As global temperatures continue to rise, more and more methane bubbles are being released from lakes and rivers, a new study has revealed.
The bubbles develop in the sediment at the bottom of water bodies, and release the gas into the atmosphere when they reach the surface.
If global temperatures rise by just 1°C, researchers suggest that methane bubble emissions could increase by as much as 20 per cent.
The excess methane leads to an additional temperature increase, resulting in a vicious cycle.
As global temperatures continue to rise, more and more methane bubbles are being released from lakes and rivers, a new study has revealed. The bubbles develop in the sediment at the bottom of water bodies, and release the gas into the atmosphere when they reach the surface
Shallow lakes, ponds and rivers are known to be responsible for a high percentage of global greenhouse gas emissions.
An important part of these emissions is caused by bubbles filled with methane gas that develop in the sediment at the bottom of these water bodies.
When the bubbles reach the surface, the gas enters the atmosphere.
Now, researchers from Radboud University in the Netherlands have shown that rising temperatures increase the numbers of methane bubbles produced.
Dr Sarian Kosten, co-author of the study, said: ‘Never before have such unequivocal, strong relationships between temperature and emissions of methane bubbles been shown on such a wide, continent-spanning scale.’
The study involved two main stages.
Firstly, the scientists looked at existing research into methane bubbles collected from various locations, ranging from a fishing pond in Malden (a town near Nijmegen) to postglacial lakes in northern Sweden and forest ponds in Canada.
Dr Ralf Aben, co-author of the study, said: ‘Next, we simulated methane bubble production in 1000-litre “mini-lakes”, where we could accurately control temperature and other conditions.
‘In this way we excluded causes other than the rise in temperature.’
In eight open tanks filled with water and sediment, the researchers mimicked an annual cycle.
Four tanks had a ‘normal’ Dutch climate, while the other four tanks had a temperature 4°C higher.
The researchers predict that a temperature rise of 1°C leads to six to 20 per cent higher emission of methane bubbles. In turn, this leads to additional greenhouse gases in the atmosphere and to an additional temperature increase
Results showed that the tanks at the higher temperature produced 50 per cent more methane bubbles than those at normal temperatures.
Based on this, the researchers predict that a temperature rise of 1°C leads to six to 20 per cent higher emission of methane bubbles.
In turn, this leads to additional greenhouse gases in the atmosphere and to an additional temperature increase.
Dr Kosten added: ‘Every tonne of greenhouse gas that we emit leads to additional emissions from natural sources such as methane bubbles.
‘Luckily, the opposite is also true: if we emit less greenhouse gas and the temperature drops, we gain a bonus in the form of less methane production.
‘This bonus from nature should be our motivation to reduce greenhouse gas emissions even further.’