Environment

Greenhouse gases to leave a long-lasting legacy

Greenhouse gases to leave a lo...
Researchers of a new study say that even after short-lived gases such as methane disappear from the atmosphere, they will still make themselves felt in the form of rising sea levels for centuries to come
Researchers of a new study say that even after short-lived gases such as methane disappear from the atmosphere, they will still make themselves felt in the form of rising sea levels for centuries to come
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Researchers of a new study say that even after short-lived gases such as methane disappear from the atmosphere, they will still make themselves felt in the form of rising sea levels for centuries to come
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Researchers of a new study say that even after short-lived gases such as methane disappear from the atmosphere, they will still make themselves felt in the form of rising sea levels for centuries to come

As the world waits to see whether US President-elect Donald Trump will scrap the Obama administration's Climate Action Plan, a new study suggests that like a bad smell that continues to linger in a room, even when short-lived greenhouse gases disappear from the atmosphere, they'll continue to have effects in the form of rising sea levels for centuries to come.

The study, which was conducted by MIT and Simon Fraser University researchers, focuses on the impact of short-lived greenhouse gasses, such as methane and chlorofluorocarbons, on sea levels. Though most of the attention on global warming has focused on carbon dioxide (CO₂), methane is proving itself to be just as formidable a foe.

For starters, it's a heat absorbing powerhouse that, according to the Intergovernmental Panel on Climate Change, can warm the planet up to 86 times more than CO₂ during its decade-long spell on earth. Its long-term effects are equally worrisome. According to the study, while methane-induced atmospheric warming might decrease as the gas dissipates, the same cannot be said about its warming effect on oceans, which manifests itself in the form of rising sea levels, even centuries after the gas molecules have disappeared.

This is due to ocean inertia, says study author Susan Solomon, a professor of atmospheric science at MIT. There's a reason, despite all the warnings from climate scientists, that we are not experiencing any noticeable change in ocean temperatures or sea levels yet and that's because it takes a very long time to warm up the waters given their vast size. However once they do heat up, the bad news is that it will take an equally long time for them to cool down again. And you know the drill: once the waters expand, sea levels will follow suit and rise as well.

"As the heat goes into the ocean, it goes deeper and deeper, giving you continued thermal expansion," explains Solomon. "Then it has to get transferred back to the atmosphere and emitted back into space to cool off, and that's a very slow process of hundreds of years."

In their study, the researchers used a climate model called the Earth Systems Model of Intermediate Complexity to project various climate change scenarios. In the case of methane, even if countries found a way to stop emissions by 2050, rising sea levels would still be a problem as far down the road as 2900 due to the residual heat trapped in the oceans.

The projections get grimmer when carbon dioxide and nitrous oxide are added to the equation. If emissions continue to accelerate till 2050, sea-levels would rise by three feet (0.9 m) via thermal expansion alone by 2900, and continue increasing after that. For island nations that are barely above sea level, like Tuvalu, this is worrying news, indeed.

The study also corroborated previous predictions about the impact of carbon dioxide and showed that even if the world managed to curb emissions by 2050, up to half the gas would still be in the atmosphere more than 750 years later. Sea levels would also rise, measuring twice the level of 2050 estimates for 100 years, and four times that value for another 500 years.

In a nutshell: climate effects are here to stay. Slashing greenhouse gas emissions doesn't mean we'll see a corresponding turnaround in climate change problems. In fact, things might have to get worse before they get better.

"Amazingly, a gas with a 10-year lifetime can actually cause enduring sea-level changes," says Solomon. "So you don't just get to stop emitting and have everything go back to a preindustrial state. You are going to live with this for a very long time."

This study comes at a time when an increasing body of research is showing that atmospheric methane and carbon dioxide levels are rising, a problem that might be compounded by thawing Arctic permafrost, which scientists such as Peter Wadhams, head of the Polar ocean physics group at Cambridge University, have warned could cause severe global economic repercussions, as The Guardian reports.

This threat reinforces why it is vital for governments to commit to regulating greenhouse gases. While cynics might question whether countries can put their self-interests aside, the success of the Montreal Protocol, an international treaty drawn up to protect the Earth's ozone layer by phasing out the production of ozone-depleting pollutants such as chlorofluorocarbons, shows that such regulations can and do work. Not only is the ozone layer recovering, the researchers found that it has also had an unintentional, albeit positive, impact on sea levels, which would have risen an extra six inches (15 cm) by 2050 if the treaty ban had not come into effect.

