poses a warning that "if left unchecked, it might exceed the worst-case scenario," while simultaneously offering a choice that "if we act now, we can even suppress additional emissions from nature." Whether we can reduce methane rising from lakes by our own will—the answer depends on our actions in the coming decades.