"Half a foot is pretty significant," says Solomon, who led the first Antarctic expedition to study the hole in the ozone layer and whose work helped pave the way for the treaty. "It's yet another tremendous reason why the Montreal Protocol has been a pretty good thing for the planet."

The Kyoto Protocol, the world's first international agreement to combat climate change and greenhouse gas emissions, has been far from successful in addressing the issue. While 21 countries, including Latvia and Romania, met their emission targets, they are hardly the world's biggest emitters. In hindsight, the fact that the three countries with the world's highest CO₂ emission rates – China, India and the US – were not part of the treaty shows how flawed it was right from the start. With the lessons learnt from this first agreement, which ought to be seen as an experiment instead, can the Paris Agreement do for climate change what the Montreal Protocol has done for the ozone layer?

The issue of global warming is one that invokes polarizing opinions across the board and one of the problems, where skeptics are concerned, is that predictions are just that – predictions. However if the authors of this study are correct, then it would probably be advisable to not wait for these forecasts to become a reality before coming up with a contingency plan. Curbing greenhouse emissions now will not magically lower sea levels immediately but the idea is to focus on playing the long game.

"The primary policy conclusion of this study," say the study's authors, "is that the long-lasting nature of sea-level rise heightens the importance of earlier mitigation actions."

The study was published in PNAS.

Source: MIT

15 comments
Nik
Oh dear! The ''CO2 panic button'' isnt working very well, non of our panic predictions have happened. We'll have to try another one. Perhaps methane will do the trick. Or maybe not.
Grumpyrelic
"the study suggests..." This sure sounds like wishful thinking. I hope the CO2 crowd is successful in removing carbon from the world. I would hope they start by extracting the 25lbs of it from their own bodies first to show some sincerity and conviction in their beliefs. What is sad is that somebody with letters after their name can write something like this and get paid for it. Carbon, along with the rest of the elements have been here for 4 billion years. They will remain here until the sun reabsorbs us in another 4 billion. Stop wasting our time and concentrate on getting us off this rock before we burn up.
CarlUsick
Denier! Denier! Denier! 97% consensus that CO2 and only CO2 is causing all the warming. Stop being anti-science and pro-big oil, you Faux News Trumpster shills. Submit to the consensus or pay the price!
Helmetbuster
Good call Nik. And they've even "improved" it by deciding it will cause indeterminate length problems. No end in sight.
Robert in Vancouver
I have lived 50 metres from the Pacific Ocean for the last 48 years of my adult life but have not seen any change in sea levels during that time. If there was a change I would see higher tides marks change on piers, cliffs, and beaches, but there's no change. I would have seen floods in nearby areas that are below sea level and protected by dikes, but there's no floods. Facts just don't matter when you believe in the "Man-made Global Warming Religion".
Rann Xeroxx
The oceans have been rising at an accelerated rate since ocean rise started to be measured long before the 1950's (the point of massive human release of CO2). And if you look at core samples there is nothing unprecedented about modern warming. Considering the cycles of El Niño & La Niña along with other factors there is nothing unusual about Arctic and Antarctic ice. CO2 is a GH gas but it simply is not a very powerful one and all of these computer model require strong positive feedback loops with water vapor for CO2 increase to have any significance and that feedback simply is not occurring.
The biggest driver to long term climate is the Sun both directly with illumination but also indirectly with the retreat of the solar wind and increase in cosmic rays causing cloud formation and cooling. Couple this with El Niño & La Niña, the Earth's wobble on its axis, and if you look into the millions of years even the bobbing of our star within the galactic arm as the Milky Way rotates, you can see clear patterns that emerge that far better match the temp data.
watersworm
OMG 3 feet in ... 2900; I'am so scared... i go back sleeping in my bed, just wake me up on January 1st 2900.
Bruce Warren
The coefficient of thermal expansion of water = 0.00021 per degree C. The verage depth of the oceans is 12,100 ft. If temperature rises one degree the depth would increase 2.5ft. I own a beach house and the tide does that now. So I know it would not be a problem at my place. And we are supposed to be fretting about a tiny Pacific island 850 years from now.... you gotta come with something scarier than that to get my attention.
Ken Brody
Don't worry. Those ginormous ice cubes called ice shelfs and glaciers will cool off the oceans faster than predicted.
I'll have ocean front property in central Florida if I live just another 600 years. Goody!
Douglas Bennett Rogers
About 80% of the AGW is probably due to pumping water in the dessert. This can be seen from the pronounced rise in afternoon wet bulbs and morning lows.